THE UNIVERSITY OF MICHIGAN AFAL-TR-66-169 7274-1-F INVESTIGATION OF MEASUREMENT TECHNIQUES FOR OBTAINING AIRBORNE ANTENNA SPECTRUM SIGNATURES Final Technical Report April 1965 to April 1966 June 1966 Prepared by J. E. Ferris, W. R. DeHart, R. L. Wolford and W. B. Henry This document is subject to special export controls and each transmittal to foreign governments or foreign nationals may be made only with prior approval of AFAL (AVPT), Wright-Patterson AFB Ohio 45433. Contract No. AF 33 (615) -2606 Project No. 4357, Task No. 435703 K. W. Tomlinson, Contract Monitor Air Force;Avioniics Laboratory AVWE Research and:Technology Division, AFSC Wright- Patterson Air Force' Base,- Ohio 45433

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THE UNIVERSITY OF MICHIGAN 7274-1-F FOREWORD This report was prepared by The University of Michigan, under USAF Contract No. AF 33 (615) - 2606. The contract was initiated under Project No. 4357, "Electromagnetic Compatibility Techniques" and Task No. 435703, "Interference Measurement Techniques. " This was administered under the direction of the Electronics Warfare Division, Air Force Avionics Laboratory at Wright Patterson Air Force Base, Ohio, with Mr. H. M. Bartman as Project Manager and Mr. K. W. Tomlinson as Contract Monitor. This report covers work conducted from April 1965 to April 1966. This report was submitted by the authors, 15 April 1966. PUBLICATION 1EVIEW This technical report has been reviewed and is approved. OE H A. DOMBROWSKI.Lt Colonel, USAF / hief, Electronic Warfare Division - - ~~~~~~~~~111

THE UNIVERSITY OF MICHIGAN 7274-1-F TABLE OF CONTENTS Page FOREWORD iii LIST OF FIGURES v ABSTRACT x I INTRODUCTION 1 II SIMPLIFIED MODELING 3 2.1 Antenna Configurations 3 2.2 Modified Monopole 4 2.3 k/4 Monopole 40 2.4 Slot Antenna 73 2.5 Concluding Remarks to the Simplified Model 73 III DATA RECORDING TECHNIQUES 92 3.1 ECAC Data Format 92 3.2 Manual Digitalizing Technique 93 3.3 Semi-Automatic Digitalizing Technique 94 3.4 Automatic Digitalizing Technique 96 IV TRANSMITTER OUTPUT CHARACTERISTICS 105 4. 1 A Multiple Generator Model for Spurious -and Harmonic Frequencies 105 4.2 Power Transfer Considerations 107 4.3 Source Impedance Measurements 111 4. 3. 1 Experimental Verification of the Source Impedance Measurement Using a Short Circuit Load 116 4. 3. 2 Measurement of Transmitter Impedance Using a Complex Load 119 4.3.3 Experimental Data 126 V CONCLUSIONS AND RECOMMENDATIONS 129 APPENDIX 131 RE FERENCES 139 ~__ __.....iv. __ _ _

THE UNIVERSITY OF MICHIGAN 7274-1-F LIST OF FIGURES Page 1A Precision T-33 Model 5 1B Simplified T-33 Model 6 2 Spherical Coordinate System 7 3 Modified Monopole 7.2 GHz Simplified T-33 0 = 90~/0 = 2700 8 4 Modified Monopole 7.2 GHz Precision T-33 p = 90 /0 = 270 9 5 Modified Monopole 7.2 GHz Simplified T-33 0 = 100~/0 = 2800 10 6 Modified Monopole, 7.2 GHz, Precision T-33 0 = 100~/0 = 2800 11 7 Modified Monopole, 7. 2 GHz, Simplified T-33 0 = 110~/0 = 2900 12 8 Modified Monopole, 7.2 GHz, Precision T-33 0 = 110o/0 = 2900 13 9 Modified Monopole, 7. 2 GHz, Simplified T-33 0 = 120 /0 = 3000 14 10 Modified Monopole, 7.2 GHz, Precision T-33 0 = 1200/0 = 3000 15 11 Modified Monopole, 7.2 GHz, Simplified T-33 0 = 1300/0 = 3100 16 12 Modified Monopole, 7.2 GHz, Precision T-33 0 = 1300/0 = 3100 17 13 Modified Monopole, 7. 2 GHz, Simplified T-33 ~0 = 140 0/ = 3200 18 14 Modified Monopole, 7.2 GHz, Precision T-33 0 = 140 /0 = 3200 19 15 Modified Monopole, 7. 2 GHz, Simplified T-33 0 = 150~/0 = 3300 20 16 Modified Monopole, 7.2 GHz, Precision T-33 0 = 150 /0 = 3300 21 17 Modified Monopole, 7.2 GHz, Simplified T-33 0 = 160 0/ = 3400 22 18 Modified Monopole, 7. 2 GHz, Precision T-33 0 = 160 0/ = 3400 23 19 Modified Monopole, 7.2 GHz, Simplified T-33 0 = 1700/0 = 3500 24 20 Modified Monopole, 7.2 GHz, Precision T-33 0 = 1700/0 = 3500 25 21 Modified Monopole, 7.2 GHz, Simplified T-33 0 = 1800/0 = 00 26 22 Modified Monopole, 7. 2 GHz, Precision T-33 0 = 1800/0 = 0 ~ 27 V

THE UNIVERSITY OF MICHIGAN 7274-1-F LIST OF FIGURES (continued) Page 23 Cumulative Gain Distributions of Precision and Simplified Models 28 24 Cumulative Gain Distributions of Precision and Simplified Models 29 25 Cumulative Gain Distributions of Precision and Simplified Models 30 26 Cumulative Gain Distributions of Precision and Simplified Models 31 27 Cumulative Gain Distributions of Precision and Simplified Models 32 28 Cumulative Gain Distributions of Precision and Simplified Models 33 29 Cumulative Gain Distributions of Precision and Simplified Models 34 30 Cumulative Gain Distributions of Precision and Simplified Models 35 31 Cumulative Gain Distributions of Precision and Simplified Models 36 32 Cumulative Gain Distributions of Precision and Simplified Models 37 33a Average of Sliding Sector of Precision and Simplified Models 38 33b Sliding Sector Description 39 34a X/4 Monopole Antenna on Precision Model T-33 41 34b X/4 Monopole Antenna on Simplified Model T-33 42 35 X/4 Monopole, 2. 4 GHz, Precision T-33 0 = 900 and 2700 43 36 X/4 Monopole, 2.4 GHz, Simplified T-33 p = 900 and 2700 44 37 X/4 Monopole, 2.4 GHz, Precision T-33 p = 800 and 2600 45 38 X/4 Monopole, 2.4 GHz, Simplified T-33 p = 80 and 260 46 39 X/4 Monopole, 2.4 GHz, Precision T-33 = 700 and 2500 47 40 X/4 Monopole, 2. 4 GHz, Simplified T-33 = 700 and 2500 48 41 X/4 Monopole, 2.4 GHz, Precision T-33 0 = 600 and 2400 49 42 X/4 Monopole, 2.4 GHz, Simplified T-33 = 600 and 2400 50 4 4Moo.24G,PeioT3 a 23 viO — ~~~~~v..'''.'-Vi1.....

THE UNIVERSITY OF MICHIGAN 7274-1-F LIST OF FIGURES (continued) Page 44 X/4 Monopole, 2.4 GHz, Precision T-33 ~ = 500 and 2300 52 45 X/4 Monopole, 2.4 GHz, Simplified T-33 p = 500 and 2300 53 46 X/4 Monopole, 2.4 GHz, Precision T-33 ~ = 400 and 2200 54 47 X/4 Monopole, 2.4 GHz, Precision T-33 0 = 300 and 2100 55 48 X/4 Monopole, 2.4 GHz, Simplified T-33, = 300 and 2100 56 49 X/4 Monopole, 2. 4 GHz, Precision T-33 0 = 200 and 2000 57 50 X/4 Monopole, 2.4 GHz, Simplified T-33 ~ = 200 and 2000 58 51 A/4 Monopole, 2.4 GHz, Precision T-33 p = 100 and 1900 59 52 X/4 Monopole, 2.4 GHz, Simplified T-33 p = 100 and 1900 60 5 3 X/4 Monopole, 2. 4 GHz, Precision T-33 0 = 00 and 1800 61 54 X/4 Monopole, 2. 4 GHz, Simplified T-33 0 = 00 and 1800 62 55 Cumulative Gain Distributions of Precision and Simplified Models 63 56 Cumulative Gain Distributions of Precision and Simplified Models 64 57 Cumulative Gain Distributions of Precision and Simplified Models 65 58 Cumulative Gain Distributions of Precision and Simplified Models 66 59 Cumulative Gain Distributions of Precision and Simplified Models 67 60 Cumulative Gain Distributions of Precision and Simplified Models 68 61 Cumulative Gain Distributions of Precision and Simplified Models 69 62 Cumulative Gain Distributions of Precision and Simplified Models 70 63 Cumulative Gain Distributions of Precision and Simplified Models 71 64 Cumulative Gain Distributions of Precision and Simplified Models 72 65 Slot Antenna on Precision Model T-33 74 66 Slot Antenna on Simplified Model T-33 75 Vii

THE UNIVERSITY OF MICHIGAN 7274-1-F LIST OF FIGURES (continued) Page 67 X-Band Slot, 8.0 GHz, Precision T-33 0 = 900 and 2700 76 68 X-Band Slot, 8.0 GHz, Simplified T-33 0 = 900 and 2700 77 69 X-Band Slot, 16.0 GHz, Precision T-33 0 = 900 and 2700 78 70 X-Band Slot, 16.0 GHz, 0 = 900 and 2700, Simplified T-33 79 71 X-Band Slot, 24. GHz, Precision T-33, 0 = 900 and 2700 80 72 X-Band Slot, 24.0 GHz, Simplified T-33, 0 = 900 and 2700 81 73 X-Band Slot, 32.0 GHz, Precision T-33 0 = 900 and 2700 82 74 X-Band Slot, 32.0 GHz, Simplified T-33 0 = 900 and 2700 83 75 X-Band Slot, 40.0 GHz, Precision T-33 0 = 900 and 2700 84 76 X-Band Slot, 40.0 GHz, Simplified T-33 0 = 900 and 2700 85 77 Cumulative Gain Distributions of Precision and Simplified Models 86 78 Cumulative Gain Distributions of Precision and Simplified Models 87 79 Cumulative Gain Distributions of Precision and Simplified Models 88 80 Cumulative Gain Distributions of Precision and Simplified Models 89 81 Cumulative Gain Distributions of Precision and Simplified Models 90 82 Semi-Automatic Digital Recording Equipment 95 83 Automatic Digital Recording System 97 84 Wide-Range, High-Gain Receiving System 98 85 U of M Analog-to-Digital Converter 99 86 General Purpose Tape Recorder 100 87 Raytheon Analog-Digital Converter and Associated Logic Racks (North Campus) 101 88 X-Band Slot, 16.0 Gc, Simplified T-33 103 89 X/4 Monopole, 2.4 Gc, Precision T-33 104.......~ -viii "

THE UNIVERSITY OF MICHIGAN 7274-1-F LIST OF FIGURES (continued) Page 90 Elementary Generator 106 91 Multiple Generator Model For a Transmitter 106 92 General Transmission Line Problem 108 93 Modified Transmission Line Problem 108 94 Power Transfereas a Function of Transmission Line Length 110 95 Generator Impedance Measurement Circuit (using a short-circuit load) 112 96 Equipment Organization for Generator Impedance Measurement 117 97 Impdeance of Generator in Series With Stub Tuner (using a shortcircuit load) 118 98 Equipment Organization for 50 2 and Tuning Stub Impedance Measurement 120 99 Generator Impedance Measurement Circuit (using a complex load) 122 100 Circuit for the Determination of I1 125 101 Equivalent Circuit of Fig. 100 127 102 Impedance of Generator in Series With Stub Tuner (using a complex load) 128 A-1 Equivalent Circuit for the Transmission Line Problem 133 ix

THE UNIVERSITY OF MICHIGAN 7274-1-F ABSTRACT This report discusses three areas which are of importance to the Electromagnetic Compatibility program presently being conducted by the U. S. Government. The areas discussed in this-report are: 1) methods for obtaining spectrum signatures at a minimum of cost, 2) data recording techniques, and 3) methods for obtaining transmitter signature characteristics. The methods for obtaining antenna spectrum signatures discusses the use of simplifed models together with typical results for three different antenna configurations. The three antenna configurations were tested on both a simplified and a precision model of a jet aircraft at a fundamental and four harmonic frequencies. In the data recording section the data format for antenna signatures is presented. A recommendation as to the format in which the data should be collected and forwarded to ECAC for prediction analysis is made. A discussion of a technique for digitally recording signature data at a minimum of cost is presented. Under the final section, techniques for determining the signature characteristics of a communications type system are discussed and some preliminary results are presented.

THE UNIVERSITY OF MICHIGAN 7274-1-F INTRODUCTION The present study has been divided into three areas. Each has been concerned with the determination of the Spectrum Signature of airborne electronics systems. The three areas considered during this study were: 1) methods for obtaining the antenna pattern spectrum signature at a minimum of cost, 2) data recording and reduction techniques, and 3) methods for obtaining transmitter output characteristics. To obtain antenna spectrum signatures, consideration has been given to the use of simplified models rather than precision models or instrumented airborne systems. An extensive experimental study has been conducted to determine the feasibility of the simplified modeling technique. The initial investigation of simplified models, as they may apply to airborne antenna spectrum signatures, is presented in a report by Ferris, et al (1965). This study has been continued, and typical results are presented. In addition to simplified models, further consideration has been given to fly-by tests (employing an instrumented full-scale aircraft). Because of costs and the complexity of the technique, it has been rejected as a practical means for obtaining spectrum signature data. Techniques for recording spectrum signature data of airborne antennas in a digital format have also been investigated during this study. Several digital recording procedures have been considered such that the data could be efficiently stored by the Electromagnetic Compatibility Analysis Center (ECAC). X 1

THE UNIVERSITY.OF MICHIGAN 7274-1-F Supplement I (Dute et al 1966) of this report discusses these techniques in further detail. Digital techniques for recording and storing the original antenna signature data are desirable since ECAC prefers to use statistical procedures when making interference predictions. Consideration has also been given to procedures that would be applicable to accurately determining the spectrum signature of airborne transmitters. Present measurement techniques employed to obtain signature data from which interference predictions may be calculated are relatively crude. Therefore, the interference predictions are generally unreliable. The present study has been directed to a level which is relatively basic in principle. From this study a better understanding of the measurement procedures as applicable to obtaining the output characteristics of the transmitter can be achieved. The study also provides a more accurate picture of the electronic phenomenon that takes place between the transmitter and antenna at the fundamental, spurious and harmonic frequencies. 2

THE UNIVERSITY OF MICHIGAN 7274-1-F SIMPLIFIED MODELING In a previous report, Ferris et al (1965), op. cit. it was shown that the technique of simplified modeling appeared feasible. Therefore, the present contract was initiated to complete the study. During the period covered by the present contract, three antennas located on both the simplified and precision models have been considered. In addition to the study of simplified and precision models, the need for employing full scale aircraft antenna techniques has been considered. 2.1 Antenna Configurations Two VHF and one UHF antenna configurations were employed during the study of the simplified modeling technique. The VHF antennas were a modified monopole and a conventional X/4 monopole antenna. The full-scale modified monopole antenna is designed to operate over a 2:1 frequency range of 200 to 400 MHz, and the simple full-scale X/4 monopole is anarrow-band antennathat operates at 300 MHz. Both of these antennas were scaled by a factor of 8 so that they operated in the UHF frequency range at approximately 2. 4 GHz center frequency. The modified monopole was located on scale models of a jet aircraft directly beneath the wings. Three-dimensional antenna spectrum signatures were collected at the fundamental and four harmonic frequencies. The X/4 monopole was located onthe underside of the nose of the aircraft. Three-dimensional data was collected at the fundamental frequency and principal plane patterns were obtained at four harmonic frequencies. The UHF antenna simulated a full-scale 1. 0 GHz antenna. The scale model antenna consisted of a short section of open ended X-band waveguide operating at a fundamental frequency of 8. 0 GHz. Principal plane pattern datawas collected at the fundamental and four harmonic frequencies. This antenna was located in the underside of the fuselage midway between the wings.

THE UNIVERSITY OF MICHIGAN 7274-1-F Pattern data was collected both on the simplified and precision models of the jet aircraft. This data was reduced to typical statistical formats used by ECAC. The statistical data was compared to determine the validity of simplified model data. 2.2 Modified Monopole Figures la and lb show the modified monopole located on the precision and simplified models respectively. Some data, demonstrating the feasibility of the simplified modeling technique for the modified monopole, was presented in a previous report (Ferris, et al 1965). During the period covered by the present contract, additional data was obtained for the modified monopole antenna at the fundamental and four harmonic frequencies. This data was collected such that the threedimensional pattern characteristics of the antenna were obtained at each of the above frequencies. All pattern data collected with the aircraft employed the spherical coordinate system shown in Fig. 2. The three-dimensional antenna patterns were recorded in the 0-variable plane with p varied in increments of 100. The polarization of the transmitting antenna was constant E A typical set of three-dimensional pattern data is shown in Figs. 3-22. The dat is for 7.2 GHz and alternate patterns show results first for the simplified and then for the precision model for various values of 0 and p. This data was reduced to a cumulative gain distribution (statistical) format for further comparison. Typical cumulative gain distributions for the above patterns are shown in Figs. 23-32. An example of an alternate data reduction technique that was employed to compare the simplified and precision models is illustrated in Figure 33a. The conventional antenna patterns shown in Figs. 3 and 4 have been reduced to statistical patterns in Fig. 33a. Pattern data, when placed in this statistical format by an averaging process, may be effectively compared due to the smoothing of the pattern in cluttered, narrow-lobe regions. This alternate technique employs a sliding sector as illustraged in Fig. 33b. Here it is seen that the sector width (in degrees) is denoted as a, and the sector slide increment (in degrees) as j. The sector ca is, - - 4 1 --- -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

THE UNIVERSITY OF MICHIGAN 7274-1-F FIG. la: PRECISION T-33 MODEL

THE UNIVERSITY OF MICHIGAN 7274-1-F FIG. lb: SIMPLIFIED T-33 MODEL

THE UNIVERSITY OF MICHIGAN 7274-1-F 8=oE t ~~0 6 900 = 270~ 8 = 90~ FIG. 2: SPHERICAL COORDINATE SYSTEM

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c-,L CEIaIdIAiIS'ZHo z L'30'iOdONO IAIa iciO w LI'DIa C\ oOV' = 0/o091 = 0 Z 0 H I;::lI II I I II I 1Y 4 }4A]V X E IIT~il19:tf1 IITTIIIIIIIIIIIIII1T 1T~llilIIII1IIIIIIIIIIIIIIIIIL I I I I I ITIll, I II I I'll IuIl I > < I l l l l l l l l 11 l EXT IX1JSIIIIIIIIISI Ilrlflilliiliiliiliilil~E~l~ll 1 11 11111111111<11111111I111111I11I1111I11I11111111 H > T f T 1111 1111 lililill~~~~~~lilililil~~~l~lililililill~~~lillfililililililililililililililill~~~-11

~-JL NOISI31II1d'ZHO Z L'3rIOdONO (I[IaII(OIW:'81'DI cO Cl o0I' = 0/o091 = 0 0 II |I I Ic13iS hfIIHIIIII1IIIIIIIIIILI111III 11111 11 I II I z 11I1 1 d h1 d htdSIIIIIIIMLll\I~iiiiiiiiiiiiiiii~lllgIIIIILIIIIIIIIIIIIT H 11I1 1 0if ~ ~0i~SIIIIIIZIIIIIiIIIlH~il0L ll0~ilLtE LLLIIIIIIIIIII

THE UNIVERSITY OF MICHIGAN 7274-1-F CO z~~~~~~~v CY) ol~~~~~~~P cr cc I CrL O,~~~~~~ c II gseO w ~~~~~~~~~~~~..q ~24

tTX TW~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~T....' ANGLES C 0o 0 = 170o/!:0 3I0o FI._0 II O 111 1111I Ilill~l~l iijlf l 111111111 IIII IIII IILIIIII jal I Y2 I I IlIIlIlII llLLIII IiIlII I II I I I i.. GA NrT ICN............CHART.....III ANGLE 74 1L CHART.. 24. i.................... 0 = 1700/0 = 3500 cnl FIG. 20: MODIFIED MONOPOLE, 7.2 GHz, PRECISION T-33

- M LT T 1 11TT T TTT T TT i11I 1l. 1OIIl& 1 11 fIIIIt II sIz II I I I I IIANGLE 4 Im IIT TT 1 X X 1 TTT TT TTIT- III~Al A I 1r II I I I I I I I I I I I I I I I I I I I I I [ 0 = 18oo/ = II FIG. 21: MODIFIED MONOPOLE, 7.2 GHz, SIMPLIFIED T-33 T 4 f 1 T F ~iF i3g T4 3gTZH TT |t |0 |b 6| tt t| |8 |+ |1l1 111 11 TR|| || ||| || ||| F| |$| || $|I i| ||| i| 1l1 l l 1ii80 0/0 i0i0 1l]ll i T c n I1 1II1 T 1 TT 1~ 41 1111111111111111111111I lnIlllllfllllllllll411Iiiiiiil~illlllLllllll~iii11 TTTI 1 1 1 I1TIT TT T l1 T 1 TIIIIIIIIIILIIIIIIIIIIIIII 21: O IID M N P L,72G zS I MPLII I FII I ED T-33IIIIIIIIIIIIIIIIIIIIIIItIIIIIIIII~

8g-JL NOISID3Id'ZHD g'L'S3IOdONOO aIjIaIIOWI:' DI oO = 0/os81 = 0 z H t~(~~~~~~~~~~~~~~~~111N II IILy

. I I I I Antennas Modified Monopole Frequency: 7.2GHz Orientation: = 900and 2700 -40 ~~~-2.4 ~~~~~~~z C) 0.Precision T -.33 -40 1 1 I - I - I I I I 1. - FIG. 23: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS lII FTG. 23'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I

Antennas Modified Monopole Frequency: 7.2 GHz Orientation: =100~ and2800 lCD* I -32 - Precision T - 33..-Simplified T-33 -40 02 0.5 1 2 5 10 20 30 40 50 60 T70 80 90 95 98 99 99.8 998C) Probability That Relative Power Level Is Exceeded FIG. 24: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

0~~~~~~~~~~~~~~~~~ Antennas Modified Monopole Frequency: 7.2 GHz Orientation: 0=1100 and 2900.0 -16 24 CL~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I 5 -32 ~T -Precision T- 33 Simplified T-33 C ~Ill I I 0:~ = 1 140 \I 1 1 1 020.51 2 5 10 20304050601080 9095 989999.599.8 Probab lity That Relative Power Level Is Exceeded FIG. 25: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

Antennas Modified Monopole 3 Frequency: 7.2 GHz __""__- ~Orientation:: 1200 and 300 m | 2_ zn -40 FIG-16 26 CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS 0_-24 --- _ - ~ 3 -- - - - - - - ___ - Precision T - 53...... Simplified T-33 -40o I - 0.2 0, 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 9.,5 99.8 Probability That Relative Power Level Is Exceeded - FIG. 26: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

Antennas Modified Monopole | Frequency: 7.2 GHz Orientation: = 130 and 3100 -8 P ~ I==( P e is E -6 -'I -24.. -3 c:- Precision T - 33 ~ -. — Simplified T-35..40 1 1.. 02 0.5 1 2 5 10 20 30 4050 60 70 80 90 95 98 99 95 9598 Probability That, Relative Power Level Is Exceeded FIG. 27: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

Antenna: Modified Monopole Frequency: 7.2 GHz Orientation: - = 1400 and 320~ -16. o0 -24~,-3) 40 02 0.512 5 20304050607080 9095 98 99-99.5 Probability That Relative Power Level Is Exceeded - FIG. 28: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

"' I ~ ~ ~ ~ ~~~~~~~~~~~~~~~~~I I I I I l~~~ F Antenna: Modified Monopole H I I I I * I I I I I Frequency: 7.2 GHz Orientation: 0- 150~ and 330~ 8~ ~ -16.J o -2.4,P ~* C /) X 0 L24 ___-Precisin T- 33 - co~~~ t -Precision T -33 ~ -40 ~..Simplified T-33 - -40 I I L I 02 0.5 I 2 5 1 0 20 30 40 50 60 70 80 90 95 98 99 995 9.8 Probability That Relative Power Level Is Exceeded z FIG. 29: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

Antennas Modified Monpole 3 Frequency: 7.2 GHz Orientation: = 1600 and 340.0) " I I I I I, I I 1 1 1 1 1 1 1 1 -I a F. 30! GIUIN F CION A S GO-24 ac S - Precision T- 33 -.... Simplified T-33 5 -40 I I O 0.5 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 995 99,8 Probobility That Relative Power Lbvel Is Exceeded - Z FIG. 30: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS I~~~~~ i ii

Antenna: Modified Monopole Frequency: 7.2 GHz -40 40I I I -I I I I I II I - I 40' " 1 - - - -. 02 5 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 99 Probability That Relative Power Level Is Exceeded FIG. 31: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

Antennas Modified Monopole Frequency: 7.2 GHz Orientation: 0 = 1800 and 00 -8 40 L - Simplified T-33 -. -40 I I 02 0.5 1 2 5 10 20 30 40 50 60 70 80 90 95 98 9 9.5 998 Probability That Relative Power Level Is Exceeded FIG. 32: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

180 150 100 50 0 5 ~~~~~~~~0 10 1008 -10 o~ =220~ *~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -30 &4 0 I Angle 9 (Degrees) C FIG. 33a: AVERAGE OF SLIDING SECTOR OF PRECISION AND SIMPLIFIED MODELS. Antenna: Modified Monopole. Freq. = 7.2 Gc. -. ~ - ~ -30.. O~ 0 I 0 0 -0 I -40 1 _________ _________ ~~~~~~~~~~~~~~~~~~~~~~~~~~~ L...... _____ -~~~~~~~~~~~~. ~8'5 - 0 SO 10C Anena Moiie Moooe Fe. = 7. G...

THE UNIVERSITY OF MICHI'GAN 7274-1-F F II I 1 1 H 1 1 11111 H I<!9 Millllil~I I;X00t i tE I I t I I a, --- 002LL0~~~~~~~~~~r SectorSS4 Wldth<N (Dgres t~~~~~~~~ iL; it iX:9 a X'VI I S1 1iIde Increment (Degrees) NYi;1lt1 1 S 01 1 1N1 a2 W>XEI II HIM WX~tl~l W3 1 1 1 Hill iS I I:E H Ill 3LL 11i i 7 I fill i> > > L I 4 41 1 11111 Is 1S6 P~"TO N.S^.CHART No. 121 ANGLE FIG. 33b: SLIDING SECTOR DESCRIPTION 39

THE UNIVERSITY OF MICHIGAN 7274-1-F is slid in steps of 13 across the 360-degree width of the conventional antenna pattern. As the sector is slid, statistical data is calculated and plotted as follows: (1) the average gain within the sector a 1 is determined and recorded at a1/2; (2) the sector al is slid 1o becoming a2 and the above calculation repeated and plotted at a2/2 = a1/2 + B; (3) the process is repeated for a3, a4, etc. across the pattern (Note: al = a2 = a3, etc.). Figure 33a is a composite (precision versus simplified model) of average data for the modified monopole with a = 200 and 3 = 40 To aid.in the reduction of the data into statistical formats all data has been recorded in a digital, as well as analog, format (the pattern data in this report is in analog format). The instrumentation employed to obtain the digital data is discussed in a later section of the report. 2.3 X/4 Monopole The X/4 monopole was also discussed in the previous report (Ferris et al 1965). Since the writing of that report, additional data has been obtained at the fundamental and harmonic frequencies. A complete set of three-dimensional data has been obtainedforthe X/4 monopole at the scaled fundamental frequency of 2.4 GHz. Figures 34a and 34b show the antenna mounted on the underside of the nose of the precision and simplified jet aircraft models. Figures 35-54 constitute a set of threedimensional data for the X/4 monopole at 2.4 GHz. It is interesting to note the similarity between the patterns of the precision and simplified models in spite of the streamlined contour of the precision model. Cumulative gain distributions (statistical) were plotted to aid in their comparison as shown in Figs. 55-64. The University of Michigan analog-to-digital converter was employed to record the above antenna pattern data in digital form on magnetic tape as the analog pattern was being plotted on chart paper. The digitalized data was later automatically processed, reduced and plotted in a form of cumulative gain distributions as will be discussed later in this report. During the period covered by the present contract, the recording system was modified to include a 60 db dynamic range and this was employed to obtain the above patterns. 440

THE UNIVERSITY OF MICHIGAN 7274-1-F FIG. 34a: X /4 MONOPOLE ANTENNA ON PRECISION MODEL T-33 41

THE UNIVERSITY OF MICHIGAN 7274-1-F FIG. 34b: X /4 MONOPOLE ANTENNA ON SIMPLIFIED MODEL T-33 42

o~o O'q H 0 0 0" ~ L~~~~~~c'~ M ----------— ~~~CAD,~ cn a~~~~~~l T 10 - 0 o ~~~~~~~~~~~~~~~~~~~-RELATIVE;, POWER ]ONE!i WAY (db 0~~~~~~~~~~~~~~~ z 0 9~~~~~~~~~~~~~~~ CD >~~~~~~~~~~~~~~~~ CAD - - ------ ---- -- M_ 00 1 r ~ ~ ~~~~~~~~~~~~".. -...,~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~...... L -1 — t~..i.,. -._..OD. L. I. —L

THE UNIVERSITY OF MICHIGAN 7274-1-F 0 igS~~i II II - ~-I2 - 4- -!-.-L ci.-~ 4 *1 I~~T- t I T I I i I X F II' ~i-1l-4-i -i-iV-i ~-tt-i —i-t-1+~- 1~t -t —-t-t-ii 4-~ -t —tir-1t-t!i-t ~t~ -ii -- i )6 ~ ~ ~ ~ ~ ~ 6:ii~- X!1.X ii I 40,-t- I., -{-4 300 a 1 I [7 <ii i Ji2 -I 0!-1I- li' —!'iI i I~ lf~-c_1. -O180,~ ~ O~' i _.. F. I-;-~ -tr ftIC-C ~ —~ I —- - -t i — iFIG 36: X/4 MONOPOLE, 2.4 GHz, SIMPLIFIED T 33 44 LJ. I-~I --' —-i —- L... I ~l. —i- _1_..i-~ r -i -t4 CL j-t- -: -~t~ —._f1-~~~~~~~~~~~~~~~~~~~~~~~~~~~~I T F~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 40r —-- t- -.-. —t ---— i._ -i- -i —-,!~i~ — l — iii~~t tt —t t-i-i- — t —— t-t -t~ iI- ----— CiJ — i —-i-Ji —... -C -t-t —-$- 1 —i —-~ —— 1 i-~ i i -i i-i-~- -— it7 L~~~~~~~~~~~~~~~~~~~~~~~ 4 4~~~~~ 01 0 1i —i — I. B- - Ji —ti o o+-~"I _io~I 5 -4 -301~ — t- — i —!!7-~ — ~-i - -1 r 4''t-.-. 3b0~~~~~~~ —~~~ I w- 24 — V~1~ 0-~~~~~~iitir" ii- 6~i -i18 8! 1 18"11i 1440 8 0 -72R, 0-i —7" —i-i- -36~ —-~i- - 6d — 60 CHART 140. 128-60 PRINTED IN U.S.A. ANGLE 9 SCIENTIFIC-ATLANTA. INC.. ATLANTA. GEORGIA 9OO 90 and 2 700

THE UNIVERSITY OF MICHIGAN 7274-1-F 1 0 4 6 — t —::|:I t! I li M tA10X-~~~~~~ ILL FIG. 37 X-;/4 MONOPOLE, 2. 4 GHz, PRECISION T-33 —- - 1-l —........ 45.............4 5 CA NO. 1 - P I U' A G f S I ATLANTA. G I CHR O 86 RNTUI..A N L SINII-A.AT.IN. TATA ERI' j-:- t! — 8 00 and 2600 ~~c-c i_

THE UNIVERSITY OF MICHIGAN 7274-1-F 2 I -- -- - i46 -i —1i - ---- i a. -t t —i - i t-i -8Oi and 26OI

THE UNIVERSITY OF MICHIGAN 7274-1-F 14'i 6 I / i:, i,! I -Ij~ ~ =l'!- 0 —-+- i - - --— i-! -i-t 1 1 i i'i' I iT! — ~-,-,-......~ ~ ~ ~- -—,,...... -i -t — -— i — 1 —-l — r -- It. - i — "i~ i~ I 4 ~ 1 J'' I~;' ji-; —-< - [h-' —I -S-pP i —i i= II ~- I1::1u 1: 1:1..1 - -4H 1..... t, - tr-L I I I i_ — I — J I - I I. -ii 1-1't. t 401 50 t- I -- I i —-- --- -- 41180-I j' i -f8F -[12ji-it- 60VH PI 12 I18-` —-~ 24~~ 4- 3 - i t — X {0 p2 1 i.l._ F W. g t t36 -H I K 3 7 1I-t-l t- 1-t -1 0 - 700 ad 250~ - 47 t,0~~i I.! - t i~-t- -t- J,- t — l-~......... --- "" "'f7 180; 8,,-' F 0!36 I i 2 11 -'i 4 ti

THE UNIVERSITY OF MICHIGAN 7274-1-F 1 I I'I I I i --- t —. ----- 54'4 1 i 301 I - 20 1 /1 i Ib i i 3Q0 4-,40 eI0 i i,' i i L i - I~.I i. I if I 72fi4 3 I i-f 4.!'4 i H - i - 1 < 1mjt 18,0:, —-: — 1...............L... ATLANTA. O w.!. -~i - ~! -i- t i — -i LI -c-~i —— i - 1; —-— i ~ i r-:-II-~ —-- -2 —ii ~~~~~8i~~~~~~ ~~~61'''~~~~~~~~ i~ i-i-i I. I —i —l-.i 1 1 i -~- -.- I --- i —t — -- — i 1._L i~l.._l~ i —-'-J

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THE UNIVERSITY OF MICHIGAN 7274-1-F 0 ' —--— [ [ ~i....!......!........ iX.I. -i-.t-~it'r l 4 1g li -lF... I IL._LL _ iF.::: 1 1 —:1:: X A[, ][:,]i, _I_.l\.... + —A —4 —4t- ~ ~ —-f,-.... -i-t -t7\ t.. -. —— ~-..-!._L.... i!...., ~~~~~~~~~~~~L i ii t i i-! -! /!- | [/ i: I i~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~i _T_~~~~~~~ <W t i 0 < ir =4 IF JI L- 1 — I T1Wi -l —-i —-i —i ~ ~I~ I-i~~ I ~~~Iii ii ~ l. - 4-...... -...... 4-4 - - I..,..: I 3 i 1 -" t. "i..... 1' 1 11.......... -- - 1-:- - I -t i t-l- 1 1 — -r~~ Iii i~iii~ c t -r; r S 0 11 1f X 1 1 I 1 1 U CHART NO~~~............... 128-60 PIT.......... ANL1 CETFI-TAT N................-............ L4....... 1. —. —TLANT..GEO.R-GIA — t- i -- ilt-C-I,__t~'l'- t-t i —-ltt!I-, t1 —. t~ t..... I!..... - 6-0.. 240~ -~~~~~~~~~~~~~~~~~~~~....i.... —-A L_.__..l_....... tJ-,CII —.......t.. -......... -Ft~ —-i —-',-?-i~i-i.................'it~l..... iti'~,! ~l 1!![~ L,-i,,' ~,l.iF..............'......... i 2 ~ i,:, I I-".M... L. 2-3-............l t — t -l.......-~ t..I.....I' -....l~_.l_.'/,,''- ---,,.!~,, l —~ —,,1,,i-il.-,m, I -I -I —~~~~~~~~~~~~~~~ ~~~~... ~........... 1 -',- 1............. t..[-r.......'- t-'-,, /'i ~i i r,,i'!,',-........... r''T"-, —' — r-~: C --— i- - — l~ —! -+-I..... l —— ~-\......... 4-t —.i — W~~~~~~~~ i.t-I... — ~' — — LL -::-~... _.i.. -— i4..1..... —, —J-... -4- - i- - i. —! —j —i —-i~- J! —i — i —J... -i.i-'l......... i"-If —l —?-! /! ]i J L i L I L'_ __............ -__~.... _.L._.......'-~ —'I..... _ _ *~ ers --- - -!....... i -4.......-l. — C — - -tr / / - j!!f j i- ]t - i -1!i- i' i~' i' I I I I I ~' T.....................J [i — I!,_ t-', i Iti-tt i i! ~ -i.: ~1/` L- -t! 11- -f -t i-'T" —r —i'v4 —1 ~-" /.~~~~~~~~~~~~ I, -:t:ic~-t-i:';,~~~~~~~~~~~~~~~~~~~~-........',i-....~ i —-........ -' — i-'!.... j -I,. i! ~~! I — 4..''''' 8t~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ t~~~~ ~ L ~'~, i i 1 i', I i i i''i''': i l [__L...[..L.I..... _j..-lt _ I~~~~~~1"-~ t r I' I i -I I — i........... -- —'.............. —'....... l- - I]'-I'-'!''-l"_u-J.......i.:.....~- ]"-J-. -"'' j j".... t?... -~i" —JJ',-iigi-t -t-I,4t-!,-L, ~;:~ti-~ -- -: j.2~~~4 t~ —l ~!- 1-~~! 18 0;-4, 30'..!..ic'~ J's I- l —..... Ji08 —.i-i-J44-i-.f — i1 8 180~~~~~~~'-!... i'" i l!";- I'I'-I' —I-T i —iC8,/ —~ I- i,20.i 3- — t- ~ J;. FIG.~~~~~~~~~~~~ J2 |, J':',,,!, 2!, I, SIPIIE II~ L.....-...... —.-. -. I''~~~~~~~~~~~~~~~~~~~~~~i o-4-,01 3 -4 —20 -0.......;.._....-20'4 ——,-0 _ 4._.._.. 180~~~~..........* —--— f-... I-.-i-'.... -,- -?-: —-j-.... —. —- 1... SC 8;~ ~ ~ ~ ~ ~ ~ ~ ~~il l6!!! 1:. i 1 i i' 6~~~~l[i, CHART~~~~~~~~~~........ NO ~ —.;. 12-60i PRNE IN U:.S.A.' A —L. -9 SINFC-AT....... INC;-..' ATLNT. GEORGIA.,-~

THE UNIVERSITY OF MICHIGAN 7274-1-F:: I ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~i.- i i / —:wisI tiiitti~~...... iti —-i-i'..' i-.j —ilit ~ ~ ~ —' I —~- I.... tc-' ~ -ittt!, I- i Ij ~ I I i 4, i +t i ~ J'-$ i — ti'; i..': - i --.+ —% —--- f-t -_... ~ i - i ri i j, i iS fi! I0~~~~~~i:,'!! t —-, —!t,' ]L~tii -~ —t -~ —i —.._ t-' i- I-'- il \ i -: —', t- i i ~. i; t~ i I!t i!il I' I i. I t i T t I J'i r -''' ~'. i -~ ~ ~i~ ~li t~~~~t, — t ~~~~~t i i f~~~~~i-t-i-it~~~~~~c, iI - -1 -- F.....r. 00 -i —i-~i,I -C -C- I~C —l -i —l~-i- -i-Ct i-'l J~ivi I! - i -!- i - iIi r i-. — ~~~.i- t!f~~~~t II'i''T ~ ~ i:i i I f,-x i -j-i ~~~~Y 4~~~~~~, —i — ti t~i —t-: —i-i _._....... i._. I'...... If1-J- _;.-~i_.:it-t -— 1 —--.-. L —-i, —i ~ ~~~~~~~~~~~~~~~~~~T',,, - Jr I ~ i I!!, i i... —~ -J-. l-.l......... -'~~~~~~~~~~~~~~~~~~~~~~~-, -1-..-'J I1 -!-~-!..... _..i -. 30,;- I -f — i-i - I - — T i-~ I ~ -~-4'! i1 I i i Cl~~~~~~~~~~~~~~~~~~.!.~i ~....:.,..: i.'I1i i't — i -— l-, -l-....., —..... -r...~,_..., 4!- -I',, —t-t- t6 J I,~i i _:~~~~~ ~'-'"-I-...: -t —i —', —ii-! —-i — i-1... I...- - 1-1 ~'i-'...'' i,,,, -t-i- 1 i, CHARTNO. 18-60PRINTLI I U.S.. ANLE iSCIENIFICATLANA. IC.. ALANT. GEORGIA-ii ~1 —T.:~ i i i 3 0 0 i i j I I ~ i!!: ~ I;, j:-1.. i.':._.:! i~__ i -... - -.i-,:'.~t""i —~ —-l.... _]..... ~_.__:.-... — ~.I._....~_.,__1...__.~_. -..-.-:T-I i ~ ~.;,',~ ~,i' "!'....:'t-t i J i J -.iL..IZ -I.! ~ i!~ iT~ I t-::l!-i- i~-'' J- I i! ~ i I', i —-i~ —i — i, —':S~~~~~~~~~ —"'-r"-:C-'Tl-i-ot -.' —-r-'-: ol... _. t"'l... t-i-i'ilt~ iJ -J —— r-'-' -- -'"' /-ji'~~!11,,,I]_ g. "-12"'"-1....,_.,_ 1.~ _,..tflWlt~2;~ 1~~~ ~ ~ 80 — / i.,'!f+t..' i~" J- i I-t~j-3d f-2~~ —- 1~P~ — i 41 —-1~! ~,NL 8. SINIICALN. IN.'TANA' ~~,'~:.! ii CHART~~~~~~~~~~ ~ ~ ~~~~~~~~~~~~~~~~~~~ iO j2-6:,IT IN U. i j i i; I' ~'! ~~ ~ ~~I I; FIG,3,/,OOOE, 4:, [RCSO, l3

THE UNIVERSITY OF MICHIGAN 7274-1-F -0 I! I I 1 —,I-1- i -.... -J — 61' i - k' iit —t tf-1-i-i i- i-,, - I i.[,,.,,t, i..i, I', i? --- i f i I I i —-I —~~~~~~~~~~~~~~~~~~~~~~~~ i11I,,,,~ ~ ~ ~~ ~~i-,1,t!h, r! t,~rt ni...ri-hl1..... - t i -A 1.I. I i —i / I I -j - i l i~ i/iii i i i, i -— 1: ti I - l -........._................. tif —- i,t —...,- "......... -...... i 4......................~.............. _ I''i i'i I I.,. I i. ~l..... -I-~... -:j — 4.j —i-i i,i'tt!..-~ —!.t.......... I........................... ~-4.......:i i~i -t ti ~~~~~~~~~~~~~~~~~~ -t i —]-L-~.....I_..... 1i;,,- k t ~ J,l,, i —r I /-fr, --- 401111130 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~I;T -, 1 0 10!~ I 0 / / ~ 1' 241 j: -[12 - 6I. — -[-, - }-f —6~-[ t- 12-~ t-.~ 18~-t 24!' I. i180!:!i~i2 -V-J,4 T-,,,, / t CLCI~iH~1.~LJj.,7 36 — ui36,, 72,-18 44,,,1,, FIG. 44: X/4 MONOPOLE,: Gz PRECi T-i3i LLu 5 i-i~~~~........ i ~.-.'!................ L...... 4.......t- f ii-.-itHt i-' -'"..., 1- TM..... t-~-i-...,-'1....-f.. 0~~~~~~~~~~~~~~~~~ i i i!!i:. -Ci~i-~~~~~~~~~~~~~~~~~_._~......- -.. Li i.._1._I_~...-t-i-$-..._, u. I T i ii i i: I! i j f i ttC~; - 1' -' t- ~~' I~..i'.,,i-t~ —,,,:-~t o~-,1 —:~-i —!..... i!i iiL-i f! —-~......! htl....!...... i.., 4: -,' _ i -T!'~,. —[-i r —it~-i -t-i f-............: A _. ~i 4 i -42~ I~~~~~~~~~~~~~~L I-.'-.....4i-..... 4-4 —---....4-._;._ ii J'; i ---—,.' I- t-.-JI-'-F -~ I. -.. —! I! I' I i I I! -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~4 -";!,- Ifi i, r~ t-l-i i1 [ / i ti —i~ i/.! —; l-$t i'i;. -.i,, 1' i i i ~ IT I. i, —,,- Ii Ii!i,1+;t, i i -!.'- -i -; - i;~, ---—! i....~~~~~~~~~~~~~~~~~~~~~~~~~_ _........,'..... I! —'!i...... f' -t-l~ ~,! i,,,,,:~-+ I~1~tt-~iit — ii~~~~~~~~~~~~,,:iiit-',!-!-'-?.. i? " "' 18'- i-~A i0"C- -i-/Li' I I''''l-Iti 305AR. -;' "'' - 6''' " ~~~~~~~~~~~~~~~~~~~~~~~~~ —-b — 72. 36 -i.... 4...i.:i...-:....~~... -~pit500 and 2300 FIG ~ ~ ~'.. 4: I/''POL, 24 z,,R CSO, i:;i i'! i' I' i i!! i i i ~: ~

THE UNIVERSITY OF MICHIGAN 7274-1-F "i i ": IiIi i I I / I|I'; FLi-C-~_.' —I -:- -S - i -...... 1 —-i...... 1-.- -I __ 1.. - - I X..... I _. +1- -l..r... — t-,-,< —t-...... ----. -i - -- — l — -. j-.. -c —-.-!;- -r-t —- 1 - - i —1 - I 1- i — i ---- i;, _ i -; F I n i - Hi 2 K - 1 — i 4 4i I I ~,'~ -'-7-t r IA-h0 -<-y ~- -- 4i''- --...4.. t... —..i-tt-i.... i-i" i-' -' 1 i i C,_ 1 1 —A':|4 -j-.i:!..-.. I. il..' ~ I I I''I 4 18001'44-ti' -- 108 -/i /!: LI Ii' I —'-'<h+< t j 3, j-' j " t+' 1' -'-ti! - ~ | i -! -- -- L i i i Ltitt-'' /' - J i:- - — 1-t ---' —l-l i- - i',t i - 1'- -t -,f —3l LI......' I'6.. 0 i'2,1' r - -tI- 4 36K- 1-72 -, I,080 4 44p 1 l CHART NO. 128 —— 0 P -— RNTD I —N... ANGLE. S -ATAT. --, —INC:-...ATNA. N. — _ GEORGIA - FIG.: /4 MONOPOLE 2 I 4GHz SIMPLIFIED T-33__ 53 18 i L 4 0 I 2''' 180 — 144",72 04 i- I i I /.I44/.'I I /''1 "' 36 i436 b -—.II....'' CHART NO. ~. 60 /,_u_.... _~......PRITE IN.U.S.A., AGE' TIFI INC.AA- N,, 0 an 2300

THE UNIVERSITY OF MICHIGAN 7274-1-F' — l i — [ ii- f i: i i i: I i - i —; - i - i- i I i: -f,- i 41 I 2 -' I j 1 i 0 Ii', |i,i i0~ i-. 1 -:-!i j 4.i,, 19 i.~~~~. —— l-;.i.-..~.. 4;.-:i....;.... i-.t-.-.:....'.._.: i:- -~-'.:i_ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~!4! J!.:.i Ii t!i i 1i li'' j2!.!.!.~' Ltt-~ — — i --....~ f, i- J — I-~:-..i. I4 I - t!! ~i4I t,./ 1111 — iitI I~ 1 i -i i i..l-..i.. i. -i~~I.t~ 66 8 i l i I' I t I t i: i i' It 40~~~~~~~~~~~~~~~~~ It I ~:t — t i'::, I'!,i' i.1- i t'~ it —-'t.... —,...'. —... i —i-i~.', - -~..,...'....... —.....,............. 2,,., t i, I'', i i~1, i t Ef /i..? t f. —i-........ I.iti t- L i'~, i _j! l[!kl i j' i l~.i- ~ ~$I',,,F.;~ii L. i:~ — fI! i! J i i!;;! i I. t.1-.I i, I" j t tl -r~.. --— t..j i'"'-i.... i~l...... -~;''i'[' i'";:-,... l"-i t- -:' - t- 1: —-.!-~- /-'t i - 4_~~~~~~~i tI t I t ~~~~~IJJI,, 1.1... [iii t~[:: i,!'li, O~~~~~~~~~~~ i i j e I i~~~~-:-. -...... ——.. 1'! L_, i4 - -l-~-L-:-~' — t-~-4 -~,__,.._.! L.:. [.. _'r 4',,, t,-d..,. ~,! I 2 I,, I I ~~~~~~~~~~~~~~~~~~~~~~~~~~4~~~~~~~~~~~4 3Q'..... - 12 L i 4..2......i 4 I -}4 -I -A 8% — I I I 2! i o2 i! t i i t _ _ i _ i [ —' ~~~~~~~~~~~~~~~~~~~~~..........-.L+ —... -,........,0.. I_..1.._' t.-li i'~i' i..-I i,I_..i_.1 ni ~Ii~-I~,:-!'! —i i i ~| I -l- ici- I- i, - I i i.! " ~' ~ i -1':''''-'...c. —... i..;. i ii itt I i'i I 54 30 -i i r - c.. i - - i -i- j- i-i 2i+t -- t —--' -.. -—. —-i —j —...... 1,::-8l' 3 ~~~~~~~~81~~~~~~~~~~~~6 -i —i~ ~~-! ~i.... i'ii —-'. " ~',' — I-t I- Ii't 1-i. I i; i J-: t-':t- i /tt — ~-I -i i..~~ ~ ~ ~ 1!, ~i i I'" —-~'? I.i i! ~-i — t!-r'_ —--: i i -,-t —i~:-:: ii..k.i I.'-1 —;- r~~ - ~i......: i —t -i —1 i I Ii i 4 —'i~~~~~ il lij,,,,j! ii —i-i,,,:p~i~ -t -1-~I-18ol —i-i i-l-ll _I_ —t-i-~-....3... 08 0 I~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~ —.!.I- -~- i...:.-.._i... hl i —I.i.39; —- H-... iL.i.-' —.i-3d —!- 711~~ ~~~~~~~~ ~~~ ~ ~~~~~~~~~~~~-. I- i —...... 72: 36..' — -~-..,. -'-.. 180 1 4 i ~ ~~ ~ ~ ~~~.~. i I:,;j i;;'I'i; CHART NO. 128-60 PRINTEL IN U.S.A. ANGLE 0 SCIENTIFIC-ATLANTA. INC.. ATLANTA. GEORGIA FIG. 46: X/4' I i i, i G~,,RCSONT3 54~ ~ ~~~-:..-:.+,ki.-k....i-F i

THE UNIVERSITY OF MICHIGAN 7274-1-F -.077~~~~~~~~~~~~~~~~~~~~:~~~~ u~~~~~~l 4tX I 1 ++ H 41 W T ~~- M W11 IAR i.~+m-4_E +11:ilF: -ill 1 1 -20i-$-~~~~~~~~~7 i~~~~~~~~~~~~~~~~~~~~~~~~~~~~~II - +- tL l -t — 1 L ltA-l -- i —L- +-1 - a —-i | -C-1I- 11{ti +-i —l — _ I L~ v| X iiLf'I 14 i L tt h I 4 1 0 [ -lt 2 I r3 tti 49 50I 30 i- -i24 S -- t — g-H — AI-t-t I l-40tA {2~ 4 160 12 180 - - t4LL C f t iii _i T 1 i w I 180"- _ ++ t 7 144C - -11 CHART NO. 128-60 PRtNTED IN U.S.A. ANGLE 9 SCIENTIFIC-ATLANTA. INC.................................................. ATLANTA GEORGIA 0 = 300 and 2100 FIG. 47: X/4 MONOPOLE, 2.4GHz, PRECISION T-33 r C-l- — 5 LL.ii~~~~~~l4 Tt~~~~~~~~~~~~~~~ 300I -4 4 1 819 ~it;- I-l — -l i -6q 60 1 tlt- - -4. 4~~~~~~-t — -4 —j-'618114~-f- 18 1 0 81, -47 72- 360'T 30- -+~ —-- i21~ —i-t = 300 and 21002 r ~

THE UNIVERSITY OF MICHIGAN 7274-1-F,i::-l/ I/i I t4 | tl J.- I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. 0 ot801 t~~~ i01 1 0- i r il 1 Iiit —I-C-|'4 C - |tt 40 4- -t1 11 -11 I''!''1i I4-1v JX4 0 Ii114 -I I tl — it —— 11 1' — i' -I ~III'/~ i-':", t<,,A /6 I o, --- -- ~ ~r --— ~..I!!.._i!,,!! / i~_!!!l/ill i ~~~i 81 I ~ ii i I ~ ~ i'~~~~~~~~~~~~~~~~~~~~~~~~4 10 ~ ~ =0~n20.-._l... L......... -C.................. 1...... i......... I,, I, ~,t 4.~~~~~~~~~~~~~~~~~~~~. FIG.,48: —, MONOPOLE,2.4Gz,S LF -3 i: i { — I {i i~ J~ i- ]_ / mI iiii /! {_jI I {!!'l!ll i~j t-l —-i....'r.................... I...........~ t...i... -1...'......... -t-v —-} i-i:t -f-{....C.li r — -,- ~~~~I r~~~~~~~~ ~~~~~~~~~~~~~~~~-: —'qLt!..., —~-.......!- t........:-L....... -k —~-J.tt-. { - -{-. $ f-i t-lt- i —-~...._..?-l-{- -i — i-!-\i -l i-'-;l,~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ i- -i~~~~~ —- I / /i / T l _{' i.. i 1 - 30 I i - -i ~ I i'- I'''!t''';t.- i I,,d It j.' _'' ~ I I I'''I t i ti i-:' J_ A- - ~.I ------...... -~....:............... i..........,.-{...... -,t..i...: —.......... i -flIil-+....... - i...-.. ~~~~~~~~~~.... — ~-T..'-........ -~.......'~....... q-... t-'~.................. -:-;-~t -{-{..... -.. " -I.......... -'-f -J 6~~~~ i-I,,,~! - ~I ~t 9wf - l, i I —I — [ i: i-,,'1 t t- I ~ J-N-l 1, -!I ~' I —-4'-T i' I T -:',, 50 -4 30 - -20 0_- ~ 1 4-i- - -!.. — t-i'iiiI --- — i~ — f i' " ~ i 6 I I ____ I_ ~6,'4 I,, i/ / ~!~,.,...18-..-.,1 -30,,lI i i i 1'-' iI i J'. i -I ti'' i i - - i 3 id.'' li'! ---—:....' -t-.. —-7-2.. [....., ".,, 4f-+, i i I',. i CHART NO.- 1 Ti-6:0''', -NTE I U.S.A.ANLECIETIIC-TLAT.. A-TLANTA GEOR,~~~~~~~~~~ - i'li m-ti-tt'11"t —-! ii-,'- J-'-i~~tt"ttt~tlt i ii' t- i':',-''' -i Oi' ~'tS- ~ -i ~ ~+~ 49 -tiL,, ],,, ~tt24-C —Bt —— I, /]t-, - ti I/'~-~t~ —12"I ~, I ~~'i r_, 11 Ij,~~'4t —H/,30 "- "j'T''.......r......:-,.... -C -t-'1~-:..r-... T...... -~...r...... 1... 1'.... iC... ":..... —J-t.... — 1 —C?-C' ic -' CA N. i 2-6, RNE 1N I..A, [GL 8 i ]i' -I LAN, -[C. iTANA [ i~ - - ~ I'i-'~ ~ ~ ~ ~ ~~9 I j'0 an ~'~j!I' 1':{! 0 i; ii jIG, 8, /, IPO, i ~,, ~ P IFE,, i,,....!-h...?-?.....,...... lr —t'...................

THE UNIVERSITY OF MICHIGAN 7274-1-F -i- [ i, ~ i!.~!;'. i..i_... t i.,,i l 11:'':, I I M I, i I I;':. -!. I —t —fi i i' ~!i' i i" 2 I i-~~~~~~~~~~~~~~~~, 1i''j~ 811!O~~~~~~~~~~~~~~~~~4 t!.,'.... -t,2;8!! i'':~I' I'''' I[ I I.... -- I.. — I I 4I ~ ~ ~ ~ I' i I't'+ -r....-.. ---!' -— r -'..r -I f ~. i, liii i! I K' iNi 0 50i~ L -~~~~~~i' i-t....... n f — i r"-t-:' -...." I i - " "-j....'r-,.f-t-. f —'- - ---— f —t..... t —-J —... "-'30 " b2~VLl i0' 10;:21, 50 ~~ ~; 1~~~~~~~~~~4 4-1~ i,' I i, I' - 24t t. 110 Tt.,,, 0 I l t ~li -1'' 36'' 6, I i I! i- 12f / 0;u'1 i! j ~ i Ii1 l N/'111 i II 180 ~ ~ ~ ~ I v' ~''14 18'''4.' 1- 30 ~f, ~............-..... ~_L, _.t tt I 11__~__._~.~__,___~ I I ~~~~; ~ i iI;I ] i [ i i' i i'f I.,i —'''-; - i il i i 60 I,108011I ~1, III -/3 721-... — Ii-1''8 CHART~~~~.... NO-,-~:-,,..... 128-60 —1 P..T. 4-JN- - U...... ANL... CTII-AANA IN..ATNA.....GEORGIA............... 4 0 A0 2OAad OO 50 4~~~~~~~~5, ~ 0.,,,,,,,,1,,,i —-il t —- tit —--— Sf- Ii —' -i.. i. l'-. 1-"-1. i.....!:. i' J-1-0-11 -. —!.,, I....... 4 -...... -rt-............ ]I —- I -i, --- —,,~ ~.-. —--.~~ _.t..... I -i — t 4,, -— I..................... ~,!t,~ ~ I.t 18: 10!.-.................0.......... -— ~. r-. -r. ~. -- --..-i ~' I'' I i' ~~,!I;::,i iii I i I i I i! ~t ii i i I i i i ~~ft~ 18I.I I!'~~!:- I,', I [!-~i!; ~ I I~/ CHART NO. 12 8 6 i i; I U A I i E N T F! i; LNAi I ATA T: i GO RGIA [i cI i:! i / i-;/- llt-~~tt ~ M j~~~~~~~~i~~~ tt -4',3- ~ j__P " —- - it~ ---,i-~-. J ~ I, 3~~4 ~i I I'2~i j: l~ti-i:d-i ji:I B~Li —t Clti/ j i ll:.':si! i~ 189+i-t ll I 111 180B~~ j~ I-i- j j i i4...~!,i i ii,;- itt — ti -t-I! ii!1!i I ji il! i.;, CHART~~~~~~~...... 4- +''... F. —-.. — + —T~ iN.... ~-.A.,!.. GL 4-.- —.~ —.-.... SI-4 —.I-.-..I —-PT. —-— t. —-- —'-i.-~_u_~_,,,.,9,,,,., tOPL, 24H, 44 f-,r r I, i i' I J I i i i

THE UNIVERSITY OF MICHIGAN 7274-1-F 2I —, {tt — -- Ijtf, -.. t':i i,'I4N I I' i, - L':-. - i -- -— I I — t- it i.......-. —, -..-... — i. —.-.=,-+..-.l:' —-.-~......... -----..... [. i'' \ -! — i i _ i.i 1., i1 9' i. i —' ILi'' i - i i i-' j I i -2 — - I: --- [ — I 1 t I0XT'4' r 50 - - - 404 -h 34 2 A-1-t0- 0 —;- -1- -[1 2J 4 3- h! ] 50..t.-.,. |-.2.......... t... i- +...t —— 8- ---''-....!"' | 6 0. I, ~..:, 4,.i, I 8, I, r it] 1 -F, 1-44 t-.!8-i8~ ~58....,0 i t I. ~ i! ii i / / i i -i 0 i i; 0. 1 4..-.. ~4 (.A, — 4...... —.-~.... 20 an i-i~:...i-T-..........I.....,_ FIG. 50: )1/4 MONOPOLE,~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2............EDT-3 -:.....'...i "

THE UNIVERSITY OF MICHIGAN 7274-1-F t Iiii Ii.iiiLi,:: ~ ~r —— t-l —-' ~ ~f4Ti Ir! i-..14 i?I 7-1; i! Io!t:, tf l - i i-;,to!it; i -t; I-li' i- i [ ~ i i i i i' i: A,i:I: I', i: I:i' tI S I - 1-2 t —f..... -1 —- 1-1 --— r —l-.'-''I —il 60| - -- 1 6!::- I-:; 0 V 1. i -~,-'?- il J 1i2 Ii i' i! t1 30 - 436~-T-20 —-f —36 -| 72 Fr 1 14 4 1 hoi~_ I- I -i — 4I CHAR N. 12-6 o T..A.. ANGLE SCIENTIFIC-ATLANTA.... INC.... ATLANTA....... GEORGIA 0 = 10~ and 190~ FIG. 51: X/4 MONOPOLE, 2.4GHz, PRECISION T-33 59

THE UNIVERSITY OF MICHIGAN 7274-1-F F~-t1it' -. - i t /.i ii i —-— i — tii I "i — l — P1t~ oSL0t, [ -li,-lt-i -i -t-, i. I ~ I' i'' 1 f I 4 J T I 1.,/// i, I /! /./.! Ii,. ii. i i- 1'!'' i-i + ICH JRi l, i i0.i 128-60 /RNE II U A a IE IF IC-ATLANTA. INC. ii A. G-R i "i —~t-t~ —~t~tl i; —B l-i-ti4........!-iJ —. F -IG' 5M.... - - - -...... i, SML-F-3 t i l___ I6................ -o -...' - i <117~-~6......... t-it -.. -— t-Ct.-t i Ii 66 I.....!'-i' —!-1..... i- 1-i-"t................. -r 309i4Q, -— t!/., I'-i'- _4-6i- i -' -I.. ~it......,~ —Jit........'~._~;___,,,,,

THE UNIVERSITY OF MICHIGAN 7274-1-F 8 WeA1'100 W11 IILL 3FH r T I I 1 Ll L. _ 11 1 II - I I. i-I I1 102- 43+ m xIL40+~0 m t L I 1..0... X_[0__ T~~~~~l ~- L —0_TXLII I II I I 1 L 111III 111111.1 11t,02?6. -.2 2 -50 —00~nd80 -2 FIG. 5... A -8- / I~~~~~6- I I I CHAR NO.20PITDI U.S.A.... ANGE SINFC-TA A..IN...ALAT. GEOGI 8 I l l l' -~~~~~~~~~~,Ii-',4t 8~~~~~~~~~~~~~~'!111!~~~~ ~ ~._3o --- ii IA!Ii FIG. 53: X/4 MONOPOLE, 2.4 G~~~~~z, PRECISION T-33.~ I~~~~~~~~~t~~~1

THE UNIVERSITY OF MICHIGAN 7274-1-F 6 I I. -.... CHART NO. 128-60 PRINTED IN U.S.A. ANGLE O SCIENTIFIC-ATLANTA. INC.. ATLANTA. GEORGIA 0 = 0~ and 180~ FIG. 54:,/4 MONOPOLE, 2.4 GHz, SIMPLIFIED T-33. 62 4 ~ ~ ~ ~ ~ I CHART NO 128-60 RINTED N U.S.A.ANGLE 4 SCIENTIIC-ATLANA. INC. ATLANTA GEORGI

Antenna: 4 Monopole Frequency: 2.4 GHz - 10 Orientation: =900 and 270~ 20 _ 3t - 30~~~~~~~~~ n-20 __ __ t -40 -30 — __ — -__ T 0 0 C~ - 50 - - ___ _ _ - - __ Precision T- 33 Simplified T- 33 -60o I I I I I I 0.2 0.5 1 2 5 10 20 30 40 50 60 70 80 90 95 98 9999.5 99.8 O Probability That Relative Power Level Is Exceeded FIG. 55: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

Antenna: /4 Monopole Frequency: 2.4 GHz Orientation. 0=O and 2600 02 -j ~-0 0(1 -40 ___ -Precision T- 33****Simplifiled T- 33 - 6 0 _ _ _ _ _ _ _ _ _ _ __I - - I - I -I1 0.2 0.5 I 2 5 10 20 30 40 5060 70 80 90 95 98 99 99.59. Probability That Relative Power Level Is ExceededZ FIG. 56: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

Antenna: V/4 Monopole Frequency: 2.4 GHz Orientation: = 70 and 250 X 3. -40 L I I I i II I 1 I ~ 0, 0. ~ soL I I IPrecision T i l ~ 1 3 3 I.-.0 - --- <SimplifI I T-33 02 05 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 9.9 FIG. 57. CUMUJLATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS - 40 -50 - __ --- Precision T- 33 0 ~*-'-." Simplified T- 33 -60 0.2 0.5 1 2 5 10 20:30 40 50 60 70 80 90 95 98 99 99.5 99 C) Probability That Relative Power Level Is Exceeded Z FIG. 57: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIM PIFIED MODELS

Antenna: V/4 Monopole Frequency: 2.4 GHz Orientation: = 60~ and 240~ - 10. - -20 - _ 3r- 30 - _40' O, 0 -50 _ P_.Precision T- 33 ~ "-"- Simplified T- 33 0.2 0.5 I1 2 5 10 20 30 40 50 60 70 80 90 95 98 99995 9988 Probability That Relative Power Level Is Exceeded 2 FIG. 58: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

Antenna: A/4 Monopole Frequency: 2.4 GHz Orientation: = 50 and 230~ -20. - - - _ _ - 40 I I I I I I I 0 — Simpli led T- 33 - | - 0 -60 " -40 1 - - - - - - - - - - - 0.2 0.5 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 99.5998 Probability That Relative Power Level Is Exceeded Z FIG. 59: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS l~~~~~~~ i!

Antenna: 44 Monopole H Frequency: 2.4 GHz Orientation: B=400andd220O - 10 -20 O 30 - _ _ __ - --- _ 0. -40~~~~~~~~~~~4 -4_ o =T -50 _ - - - _ - Precision T- 33 - Simplified T- 33 o -60 I I - - - - - - - - -I 02 0.5 I 2 5 10 20 30 40 50 60 70 80 90 95 98 99 99.5998 Probability That Relative Power Level Is Exceeded FIG. 60: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

0 - - - - - II Antenna: V4 Monopole Frequency: 2.4 GHz Orientation: = 30 and210~ - 20, _ 0I= CL 04 0'i2 -0 - Precision T- 33: Simplified T- 33: - 60 1 1 I 1 1 I — I I r - 0.2 0.5 2 5 I0 20 30 40 50 60 70 80 90 95 98 99 99 998 Probability That Relative Power Level Is Exceeded z FIG. 61: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

Antenna: V4 Monopole Frequency: 2.4 GHz Orientation: = 20~ and 2000 -,o - -20. 0 - -40 - _ _ O' m' - D A']'A I]~[COI~[DL ATE i-1 -50 - Precision T- 33 0 ~""Simplified T- 33: 0.2 0.5 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 95 99.8 Probability That Relative Power Level Is Exceeded FIG. 62: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

Antenna: 4 Monopole Frequency: 2.4 GHz._.__ OWN-MplifOrientation: 10~ and 190 -10 - I I I I - I I I I I I I 1 1.'Il I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~t r- 30 -—. -7 0= -, Precision T- 33 0 ~ -....-Simplified T- 33 0.2 0.5 I 2 5 10 20 30 40 50 60 70 80 90 95 98 99 99.5 99.8 Probability That Relative Power Level Is Exceeded Z FIG. 63: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

Antenna: /4 Monopole Frequency: 2.4 GHz — 0 lo L | | _... 1 11~Orientation: 0- o and 180. 10 S~ L. -60.J -- Simplif ed T- 33 | 3 -30 2 5 1 2 5 10 50 60 70 80 90 95 98 99 95 - 40 I- " i T -- - - - - _ _ - - - J J L I... - __ - - - Probability That Relative Power Level Is Exceeded Z FIG. 64: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

THE UNIVERSITY OF MICHIGAN 7274-1-F 2.4 Slot Antenna The two previous antenna types discussed were an omnidirectional split-beam configuration. It is also of interest to examine a unilobe structure similar to antenna configurations used in the UHF frequency band for airborne systems. To simulate such an antenna, an open-ended section (Figs. 65-66) of waveguide was employed. This antenna was used to simulate typical antenna types that operate in the 1 GHz frequency range. Therefore, the scale frequency was 8.0 GHz. Signature data was collected at the fundamental and four harmonic frequencies to compare the simplified versus the precision modeling technique. The proper waveguide transitions were used between waveguide bands to minimize the probability of higher order modes being excited in the waveguide. A typical set of pattern data obtained at the fundamental through thefifth harmonic is shown in Figs. 67-76. There are some slight discrepancies in the patterns. However, good agreement is bound to occur in the statistical data shown in Figs. 77-81. It is to be noted that all data was collected using the U of M digital recording system to facilitate the reduction of the data into the proper format for final analysis. 2. 5 Concluding Remarks to the Simplified Model Three antenna configurations have been considered using the simplified modeling technique to obtain antenna spectrum signature data that can be forwarded to ECAC for further interference analysis purposes. Further, it will be noted that one simplified modeling configuration was employed during this study. In the event that more accurate statistical data is required, it is felt that the simplified modeling technique could be modified and still retain its simplicity and low-cost features. For example, in the case of the jet aircraft, one might consider the feasibility of modeling the nose region by a conic section that could easily be turned on a lathe. The fuselage might remain a cylinder and the tail section could be another conic section. The three parts could then be glued or pinned together. Also, extra care may be required in fitting of wings into the fuselage to minimize discontinuities. However, 73

THE UNIVERSITY OF MICHIGAN 7274-1-F FIG. 65' SLOT ANTENNA ON PRECISION MODEL T-33 74

THE UNIVERSITY OF MICHIGAN 7274-1-F FIG. 66: SLOT ANTENNA ON SIMPLIFIED MODEL T-33 75

THE UNIVERSITY OF MICHIGAN 7274-1-F 1 0 I 501 vT-h ig< 401. 30 2: 1+T4- 0 —t- VI t 2 q^;-l —f -0- 13 411 110 - 50-1;] 5180111- 144?-I — T 1W 18?-4 —I-' 7 -4- -36I i-.X136 — t- -t —72 -1 44 —i —- - 18 60CHART NO. 128-60 PRINTEt) IN U S. ANGLE B SCIENTIFIC-ATLANTA. INC.. ATLANTA. GEORGIA _ l FIG. 67: X-BAND SLOT, 8.0GHz, PRECISION T-33, 0 = 900 and 2700 76

THE UNIVERSITY OF MICHIGAN 7274-1-F O~~~~~~~~~~~~~~O 8 i I X 4dI,1; t i!g X~~~~~~~~~~~~~~~k H~~~~~~~~~~~~~~~~~~~~ 8~~~~~~~~~I —iJ 20 —'f~d-2 " i I H'~...... I 4<+ —40- -, 6, 51 Il-F-4 I~~V lllll I 1 IIj1 11IIlil Iur i -18 0 Fr, 14 I I I 1I' 1181I I I I' I 11I I LL I I I I 1 C N 26I I.AS N - N I A T E XS~~~~~~~~~~~~~~~~~~~~ I 121111....iI21 [ 11l11 W 00t~~~~~~~~~~~~~~i~~~~~~t 1W~~~~~~~~~~ I \E 1111 1111f'E 0 1~~~~~~~~~~~~~~~l IIiil Ei,, IIIIit, 5r S+F; +2~t!Jo )'',I Ill l,lll it9, [ e|1|11 i 5g i l_ I i~,l ~' l'tll!kdln. r! 82 X~~ FiG. 6, lib 108 2"7 36 1 187 CtIART NO. 18-60 PRIHT, I US~ NL SIENIFCALN. Il l, 1l. ALN. ERI Mill 4o:!-AN SllllllG~, IMlillIT3, 0 ad2 - I, Illrllll

THE UNIVERSITY OF MICHIGAN 7274-1-F _~~~~~~~~~~~~~~~~~~~~~~~.., 411 A 2 —— r — Itt.~~~,.._ i~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~..! L_,:' __!...L. ~ C 3-~~ -- -— ~6 I lil F L ~~ —~~~~ —-~~~~-1-j- I J-i CHAR|| ~T NO 12-6 P I TE iN U..A C-TATA. +tC ATAT GEORGIA2F00|| t I- 1S! t-I i, F ---- -— t[ t0 X 0 1t I S;-ilH~r~L~fYHI-I~t~i —t-i-F5t~-t-it + t-tt-l L L | Lt-l- -F L t-; L-L- d — - 1 o~~~~~~~1 4144 108 724-1~-f-++-t-f -~ --- l e_, -t-0- i. ft — t — -i.-i;it- -6t.$- J 7 - V8o II 4-Tr CHART Nb' 128-60 PRINTED IN U.S.A. ANGLE G -SCIENTIFIC-ATLANTA. INC.. ATLANTA. GEOR IGII'.1 A~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

THE UNIVERSITY OF MICHIGAN 7274-1-F 818 144 108 720 3630 72 1I0 1 80 CHART NO. 128-60..........U.S.. ANGLE SCIENTIFIC-ATLANTA. INC.. ATLANTA. GEOR 1 50 -10 -2 FIG. 70. X-BAND SLOT, 16.0 GHz,' = 90 and 270 ~, SIMPLIFIED T-33 II-~ iiilll ll I11 |lk 11 Il lI i I i 1111 Wll~ii~lLIIF IIIIIII II|Ii IIII111lLIIII w lrl |SSs sS]I 1 Sr l ll ML III 1 liII8biii I 1 l 111 8LI IIIIII rr I lllll 2r lla I lllDI 111II _II 1 lIIII1 _IIIII 1 11111F I lt L H Zt11 04t 15l ~N [ ['wb5

., _t 4 t~~~~~~~~~~~~~~~ —-REL ATIV;, POWRONE tWAYI (db)t - |t < Xjjt co FdiiX —la WT X H ark~~~~~~~~~~~~~P c o _ _ _ _ _ ~~~~-.. I'd W fiVz Iz 00 --- I0 1f> CAD~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~C t I I z 0 | N X = | >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I. lk. Ad

THE UNIVERSITY OF MICHIGAN 7274-1-F 0 — 4I I c....... --— l- A I-GL-I --— 4 I I [I FIG. 72: X-BAND SLOT, 24.0 GHz, SIMPLIFIED T-33, ~ = 900 and 2700 - 81 w — ~~- -i —..iPRINTED IN U.S.A. ANGLE a P. rf a —— iM — "t %N..x __ I

THE UNIVERSITY OF MICHIGAN 7274-1-F 0 t 6,' 1. —L1-.- i._It 4,:X —- 1-111 I-l$i X-i- X -- c-; —1 —.-mcl-l -~t-:, -— r mXY1 -- i -i:-1 — X~~~tt1 —i i — <-i~ -i 2 - r 3 -'' 8''I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ FIG. 73: X-BAND SLOT, 32.0 GHZ, PRECISION T-33, 0 900 and 2700 2-82 - i —-i~~~~-i —-l —Ti 611 — ~-~ctf~Ii t~tii l~i/ i:I ~ ~;If4i i-~ —--- - tr i — t —ti -i —~ —l-~~ —- ~ i i-J-] - 1846 1 —c —~-t -i- -- -72 — 316 8/Ijj CH T.... SA.AN L 4 SIETFI-AL I

THE UNIVERSITY OF MICHIGAN 7274-1-F -.0 FIG 74:JX-BAND SLOT, 32.0 GHZ, SIMPLIFIED T -33, 0 = 90 and 270 2-~i..il~l -. - - i. i 83i 4 - T - ----- i4~~~~~~~~~~~~~~~~~ i~~~~~~~~1 I - - -I-CC-iIT —`-S —- — C - - ti — t 4 III I -. it'i -C — 8' ~ ~ 1 -1 i -iI~ __ III 21 i-i tI 1111-t8i I i l i i ~~-~ i- i'OJ — I -- I. i 1/ t-t t i-i i _1... I t~~ I I III'' I I I -2~ i- -l-i {2o i- 1o I o -t~ ~ t — I _ —-- 20 f-i 50 — i i tI FIG 74 X BAND SO320Gz! 8 12~~ -— i -i - i -i I~~~~ i ~~t —-t0-1.i.. ~ oi 2 t - -I 1- I~~~~~~~~~~~ 3 d~2jt VL 6 --- -i —2 0 12 6 PRINTED IN U.S.A. ANGLE 49 SCIENTIFIC;-ATLAIYTA. I

THE UNIVERSITY OF MICHIGAN 7274-1-F... I i I I I l I i I i. 2, iii i i -i-+-t l —i,- i I I.- t -.. "'I 1 1, I i:,, i L ii- -F —, --— t- I i + 2 I-i t:1 11 T I -4I tA-1.. 3_ 18l — -I-~-lili L tSi- t f < I - 1!-"t" i i"26 1......!. —-4 i L| -..Ti I~l —' / IN I U ANGL I-ATL ANT. I1 -. —:._.84 -~ ~~-1. -i -.-i...!_.. i. I.i._i. i~..- i...!_ - _ I. I... I Ii j i I, iI

THE UNIVERSITY OF MICHIGAN 7274-1-F 2' I 1 I I Ii if1 ~6 1~~~~~ ~.i i i; ~i~i —-- -c — icl.-~ 8 + 1_1 r-~~~2 i-T ~ ~~ ANL 0 CETII TLNA LU I F 8 C L i1-1~..i-Ll~~.~..iiiii_. - 2 - 1.. —-, —~-1. —.I...r..c~.. —-I.~~~.1.. —~.1rC~~v iM..I_..IL L....1_1_ —- -- Ii~~~~~~~~il~~~~ " 30~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ o r~~~~~~~~~~~~61 a i 1- i r i Ir iur 1-3r 6 r r -1 6i ~ ~ 72, —317 C H 9M2ORM PRNTE IN.S.. AGLE SCENTFIC-TLATA.I.0w-qowj

I I I I I I Antenna: Open Ended Wavegu Frequency: 8.0 GHz _-o [.|| Orientation: = 90~ and 2700 H;-20 Z =-40 r r r r 7 1 I lr' 1 1 n 1 1 -50 I I I I I -33 lI T 1 I 1 1 I o'. -30 co -50 1 1 I r I 1 I I 1 I 1 1 1.. 1 -30 - -- I _ - I - - - - - I I 0-2 CL5 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 9I5 Probability That Relative Power Level Is Exceeded FIG. 77: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

Frequency: 16.0 GHz Orientation: 900 and 2700 -20 - 30 I I I I I I I I 0 -0.H <: C -60 1 "'20o51 2 040 20304050607080 9095 9899995998 Prcirion T-y That Relative Power Level I Eceeded ~I. 78 CSimplified T- 33 O -60 I0.2 0,5 I 2 5 I0 20 30 40 50 60 70 80 90 95 98 99 995 99.8 0 Probability That Relative Power Level Is Exceeded FIG. 78: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

Antenna: Open Ended Waveguide Frequency: 24.0 GHz Orientation: 9: 900 and 2700 H -20... -I < 0.'- iPrecision.T- -' Probability That Reltive Power Level Is Exceeded FIG. 79 CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION0AND SIMPLIFIED MODELS -L P T- i3 - — 40 -50 0.5 I 2 5 1 2 3 8 9 9 9 9999.5..8 Probability That Relative Power Level Is Exceeded Z FIG. 79: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELSJ

Antenna: Open Ended Waveguide Frequency: 32.0 GHz Orientation: p =900 and 270 I.130 - I 1_1 - 1 1 I - 1 - -50 - 1 - _ _ 1 - FIG. 80 CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS (I 0 FIG. 80: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS

~~~0 - - ~ --- Antenna: Open Ended Waveguide — F~~~~~~~ ~ ~ ~ | |g|Frequency: 40.0 GHz ~ ____~ 0C:: = Orientation: =90 and 270 -1o.0 ~4 -20 3-30 - - - __l - d 3 Q.2 0L5 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 99%5 99w Probability That Relative Power Level Is Exceeded FIG 81: CUMULATIVE GAIN DISTRIBUTIONS OF PRECISION AND SIMPLIFIED MODELS 0 I -.50 -. _ - - - -- _ - Pralecisin T- 33 ~ - - -.-Simplified T- 33 ~. -60 I I m t - 0.2 0.5 I 2 5 I0 20 30 40 5060 70 80 90 95 98 99 99.5 9.8 C) Probability That Relative Power Level Is Exceeded Z FIG. 81: CUUAIEGI~ITIUIN F RCSO N IPIIDMDL

THE UNIVERSITY OF MICHIGAN 7274-1-F the main purpose of this study has been to show that a relatively simple model may be used to obtain reasonably accurate signature data for interference prediction analysis. It is also feasible that further simplification of the modeling technique could be employed; e.g., rather than using surfaces of revolution, flat plane surface could be employed to simulate an aircraft. One such technique that has been suggested, but not investigated, is the possibility of modeling the fuselage of an aircraft with a plane surface having a silhouette outline of the fuselage. As a result of this study, it is felt that the simplified modeling technique is justified for use in the collection of signature dataforECAC and that the next area of concern involves the techniques that may be employed to collect the data so that it c be properly transferred and stored by ECAC. 91

THE UNIVERSITY OF MICHIGAN 7274-1-F III DATA RECORDING TECHNIQUES A second aspect of the present contract has been an investigation of data handling techniques and procedures presenting the data obtained by the Air Force or other services to ECAC. To ensure that recommendations resulting from the techniques and procedures developed by The University of Michigan are compatible with both ECAC and the Air Force, close liaison has been maintained with these organizations. During this study the following digital techniques were considered: 1) manual, 2) semi-automatic, and 3) automatic. In addition to investigating recording techniques, consideration has been given to the form in which the data should be collected. Therefore, a data format that has been discussed with both ECAC and the Air Force is presented as a part of this report. 3. 1 ECAC Data Format During discussions with ECAC personnel, it was learned that pattern data in the form of number-pairs is preferred. The desired number-pair consists of the antenna gain value and the associated angle (azimuth or elevation) for a given data point. Personnel of ECAC have found that it is less complicated to write the various programs required for interference predictions with the antenna pattern data in the number-pair format. This format relieves the interference program of the burden of having to search the input data to match a given gain value with its correct angle in the event data is accidentally placed in the computer in the wrong sequence. Further, if a single data format is adhered to by the Air Force and other military organizations, only one computer program will be required at ECAC to reduce antenna pattern data for statistical analysis. Therefore, costs and time will be minimized in the prediction of interference. 92

THE UNIVERSITY OF MICHIGAN 7274-1-F The medium by which data is to be stored at ECAC is IBM cards rather than magnetic tapes since cards are less susceptible to deterioration or damage. It is recommended that the antenna gain value be represented by four digits, thus enabling an amplitude to be recorded to aone-half db increment, typical of microwave measurement accuracy. It is also suggested that the angle associated with the antenna gain be represented by four digits allowing an increment of 0. 50 to be recorded. The one-half degree increment will enable agencies to measure high-gain, narrow-beam antennas. Following the above format, a card will consist of nine data points and an identification code. Basically, the data will be arranged on the card as follows:nine data points will be placed on each card consuming 72 columns, and the remaining 8 columns will be used for the identification code. A total of 80 cards will be required for each antenna pattern. In addition to the data cards, it will be necessary for each set forwarded to ECAC to be accompanied with a data sheet describing the card content, i. e. antenna model, type, etc. This sheet could very well be a punched card. 3.2 Manual Digitalizing Technicue The manual procedure consists of employing an individual to examine the analog plot of the antenna pattern and record on a suitable data sheet the antenna gain, relative to the pattern maximum, at discrete angular increments. In the event the pattern is aside angle pattern configuration (half-power beamwidth > 50), data is recorded at 10 increments for the full 3600 of the pattern. In those cases where the pattern has a narrow beam (half-power beamwidth < 50), data is recorded in increments of 0. 5~. The relative gain is recordedto the nearest one-half db. After the pattern data has been recorded, the data sheet is forwarded to a card punch operator, who punches both the angular position and the relative gain onto an IBM card. These cards can then be forwarded to ECAC to become a part of their data base files. 93

THE UNIVERSITY OF MICHIGAN 7274-1-F The principal disadvantage of the manual technique is the probability of human error occurring in the recording of the data. A further disadvantage is that the process is time consuming and costly. 3. 3 Semi-Automatic Digitalizing Technique A semi-automatic procedure has been considered that requires manual sampling of an analog antenna pattern. An operator manipulates a pair of cursors on a machine on which pattern data is placed. The machine is manually directed to sample the analog waveform at any selected point and supply only the magnitude of the sample value to an analog-to-digital converter unit (no provision is made to include angle information). The converter unit digitalizes the data and feeds a card punch unit which automatically punches the data onto cards (thus negating the need for one operator). Figure 82 shows the equipment used in this procedure. The analog-to-digital converter unit is seen at the left in the photo. The sampling machine "Oscar" is shown in the center and the card punch unit on the right. This semi-automatic procedure has several drawbacks not found in the completely automatic system to be described in the following section. First, it is doubtful that it is feasible to use this system to punch the digitalized data onto IBM cards in the format suggested above, as no angle data is available. Second, the analog waveform must be sampled manually by an operator. Our investigation has shown that when the equipment is operated by an individual unfamiliar with antenna problems, there is a high probability of errors appearing in the final data. These errors are usually difficult to locate and costly to correct. Third, the curve sampling procedure is tiring to an operator's eyes and this also increases the probability of errors in the data. We have investigated the use of untrained personnel (such as may be employed if the data were sent to a commercial facility) and also antenna trained personnel to reduce analog data into digital form using the above semi-automatic procedure. The 94

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THE UNIVERSITY OF MICHIGAN 7274-1-F errors introduced into the data by the operator were found to be much higher when using untrained personnel. Because of these problems it is recommended that the semi-automatic procedure be avoided if at all possible and in lieu of it employ the automatic procedure discussed next. 3.4 Automatic Digitalizing Technique An automatic digital recording technique has been developed by The University of Michigan. Figure 83 is a block diagram of that system. A high-gain receiver is employed to measure the antenna radiation characteristics and an antenna pattern recorder plots the characteristics in analog form on standard chart paper. Simultaneously, the analogwaveform is sampled at 10 intervals (for 3600 coverage) by an analog-to-digital converter and the magnitude of the sampled values are recorded on a general purpose tape rbecorder in the form of binary coded numbers. Figure 84 shows the wide-range high-gain receiving system which incorporates the analog recorder and the analog-to-digital converter. Figure 85 is a close-up view of the U of M analog-to-digital converter. The basic operation of the analog to digital converter is discussed in Supplement I (Dute et al 1966). Figure 86 shows the general purpose tape recorder which places the digital data on quarter-inch magnetic tape. Upon completion of the antenna measurements the general purpose tape recorder is transferred to another analog-to-digital converter facility. Here the quarter-inch magnetic tape is played back into a converter unit which transfers the data onto half-inch magnetic tape in a format which is compatible with the U of M IBM 7090 computer. The equipment used to effect the data transfer is shown in Fig. 87. The antenna data now on tape is subsequently transferred to the punch card form by employing IBM processing equipment. A computer program, which is required to direct the processing, is read into an IBM 1401 processing unit along with the antenna data on magnetic tape, The digital data is processed and automatically -_ 96 -9

THE UNIVERSITY OF MICHIGAN 7274-1-F Ot ~ 97co~~~~~~co 1C

THE UNIVERSITY OF MICHIGAN 7274-1-F i~~~~~~~~~~~~~~~ FIG.~l_ 4W-A-I 98. i...-s S -:-:_::::::: *., S-::::-i ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:: i'riii-i li-i'-'''~ii'i' 2' ~ ~ iiiii:0 n 0~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:~:i;iili".-~-: ~~ii:;~~f~~:i:riili::_ FIG. ~ ~ ~ ~ i 84 IERNE IHGANRCIIGSSE i~~-~-i~: i~iiiiiii —iiiii~ii ~~i- ii i —:-_- i-:u _~ —: —-:: —-:::.:i-::::_:-__.-:-::98 — —:-..:

THE UNIVERSITY OF MICHIGAN 7274-1-F H!OiO!Africa~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~r..).! z U:, ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~, r,3 0?ii~~~~~~~~~~~~i~~~~~~;_iiliiiiiiiiiiiii~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~iiii-i~~~~~~~~~~~~~~~~~~~iii~~~~~~~~~~~~i ~~~ ~ ~ ilta O 00 H.. 0 0 S~~~,< z eo t.o CO 99

THE UNIVERSITY OF MICHIGAN 7274-1-F P2 0 r4 O Z co 100

THE UNIVERSITY OF MICHIGAN 7274-1-F X | 11 I l __________________ _ _............i..:-. i ~~iii~~,iiii-liiiiiii iiiliiiiiiiiiii~ ~ ~"~~ii'i,, FIG. 87: RAYTHEON ANALOG-DIGITAL CONVERTER AND ASSOCIATED LOGIC RACKS (NORTH CAMPUS)

THE UNIVERSITY OF MICHIGAN 7274-1-F punched onto IBM cards for storage at ECAC. Although the above procedure may appear lengthy and cumbersome, it was developed to demonstrate the feasibility of recording antenna patterns in both analog and digital form simultaneously, and the subsequent transfer of digital data to punched cards for storage. In spite of the complexity of the procedure, it was found to provide a high degree of accuracy in a shorter period than either the manual or semi-automatic procedure. This accuracy is illustrated by Figs. 88-89 which are typical analog patterns selected at random from pattern sets. Plotted as circles on these analog patterns are the digital data as read from the punched IBM cards after completion of the digitalizing procedure. Only 60 of the total 361 values sampled by the digital converter are shown on each pattern to avoid the clutter of too many points. 102

THE UNIVERSITY OF MICHIGAN 7274-1-F I~ i~:.l~.:~~~~~~~~~~~~~~~~~~~AII O.I~~~~~~~~~~~~~~~~~. LL'"t i**,.'1 11111111111: _tt6 t-~f -1- -H-~I m W H40 4HH1111 7~~~~~~~~ w,.. J e l T1! A 40 M i 4t~~~~~~~~~~~f i. -t.-I-.:-t-. t~~~~~~I -4 1 r 8~~~~~~~~~4f ~~1.4 CHART r4O. 128-4so ewsxttn~"u.5. ANG SCIETIFIC-ATLAT. INC... SLANTA, GEON FIG. 88: X-BAND SL.,OT, 16.0 Gc, SIMPLIFIED T-33 103,;I i 30., J [W14 w I?~-/ -~ )~~t~~ I I I~FII.._.i.,I +1 4ij-Hi~-f. i.._l - 1' i~~~~~~ i.~~~~~~~~~~~~~~~~~~~~~~~~~~~3' ~ Ii. j-i~~~~~~~~~~~~~~~~~~-'X 1 F! 1 4140: ~1~~~~ cHAR?4.12.60ANGE SIIETIVC ALANA. NC-ATLNTA GERGI FI. 8:X-AN LOJ,16 0Gc IMLIIE T3

THE UNIVERSITY OF MICHIGAN 7274-1-F I =f I:1 -1-i- - ~1 -1;it-.'. L...'....:~ t:.:-':.... 1 t i".' "" -:'1 1 -:1't 1' -i:, j: t:-,:!: JL,.J,.11,-2;4:' -l-tif f Xh. -.::._..:j':-' ~:''~ " ~,':, "-':-I:::,:: +, t!~,!,: I ~. ~M + X tf ~ T-.'i 7i'. i. X L~~~~~~~~~4 9i[X riS i-XiWE1i I~;~ ~ ~ ~ ~~~~T 1 ~''.:: ~'" i;.- r.'::4 1-: L:. 4: 4:: 1::t:.- L4. -l:i./-l z0.-:=:,-;. -1:-1,;.. [..'-.! I~ ~1; ~ 1 m =C: f- 7j,..;-.... "... 1'''..i. (;j@...'.-.' - - C'....,.o.......:. t....-'j'-:!,.?....i.. _.'..:'J,: -'. ~'.. -;t.... ~! Ii:'.. i! 4- I 104 I i I - I, I. 1:i.i.-.-i1 i -. j..'' -..' t,.... i-: 44.C - - t 6 A:'o,'N:"E h 1.... ATLANTA.- ~_ _, i FIG. 9:i X-...LE,' 2.4 -..- P-."Ci. S.. T-3 i;.-i~~~~~~~~~t~~~t..}!"i,'~,~~~~~~~~~~~~~:-...,., ~. -...~.....~.,.. w. __., I I',:i..-,C~ -~~ --..,-.T... ~-1-,. q1 h.t...,, ~H. I: I........,,:- 1.,,,,,.' i / " "' — i...-'.....i.!-'.i ~.i.-i.-_r.~ i ~.~. i: i. —-~i ii..I: ~......:I.. —.'': —i',':-:~f f~"'-~ — - -~~"~ —I i...... i~-~I~~~~~~:.-:l. j..j.:Iii.i-;j. i-'.; [l.L'':.l,]!:_:-'.".::.: -:t I i._: - -. ].:. -..i i.if:.;.'.:.l Ii.t.! i,!,'.'.... I.'l.-.'1.1=i.. - 1'-"" ~":'. i-i].l'"" ~~~i-i- -;..-.i..1....'i I,._,-I:,:...::~...... I,.:?..!..,,..-tt-, t,.,.:..,,~~?~ i-'6'.:.f —! i:;',:~ ~''~:'':: t?...~- 4.,!..I~-'-! -i.L':_... ~.:. -'.,,=..,i.z. __~...J_......_.- i,....i. j.I, —.-' I.' it,''jl. l~ ~:..,_~:;', -'-...,~-...,.,-,t.-,:.,.. —....,: —... ~ —,.. -:.... 1-j J =., _~~.t_,,,,.=~,,t. F,,if,,.i-i. - ~~~~~:iI i I I' I j j't'JJT. II t~.fl.,'"'II I!'!'l' j;ii~~':"'~~~~~ ~~~~~~~ -,14' " -'i~. —:.''0It- 7:-.1-...... t-36'~.-.I-I.. —-...3"1..-t-,` -.-.7-$-.- i8-!-,..,14, - 4 —i~-'1:__', It -_ i' I~!. 15! ~_l i_! I!,i'''.II.1.i/I.,I/, i I'II;JI.!'Ii',;':,,;,.... ~,;,1~' --.~,,~,,,,,- c.....', ANGLE I~lIINf~i~TItI~AT1,NTA. INC.. AtLA~t'~. OI!OI~OI FIG. 89' t./4 MONOPOLE, 2, 4 Go, ~PECISlON T-33 104'

THE UNIVERSITY OF MICHIGAN 7274-1-F IV TRANSMITTER OUTPUT CHARACTERISTICS A third aspect of the present contract is the consideration of the overall system. Here, one must determine what data is to be collected by the military (Air Force, etc. ), and supplied to ECAC for interference predictions. Since there are many types of systems in use today, the systems study has been initially limited to one of the more popular and less complicated systems. As our knowledge of this system increases, the techniques developed will be refined so that they can be employed with more complicated systems. The system initially under consideration is a communication system that functions in the VHF and UHF frequency range and employs coaxial cables as the transmission lines. To further simplify the study, only the transmitter associated with the communication system will be evaluated. With an antenna connected to the transmitter it is necessary to show how to calculate the power available to the antenna. To aid in this study, it has been broken into three parts: 1) the multiple generator problem, 2) power transfer considerations, and 3) source impedance measurements. Each of these will be discussed in the following sections. 4. 1 A Multiple Generator Model for Spurious and Harmonic Frequencies An elementary generator can be modeled as a voltage source connected in series with an internal impedance as in Fig. 90. Such an equivalent circuit can represent a transmitter. For the electromagnetic compatibility study, one must understand that transmitters produce spurious and harmonic outputs in addition to the fundamental. Therefore, the elementary generator is inadequate and a multiple generator model is required. Such a model is depicted in Fig. 91. For the multiple generator model, each spurious (or harmonic) frequency is represented by its own generator and internal impedance. 105

THE UNIVERSITY OF MICHIGAN 7274-1-F FIG. 90: ELEMENTARY GENERATOR Z Z gl g Eg1 Eg z gn Egn FIG. 91: MULTIPLE GENERATOR MODEL FOR A TRANSMITTER 106

THE UNIVERSITY OF MICHIGAN 7274-1-F A key consideration is the aspect of interactions between the elementary generators, which are the components of the multiple generator model. By interactions we mean the following. Suppose a load Zlk is attached to generator (Egk, Zgk). Let Zlk vary and observe generator (Egj, Zgj) If (Eg, Z gj) is constant as Zlk is varied, then the model is considered to be free of interaction. If the model is assumed to be free of interaction, then the computation of power absorbed by an antenna is readily made by techniques described later. If the model is not free of interaction, then a linear correction term added to Egk and Zgk may provide a model with sufficient accuracy for ECAC purposes. It is necessary to gather experimental evidence to determine the extent of interaction for a real transmitter. Since the elementary generator model must be completely understood before the multiple generator model can be adequately described, the multiple generator model will not be used in the following discussion. The calculation and measurement procedures described apply to elementary generators, which are the components of the multiple generator model. 4.2 Power Transfer Considerations In the electromagnetic compatibility program there is need for a simple method for computing the power absorbed by a load (an antenna) when the antenna impedance, Za, transmission line impedance, ZO, and source impedance, Zg, are far from equal. A general method is desired for computing the maximum and minimum power for a given Za, Z and Zg, if the transmission line length is varied. For some purposes, a method is necessary for determining the probability that the power absorbed by Za will exceed a stated power if a random length of transmission line is used. It will be assumed that the transmission line is lossless, hence Z = R The general situation is as shown in Fig. 92. For a precise formulation O O of the problem, more dimensions should be added to Fig. 92, as shown in Fig. 93, 107

THE UNIVERSITY OF MICHIGAN 7274-1-F z 7 Transmission Line ~d I ~a FIG. 92: GENERAL TRANSMISSION LINE PROBLEM zg z g aZa FIG. 93: MODIFIED TRANSMISSION LINE PROBLEM 108 -

THE UNIVERSITY OF MICHIGAN 7274-1-F where the distance d has been broken up into four distances d', dg, da, and d' 0 ga a such that d +d +d +d =d. (1) g g a a o The two distances d' and d' have been chosen in the following manner. Consider g a first d. The antenna impedance Z will produce a standing wave on the transg a mission line; the point Pa is chosen at one of the minima of this standing wave. Then d' is the distance from the antenna to this point P. At P the antenna a a a load impedance Z will be transformed to an impedance Z = R' and R'< R The distance d' to point P is determined in the same manner but using Z as g g s the terminating impedance. Now we can write equations for the impedance seen at points P, Z' and Z' g a Z' is the impedance at P seen looking toward the source, and Z' is the impedance at s a P seenlooking toward the antenna. From these equations, an expression for the ratio of the power available at the antenna (P) to the maximum power available from the transmitter (P ) may be derived as shown in the Appendix as P 1 (2) max a cos kd +sin2 kd a a Figure 94 is a set of universal curves calculated from the above equation showing the variation of power delivered to the antenna as a function of the transmission line length, d. From these curves, it is a simple matter to determine the probability that, with a particular transmitter and antenna, the power radiated by the antenna will exceed some arbitrary power level when the exact length of the transmission line is not known. This information may be obtained from three measurements: 1) the antenna standing wave ratio, 2) the transmitter standing wave 109

THE UNIVERSITY OF MICHIGAN 7274-1-F -0- C -a = Odb -5 a = 5db - 01 -10 l 20db z z -15 __l -40 a = 40db -43 90 80 70 60 50 40 30 20 10 0 TRANSMISSION LINE LENGTH (kda, degrees) 110

THE UNIVERSITY OF MICHIGAN 7274-1-F ratio, and 3) the maximum power available from the transmitter. These three measurements should be made at a point on the transmission line near the antenna to minimize the effects of transmission line losses. Techniques for the first and third measurements are relatively simple, but the measurement of the transmitter standing wave ratio is not well understood. Therefore, a technique of obtaining this data must be developed. 4. 3 Source Impedance Measurements Here it will be shown that, if the transmitter impedance is not a function of the termination, the impedance can be measured with a line stretcher terminated in a short circuit and a detector tuned to the frequency of interest. The measurement procedure is very similar to that for measuring a termination impedance with a slotted line. The circuit used is shown schematically in Fig. 95. The transmitter is represented by a voltage source E and a series impedance Zg. Neither E nor Z are a function of the termination. The transmitter terminals AB are connected g to a transmission line of variable length, Q. A detector is placed across the line a fixed distance, d, from the short circuit. The exact value of d is not important but should remain fixed throughout a measurement. The largest voltage for the detector is obtained when d = X/4, 3X/4, etc, but the effect of detector loading is most pronounced at these points. For a measurement device, d = X/8 may be a good compromise. The impedance Zt seen at the input of a shorted transmission line of length 2 and propagation constant k is given by: Zt = jXt = jRo tan k2 (3) This is the impedance seen looking to the right of terminals AB of Fig. 95. The voltage V1 across terminals AB is given by: 111'

THE UNIVERSITY OF MICHIGAN 7274-1-F 4-} o C) o a) ka! a) U. 112

THE UNIVERSITY OF MICHIGAN 7274-1-F V1= II1 jXt (4) E X (5) Izg+ jXj let Z =R +jX (6) g g g then V1 = i t (7) R2 + (X +Xt)2 g g t E R tan ki ______________g o (8) +g g tntn Because the transmission line is shorted at the far end, an infinite sinusoidal standing wave appears on the line such that V1 = V (sin k). (9) The quantity V represents the peak value of the standing wave appearing at every odd number of quarter wavelengths from the short. The voltage, V, indicated by the detector will be some fixed fraction, a, of this peak voltage. Hence, V = aV. (10) Combining equations (8), (9) and (10), we obtain 113

THE UNIVERSITY OF MICHIGAN 7274-1-F V Isinkl = EgRoltankil (11) a R2 +(X + R tan k )2 g g o from which aE ok sin (12) R X2 cosCO2 ke + ( -— ELcos ki + sin k1)2 0 In equation (1i the magnitude signs are no longer necessary; the positive sign is attached to the radical in the denominator. Now let us examine equation (12) for the condition of R = R and X = 0. g o g Equation 02) becomes aE V g R= R g 0 o X =0 cos kk + sin k = aE (14) s Thus when the source impedance matches the line impedance (Z = R ) the detector reading is independent of the line length 1. This condition is equivalent to the matched termination of a line that produces a flat line. The flat line counterpart for a "source standing wave" is demonstrated by equation (14). Now what happens when Zg R., i. e., the source impedance is not matched. For this situation, let us consider, in general, the situation viewed at terminals AB but at terminals A'B' a distance I1 from the transmitter. Let us choose I1 so that the transmitter impedance Z is transformed to a pure resistance R' so that R'> R. Equation (12) then becomes g- o 114

THE UNIVERSITY OF MICHIGAN 7274-1-F aE' g V= (15) 2 R [ cos -I)kin k(-l)k+sin k(-1) Equation (15)has a maximum value when cos k (-l1) = 0 and a minimum value when sin k (U - 1) = 0. To show this, differentiate the quantity under the radical and set it equal to zero. [dked 3- L LF J cos k( - I) + sin2 k ( - ) o.J [ R 2 =-2 L.sin k ( -1) eos k ( - 1) + 2 sin k ( - 1) cos k ( 1) (16) R 2 =2 {1 - ] sink (U - l) cos k (i -I 1) (17) Equation a7) is zero when sink (Q - I ) = 0 (18) or cos k (U - 1) = 0 (19) Using equation ([8) in ( 5)we have R Vmin' 0 (20)

THE UNIVERSITY OF MICHIGAN 7274-1-F Using equation(19) in (15) we have V =aE'. (21) max g Equation (2 gives Vmin because R' >R. Now, dividing equation(20) by equation (21) gives V R' max = (22) V112~~~~ R-~ -g (22) V R min 0 To determine the impedance seen looking back into the transmitter terminals, AB, we must enter the Smith Chart at R' V = max = VSWR (23) R V. o min and go around the chart a distance equivalent to 21 in the direction "toward the load" indicated on the chart. This point on the chart represents the transmitter impedance Zg. 4. 3. 1 Experimental Verification of the Source Impedance Measurement Using a Short Circuit Load To experimentally verify the above analysis, a signal generator and a variable reactive load have been employed. The system block diagram is shown in Fig. 96. The slotted line was employed to determine the distance between the generator terminals and a null of the standing wave pattern (which is equivalent to finding AB/Xg since a null occurs every Xg/2). The results of this experiment are shown in Fig. 97. Assuming the generator impedance Zg is 50 + jO and the stub introduces an imaginary component only, one would expect the locus of points on the Smith Chart to form a circle tangent to the 116

THE UNIVERSITY OF MICHIGAN 7274-1-F 3 3 FIG. 96' EQUIPMENT ORGANIZATION FOR GENERATOR IMPEDANCE MEASUREMENT Equipment List 1) 600 MHz Standard Laboratory Signal Generator 2) Coaxial Slotted Line 3) VSWR Detector 4) Variable Stub Tuner 5) Standard Laborator 50 OHM Coaxial Termination 6) Variable Length, Constant Impedance Coaxial Line 7) Signal Probe 8) Standard Coaxial Short Circuit Termination 9) Bolometer Detector 117

THE UNIVERSITY OF MICHIGAN 7274-1-F z =1+ ix ---- Area of Uncertainty Due to Minimum VSWR> 1: 1 o. FIG. 97: IMPEDANCE OF GENERATOR IN SERIES WITH STUB TUNER (using a short-circuit load) o.&1 4o~ ~' ~~~~~~~~~~~~~~~~~~~~~~~~~~~o,.f,, $~~~~~~~~~~~ $.(a~~ 9 Y~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~,~~ 118

THE UNIVERSITY OF MICHIGAN 7274-1-F points Z = 1. 0 + jO and Z = 0 + jO with the real axis including these points as the diameter. However, the minimum measurable VSWR was 1. 09 and the experimental data points vary by approximately this amount from the ideal circle. No data points corresponding to large values of stub reactance appear on the generator impedance plot. The mismatch between the generator and the tuning stub was so great in this region that the energy transfer to the line is insufficient to make accurate measurements. These results has been verified by comparing them to the impedance of the stub tuner in series with a standard laboratory 50 ohm termination. These measurements were obtained using standard slotted line techniques. The block diagram for the equipment appears in Fig. 98. The latter results were in excellent agreement with the source impedance measurements, the only difference being that data points were available for large values of stub reactance. 4. 3.2 Measurement of Transmitter Impedance Using a Complex Load A technique for measuring the impedance of a transmitter using a short circuit has been discussed above. This may be found to be impractical for many transmitters since they are generally designed to work into a well-matched load at the fundamental frequency. In this section, a similar measurement procedure will be discussed utilizing a complex load. It will be necessary for the VSWR of the load to be accurately known at the frequency of interest. A test setup similar to that shown in Fig. 96 will be used to measure the impedance (and VSWR) of the transmitter. The only difference being that the short circuit termination is replaced by a load. The slotted line is employed to measure the load impedance, e.g., an antenna. The variable line is then adjusted to obtain both a voltage maximum, Vc(max) and minimum, V c(max)' c(min) With the line adjusted for a voltage minimum, a null on the slotted line is recorded. The VSWR of the source is then calculated from the following expression: 119

THE UNIVERSITY OF MICHIGAN 7274-1-F 1 --— ~ 4 1 5 FIG. 98: EQUIPMENT ORGANIZATION FOR 50 f2 AND TUNING STUB IMPEDANCE MEASUREMENT (See Equipment List in Fig. 96) 120

THE UNIVERSITY OF MICHIGAN 7274-1-F Kr - 1 V (max) VSWR K here K is (min) and ra is the load VSWR. C To determine the transmitter impedance, one must enter the Smith Chart at the top along the R +jO (where R = 1/VSWR such that 0 < R < 1) line and rotate along the generator VSWR circle (from the expression above) a distance l%/X toward the load. I1 is the distance from the null on the slotted line to the generator terminals when V is aminimum (see Fig. 100), and X is the wavelength of the signal inthe transmission line. The transmitter and load are shown schematically in Fig. 99. The transmitter is modeled as a voltage source E in series with impedance Z. The variable length of the constant impedance transmission line, AC, is terminated by a known load Z1 at B. Distance BC is constant. A detector is included at C. Let V. be the total forward going voltage incident on the load and V the 1 r reflected voltage propagating from the load. At any point along the line the voltage will be given by t i r (24) The reflection coefficient at the load is defined as p. V P1 V Let V.' be the reflected voltage incident on the generator. Further, let V' be the 1 r incident voltage reflected from the generator. The reflection coefficient at the generator is defined as pgI V' = r (26) g V' 121

THE UNIVERSITY OF MICHIGAN 7274-1-F I vI I Ig Z1 I,=V' V. _' I r l I A C B FIG. 99: GENERATOR IMPEDANCE MEASUREMENT CIRCUIT (using a complex load) 122

THE UNIVERSITY OF MICHIGAN 7274-1-F The VSWR of the source is then equal to Vt V' + V' 1 r i r V' VSWR = 1+ (27) Vi - VI- i r V' r Substituting equation (26), 1+ I PgI VSWR = I (28) The maximum voltage measured by the detector at C as the line length AC is varied will be V( = IV. + Vr The minimum is c (max) V (min) = Vi - (29) c 1 r Consider the ratio V I (+ VxI c (max) 1 r c (min) Iv I IYiV1 + lIr A Igl IVi - 1+ jP11 I~gl -I vllg lv IP-g-l(PJ I (30) |Then, K [1 - j PgIv IpPl I pg I+ IPg (32) 123

THE UNIVERSITY OF MICHIGAN 7274-1-F or IPI K- 1) (33) pi1(K+i) Substituting equation 28 into equation 33, 1 + K - 1 (K + 1) (I p4 VSWR (Source) (34a) 1-(K+1) I P, K(i + Ip ) - (1- Ipl (34b) -K(1 - IP1) +(1 + IPl ) Let VSWR (Load)= r2. Dividing equation (34a) by(1 - Ipil ) and recalling that VSWR (Load) = pl one has Krp-i VSWR (Source) = r - (35) r, - K V where K is c (max) and r, is the load VSWR. V c (min) A simple determination of the source VSWR with any complex load is now possible with two voltage measurements. If the load VSWR is known, the source impedance can be determined with the aid of a Smith Chart. Consider Fig. 100. Let I1 be the distance from the generator terminals to the point D along the transmission line AC where Zg appears to be purely resistive when looking back toward the generator. Let this value be Rg. Further, select I1 so that Rg < Z, the characteristic impedance of the transmission line. If the line length AB is adjusted so that the voltage measured at B is a minimum, a null 124

THE UNIVERSITY OF MICHIGAN 7274-1-F I I I 1 I _ _ _ _ I _ _ _ [X 1I-.g~? I I 1 —-1 --- A D C B FIG. 100: CIRCUIT FOR THE DETERMINATION OF 1 125

THE UNIVERSITY OF MICHIGAN 7274-1-F in the standing wave along the line due to the load will occur precisely at D. Suppose the generator impedance is R' and the generator terminals are located at g D. Further, represent the load and line length DB by a variable impedance ZI at D, as in Fig. 101. Clearly, the voltage V' across Z1 will be a minimum when Z1 is a minimum. This is exactly analogous to the case discussed above. Thus the voltage V at C will be a minimum when the length AC is adjusted so that a null occurs at D. Therefore, to find the generator impedance, it is necessary to enter the Smith Chart at the top along the R +jO0 line and rotate along the generator VSWR circle a distance ll/ko toward the load. 4.3.3 Experimental Data The technique described above has been used experimentally with a stub tuner in series with the generator. The load consisted of a 100 ohm coaxial termination and a short (random) length of transmission line. Experimental data is given in Fig. 102. No data points corresponding to large values of stub reactance appear in Fig. 102. The mismatch between the generator and tuning stub was so great in this region that the energy transfer to the line was insufficiently large to make accurate measurements. It will be noted that the data in Fig. 102, obtained with a complexload, is in excellent agreement with the data in Fig. 97, which is an impedance measurement of the same generator and tuning stub utilizing a short circuit termination. The technique described above should prove useful for measuring complex generator impedances using a complexload, provided all harmonics or spurious outputs are far below the level of the fundamental frequency. Techniques for measuring the generator impedance at spurious and harmonic frequencies with energy being generated simultaneously at these frequencies are presently under consideration. 126

THE UNIVERSITY OF MICHIGAN 7274-1-F Hi FIG. 101- EQUIVALENT CIRCUIT OF FIG. 100 127

THE UNIVERSITY OF MICHIGAN 7274-1-F z = 1+j x ---- AreaofUncertaintyDuetoMinimumVSWR > 1:1 FIG. 102: IMPEDANCE OF GENERATOR IN SERIES WITH STUB TUNER (using a complex load) 128 128,

THE UNIVERSITY OF MICHIGAN 7274-1-F V CONCLUSIONS AND RECOMMENDATIONS A simplified modeling technique applicable to obtaining three-dimensional spectrum signatures of airborne antennas has been presented. Employing this technique, three antenna configurations have been used, and typical data shown. The three antenna configurations were a modified monopole, X /4 monopole and a slot antenna. The modified and X /4 monopoles operated at a full scale frequency of approximately 300 MHz, and the slot antenna at 1. 0 GHz. For the purposes of this study these antennas were scaled by a factor of 8 such that the VHF antennas operated at 2. 4 GHz and the UHF antenna at 8. 0 GHz. Data was collected at the fundamental and four harmonics of each of these antennas and is presented in both analog and statistical form. From a rewiew of this data, it can be seen that simplified modeling is an acceptable low cost technique for obtaining antenna spectrum signature data for future interference predictions. A second aspect of the program has been an investigation of recording techniques applicable to obtaining spectrum signature data in a digital format. Three techniques were considered; 1) manual, 2) semi-automatic and 3) automatic. Limitations of these are discussed in the report along with a discussion of the automatic technique developed and employed by The University of Michigan. From this study, a recommendation can be made that automatic recording techniques be employed to obtain antenna spectrum signature data in a digital format. This digital data can then be placed in a universal format for storage at ECAC. Therefore, a standard data format is presented to ensure that all antenna signature data sent to ECAC is the same. Here, it is recommended this data be placed on IBM cards. A third aspect of the study has been an investigation of an improved signature collection technique applicable to transmitters. An analysis of the problem is presented together with possible techniques of acquiring the needed data. From 129

THE UNIVERSITY OF MICHIGAN 7274-1-F this analysis it has been determined that three items of information should be collected and stored by ECAC: 1) the transmitter VSWR 2) antenna VSWR 3) maximum power available from the transmitter. It is felt that the antenna VSWR and transmitter power can easily be obtained by standard measurement techniques. However, a new technique is required to obtain the transmitter VSWR. A suggested technique is described, from which the transmitter VSWR may be obtained at the fundamental and harmonic frequencies, along with some experimental verification. It is recommended that this work be continued since, at the present time, only the VSWR of laboratory type generators have been measured. To further -evaluate the technique it will be necessary to measure the VSWR of typical transmitters used by the military. The purpose for carrying on this study is that more accurate transmitter spectrum signature data is required from which interference prediction analyses can be made. Presently, because the data collected is relatively crude and inaccurate, interference prediction analyses are inaccurate. 130

THE UNIVERSITY OF MICHIGAN 7274-1-F APPENDIX Referring to Fig. 93, we can write equations for the impedance seen at points P, Z' and Z. Z' is the impedance at P seen looking toward the source, and g a g Z' is the impedance seen at P looking toward the antenna. Expressions for the a resistive and reactive components on transmission lines are well known. A particularly clear and compact form is given in Montogomery et al (1948). Let Z' = R+X (Al) g g g and Z'= R' +X' (A2) a a a For the source r R' Z (A3) g o2 2 2 r cos kd + sin kd g g g (1 -r) sinkd coskd X' Z= (A4) g o2 2 2 g r2 cos kd +sin kd g g g and for the antenna r R=Z a R Z (A5) a ~ r2 cos kd + sin2 kd a a a 131

THE UNIVERSITY OF MICHIGAN 7274-1-F (1 - r ) sinkd coskd a a a X Z (A6) Xa ~ r2 cos2 kd + sin kd a a a In these equations, rg is the standing wave ratio on a line of characteristic impedance ZO terminated in Zg k is the propagation constant of this line. Likewise, r is the standing wave ratio on the same line terminated in Za a a Now let kd = r /2 to establish point P, then R = Z r (A7) g o g X' = 0. (A8) g For any arbitrary length of transmission line between the source and the antenna, the antenna impedance seen at point P will be Z =R +jX. (A9) a a a Now let us compute the power absorbed by the antenna. The equivalent circuit is as shown in Fig. A-1. Note that in Fig. A-i, E' is not, in general, the same as g E in Figs. 92 and 93. The equivalent source voltage has been transformed by the g transmission line. As will be shown presently, this transformation need not be calculated; a measurement of maximum power available from the source will suffice to define E' so that the E or E' need be measured explicitly. g g g From Fig. A-1 the power absorbed by the antenna is E I = (A10) (R' +R 2 (X,1 )2 g 1 a3 132

THE UNIVERSITY OF MICHIGAN 7274-1-F Z' g I B R + iX' a a FIG. A-i: EQUIVALENT CIRCUIT FOR THE TRANSMISSION LINE PROBLEM 133

THE UNIVERSITY OF MICHIGAN 7274-1-F E'2 R V = 12 Ra (All) a (R' + R,)2 +(X,)2 s a a Equation (All) may be normalized by computing the maximum power that any load might draw from the source. For the maximum power, the transmission line should be terminated by a load R' at kd = 7r/2. For this condition the maximum power g g is given by PM =I2 R (A12) M g E i —2R - (A13) 2R' g 412 g Now, Equation (All) can be written in normalized form. E'2 R' 4R' =_ -— g (A15) PIM (R'+R) 2+(X )2 E' g a a g 4R' R' p _ ga (A16) PM (R' + R' )2 +(X )2 g a a 134

THE UNIVERSITY OF MICHIGAN 7274-1-F Substituting the relations (A3, (A5), and (Ak (remembering that kd = r /2) Equation g (A16) becomes Z r 4Z r o a r cos kd +sin 2kd P a a a (Zr+ 2 2 Z (1 -ra) cos kd sin kd) r cos kd + sin kd r cos d +sin kd a a a a a a (A17) Simplifying Equation (A17) results in 4r r (r cos kd +sin kd ) P g a a a a M r (r2 cos2kd + sin2 kd ) + (1 2)2 sin2 kd) + ra kd g a a a a a a a Now for certain values of da P/PM will be maximum or minimum. if kd =n7r n = 0, 1, 2,... 2 4r r r ms a a (A19) nr min M (r r2 +ra) +0 g a a 4r r =P ( a (A20) M (r r +1)2 g a 135

THE UNIVERSITY OF MICHIGAN 7274-1-F 2n +1 If kd = 2n n= 0, 1, 2, a 2..... 4r r g a ax = p = p 2 (A21) + 1) max M (r + 2 (2n+l)rr +r) ~2 ~g a P r r +1 2 max a 2 r g a (A22) P r +r min g a Equation(A22) is a simple equation that determines the ratio of the maximum power to the minimum power delivered to an antenna from a course using any aribtrary length of the transmission line. The only quantities that need to be measured are the standing wave ratios for the antenna and the source impedance. Equation (A21) gives the ratio of the maximum power delivered to an arbitrary impedance to the maximum power available from the source using an impedance matched to the sourc The equations of greatest interest at this point are Eqs. (A14), (A18), and (A22). First, Eq. (A14). E 2 M =4R (A14) g This equation establishes the absolute maximum power available from the sources using a matched load; no other load can extract more power from the source. Now consider Eq. (A18): 4r r (r cos kd +sin kd ) PM [r (r cos kd+sinkd + (1 - 2)sin kd sin2 kd a a a a a a 136

THE UNIVERSITY OF MICHIGAN 7274-1-F For fixed r and r a the power, P, absorbed by the load will vary between the two values given by Eqs. (A20) and (A21). 4r r P ~P 94 a (A20) Pmin M (r r +1)2 g a 4r r P = P g a (A21) max M (r +r )2 g a Thus, P can never be greater than P no less than Pmin regardless of the max mm transmission line length*. These equations (A20 and A21) are relatively simple and will predict the maximum and minimum power radiated by an antenna when connected to a specified source. The data necessary from measurements consists of two standing wave ratio measurements and one power measurement. Predicting the power delivered to the antenna as a function of the transmission line length is somewhat more complicated and requires additional work. For this problem, we have to turn our attention to Eqs. (A18) and (A21). Recall the assumption that the transmission line is lossless and contains no reflection from connectors or other discontinuities. This lossless condition can be removed if the standing wave ratio rg and the power available, PM', are measured through a length of transmission line approximately equal to the length used in a typical installation. The reflectionless condition will also be removed for a given installation by this technique, but the variation from one installation to another will not. Normal connector reflections are small and should not affecbhe prediction appreciably. 137

THE UNIVERSITY OF MICHIGAN 7274-1-F 4r r (r cos kd +sin kd ) P g a a a a g a a a a a a a P 4r r max _ g a (A21) P M (r +r) g a Dividing Equation (A18) by Equation (A21), we obtain 22 2 2 (r +r) (r cos kd +sin kd) P g a a a a (A23) max r (r cos kd +sin kd )+r 2 +(r - 1) cos2 kd sin2 kd g a a a a a a Fortunately, this expression can be simplified greatly to the following: p 1 (A24) P 2 2 2 max ae cos kd +sin kd a a in which g=a )2=max (A22) r +r P g a min In Figure 94, a set of universal curves calculated from Equation(A24) show the variation of power delivered to the antenna as a function of the transmission line length, d. - a 138

- THE UNIVERSITY OF MICHIGAN 7274-1-F RE FERENC ES 1. Dute, J. C., J. E. Ferris and R. B. Harris (1966), "Antenna Spectrum Signature DataRecording Techniques,1 The University of Michigan Radiation Laboratory Report 7274-4-T, AFAL-TR-66-169, Supplement I (June 1966). 2. Ferris, J. E., S. E. Stone and R. L. Wolford (1965), "Investigation of Measurement Techniques for Obtaining Airborne Antenna Spectrum Signatures," The University of Michigan Radiation Laboratory Report 6664-1-F, AFAL-TR-104. UNCLASSIFIED. 105 pp. 3. Montgomery, C. G., R. H. Dicke and E. M. Purcell (1948), "Waveguides as Transmission Lines, " Chapter 3, p. 72, Principles of Microwave Circuits, 8, Radiation Laboratory Series, Boston Technical Lithographers, Inc., Lexington, Massachusetts..........L~ 139

unclassified Security Classification DOCUMENT CONTROL DATA - R&D (Security classification of title, body of abstract and indexing annotation must be entered when the overall report is classified) 1. ORIGINATING ACTIVITY (Corporate author) 2a. REPORT SECURITY C LA$SIFICATION The University of Michigan unclassified Department of Electrical Engineering 2b. GROUP Radiation Laboratory 3. REPORT TITLE Investigation of Measurement Techniques for Obtaining Airborne Antenna Spectrum Signatures 4. DESCRIPTIVE NOTES (Type of report and inclusive dames) Final Technical Report 5. AUTHOR(S) (Last name, first name, initial) Ferris, Joseph E., DeHart, Wilbur R., Wolford, Ronald L., Henry, William B. 6. REPO RT DATE 70. TOTAL NO. OF PAGES 7b. NO. OF REFS June 1966 139 3 8a. CONTRACT OR GRANT NO. AF 33(615)-2606 |4. ORIGINATOR'S REPORT NUMBER(S) b. PROJECT NO. 4357 7274-1-F c. Task No. 435703 S b. OTH ER REPORT NO() (Any other nmb.rs that-may beo eaigned this report) 1 0. A V A IL ABILITY/LIMITATION NOTICESQualified requesters may obtain copies of this report from DDC This document is subject to special export controls and eachtransmittal to foreign governments or foreign nationals may be made only with prior approval of AFAL (AVPT), WrightPatterson AFB Ohio 45433. 1. SUPPL EMENTARY NOTES 12. IPONSORING MILITARY ACT IVITY Air Force Avionics Laboratory Air Force Systems Command Wright Patterson AFB, Ohio 13. ABSTRACT This report discusses three areas which are of importance to the Electromagnetic Compatibility program presently being conducted by the U. S. Government. The areas discussed in this report are: 1) methods for obtaining spectrum signatures at a minimum of cost, 2) data recording techniques, and 3) methods for obtaining transmitter signature characteristics. The methods for obtaining antenna spectrum signatures discusses the use of simplified models along with typical results for three different antenna configurations. The three antenna configurations were tested on both a simplified and a precision model of a jet aircraft at a fundamental and four harmonic frequencies. In the data recording section the data format for antenna signature is presented. A recommendation as to the format in which the data should be collected and forwarded to ECAC for prediction analysis is made. A discussion of a technique for digitally recording signature data at a minimum of cost is presented. Under the final section techniques for determining the signature characteristics of a communications type system is discussed and some preliminary results. DD JAN4 1473 unclassified Security Classification

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