Technical Report ECOM-01521(E)- - P October 1t 965 LOW NOISE TUNABLE VHF FREQUENCY CONVERTER DESIGN 1st Quarterly Report 1 July 1965 to 30-September.1965 Report No. I Contract No. DA- 8-043-AMC-01:521(E) DA Project NQ. 5A 6-7b19i-D P902-02-05 Prepared by P. J. Kan. P. Greiling W. B. Ribbens R. Talsky COOLEY ELECTRONlCS LABORATORY Department of Electrical Engineering The University of Michigan Ann Arbor, Michigan for t. S, Army Electronics Command, Fort Mormouth, N. J.

TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS iv 1 PURPOSE 1 2. ABSTRACT 2 3. PUBLICATIONS, LECTURES, CONFERENCES AND TRAVEL 3 4. FACTUAL INFORMATION 4 4. 1 Introduction 4 4. 2 Theoretical Studies 4 4. 2. 1 Tunable Up-Converter Design Theory 5 4. 2.2 Coupling Network Design for Pump and Signal Circuits 9 4. 2. 3 Unwanted Sideband Eflects 13 4. 3 Experimental Studies 16 4. 3. 1 VHF Up-Converter Experiments 16 4 3. 2 UHF Up-Converter Experiments 20 4. 4 Conclusions 25 5. ilA'OGRAM FOR THE NEXT IN'IERVAL 26 REFERENCES 27 DISTRIBUTION LIST 28 iii

LIST OF ILLUSTRATIONS Figure Title Page I Equivalent circuit of a lower sideband up-converter: (a) circuit diagram; (b) the signal frequency equivalent circuit; (c) the output frequency equivalent circuit. $ Equivalent circuit of an upper sideband up-converter: (a) circuit diagram; (b) the signal frequency equialent circuit; (c) the output frequency equivalent eirut. 3 Signal input coupling networks for parametric up-converters: (a) the lower-sideband up-converter, and (b) the uppersideband up- converter. 12 4 Possible circuit design fur up-converter signl input coupling network. 13 5 Frequency spectra of signals presert in a tunable parametric up-converter: (a) with a fixed lower-sideband output frequency, and (b) with a fixed upper-sideband output frequency. 14 6 Equivalent circuit of a geferal paramuetric up-converter: (a) single frequency circuit; (b) iowtr — sideband tircuit, (c) upper-sideband circuit. 15 7 Block diagram of experimental setup for VHF up-converter. 18 8 VHF tunable upper-sideband up-converter transducer- gaT as a function of signal frequency. 19 9 VHF tunable lower-sideband up-converter transducer gain as a function of signal frequency. 21 10 Block diagram of experimental setup for UHF up-converter. 22 11 UHF tunable upper-sideband up-converter transducer gain as a function of signal frequency. 23 12 Transducer gain of UHF upper-sideband and lower-sideband up-converters as a function of signal frequency. 24 iv

1. PURPOSE A study is to be conducted, consisting of the following: 1. An analysis of independently-loaded parametric up-converters with the output taken from one sideband, will be undertaken to determine optimum design with regard to: gain-bandwidth product, noise figure, gain sensitivity, and dynamic range. This analysis will be corroborated experimentally and will result in "breadboard" amplifiers in 30-300 Mc, 300-1000 Mc, and the 3 Kc-30 Mc ranges. (The frequency ranges listed here are in order of importance.) 4. At least one'"breadboard" amplifier (highest range) with a suitable IF output reflective of the results obtained in the research investigation will be supplied upon completion of the contract. 3. A study will be made of the design and realization of wideband tuning circuits for varactor diodes for application to up-converter design. 4. The relative merits of various down-converters, including tunnel diode mixers, will be considered. However, no development work will be done on down-converters. 5. The effect of tunable electron beam osclliator pump sources on converter noise figure, and methods of reducing this contribution will be studied. The application of available solid state tunable harmonic multipliers will also be considered. - uch sources will not be further developed. 6. Methods of achieving pump frequency stability will be studied since the application of tunable up-converters strongly depends upon this stability.

2. ABSTRACT Studies have been carried out on the design of parametric up-converters tunable over a signal frequency exceeding oneoctave. Equivalent circuits have been derived for the parametric networks, taking account o- simultaneous propagation at the upper and lower sidebands. Circuit designs giving constant transducer gain over the frequency range have been investigated, and wideband pump and signatoequency coupling networks have been studied. Experimental studies hav'e l:e<n iditiated on oth lower and upper sideband up-converters tunable over the 30-300 Mc and 300-1000 Me ranges, having an output frequency approximately ten times the highest signal frequency.

3. PUBLICATIONS, LECTURES, CONFERENCES AND TRAVEL Publications and Lectures: None. Conferences and Travel: Dr. P. J. Khan conferred with Mr. J. Walsh of USAEL at Fort Monmouth, New Jersey, on July 14, 195, regarding this contract. Conferences were held at Cooley Electronics Laboratory with Mr. J. Walsh of UtAEL on August 26, 1985, and with Mr. S. Stiber of USAEL on August 27, 1965. 3

4. FACTUAL INFORMATION 4. 1 Introduction Research studies on this contract were initiated during the pat quarter. t was decided that these studies should consist of parallel theoretical and experimental investigations. The theoretical studies are directed toward the goal of determining performance limits and design procedures for up-converters tunable over a wide range. Consideration of sideband frequency generation indicates that tie design becomes appreciably more difficult when the tuning range exceeds one octave, The theoretical studies carried out during the past quarter are reported in Section 4. 2. The equivalent circuit approach to parametricallly-coupled networks has been developed to gain forther insight into the operation of a tunable up-.converter. These circuits are discussed in Section 4.2. 1 and are shown in Figs. I and 2. The factors which influence the design of pump and signal coupling networks are examined in Section 4. 2. 2. The equivalent circuits are modified in Section 4. 2. 3, to take into account the propagation at the unwanted sideband frequency. Titc tfet ct thlo; l.s propgation is as~sessed. Experimental studies on buth the/ VHF and the U-hf up-converters are reported in Sections 4. 3. 1 and 4. 3.2, respectively. These studies ihav provided experience in circuit techniques for parametric up- converter,optra ton and have indicated the areas where future research should be directed. 4.2 Theoretical Audies The theoretical analysis of parametric up-converter circuits has been initiated to derive limits on up-converter performance in regard to gain, tuning range, and noise figure. This analysis also provides design principles for use in the experimental studies. The analysis is not yet complete, but it does show promise of providing much useful information about this largely unexplored subject. General equations for input and output impedances and transducer gain, when frequency conversion occurs to both the output sideband and the unwanted sideband, have been derived. Study of these equations has 4

indicated the need for further investigation of coupling networks, with unusual impedance characteristics, to obtain constant gain over the tuning range. The effect of unwanted harmonic sideband components also rtquires further study. The;nmlysis 8has thus far neglected harmonic elastance coefficients. However, it will be necessary to study the second harmonic pump conponent to obtain an accurate theoretical model of a stronglypumped up-converter. 4. 2. Tunable Up-Converter Design Theoy. The design of parametric upconverters tunable through, variation of the pump frequency has received little attention in the literature. Emphasis has principally tben placed on the design of wideband converters through the application of broadband matching theory to the design of coupling networks at signal and sideband frequencies. Some tunable up-convertcer studiet have been reported by Matthaei (Refs. 1, ~4, who developed a unit converiiig the 760 Mc-t'140 Mi band with a pump source mechanically tuned to maintain a constant lower-sideiun.td iutput frequency of 4037 Mc. However, no limit has been found for the product of gat.n and tunin g range, now has an optimum design theory been developed for the parametric c:overter. Consequently, theoretical:idy th t t nh tnablte pairametric up-converter circuit has been initiated to investigate the possiible performance thro.ugph loptimum circuit design. The analysis of a lower-sideband parametric com'vrtet r't, X t, ual.tt, 1r tiw a.s.umptions of fundamental-frequency current pumping;tit opten circuit terminations at tht unwanted sideband frequencies. yields the equivalent circuit show n in 1 ig. 1 The tuned circuits are assumed to be sufficiently selective to avoid )powir dissipation at uen:anvtd sniebtnUid frequencies. The higher pumped elastance coeificients. S., S3.. a, arre assumed to be zero. A similai analysis for the upper-sideband up-converter results in tile equivalert ircutt shown in F ig. 2. In general, a practical parametric up-converter circu!t will have significantly greater complexity than the circuits s-hown in Figs. i(a) and 2(a). The diode mean elastance, S, varies with the pump level anld, under large signal conditions, with the signal level. Unwanted sideband components are not completely suppressed by the microwave structurie. Beeause of the parametric mixing process their propagation affects the output 5

(a) LD ZJ+ jL Diode Z I:mR1 +R+ J(w1,L- -) 1I S So + S cos upt so z2Z R2 + Res..,,2L2 - 7 ) ZaSI~+RII1~Z~,) f- + f2 1 2 lw2Z22* (b) (c) Fig. 1. Equivalent circuit of a lower sideband up-converter: (a) circuit diagram; (b) the signal frequency equivaletnt cilcuit: (c) the output trequency equivalent circuit. at the desired sideband. Because of the parasitic elements associated with the varactor diode mounting and also because the need for broadband matchlnr and impedance transformation in these circuits, the tuning networks at signal and output frequencies are generally more complex than the simple series-tuned circuits shown here. Nevertheless, these circuits provide a useful starting point for the analysis of parametric up-converter circuits. The general gain expressions and network properties, such as input impedance and output impedance, are readily otrived from these equivalent circuits. For the lowersideband up-converter, the transducer power gain GC 1 is given by: 6

4 Q11 R1R2 R2 4' Il R 1 d.s Gu = 14 (1) z z * L21 Q QBL R 2 2 S. where Q iR ij vJ.R I s (a) Lt L3 1 3: I I i I' I I I i _L_ Signal Diode Zl 1 Source r-q 3 Iload _J _ —J s + Rs.+ j (w lL- So + R + j (33 L-S) S' 3 3 w Z33 = R3 =S S+ S cos U' t o 1 p f + 1:: f3 1 2 (b) (c) Fig. 2. Equivalent circuit of an upper sideband up-converter: (a) circuit diagram; (b) the signal frequency equivalent circuit; (c) the output frequency equivalent circuit. The corresponding expression for the upper-sideband up-converter is: 4 Q2 R R3R 2 I 11z 33 1131 s 12 (2) 7

The input impedance expressions come directly from the equivalent circuits of Figs. l(b) and 2(b), and are: Qi Q,1 R,2 Zin = Z- ll- for the lower-sideband up-converter (3a) 22 l Q31 Q31 Rs Zin = Zll+ Q 5- for the upper-sideband up-converter (3b) 33 Examination of these expressions immediately indicates some of the problems associated with the design of a tunable up-converter covering a wide tuning range. The output circuit parameters, determined by Z2 and Z33, remain constant, since the pump frequency is adjusted to provide constancy of output frequency. However, the parameters Zl and Q1 are dependent on the signal frequency. Their variation with frequency introduces a corresponding variation in the gain characteristic. The situation here, where the signal frequency varies in one instance from 30 Mc to 300 Mc, is markedly different from that of the simple up-converter where the bandwidth is typically around 10 percent. Calculations carried out for the 30 Me to 300 Mc converter with an output frequenc; of 3000 Mc show that a typical lower-sideband up-converter adjusted for 15 db gain at 30 Mc, will have a gain of -9 db at 300 Mc, assuming that Z1l remains constant as the signal frequency is changed. Likewise, an upper-sideband up-converter adjusted for 15 db at 30 Mc will have a gain of -0. 2 db at 300 Mc. These figures indicate the magnitude of the gain variation problem, and also show the comparative sensitivity of the lower-sideband circuit to parameter variations. It is apparent that wide-range tunable up-converter design requires some form of compensation for the reduction in gain caused by increasing signal frequency. Ideally, this adjustment should also maintain the low noise figure of the up-converter stage as the signal frequency is changed. The solution to this problem is not usually found by the appropriate choice of the impedance levels at signal and output frequencies. Adjustment of the lower-sideband up-converter for about 10 db gain at 300Me would result in oscillation 8

as the signal frequency is reduced. When a similar adjustment is made for the up'ersideband up-converter at 300 Me, the gain rises with decreasing frequency but the upconverter stage noise figure also rises. Several ways to achieve gain constancy with variation in the sbgnal frequency include: the design of a suitable signal circuit so that Z I decreases with increasing signal frequency; punmp circcit design so that the amount of pump voltage applied to the varactor junction and, consequently, S, i:n increased as the pump frequency is varied to accommo — date an increasing signal frequency; and, appropriate loading of the unwanted sideband, which varies over a frequency range twice that of the signal frequency. Each of these methods is di5scussed iln some detail in the;u Slcc(.tdinlr sections. 4. 2.2 Coupling Network Design for PumE and Signal Circuits. The design of coupling networks for pump and signal circulits requires the application of broadband tuning methods, because (o the wide tuniin, ri\.;?:. ec:ing consiitlert.:. The design is complicated by the parasitic elements associated with the diode package and mounting, and also by nonlinear effects occurring in low-loss networks. Pump circuit network desion oi:v'io -,;.frltiid out t.sing broadband itpedancematching network theory to derive a netwlork matchiig the- source resistance to the diode series resistance. This design negl(r-t t}:c'iSiotHf.i ot[h (n;iw(t'-oil,.i\.'i. resistian ce introducedt: into the pump circuit by the f're:utmnly tcoinvrs;lnt pr-c(t.es, s;i:-e this resistance is usually small compared to the equivalont. s isries resist.lntce. Assuming that thtl diodie may be represfroti-t d by a series PtiC netwo, Ik, t 13 possible t.) apply'.'l'ibviStchet'tf tatching networs'k desitn theory (I[Rf. 3) to t lhe -nyco.mlUi-atulll. t._ut:' fs t ihe- ump c irctuit insertI 1o lo-ss associ ated with a given degree of broadlbanding. Tilw omrputat on is; carried out in terms of the parameter.. 6, defin(:i b}y 6 = h: —-— f.,:e tR iand C ar - the values of the equivalent 2"b parallel R C network. The diode series R C network, with parameters R and Co, has a f 2 S value of 6 = -- where f is the center frequency of the pump circuit, and f is the h c diodle cart;i' irequency defined by fc =- - s o A punmp circuit designed for a 30 -300 Mc up-converter with an output frequency:i 3000 Mbte.. sing a diodeo with a 50 Gc cutoff frequency, has an insertion loss of 1. 6 db when the n-:twork has one tuned circuit, and 0. 4 db loss when there are two such circuits. The 9

corresponding figures for a 300-1000 Me up-converter with a 9000 Me output, using a 100 Gc varactor, are 0.7 db and 0.15 db. These calculations neglect the effect of loss in the pump circuit, and lso take no account of the parasitic elements characterizing the mounting of a varactor diode in a coaxial or waveguide transmission line. Both of these factors will tend to complicate the matching network design and will increase the pump power requirements. Nonlinear effects, because of the dependence of the diode mean capacitance on the magnitude of the applied power, are significant principally in the pump circuits, althoug they have also been experimentally observed under high gain conditions in the signal and output circuits. The principal effect is to make the pump circuit passband asymmetrical, and thus reduce the effective bandwidth. Studies of this phenomenon, documented in anther report (Ref. 4) have indicated its dependence upon the circuit, Q. Its effect here is to modify the matching network design and to increase the insertion loss. Further quantitative study of the process is now in progress. The gain equations set out in the previous section indicated the porasibility of achieving some degree of gain constancy with a variation in signal frequency through appropriate control of the manner in which the fundamental pumped elastance coefficient Si varies with signal frequency fl. This method is applicable principally t te lower-sideband upconverter, where adjustment for high gain at the high signal frequencies would lead to oscillation as the signal frequency is reduced, if Z11 were constant and SI were left unchanged. Analysis of these expressions indicates that the gain constancy requirement may be expressed by: S1 = K fln, where n has a value between 1 and 2, depending upon the gain and the choice of input and output circuit impedance levels. Generally, SI for a varactor diode has a maximum value of around 0. 28 (Ref. 5). Consequently, the S1 value at the lowest value of the signal frequency would be small, if this method of gain adjustment were utilized. This would, in turn, degrade the noise figure appreciably. No study has yet been made of the design of a pump network giving this form of power transfer characteristic from the pump source to the diode series resistance. The value of this discussion of & variation with signal frequency is principally as a guide in experimentally adjusting a pump tuning circuit and in accommodating the effects of variation with frequency in the power output of a pump source. 10

The design of a signal input coupling network is more difficult than that of the pump coupling circuit since heretihe bandwidth is a greater fraction of the passband center frequency, and the insertion loss in the network contributes directly to the noise figure. The bulk of the studies previously carried out on this subject have been concerned mainly with comparatively narrow band circuits. The choice of input and output network impedance levels to minimize the noise figure has also received lit le previous attention. A general input coupling network for a lower-sideband up-converter tl shown in ig. 3(a), which has been derived fromthe equivalent circuit of Fig. l(b). A similar circuit for the upper-sideband up-converter is shown in Fig. 3(b). The minimum noise figure of the lower-sideband up-converter has been found to occur when the impedance Z12 has a magnitude given by: SI 2 SO j(I v + (4) where e is small compared to one and has a value depdedent upon the,ain of the up-converter. Under these cir inmstances the up-convmeurt lis.t stiall positive output impedance and optimum performance is obtained when the output termination is chosen for A power match. The value of Z13 giving a mininmum noise fi ure ff i system employing an upper-sideband up-converter as the first stagc is determined by the noise figure of the succeeding stages. The limits upon Z}3 are given by: S2 SO Zi -, - - 4 1 j o1 + 5) when the succeeding stages have a high noise value, and Z I y.- +1 +^ 0 (f) 1 s +j i 13 T i (A) 11

(a) Netwr.rk N So u 8 Zl2 S_ j T~Coupling X tS l) -' Netwlrk Ssi (b) E _ ~~1 ^~~~~~A L 3 Z33 ii ^3J 33 Z13 Fig. 3. Signal input coupling ni;tW rk.-S:,r itparanmtri up-cconverters: (a) the lower —sidl):m;ini pt: -clverter. nd (t)) the upper-si dtitlli{n uj) Cii vllItv rit. when the other stages are toise!ess. Optimum plo -'trtr tl:te tht upper-sideband upconverter is obtained when the output termination is chosen fir imaxinium upower transfer. These equations provide the intorniation required titr selection of coupling network impedance levels in the comparatively narrow band case. However, the value of S 2 - 2 varies markedly as the signal frequency changes over the 30-300 Mc and 300-1000 Mc ranges. Consequently, gain constancy over these wide ranges requires that Zi2 and Z13 should vary with signal frequency, if S1 remains constant. The application of filter techniques to coupling network design is not readily possible in such circumstances and further study of suitable circuit design procedures is now in progress. It appears possible that a circuit of the form shown in Fig. 4 will be suitable for the coupling network. A detLi:. i analysis of this circuit is now being conducted. 12

1 - (= ~*.....,. o R (I * Rs 1,1 for lower-sideband up-converter l *+. ~i for upper-sideband up-converter with [ 1 sRj ntoiseless second stage lel 3 AR / noisy second stage Fig. 4. Possibole circuit design for up-Tcnverter sign.il n,)ut coupling network. 4. 2. 3 Unwanted Si,-l^d.'fei is. A niajor constieratit n in the design of a single-sideband tunable paranmer ic up cuiivertter is the naturt- of tihe ttermination at the other principal sideband frequency. It is clear from elementary conicEtratlo'ns that this termination will markedly affect the rnve lir: -}lon g ~.ml,i.t-toi tilgti a.at iput! the output at the other sideband. However, quantuttive studtita of tht&s ifiuence re le acking in the literature. The provision otf, tt:,rr:insltin t tlhf unwanrted stdelId frequency is complicated by the wide tuning range of the converter. A lotwr- sideband up-converter tunable from signal frequency fl ato fl by a pump variable in frequency from fpa to fp to provide a constant output frequency f2, has an upper-sideband output in the frequency range fpa + f to fp + zfl - fl a The frequency spectra for these signals are illustrated in Fig. 5(a), and corresponding spectra for the upper-sideband up-converter are shown in I ig. 5(b). The most significant feature indicated by these diavrams is the overlap which occurs between the pump frequency range and the unwanted sideband frequency range. This oveO lap has a bandwidth of flb - 2 fla and, consequently, occurs whenever the tuning range exceeds one octave. 13

(Signal (a) i fla (b) - if la lower sideband \ fppa ipb I Pump ] l b f2 L pa fla/ fpa+ 2fb- la upper sideband upper i /!Pump flb fpb pa f3 pa 2t2lb tfa / pa fla lower sideband sideband fig. 5. Frequency spectra of siginals pres-nt in a tunable parametric up-converter: (a) with a fixed lower-sideband output frequency, and (b) with a tixed upper- sidetband output frequency. The existence of this overlap meant s i. it i. nott possible to separate the unwanted sideband circuit from the pump circuit throug' t-iw usze of a wideibad pumnp filtel This result has an important bearing upon the witheore ttC-ii;?i.'; l-., i im'c U ii iXeitc- e,hsed fo -r,an analysis taking into account the power cenvt. rso at':I.tecl nXi-itt t equ eta tus. An analysis of general pjaolrtic' ot - Ctonvfrter yiltds. ~he ec.quvalent circuits shown in Fig. 6. The noitanitl.i in thu}: i'i4tkrit' is tttt titfineitIt l,t} I sg. i i:d<. 2. A s tigr.fic ant assunrption in the derivation of the (pt|u.ilton' yielding these equi valent circuits is that the higher haimonic elastance co eflifcients Si..I, ire aeero. A more accur.te;'trialvslis. taking account of these coefiicients, will tb undierta ketn later. The transducer power gain expressitonas, G1. for output at the lower sideband, anrd Gt t3or output at the upper sidebtand, coie directly from Fig. 6, and are given by: 4Q iI I R12 R s 1 I (7) IZIX Z w 2Rs * z33 Q3 I 112 2.I,... ^i^ -^i~i ^ii~i^s

4 Ql a R RI R3 IQ I 1 3 a 1i3 = z a i Z133 Qll3 q1 s 2 27 Q3 1 ~~ 11 ~~ 22 (8) Zlt S1" 1* 2 M (a) (b) S E 1 ZL1 l^0zl. 1 " 2 11t 22 SII. 3 Z I t (c) Fig. 6. Equivalent circuit 1i a'i:cwri.tl paramttric ui- Evcrit(-^r (a) single frequency circuit; (b) liwut -r sEitk.ind circuit; (c) upiltr-sidclbanid circuit. The design theory for current-pumped parametric up-converters usually assumes that the unwanted sideband is terminated in an open circuit. Because of the parasitic elements associated with a semicinductor dide package., such a termination is difficult to achieve in practical circuit design. The ideal condition is even more difficult to achieve in a wide-range tunable up-converter, because of the periodicity of distributednetwork Impedances and the overlap in the frequency spectra of the pump and the unwanted sideband. It is apparent from these gain equations that oscillation is possible in an uppersiadelaid up-converter, because of a small value of Z22. The existence of unwanted 15

sidebands is believed to be the cause of the spurious oscillations and abrupt changes ingain which are often experimentally observed in wideband or tunable up-converters. The form of the equations above indicates that the gain variation with frequency may be controlled by suitable adjustment of the magnitude of the unwanted termination as a function of frequency. The required frequency variation comes upon solution of the appro priate gain equation for specified input and output impedance levels. In general, the noise figure is degraded by a power conversion to an unwanted sideband because of multiple frequency conversion effects. However, this noise degradation is small for a high-quality diode terminated in a high-Q impedalrce, 4.3 Experimental Studies Experimental studies have tbeen initiated on the 30-300 Mc and 300-1000 Me up-converters to acquire familiarity with the operation of these systems: to identify experimentally the problems in the design of suitable wide-range converters; and, to indicate directions and limitations fi,- the theoretical analysis, The experimental setups used here were far from optimum, and the experimental results reported car this out. However, a number of useful results were obtained from the studies, and these have ben Atpph'-: i td t the developmtenit of inmpr ved configurations, The experiments conducted.it these two frequency ranges.re discussed In detail below. Both series of experiments ildic;itedl sevtral lrtitrul otreASA thAr futiure study, Principal among these artiasi is the develilioplf'itt o stl; it abit.u lo, s bi t dtitss ti.d dtilde mounts in coaxial-line and waveguide. The Utit up-converter required 200 mnw of X-b.amd pump power for optimum perform.nlce, much niorti tihan is usuatiy required for a fixed-pump converter. The reduction of this power requoirtt entt throughl the broadband matching circuit design will require attention. Abrupt gain variations with signal frequency were found, indicating probable interference troom uswalt ted sideb;nds. The use (f tutnble bandpass filters in the pump circuits, ano, p:rhaps directional filters, is expected to alti. future experimental control of these sidebant effects. 4. 3. I VHIF' Up-Coyert'r Experiments. tudies were carried out on lowersideblnd atd upper-sideband up-converters for the 30-300 Me signal frequency range, using a Oir.np frequency of around 2000 Mc. Both gain and useful tuning range were small because 16

of the utilization oi narrow-band tuning structures, such,is double-stub tuners, and also because of unwanted sideband effects. Measurements were carried out witth tha varactor diode located In a Microlab bruoadband coaxial mount, so that the diode is in series with the coaxial line. The tuning range was restricted by the capacitance of the mount, which is large compared to that of the diode junction. The experimental settup is shown in block diagram form in Fig. 7. t is apparent from this diagram that the optimum setting on the double-stub tuners represents a compromise between the usually-conflicting requirements of matchitg the diode to the coaxial line to provide ma;imumn pump power transfer, and providing the appropriate impedalce termination for the output signal and the other sideband. It is possible to separate these tuning requirements by utilizing a more complicated structure. F*ture studies will be directed toward this end. An upper-sideband up- conv erter was constructed with an output frequency of 2100 Mc. The tuners were aajustedl for maximum otpt at 150 Me, and the gain was measured as a function of signa, l frequency, for various values of pump power. The results are shown iin Fig. 8. The maximunim:ain values are low, for the reasons discussed above, An interesting feature of these results is that increase in pumppower beyond S mw has the principal effect of raising the gain,2 the uimtJLg rang- ftr -emilies rather than at the mid* frequency. Also shown on this graph is a gain curve:tor a tunable up-converter which is tuned for maximum gain at each signal frequency, This was in contrast to the other curves in Fig. 8. where the tuning was not altertd a's the sigtgnl frelqutley was changed frcm 109 Me, Gain curves for a lower- sideband up-converter ha.vi ng an output frequency of 1 800 Me are shown in Fig. 5. The c- nverter was tuned for maximum gatin at 150 Me and this tuning was retained as tlh. signail frequoncy %was altered. A simple lower sideband up-converter is theoretically capable of an arbitrarily high gain and of oscillation. The effect of upper-sideband propagation is indicated by the maximum gain value of 5 db. Studies are new being conducted on a CGeeral Radio diode mount, where the varactor is mounted in shunt across the coaxial line. This mount has a provision for biating the diode, and is expected to give improved performance over that achieved with the Microlab mount, because of the reduced mount capacitance. Future experiments will be conducted with an output frequency around 3000 Me. 17

Fig. 7. Block digram of experimental set-up for VHF up-converter.

+10 rF I c 0 Co ul -l E -10 1 retuied for maximum gain of each frequency Pump Power 15 mw 10 nl 15 mw -20 - -30 - Pump Power 2 -40 I i i i I I t I I I I I I I I __I I — A i t I I I I 0 20 40 60 80 100 120 140 1 0 180 200 220 240 260 280 300 Fig. 8. VHF tunable upper-sideband up-converter transducer gain as a function of signal frequency.

4.3.2 UHF Up-Converter Experiments. The 300-1000 Mc up-converter was studied, using an X-band pump source. As in the case of the VHF up-converter, the experimental setup utilized here was not optimum, but was used to obtain further insight into practical up-converter design. The setup used for the experiments is shown in Fig. 10. The diode holder consisted of a coaxial line intersecting an X-band waveguide section in the broad-face wall, with the result that the diode is mounted in shunt across the waveguide and in series with the coaxial line. No tuning was used in the signal circuit. The X-band tuning adjustments required the same degree of compromise as was necessary with the VHF up-converter setup shown in Fig. 7. Measurements were carried out with the upper-sideband output frequency constant at 1280 Mc, the center frequency of the 20 Mc:wide 2-cavity direct-coupled narrowbard filter in the output line. The up-converter was tuned:for maximum output at 650 Mc signal frequency, and the gain was measured as a function of signal frequency. It was found that a wide variety of gain responses were possible, since the gain is a multipeaked function of the E-H tuner setting and the gain value achieved by iterative tuning techniques depends upon the initial tuner setting. One representative set of gain curves are shown in Fig. 11, and another in Fig. 12. A set of gain curves for a tunable lower-sideband upconverter having an output frequency of 9280 Mc, and adjusted for maximum gain at 650 Mc is also shown in Fig. 12. The curves indicate the variety of gain responses possible with this experimental setup, and also the effect of upper-sideband propagation in limiting the maximum gain attainable with the lower-sideband up- converter. Several modifications have been made to the original setup. Studies were carried out on waveguide diode mount in which the tuning was carried out with a sliding short-circuit termination to the waveguide and a sliding coaxial short-circuit in series with the diode. It was found that this method gave much greater bandwidth than tuning with an E-H tuner. The diode mount has also been modified to provide for fixed-bias operation. A 5-stage direct-coupled waveguide band-pass filter with a 0. 1 db ripple Tchebyscheff response over 8100-9100 Me was designed and constructed, providing a broadband filter for the pump circuit in an upper-sideband up-converter. Future studies will be with a 20

0 -10 / / _~~-143~~~~0 F_-~50 mw - 40 I I 2 41 0 20 40 i60 80 100 120 I 40 160 180 200 220 240 260 280 300 Signrt.! requerncy - nrc Fig.'i. VHI tunable lower- sidtband up-converter transducer gain as a function of signal frequency.

Fig. 10. Block diagram of experimental set-up for UHF up-converter.

m H lx Ns. X^^^s Pump Power 50 mw -30 30 mw 10 mat -40 _J______.,irL _ ________ 450 500 600 (X) H0( 900 1000 Signlti i''cqu:lic'y M rgacyles Jig. 11. UHF tunable ultwpr-sidtl'badii tip)-t'tiver'tC tranlSliucer gain as a ittiOl <>t Hi1 $ilnal lrJcqtuecy, setup providing separatilon betwitr:t:i npiut ilunp and output sideband sift nals to provide some measure of independence in ih,. tuning fi these circuits. &Sme study of tunable filters will probably also be initiated, as O ip *ssible Bsulutitol to tho frequentcy overla|p problem indicated in Irig. 5. 23

Transducer Gain - db I0 II w 04 s 0 0 0 o 0 r~ r r3 E: Ct 9& g a(b 5. r &e, w LP 9F; b= n tz rrr ae: "~ os;e ft (b ft " 8;;o c, r r r 8 a I t I / / / / \ I I I I t / I / r c: I "I tcs IP-P 0 5 r" c a cL c

4. 4 Conclusions The studies of tunable parametric up-converters initiated during the past quarter have served to indicate the major problem areas where research is required, and have provided some insights into possible solutions to these problems. The principal problems concern the achievement of gain constancy over the wide signal ranges and the control of the unwanted sideband, which is propagated back from the varactor into the pump circuitry if a bractm nd pump filter is used A considerable amount of study will be required to develop broadband signal and pump coupling networlk which will provide constant gain as the parametric coupling impedance S12S13 1 1 or --- variea tver the signal frequency range. A combination of a directional filter and a tunable pump filter appears necessary to permit independent control of the unwanted sideband. 25

5. PROGRAM FOR THE NEXT INTERVAL Luring the next quartr, att;ttion will 1c directcd to the followingt 1. Theoretical study "o! brsudbantndcoupling network,. for pump and signl cirxcuits. 2.t Vilestlat lgttx l (o tht ciift i t higr hrmonic sidebtWnd components on tunable up-cunverter perforlmance. 3. Study of meth(ds f a^ thieingf constant gain as the signal frequency it varied over a wide range. 4. Further development of the experiment cornfigutra-qos for the 30-300 Mc and 300-1000 Me up-converters. using ti -ofncluaionc of'Ine thoretical studies. 5. Derivation of an optimn lU tunable up-converter dfsign theory, having regard to gain, roise figure, tuning ratge, and dynamic range. 26

HEFERENCES 1. 3Matthaei, G. L. Design theory fr upi- c.nvcerteri fir use an electronicallytunable filters, IRE Trtns. N Tirans. c T, Thi ch,, it., MTT-9, 425-435. 2. Matthaet, G. L. et al. Microwave fllterg and coupling structures. tanford Research Institute.iarterly Progrss s Retrt No. 3. (Prepared forUIA CXT1tr/" N5C;j-v$i3-J7;i b84i3r M33ti PAr i"Siifurnia: Rtnford Research ntstitute, kttober 16t, pp. 4'17f 7! 3. Matthhei, G. L. et al. Microwave it ters, timldance-matehing networf, and {cou j!gu ll^sti^ta NAw'tkToa -HiIW i^ -Pp: 120-l k130. 4. fKhan, P. J. et al. Elec'rtctla sthotrt tuable antenns. Cooy lctronic Laboratoi_ Quarteriy Progre-S i.s lort No- 2. | Prepared for EL Ft Monmnouth. New Jerysey Cot"r. No. DA-28;043 AMC-012OI4(E)J. An Arbor, Michigan: The Universiity of Mf(.chigan, Coiey Electronics Laboratory, October 16a5. 5. ftifield, P. Puiampig var..rl- in. I:w lorward r-gion. Energy Conversioa Grttp Intezrai Msrr u. 7;. CTrh rilgt, MAasa husetts: Mdis aet't* Institute of Techtl-ig7, J.J-an. 1A 3 27

UNCLASSIFIED Security Calisification DOCUMENT CONTROL DATA - R&D (fSetuty cltsoifticotion of title, body ot h O e'Yr and * ndlrxtng F notrton l muzt b* entrted when Ihe vrtet pll oltfi 0 sl*4e ltd) I09~riNATI N O AC tIV(TyY 6*p rC ff uthor.) 24, ReooT 89CURItY C LAWtrieAT~100#7 - OESCRIPTIVE NOTES (ypr of fepor't and f-inc!ev* do,*i) 1st Quarterly Report (1 July 1965 to 30 September 1965)_ S ArUTQO(S) (letrot naim Irst nimc, it b tr Khan, P.J. Ribbens, W, B. Greiling, P. Talsky, R. St REPORT DATE c' TC NO -O PAog.? 6. NO 0P stegps October 1965 S./ CONTRIACT Oft GRATNT 0N as#1 MMA TOM#n aZ004rT NuMs6est) DA-28-043-AMC-01 52, E) P b. Departmet of Elechnical Report ECOM-0152 1(E)-IethArborh h 5A6-79191 D902- 02 05.$3 *tn EsPgO RRPO TPTOD* ) (AppE pa,* m w eMbyb:Task 02 " i01'IubTask 05'10 A.;.VA KtL A LTYV;IWt ATONN OTtCES LQualified T e VF requesor y obt y f ths reprt from DDC. Foresg announcement and disseminatilf tis report by 6DC is not authorizedm f. SUPPLCEMENTARY' NOTSt * S Oi. Mt:." —(.*?i t 7 E;Ihan I, PS.. Army ElectronsW;;. ~~~ComGreiingx, A, PN: AMP aEL-WLS — _____________ Jt. MoL si ioth..eS^J * October 1965 {-:-0:;:>FMm 3. ABSTRACT ituie: s have arried lr O"tn 41 1 -l~01f i dl.ar.erter-:.s1 tunable overa signal f quenccyh Re rt E M-uivaent circuits,56-ve.been derived for the parameric networs, taki account of simultaneous propagation at the upper and owr idebands Circuit desit giving constaint transducer ain over the frequenc:i ne m i V en iig ted, and wideh a o.nd pu a si fruue-n c, - i'wrSJ:banfd up-converstrs tunable obver the 30- 00 Mef r om C00- 100o M ranges thavingt ar n d dtsemit freporueny ppr iately ten i- tte hightr, sigal frequency,. 0 I0t- JRPPLEZENtA.: Uo4^ t;; Ro~@3; j~oUNCLASSIFIED Security Classifictons: D -,,. 43UCAWE Security C~~ass~caa~n?~........~:"~:"~'-~