Contains reports on status of research and nine research projects.National Aeronautics and Space Administration (Grant NGR-22-009-163

Crochiere, Ronald E.

Gerrath, K. H.

Majer, J. W.

Mohlere, R. D. V.

Peterson, D. F.

Rudzki, J. E.

Saleh, A. A. M.

Snyder, R. E.

Steinbrecher, D. H.

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IV. SOLID-STATE MICROWAVE ELECTRONICSAcademic and Research StaffProf. R. P. Rafuse Dr. J. W. MajerDr. D. H. Steinbrecher K. A. F. R. HasanGraduate StudentsR. E. Crochiere D. F. Peterson J. E. RudzkiK. H. Gerrath H. T. Rosenstein A. A. M. SalehR. D. Mohlere R. E. SnyderA. STATUS OF RESEARCHDuring the past quarter the 23. 8-GHz low-noise receiver project under P. W.Rosenkranz1 was completed. Results are summarized in Section III-E.An investigation of the "anomalous mode" oscillations in the avalanche region of theP-N junctions was initiated by R. Crochiere. His preliminary work is described inSection IV-B.Work has continued on the 60-GHz low-noise solid-state receiver that was describedin Quarterly Progress Report No. 89 (pages 29-30). Progress on the individual projectsis described below by those responsible for the work.D. H. SteinbrecherReferences1. P. W. Rosenkranz, "A Low-Noise K-Band Radiometer for the Measurement ofNarrow Spectral Lines," S. M. Thesis, M. I. T., June 1968.B. AN INVESTIGATION OF SUB-TRANSIT TIME OSCILLATIONSIN THE AVALANCHE REGION OF A PN JUNCTIONThe object of this project is to investigate the relaxation oscillations observed inavalanche diodes. At present, a piecewise linear model of the DC diode characteristicsis used to represent junction breakdown. Various circuit arrangements are being inves-tigated to simulate the AC parasitics of the junction and the diode case. All calcula-tions are being done by a computer program. Resulting waveforms are compared withmeasured waveforms in an attempt to determine an appropriate AC model of the encaseddiode.R. E. CrochiereThis work was supported by the National Aeronautics and Space Administration(Grant NGR-22-009-163).QPR No. 90(IV. SOLID-STATE MICROWAVE ELECTRONICS)C. 60-GHz MIXERSchottky-barrier diodes are now being produced with uniform static characteristics.Typical values for a 5-p. diameter junction are a Schottky-diode exponent of 1. 1, a zerobias junction capacitance measured at 1 MHz of 0. 03-0. 04 pF, a differential resistancemeasured at 60 Hz of 10-11 Q with 10 mA of forward current, and an I sa t of 10-14-1016 A.The mechanical components of the balanced mixer are now 600 complete.J. E. RudzkiD. S-BAND MIXERA number of measurements of the intermediate-frequency impedance have been made.The impedance was measured (Fig. IV-1) as a function of short-circuit position in theimage port Zif (Zim) and in the signal port Zif (Zs). The Zif (Zim) and Zif (Zs) shouldform circles close to the r = 1 and r = 0 circles on the Smith chart.fLOLOCALOSCILLATOR /IHYBRID COUPLING IMPEDANCE50 nCIRCUIT CIRCUIT BRIDGEBANDPASS PHASEFILTER I SHIFTERSTUB TUNER I lf ANDs = LO IlF f = fLO - FIFFig. IV-1. Intermediate-frequency impedance vs short-circuitposition in the image and signal ports.The results plotted on the Smith chart form small ellipses. The disagreement isprobably due to the following factors:1. uncontrolled termination of the higher frequency products at the input of thediodes (e. g. , ellipselike shape resulting from changes of sum termination when Z orZ.im changed);2. unsymmetry of the diodes and consequent change of the drive when Z or Z. ischanged.To solve these problems a new mixer design is under way. In the meantime, furthermeasurements will be made with carefully paired diodes.The single- sideband conversion loss of the existing mixer is approximately 4.0 dB.J. W. MajerQPR No. 90(IV. SOLID-STATE MICROWAVE ELECTRONICS)E. FREQUENCY DOUBLERTwo frequency doublers for 15. 2-30.4 GHz and 30.4-60. 8 GHz have been finished inthe machine shop.The first of them (15. 2-30. 4 GHz) has been tested with and without the varactordiode. The measurements of input impedance at the 15. 2 GHz input port showed that(a) the diode is very weakly coupled, and (b) there are at least two mutually coupledresonant circuits representing a nearly matched load.Further tests will include measurements of the input impedance with the diodeplaced directly in the 15. 2-GHz port, and attempts to find the appropriate coupling(which should also affect the spurious resonances).The 30.4-60.8 GHz doubler will be tested after completing the measurements and thetuning of the first one.J. W. MajerF. L-BAND QUADRUPLERFor the purpose of computing the input, output and idler network for a multiplierwith discrete and distributed elements a computer program was developed.A quadrupler was then designed. The configuration used for this quadrupler isdetermined by the desire to be able to sample the current through the varactor diodeand to have outputs at the second and third harmonics of the input frequency. Construc-tion of the quadrupler is under way.The more general case of a multiplier delivering power at all harmonics of the inputfrequency below the output frequency was discussed. The resulting system of nonlinearequations has been solved for a quadrupler.K. H. GerrathG. AVALANCHE DIODE OSCILLATORSome preliminary measurements made on the avalanche diode oscillator have showna dependence of the output power (at the fundamental frequency) on the second harmonictermination. The terminations used were a matched load, and an adjustable short rep-resenting all reactive loads. With the adjustable short terminating, the output powervaried by a factor of about four (max/min) as the position of the short moved through ahalf wavelength. The maximum output using the short was generally 10-20 per centhigher than that available using a matched load, while the minimum output was 60-70per cent lower than that corresponding to the other terminations. The efficiency usingthe matched load was approximately 0.3 per cent, which can hopefully be improved bybetter coupling to the cavity holding the diode. These measurements were made at aQPR No. 90(IV. SOLID-STATE MICROWAVE ELECTRONICS)fundamental frequency of 9. 8 Gc; the adjustable short is expected to have a more pro-nounced effect on the efficiency at the design frequency of 11 Gc.D. F. PetersonH. HIGH DYNAMIC RANGE MIXER FOR THE 200-400 MHz BANDAt present, work is still being done on the construction of transmission-line trans-formers. Measurements on 50-0 balanced to 50-0 unbalanced transformers showstanding-wave ratios of less than 1. 1 for frequencies less than 900 MHz, with matchedbalanced output. Mid-band insertion loss was 0. 3 dB, and the lower frequency limit ofoperation (the frequency of the insertion loss is 3 dB) was approximately 300 kHz. Thisagrees well with theory. Although the transformer was not tested above 900 MHz, it isexpected to operate with low VSWR well above 1 GHz. Tests will soon be made on a50-0 unbalanced to 200-0 balanced transformer.R. E. SnyderI. MIXER THEORYIn a balanced mixer circuit there are four basic methods for terminating theout-of-band frequencies.1. Short-circuiting them at both ends (Y-mixer).2. Open-circuiting them at both ends (Z-mixer).3. Short-circuiting those appearing at the input side and open-circuiting those atthe output side (G-mixer).4. The opposite of case 3 (H-mixer).The designations Y, Z, G, and H come from the fact in the first case, forexample, the Y-matrix of the mixer is the only matrix that can be written directlywithout solving any equations, and so on for the other cases.It has long been known that the Y (or the Z) mixer can be built with one diode. Ithas been shown also that the G (or the H) mixer can be built with one diode and stillgive the same conversion loss as the balanced 2- or 4-diode circuits.A. A. M. SalehJ. D-C AMPLIFIERI have been engaged in determining the effects of using field-effect transistor bridgesto modulate waveforms. There are areas of interest ranging from very low frequencyinputs, "chopped" by a binary type reference for standard chopper amplifiers, to high-frequency mixers. In all of these areas of interest a good model is required andundesired effects such as intermodulation have to be studied. Future work will beconcentrated on better models and methods of improving the FET bridge as a mixer.R. D. MohlereQPR No. 90

Solid-State Microwave Electronics

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Solid-State Microwave Electronics

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