Contains research objectives and summary of research on four research projects.Joint Services Electronics Program (Contract DAAB07-74-C-0630)National Science Foundation (Grant GP-40485X)National Science Foundation (Grant MPS73-05043-A01

Brodsky, Wesley G.

Burke, Bernard F.

Cooper, John F.

Giuffrida, Thomas S.

Glasser, Lance A.

Gupta, Madhu S.

Gwarek, Wojciech K.

Haschick, Aubrey D.

Kyhl, Robert L.

Moinuddin, Syed A.

Montress, Gary K.

Parrish, Alan

Penfield, Paul L., Jr.

Ramon y Alarcon, Felipe D.

Staelin, David H.

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VII. MICROWAVE AND MILLIMETER WAVE TECHNIQUESAcademic and Research StaffProf. Richard B. Adler Prof. Madhu S. Gupta Prof. David H. StaelinProf. Bernard F. Burke Prof. Robert L. Kyhl Dr. Alan ParrishProf. Paul L. Penfield, Jr.Graduate StudentsWesley G. Brodsky Wojciech K. Gwarek Gary K. MontressJohn F. Cooper Aubrey D. Haschick Woo Hyun PaikPatrick C. Crane Kwok-Yung Lo Felipe D. Ramon y AlarconThomas S. Giuffrida Syed A. Moinuddin Charles E. SimmonsLance A. Glasser Robert C. WalkerRESEARCH OBJECTIVES AND SUMMARY OF RESEARCH JSEP1. Low-Temperature Millimeter Wave ReceiversJoint Services Electronics Program (Contract DAAB07-74-C-0630)Madhu S. Gupta, Robert L. Kyhl, Paul L. Penfield, Jr., David H. Staelin,Wesley G. Brodsky, John F. Cooper, Lance A. Glasser, Wojciech K. Gwarek,Syed A. Moinuddin, Felipe D. Ramon y AlarconThis program is directed toward the development of extremely sensitive coherentreceivers at millimeter wavelengths. Initial work involves development of cryogenicmixers and IF amplifiers, with emphasis placed on accurate modeling of the deviceproperties so that optimization can be performed and performance limits established.An effort to develop cooled GaAs FET IF amplifiers is also under way. Thesebroadband amplifiers will operate at frequencies as high as several gigahertz.Since antenna temperatures at these frequencies can be as low as a few degrees Kel-vin, mixer noise temperatures well below room temperature are desirable. Because ofmixer conversion loss, the IF noise temperature should be even lower to make best useof low-noise mixers.We are also making mixer studies at microwave frequencies where measurementsand modeling can be performed more easily and accurately.A 118-GHz mixer has been fabricated, but difficulties in contacting the diodes havedelayed the planned measurements. The diodes, supplied by the M. I. T. Lincoln Lab-oratory, are Pt-GaAs Schottky barrier devices, 1-12 tm in diameter. We should beable to cool the system to 770 K, and perhaps to 40 K. When the diodes are installed, weshall measure the mechanical, dc, and IF properties of the mixer and compare theresults with theoretical predictions.A model of this mixer, incorporating nonlinear resistance and capacitance, has beenused with a new computer programl to predict pump waveforms, conversion loss, non-reciprocity, and the effects of higher order harmonics. The optimum performance ofthe mixer was computed as 4. 4 dB SSB conversion loss and 6. 6 dB noise figure.In the IF amplifier program we shall study a GaAs FET amplifier cooled to 770 K,with frequency in the gigahertz range. Areas of interest are FET theory, device mea-surement and characterization, and design and testing of amplifiers. Industrial coop-eration in providing state-of-the-art microwave GaAs FETs is expected.In the past six months three theses have been submitted to the Department of JSEPPR No. 115(VII. MICROWAVE AND MILLIMETER WAVE TECHNIQUES)JSEP Electrical Engineering, M. I. T., which are related to this research:Robert W. Freund, "Microwave Parameters of a Coolable GaAs Schottky BarrierDiode Mixer," S.M. and E.E. Thesis, June 1974.Wesley G. Brodsky, "Analysis and Design of a Cooled Mixer," S.M. and E.E.Thesis, July 1974.Wojciech K. Gwarek, "Nonlinear Analysis of Microwave Mixers," S. M. Thesis,September 1974.References1. Wojciech Gwarek and Robert L. Kyhl, "Nonlinear Computer-Aided Analysis of aMicrowave Mixer," Quarterly Progress Report No. 114, Research Laboratory ofElectronics, M. I. T., July 15, 1974, pp. 57-59.2. Multiple Microwave Solid-State DevicesJoint Services Electronics Program (DAAB07-74-C-0630)a. Noise and Power Considerations in BARITT DiodesGary K. Montress, Madhu S. GuptaThe BARITT diode offers attractive possibilities for low-noise, low-power micro-wave amplifier and source applications. Fabrication of single and multiple deviceBARITT oscillators will be undertaken. Operation at lower X-band is anticipated andan investigation of thermal and noise properties of the multiple-device structure willbe carried out. It is hoped that noise and power limitations of individual BARITT diodeswill be at least partially overcome with the operation of multiple-device structures.b. Multiple- Device Power-Combining MethodsMadhu S. GuptaWe are carrying out a comparative study of various methods of combining the poweroutput of several semiconductor microwave devices. Circuit models of devices andcombining networks are being developed in order to determine the performance param-eters and to optimize the combining network. The power output, as well as the noise ofthe multidevice combination, is under study, and the combining networks for both oscil-lators and amplifiers are being considered.IMPATT diodes are being used as a vehicle for studying the power-combining meth-ods. A high-frequency limitation to the performance of IMPATT diodes that is due tocarrier diffusion has been calculated analytically. 1 A nonlinear active circuit modelfor IMPATT diodes has been constructed. 2 It is based directly upon the carrier trans-port equations, rather than upon the calculated terminal impedance of the device thathas been found for an assumed signal and, therefore, should be more generally appli-JSEP cable.PR No. 115(VII. MICROWAVE AND MILLIMETER WAVE TECHNIQUES)References JSEP1. M. S. Gupta, "A Simple Approximate Method of Estimating the Effect of CarrierDiffusion in IMPATT Diodes," Solid-State Electronics, Vol. 19 (to appear in 1975).2. M. S. Gupta, "A Nonlinear Equivalent Circuit for IMPATT Diodes" (to be submittedfor publication).3. Microwave Measurements and InstrumentationJoint Services Electronics Program (Contract DAAB07 -74-C-0630)National Science Foundation (Grants GP-40485X and MPS73-05043-A01)Bernard F. Burke, Alan Parrish, Aubrey D. Haschick, Thomas S. Giuffridaa. Atmospheric Refraction StudiesThe microwave aperture-synthesis interferometer, which is situated at the HaystackObservatory, is a system of three 18-ft antennas that will be used to measure the loca-tion and structure of celestial radio sources. The system is phase-stable to approxi-mately 1 electrical degree and, since the minimum angular separation of the fringes is6 arc seconds at K-band, the inherent accuracy of the system should be of the order of.02 arc-second at K-band. Both atmospheric absorption and refraction will be measuredover short (few-second) and long (day-to-day) periods.b. Aperture Synthesis at Microwave FrequenciesThe techniques developed for the aperture-synthesis interferometer will be general-ized to other, nonastronomical, examples. We are studying the feasibility of a passiveradiometric night-visioi apparatus that would have high angular resolution at wave-lengths of approximately 1 cm. There are two general questions that must be settled,in order to demonstrate the practicality of such a system. First, relatively smallchanges in radio brightness of a terrestrial landscape call for a system of good gainstability, and we must establish the necessary parameters. Second, the system wouldbecome much less complex if an incomplete synthesis of a field would suffice. Thestudies of brightness distributions in celestial sources provides a direct test of sucheffects, and will be used to see whether incomplete Fourier transforms could yield suf-ficient information.4. Very Long Baseline Interferometry (VLBI)Joint Services Electronics Program (Contract DAAB07-74-C-0630)National Science Foundation (Grants GP-40485X and MPS73-05043-A01)Bernard F. BurkeIn collaboration with the Naval Research Laboratory, the VLBI techniques have beenextended to 1. 3 cm wavelength and a long-term experiment on the positional stability of18 -cm OH maser sources has been carried out. The data will be analyzed to providean extensive list of sources for possible navigation and time-keeping purposes. The dis-covery of SiO maser sources at 7 mm wavelength suggests application of the methodat that wavelength, and an attempt will be made to extend VLBI methods to this region. JSEPPR No. 115

Microwave and Millimeter Wave Techniques

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Microwave and Millimeter Wave Techniques

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