388889-1-F AN AUTOMOBILE ANTENNA EVALUATION SYSTEM by Martin Kuttner, Valdis V. Liepa and Dipak L. Sengupta The Radiation Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor, Michigan 48109 +Now With: Department of Electrical Engineering University of Detroit 4001 W. McNichols Road Detroit, Michigan 48221 Final Report 15 January 1985 - 31 October 1987 November 1987 Purchase Order No. 47-J-G19813 Prepared For Ford Motor Company Electrical and Electronics Division 1700 Rotunda Drive Dearborn, Michigan 48121 388889-1-F = RL-2553

EXECUTIVE SUMMARY Normally the performance evaluation of an automobile antenna requires that the automobile be placed on a rotating platform and received signal be recorded as the automobile is rotated. Obviously, this restricts the performance to a laboratory environment. The present report describes a portable automobile antenna system which is capable of providing the antenna response at any desired location. The antenna response is obtained by driving the test car at any desired location around a chosen circle of small radius. The azimuth information is obtained from an electronic compass mounted on the roof of the car. The (commercial) air signal received by the test antenna mounted on the automobile, the signal received by a standard antenna developed for the system and the azimuth information are fed to a data acquisition system which is controlled by a small computer. All data are stored and processed digitally and results are plotted in standard polar plot format. Enough information is provided so that the absolute or the relative (to a standard antenna developed for the purpose) gain of the test antenna can be obtained. The system is portable and, hence, antenna performance can be evaluated in urban or any other desired environment. This is a first prototype system. Improvements can still be made in data storage and signal processing capability of the system. The speed of the printing system is slow at the present and can be improved if so desired. (i)

388889-1-F TABLE OF CONTENTS EXECUTIVE SUMMARY..................................... I. INTRODUCTION.................................... II. THE STANDARD ANTENNA............................ 2.1 Design of the Antenna....................... 2.2 Construction of the Antenna................ 2.3 Measured Impedance Characteristics......... 2.4 Gain Characteristics....................... III. THE SYSTEM DESCRIPTION............................ 3.1 Hardware................................... 3.2 Software................................... 3.3 Operations................................. 3.4 Data Collection Procedure.................. 3.4 Sample Results............................. IV. CONCLUSIONS..................................... V. ACKNOWLEDGEMENT................................. VI. REFERENCES...................................... VII. APPENDIX........................................ Computer Programs........................... Page No. i 1 2 2 4 6 9 13 13 15 23 25 27 37 38 39 40 40 (ii)

I. INTRODUCTION This report describes the development of a portable system capable of evaluating the performance of an automobile antenna. The objective of the program has been to design and develop a standard antenna and associated electronics system so that the performance of a variety of entertainment antennas mounted on automobiles may be evaluated by receiving commercially available signals. The frequency bands of interest are AM, FM, CB, VHF and UHF. Basically, the system compares the response of the antenna under test to a desired signal with that of the standard antenna. 1

II. THE STANDARD ANTENNA 2.1 Design of the Antenna The design of the standard antenna was obtained by using the well-known broadband properties of biconical and discone antennas [1] [2]. Figure 2.1 shows a sketch of the standard antenna system which essentially consists of a coaxial fed monopole using a 5-ft diameter circular ground plane. The monopole element is an inverted cone of angle 2a, base 2b, height h and slant-height L as shown in the figure. For convenience we have chosen a cone angle 2a = 60~ so that the geometry then indicates b = L/2 (1) L = 1.15 h. Satisfactory broadband performance from such an antenna can be obtained over a 3 to 1 band of frequencies provided the parameter L is chosen as [1,2] L = 0.38. (2) where X is the wavelength at the lowest frequency of the band. It is evident that the same antenna cannot be used satisfactorily for the AM to UHF bands of frequencies. We have designed the antenna for the following two bands of frequencies: 90-300 MHz - Band 1; 300-1000 MHz - Band 2. The required parameters L and h, as obtained from Eqs. (1) and (2) are: L % 15", h X 13" for Band II. L X 50", h X 43" for Band I. 2

2- b - 1<.-.. -— I 1 t 50 ohm coaxial line. Figure 2.1 A sketch of the standard antenna. 3

Both antennas use 60" diameter circular ground plane. It is assumed that the Band I antenna will be suitable for the AM-band also. For transportability, the Band 2 antenna and a part of its ground plane is designed as one compact unit; the full ground plane and the Band 1 antenna configuration can then be obtained as simple extension of the Band 2 antenna. The monopole element for Band 2 is fabricated as an inverted cone from a solid block of aluminum; the Band 1 cone configuration is obtained as an extension of the cone height to the required value. The extension is obtained by introducing a number of inclined metal rods along the rim of the solid cone base. The ground plane in the compact unit consists of a 15" - diameter aluminum sheet. It is extended to its full size (60" diameter) by introducing a number of radially oriented metal rods along its rod. Thus, the compact unit occupies a space of approximately 15" x 15" x 15"; the design was such that the standard whip antennas (length 32") used in automobiles can be used as the required extension rods. 2.2 Construction of the Antenna Based on the design discussed in Section 2.1, the standard antenna was constructed using twenty four (24) 32"-long standard whip antennas for ground plane and cone extensions. A photograph of the Band 1 antenna configuration is shown in Fig. 2.2. The antenna has a 15-inch diameter aluminum ground plane which i;: 4

K? 4., ~ ~ 4.~. O~4I' 4P Figure 2.2 A photograph of the standard antenna. 5

extended to the full size with the help of 12 equally spaced and radially oriented whips attached to the edge of the aluminum ground plane. A BNC antenna connector is also attached on the outer edge of the ground plane. A 0.141 semi-rigid (502 ) coaxial cable goes from the connector to the tip of the cone which rises from the center of the ground plane. The cone is made of aluminum and is 13 inches high having a total angle of 60 degrees. The cone is then extended in size by adding 12 standard whips equally spaced around edge of its base. For ruggedness, a plexiglass cylinder is used at the base of the cone as well as three nylon pillars to support the cone. The antenna is also mechanically designed for conversion to a simple monopole. In such case the cone is removed and is replaced by a single whip antenna at the center of the ground plane. 2.3 Measured Impedance Characteristics Impedance characteristics of the standard antenna were measured using a Hewlett Packard 3510A network analyzer and a capacitance meter. Since the network analyzer covers the range of frequencies 45 MHz to 18 GHz, the measurements were carried out over 45 MHz to 1000 MHz. Figures 2.3 and 2.4 show the VSWR characteristics of the antenna with and without extensions, respectively. As expected, the performance of the antenna without extensions is better (VSWR < 1.5) but over a limited frequency range. With addition of extensions the low frequency (45-100 MHz) performance is drastically improved (Fig. 2.4), 6

Figure 2. 3 Measured VSWR characteristics of the standard antenna (Band 1: with extensions) S'1 REF 1. 0 SWR 500.0 28. 165 I I - -. ---t - I. I - -- -'- - -. - -. - - - ____ I II I I I I j I i I c Ir- - I t I i I -.1 I I D I F I 6 I 3,60.I- -- T I i I I -I *-V — ---4 _L. -—. I I I i I - -- I Ii i I i I I — - --. - - -—. - - - - I i 11 I I I II I I.-,I - -- ---.. -- i I f I 4 -— - -- - - - - -- - I - ---- - - - -— i I 4 - - -. ___ /00 600'D I -— I — ---- 4 i i I I - I I I I I I I I -- - +- - - -. i I I I I i. k F~re,HHie /000 STA*,RT'e' c. &. + -.. k1 & C:-H z ~'3H z 7

Figure 2.4 Measured VSWR characteristics of the standard antenna (Band 2: without extensions). S11i SWR REF 1.-0 1 500.O0m / V 1. 4013 __ Vhp I I — I: _ _ _ NiAkR1 45 I 0 IM -o2 1x 714 7 II -----— 4 -—. --- -4 — - - -- --- I I I I II I i -- I I I 2 —*0-~ I' I I -- -1. - I - - v ~ ---~-I I i --- I I i i I I i i I I i I I I I I I i --— I -- I -4 i I i I 6. 'r- — to, I,..f;,..*...d 6 —0 100 STR L F re Ij flk /0c ST RT ") V~ * "~r~ 10 I Iit —; - T-7 -,I. 'IL *a tj J L %'.' % —I- %' - j iLj A 8

although there is a slight increase in VSWR (VSWR < 2) in the midrange (140-800 MHz). Overall, it is therefore suggested that the extensions be always used. 2.4 Gain Characteristics The gain vs frequency for the standard antenna was obtained by comparing the measured response of the standard antenna with that of three different reference antennas when they were illuminated by a signal of desired frequency. The following three different reference antennas of known gain were used: (i) Monopole. The monopole element consisted of a metallic rod of length 108" and diameter 0.75". A FET amplifier with C m 5 pF and Gv = -2.6 dB was used to couple the antenna to a 50 ohm receiver. The gain of the antenna can be obtained by using "short antenna theory" and is given by G (dB) = 20 log [( 5 )2] - 2.6dB (3) where, L = 2.8 m (108"), X = wavelength in meters, ~ = impedance of free space go = 1207T ohms. The operation of the monopole is limited to frequencies below 30 MHz. (ii) Biconical Antenna. This was a standard EMI antenna designed per MIL-STO-461A and operates in the range 30-200 MHz. Similar antennas are also available from EMI antenna manufacturers. 9

(iii) Dipole Antennas. These were tuned dipoles and (three of them) were used for measurements in the range 100-1000 MHz. The dipoles were made by Ailtech. Fig. 2.5 shows photographs the various antennas. The gain vs frequency for the standard antenna is shown in Fig. 2.6 where the values obtained from the individual reference antennas are also indicated. The gain of the standard antenna is found to be low at low frequencies because it feeds a 50 ohm load. With increase of frequency the gain increases and approaches 0 dB (isotropic) at higher frequencies. The oscillations in the results are probably due to resonances of the (whip) extensions and are also evident in the VSWR results (Fig. 2.4) around 100 MHz. 10

Figure 2.5 Photographs of standard and reference antennas (used for gain calibration) 11

12 / 1I-. --- J --- — 1 / I II 7 / / I I I -- I — I I 11 — i - I ` I.1 -- I -- I II" I -i _ —: - -, 07 0~.v I -t 0 -A) - - -Q - - --. -- i —. -.I v 'I< - — q- -9; - i I. 10 I lb - i:X. I L , cf 11 "r I-. — I,) — 1 I I - --- I — " --- 4 —, i (" — I- - I i i ') - -1 - I i -. ocl, i. t r-I 'i. C\j 2q Figure 2 t-.f 0 — I 1 i I N% ",N ""NN N -I 0 I- I - — ~ i - -- - - -- Mea~uredj -sta -da-rcL;ain charact intenn m -?ristics of ________I lhe - - 7,, I i i I I i i I i I I I 0 'I,< i V1 - I I, I i I. -1- i k II I I i I 1 Ri I I Ii 01 %-0 0

III. THE SYSTEM DESCRIPTION The complete antenna evaluation system consists of (a) an electronic package, (b) the vehicle test antenna and the standard or reference antenna and (c) an electronic compass that can be mounted on the roof of the test vehicle. The standard antenna characteristics have been discussed in Section II. In the following sections we describe the other components of the system and give some results obtained from sample measurements. 3.1 Hardware A block diagram showing the hardware configuration of the complete system is given in Fig. 3.1. For the sake of discussion the system is divided into section as shown in Fig. 3.1. The first section encompasses the analog signal path of the system. This includes the reference and test antennas, the receiver and the electronic compass. The reference and test antennas are connected to a receiver which in turn is connected to the HP 3421 A/D converter or the Data Acquisition System. At the present time the receiver is a spectrum analyzer powered by a 12 VDC to 110 V AC inverter. The electronic compass (mounted on the roof of the test vehicle) produces a continuous analog x-y pair of signals depending on the orientation of the vehicle in the earth's magnetic field contaminated by the test vehicle. These directional signals are then also fed into the HP 3421 A/D converter. In the analog section of Fig. 3.1, all of the cables are marked according to their respective function. Since the 13

EPIL digital circuit Analog data circuit Figure 3.1 Hardware configuration. 14

HPIL is a serial poll bus, the order in which the various devices are interconnected is important for proper operation of the system. Currently, the printer is the first device connected to the HP-71B followed by the disk drive and finally the HP 3421 data acquisition unit. The second section comprises of the digital processing storage and the output part of the system. It consists of an HP71B controller/computer, the HP 3421 A/D converter, an HP 9114 3.5" floppy drive and a Think-Jet printer, all connected to an HPIL bus structure for interdevice communication. The floppy drive serves to store programs, calibration and test data. The Think-Jet printer has a 640 x 640 pixel graphics capability and prints the final polar plot. The HP-71B does all the necessary data processing operations. 3.2 Software There are numerous subroutines in the software package, but there are only three main divisions on the operator level. The general layout can be followed from Fig. 3.2 showing the software configuration. We shall now look at each subroutine as it fits in the general scheme of operation (for detailed instructions on operation see Section 3.3). The first main system operation consists in collecting a compass calibration reading. As can be seen by viewing Fig. 3.3, the MAIN module (Fig. 3.3) calls the GETCAL (Fig. 3.4) subroutine which runs through the compass calibration procedure. After answering a few housekeeping questions, the routine starts to 15

Figure 3.2 Software configuration. 16

Figure 3.3 SHELL logical flow. 17

Figure 3.4 GETCAL logical flow. 18

collect data from the compass as the car drives counterclockwise in a circle. This produces a calibration file which is used to correct the angular data for the antenna measurements. The response of the compass in the most general circumstances is expected to be a rotated-and-translated ellipse. After the raw data are read in, they are processed to extract general parameters of this ellipse; its tilt with respect to the X-axis, major and minor axes, and its center are obtained. Since the car's starting position is known, any later measurements can be mapped onto this calibration ellipse. The second main system operation is the collection of the radiation pattern of an antenna. The subroutine invoked is called COLLECT (Fig. 3.5) and it performs several tasks. In the first measurement it collects a reading of the refeternce ciatenna. It then waits for the operator to switch to the test antenna and position the car before collecting radiation pattern data. After the collection run, it calculates the minimum and maximum signal levels and calls the SCALE subroutine (Fig. 3.6), which rescales the raw signal levels into dBm (SCALE must be modified if the receiver is changed in order to preserve any sense in the rescaled amplitude levels). The next subroutine called is CORRECT (Fig. 3.7) which takes the angular data and corrects them using a previous compass calibration result, storing the result. It then returns to the MAIN module. The third main system operation is (Fig. 3.7) plotting the data. Two subroutines are currently resident for this. The 19

Figure 3.5 COLLECT logical flow. 20

Figure 3.6 SCALE logical flow. 21

Figure 3.7 CORRECT logical flow. 22

first is called QWIKPLOT and it plots a rough character-oriented picture of the antenna radiation pattern; the results do not have a high level of detail and are most often used as quick checks on the validity of the data collected. The second subroutine is called SLOWPLOT and it produces a pixel-oriented picture of very high resolution. Its main disadvantage is that it is rather slow (on the order of about 15-20 minutes). The user can specify a reference value for a particular plot so that two different plots can be compared. 3.3 Operations The first program that has to be run is the MAIN module. This sets up the user-defined keys on the HP-71B and primes the system to response to the user. Note that if any of the subroutines mentioned in the SOFTWARE section are not in RAI1 then eventually there will be an error and loss of data could result; error handling is minimal due to the lack of memory on the HP71B. Make sure that all subroutines are loaded on the disk as well is SLOWPLOT is invoked; virtually all other subroutines are cleared to get enough memory to produce the image. In order to collect meaningful data, the first thing to run is the GETCAL routine by pressing the appropriately labelled key. The first question it asks is how many points are to be taken for the calibration. Although it's better to take as many data points as possible memory constraints give an upper limit of about 100. The second question it asks is what to name the calibration file - usually this is in the form of: FCxxxx where 23

xxxx is a four digit value. The second question it asks is for a title to the calibration file; it is also a good place for comments. The program then waits until the car is pointing in the starting position. A good technique is to slowly drive the car in a circle and when the start position is reached press ENDLINE (this prevents bunching of points as would happen if the car has to accelerate otherwise). Practice is a good idea to get the feel of how long the system takes to acquire the necessary number of points. After a few seconds of crunching, the program will save the calibration file and return to the MAIN module. At this point the system is ready to take data for an antenna. Press the key labelled COLLECT to start. The first question is how many data points you wish to take - usually just the same number as the calibration routine. The program then asks for the data file name (usually FDxxxx) and the file title, which will be displayed on the polar plots. The next question is whether the reference antenna is connected to the receiver. If not, connect it and then press "Y" followed by the ENDLINE key. The system will then take the reference antenna reading. After this, connect the test antenna to the receiver and press ENDLINE to start taking the test antenna pattern data. When the measurement is finished, the unit will beep and process the raw data just taken. It then asks for the transmitter frequency and location, followed by asking for any comments. When the data is corrected the system will ask for the appropriate calibration file to use. 24

The corrected data is then saved. This procedure can be repeated a number of times, but memory constraints will cause an OUT OF MEMORY error to occur; if this happens, flush the memory by purging all the current data files -- do not purge the calibration file. The other main activity is to plot the data out and see the results. There are two programs for doing this; QWIKPLOT and SLOWPLOT. Press the appropriate key to run either one. QWIKPLOT is faster, but the resolution is rather bad, especially if the antenna has a deep null pattern. SLOWPLOT is much better in detail, but takes about 15-20 minutes for a 100 point data file. When some changes are wanted in the acquired data EDITFILE can be called (Fig. 3.8). This program allows changing file names, comments, reference signal levels, etc., that otherwise may require repeating measurements. 3.4 Data Collection Procedure As mentioned in the Introduction the purpose of the Antenna Evaluation System is to obtain the performance characteristics of an automobile antenna receiving a desired signal. The system developed is capable of producing the complete horizontal plane response of the antenna to commercial signals available at a place, i.e., in effect it produces the horizontal plane pattern of the antenna mounted on the car at the desired frequency. The system requires the following data to be collected systematically at a place where the antenna response is desired. 25

EDIT SIGNAL DATA OR CALIBRATION DATA ENTER CALIBRAT I ON FILE TO EDIT CHANGE: FILE NAME FILE TITLE 1st COMMENT 2nd COMMENT CH ANGE: FILE NAME FILE TITLE FILE COMMENT ORIENTATION ANGLE CHANGE THE REFERENCE SIGNAL LEVEL CHANGE ONE OR MORE ANGLE VALUES CHANGE ONE OR MORE SIGNAL VALUES Figure 3.8 EDITFILE logical flow. 26

(a) Compass Data: With the compass placed at the roof of the antenna and connected to the system as described in section 3.2, data are collected as the car is driven slowly around a circle of convenient radius, the center of the circle being approximately the desired place. Remove the compass. (b) Reference Antenna Data: Place the standard or reference antenna at a convenient place near the circle mentioned above and connect it appropriately to the system. Then collect the data appropriate for the desired signal. Remove the standard antenna. (c) Automobile Antenna Data: Connect the antenna appropriately to the system. Collect data appropriate for the desired signal as the car is driven around the circle described earlier. Remove the antenna connection. At every place where the antenna response is desired, procedures (b) and (c) be repeated for available signals of every frequency and the data be stored for later processing. The system then processes the data and produces as output the polar plots (in dB) of the antenna response for each frequency with the response from the standard antenna and other significant levels indicated in each plot. The absolute gain and/or the gain relative to the standard antenna for the test antenna can then be obtained directly from the plots. 3.5 Sample Results Using a variety of Ford automobiles a series of antenna response measurements were carried out with the system and at a 27

number of locations. Here we present a few selected sample results for the Ford NM-12 automobile obtained from the data collected at a location near the University of Michigan Willow Run Laboratory. Test antenna used were the standard whip and a bent whip (bent approximately 12 inches from the pillar). Data were collected with commercial FM signals at 91.7, 95.0, 101.1 and 105.3 MHz available at the test location. The resultant antenna response plots are shown in Figs. 3.9 - 3.16. Each plot represents the signal received (in dB) by the NM-12 antenna (whip or the bent whip) as a function of direction or azimuth angle. In each plot the 0~ reference is in the forward direction of the test automobile (as shown by the inset) and, for convenience, the direction of the source (i.e., station originating the signal) is also indicated. From these results it is observed that the standard whip outperforms the bent version at all of the frequencies except at 105.3 MHz where both versions perform about equally. 28

29 00 N. i -...... - - - — 7. f I "IIN." I',, I',,.11 // /I Ii /7 / K / K ~' N 'N 'N 7 N / N K / ZN I I i I I I qOv i t I iI I I t, I iY, I? I i I I i 11 II i iI I i V I I I 'N / / N / 7 \ / N / 'K / / N I 'N' I'll I --- -.-I --- 0 I' I /I- - --- I i i I i 0 -.190 11 II NX,, I " —" "... \. /.11 III -... 11 X, 11 l\/ I i /", "\. v 4 'N,- -. N I'll 7 I Zoo VQF fu I I": NL LL 4L2 dr. Figure 3.9 Measured horizontal plane radiation pattern Ford MN-i? whip antennia at 91.7 MHz.

40 Z0 74 CD/ AL \Li C\j I N r)-~ - 4a0 ro o Cw r 'i- 4-).43) oSC) r — 0* (a v S.UL77U

3 1 I /( I /I / /1 / / 7' \ / / 0 / I. i/ / /1 NJ --- 'I J 'so"4 FOF IN.;. — i? JTOT. P1 0 6TH1i OT I RT. LI DEL h~LFL~LN.Ern'~~LN E - LEYLL EL I HT IK A LOEL -4S5.7' dEm. - E J i n. Figu're 3. 11 Measured horizontal plane radiation' pattern of Ford MN-12 whip antenna at 95.5 MHz. I 'i i -) - i-, i.] . -,. ) -i -j L i, I.

32 0~ i II 0.1 —.- 50 1 1 e I -- \ / 1,'1," iNN.."ll FZFZ;~~L' 0 "4F ii QQ~r ~L i L U FTF- El I, - LE'LL: i LEEL: L L-H -I E L. -47i.8 JBIY4. - F d 6ffm. Figure 3.12 Measured horizontal plane radiation pattern of Ford MN-12 bent whip antenna at 95.5 MHz. Li. I4 1 -1if -~' -Li ', 'r? r-. ni,

33 C a '4-111 7 I A -1 - I .1, -.., ---- ---- "'A.,; — l. N I f I iI 6*27 ---- L I i 'II ii I i; IiIII IY i i "I i If 1, I I i i I i I / K / if CD (= ') 0 -1 - -1I i I I i I I. i, I j, -- - f ), I I 'I II I ", "I I i -— 1900 1 1 i i i 11 j )i I VN..7I I I / I~ iI!, I \ /, 11 ik:," 11 x / = - - 7.7' K. A' j'r' H THF. 1 0 LIi 11-1 -II ---. i L I " ItEjE -z r I ~, 'i JrI ULLL -43. 7 dBii. -- F.?'dn Figure 3.13 Measured horizontal plane radiation pattern of Ford MN-12 whip antenna at 101.1 MHz.

34 0 0 / / / f I / II I" — 4 0 7/ N / 7 / N T-IRT, r - (-~ rf L9 f I H 3 I I I I 1. I. LtJ -. tJL I I:.-I I "LI' -, " Li "', I (- i, 1 1-1 1 - L-I~-I.! l'- 1I- 4L LL r Lt.L ri HJB.. L 4..L' 'E.- 4.4 dBm. ~f].3; tiE-. Figure 3.14 Measured horizontal plane radiation pattern of Ford MN-12 bent whip antenna at 101.1 MHz. C " i I _j , '.

35 0 0: I2~ ji1 Ii I ( 0 i I I I j i Ii r I I I / I flU- I 1 7F HOT SrF F b, z;- J LzrzhLKTL - z Er. F I:013Il~Q I Iz IrU~ r z 105.5I MI,. j ~ I f., IjI i.-I DEE L-SI i '-:31 -, nN YEII,~lr rl ~I iA LEV)EL T E FU 1 - 'T E" I f~I,414 r114 L E UE L, -54..0 d3rni. -S55.0 dBmr. -b.5.0 diBm. Figure 3.15 Measured horizontal plane radiation pattern of Ford MN-12 whip antenna at 105.3 MHz. I ''i i. f . "',;. r I- -, j; -, u P-1. t ".) -,

0 C~j rIN S- U-) tO CD ~4 -0 c C- 0- 0 4-3 -P( a 0 -ci) -a --- 4-4 3: (A ~ 43J cot c W a, - ' —4 a,) 5 -U 0 1 ~ fL t- IfCT —,, iIC — f C) I Lij I 17 Cl f- r r -,, I-L;- I r;-) --- I II.:D L J. I LI Li C - L U Lij Ci - II " L.U f U-) UTi J LU LLi LU Li I -.4 -1 — l i-1 I. 1 4 L ii

IV. CONCLUSIONS A portable automobile antenna evaluation system has been developed. It consists of a standard antenna of known gain and associated computer and other electronic systems. The system can be used to determine the response of an automobile antenna to available commercial signals at any desired location where the car can be driven around a circle of convenient radius. Although we have used a spectrum analyzer as the receiver, the system can also operate with the automobile receiver instead and this should be investigated further. The present system is slow due to limitations of the computer used. The speed of the system can be improved by using better computing and printing equipment. - 7 J) I

V. ACKNOWLEDGEMENT We are pleased to acknowledge the benefit of several discussions with and active participation from Mr. Robert Schuessler of the Ford Motor Company. 38

VI. REFERENCES [1] R.C. Johnson and H. Jasik, "Antenna Engineering Handbook," McGraw-Hill Book Co., N.Y., p. 27-13, 1984. [2] A.G. Kanodian, "Three New Antenna Types and Their Applications," Proc. IRE, Vol. 34, No. 2, pp. 70W-75W, February, 1945. 9Q

VII. APPENDIX COMPUTER PROGRAMS 10 l 20,0! r*..40 70 ' cO! 1 00 ' 120 2 SJ 0! 36! 1 J0 __ -' CS '! 240' 0 *! 2 0 i -jl 0! 9.! -4 '! ~* /' 0 3:0! IhELL 1s lte global environment under which all data acquisition per- tions run. In effect, it is the user interface. i. nc iudes all the necessary functions that deal with the calibration, collection, correction, and 5Lubsequent saving of field data onto the disk. h 62,a: 1'ic nOl I i n3: f. i ' )., 4 ~,_ L i. U []$ 11$ '': I 4 $ i ' ' i, F2J: C2^S: C3$: C4$ ''.*, \ '. f\..1 ' 'la jor axis of ellipse. I'linor a, is of ellipse. Test antenna maximur ilet antenna minimum Reference antenna signal Correction angle for the data (derived in the CORRECT,UbrtLii inc 0-=do not have a loaded calibration correction file. Nu 'mbe r" of antenna data points. Number of calibratio, data points. Hbcissa of calibration ellipse center ( derived in the COFiRECLiT u OrdiiJ.nte of correction ellipse ce rlter (derived inr- the lCOkf:RELCf Ior-e and per:iod of error nrotif icti on beep. L._i t ing for operator input tone and period. a ta filename Cali brat ion filename. Data fi le title. Ca iLor ation file tit le. upe rator comments on antenna data. 1tachtne comme nts on antenna data. Operator comments on calibration data. chine comment.s on calibration data. CLom-iarnd array used in the a ut oansu er mode. -ompass response which has been comfpen sated bay c- Cr-r t C i:'LECT LuL rr ntgs of an tenna data poin-ts. i' n. u 1 tude ot an t e n n a data point. Unc, mpensated ( rau comFpass input, def ines tilted, off-centered ellipse. u era- tc -r deci ion input..4-i iJI "l - 4 - Lj i I- i.14 - i-, I-.. 't -, -1: -1 4 U 4 11-1.., -t i, `-, 'ESTFR LL ': C FLn 20 9 3 CFLhG -'3 @ CFLFiG 41 0 Reiniiit/11 'e -, t e Di $[l i ',T I L, T2$ 0 ] $[ ],F21$[ ], $ 6 C15$[0 ' ],C [ ] C35 ],C45 $ ) " —O TI L i,, U0,,B,R1,F1,B1 L 'IF.T 'l t i. g or- command...';" 0 n$-rn5$L,I ] u' E r O-FR 40

a L 2`L - o 20 Uer ija u,:ing a iacrofle I I tUT (YoanJ f IlIe n a eY 'f$ 0 re' ~ 42it TO R h C R EHO) 4 12N 0 0111 C kH)[SE I RCE h 412;> Lk') _', I-103E FT tl OS I 412) TO $ F C>4~ FEi T CuC~ fS SI GN 42) TO * r~ KGrJ 'RLOD' F,.etart usinzj thes updated' Nacr~o flie. iDLi LI EUFR ie a cali'brat iorn. XOI~IF i7 O P( )' NF2$ Cli C4$ T`$ L C$ ) to I n — Jr- J EJ K lJj LIUK plot ofa file:. C C -u~ -il.L- 4 ' THLI J ri D-L 1 -4I1111Di,- IdI IT OL) i TIT1 FI CKP Lv Tl I L1II T 1 'L1" L F L L I J-L t V L 0.lFpo o l~ i J4L J It-fF, F I I T 1,1> 'I TOL ' FSLO PLOT L;- -J 1IECOLC J UG ECi UG OFVL L-1-K R )Fh C 01 C2i, TWF CC4WTZH lJ L Lt T i' aTn OYCORC: OCRRC. YtL t tLII I Ij H4 IKFO OYCLET2T OLCF ~ CI i~_W fu F LiWD'L0' 0 COPY CORRECT:? TO CORRECTT t I 01 Lii D TOKKI L 4 1

1 060 070 080 0ju 1 00 10 Ilu I JO 40 1 50 1160 1170 1180 11 80 1 200 1 210 1220 240 1 5O 12 '0 I 2ou 12 i u 1 270 1 740 I E1iF'PLf'TE': COPY TErIPLT IE: 2' TO TEHPLfITE 0 CALL TE1HPLt)TE PF LF.GE TEPL8TJE 01 ME T U R I'-FFILE' to re a f IlIe o n G" L.. i NFUE 'File riame? ';IF$ 0- IF F=' ' THEN RETURN T r4FLK 'Ne~o filename? ' N$ 0 IF N$' THEN NA$=Fs CC;PF- Ft TOD N$0& (3'SET F LL E T ra n -f e r a — file f rocm d i aLD:- t o me m o ry N FULIT F i name?;F$0 IF F$='' THEN RETURN" NFINPUT T i lenamie? ' N 0 IF N: -' THEN N$=F$ F-OP' F TO N$ 'PLOTPhRiS' Rede-fi1ne t he de f aulI t SLOUFLOT plIot t ing paramet [F D$" t"0',IOD$. R THEN 1250 I!NPU~T1 'Ov-id namie? ';61$, 0 INPUT 'hmplitude ref. ('d~p-)"? 'F IPT Otifrnc?';83 0 INPUT 'Oot per dffi? ' 83~ 0 0 5 N I FT~NumID- r Oct out1 s of th loP (U ' a IIILLER3f I time.; USE OFF IFD611H0 RIJ rIThPOPR hjI-'1# T P~lhS, f- = I -. 42

L-Iter ofX'Y olane and of elliose;. iJ, ff tj l arables used in the calculatio o nX cd <3. 1-ILJ h, 1 C vt Or Var iab~le ubse:d ini1 ma Qir a>.X I cOILcuLA rof elliobte dcet arinin nco. i-nto commiand f Ile I s a ctivea s 3Iih br.t i on f IlIe com m e nt is5 a c.t vE.I' s1br-at orn f Ile tItle is actv. Hubrof catiibrati on t s si b r-t 1o n f IlIe rlc me fom i Lsl.br'ation file tit le- Flag (1- t~ i L b at io)n f IlIe c ommre nts. C; ~ ye (I T I' r V2-iI3FF ~33 ~YJP P P4 PF2 I I I(I,1 3HL4 2FKI ~'>FFF. 4 3

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4i &AT E LL' c' TlHE~l LHLv 1144fPUT 'CAL.FL COMMNT? IE[ J F Fl ti'qJ; L 1L F LLE GF itt~ F2 Li Lit I LLIuL L uiriD FL h 21 L -i ALe fC' Lr L or- the -ifiar d r+FAKi L > LIL N2, ip L i% L L - 7K),1$ C2~E Ti F2 Ai AA Ni7:nad ft t ~c 1 J — L t- f IlIe c Can-.1je7 r-t Ist a ti v. I t ta fil ctitle a KY 7 7l-LI fue fIle nctame. 11f OI 1at ic 5~~. Liat - P ' tie- t Iitle f lag> I ~cstive reut I taL -. Ie.c file oamnert fIat> L I t. ttit: t IUfL II 0 HEN l PI1Ifl T 1 L 1,4 F i I 1LE- O F LDAtTA F) IN T S?' N I 141 1~~ 41/ T( 4 'L~i i I L ihhF I L' I fI l F 4 i-'' LD FI 'L - t IL mI adnp L 4i F ADTLiI 11 i 4114L I THILi T AlE i'4LZ4T 57 4 5

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14I- FLG 3 THE IPUIT 'C hL F I LE N M E?';F' EL 3 &QQT F H OTFG 30) THEN EEEP Co DI"-,P ' NEED HCTIY) EL. FLL' D OTFLG( 370 T THE N C 0T O 'GLO DD' '' i. 73 LA i 'D1IN) i - TD rrei'Y utF 1 Lf i t ft L L.~~- EOT c OTIHE L AU0 1 0 U - rt4 iiLt dL f t he JU 11 UK uLv 45ri'. ii~ v lth~ cd t t 0 O CJJh t LiLC L '! I ' IL tai r~0d t Ip- L0f-crwer v Lth Ipt~ft I 1 ~ L T HcC E FIo DN U 10fudiI 47

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43 Tihii c -,ion r-defiLne the default conditions under- hich LU runs 450 'r rit ii PUT 'Ne w auto file title' IiR' 4?3! R iit'ialiie the 5yster' contrCl fi,'.Cj5. 43; hUH i=20 TO 24 6 CFLH6 I L~ NEXT I t....,5 '0F t0- -' L- R i- LO i TO bJ IU, r-IciuuC';C$(L) i i.:k the user f'or the module to t4e e/:c'. C4- i — T i i L' IL f L3 P- 'ERRF;'- C, ND OvFL L; t I i0r0 u -Tu t'P n, iU E CLLL,.T'' U efine tLhe calibration auto ur' pcr ar,',ete.. j t —, tj L. t L s L Lt U iv L,"" 1 h i I I L Li u i u i r, ii b',i" ^ i',;,0,',,W L-L. po U*,?'.;<D L }-R | r.'T-i:$(N, )80 I IPUT 'i't i cai f. iienane.;D -s L.L+i ~ C$(L '=D b 0 INPuT t ' -Rques ttl7e input ',;D' C F UD I i iJ-'y' TiHL LN -L+1 ' C-' ' aiO IP "T 'P --- rient input{t C J IF D$L I 1 J=Y" THEN L-=LI - C$(i...; ' L O 'u '.,-' L the collect autu r un p ara fietur jw I r data poitY, N C L-L -t U\ L '- F 1r ' I '' L i ' - 1 i E t a i i i t a 1 i e a1 U a i L i t; L L -uL U * be;Lv Q Ii i * i LILRq e t Iti[l Jin ut ^ U4 0 IF DLi E i J-,' I Iine L-LTI U C-4E<L ' — i- i NPU -R -ue- comment inpu t Ut L IF U L i J Y' I LN L-L C L.-.; o 1; T P T F A L. LPT I re tihe auto run qwi po It pa Ir ai etir-' Li 1 i i — i I!. T4 L U f D ne the auto run parameters for- slo.plot. -. h.. -. L.i U, o4i U\L, I dta p'N'-b u ii'. 1i-' L ' ~-,it. iai datao riu n ap d r a P'ILe tie r t'o=011.. L) L. L - - U ih i - L. ri.. -i-\ L.; i i - ':::;-. t. i re' ipt" C: t - t [ i,i T -. Un Su ) L ter rat L' e, * - u D C' - i i ' -' - -; - E ';' i-. L,- - O - re au o pr' J am!, a.r, S,4 IN iUT 'rL l ";F4i,0 IF F4o-' 4 THEN,40 -... -... — -' -.-' ' tt- i < F'{ iii i j;Cj'5 j, 57

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