Search

In general, the invention according to our concept comprehends a millimeter wave oscillator which comprises, in combination, a housing or base portion which is provided with a resonating cavity, a solid state mechanically tuneable element which is adjustably moveably disposed in the housing, conveniently by means of a threaded engagement in a brass collar or the like fitting secured to the housing, which tuneable element is capable of producing millimeter-wave energy output at a frequency corresponding to its position in the resonate cavity, and a solid state electronically tuneable element arranged and physically disposed concentrically with same. Position adjustment means are provided exterior of the housing and operably connect to the mechanically tuneable element. Mechanical means connect between the mechanically tuneable element and the exteriorly located position adjustment means, and an electrical bias source is provided for each of the tuneable elements.

A millimeter wave microstrip transmission line is coupled to a solid state mechanically tunable cylindrical resonating coaxial cavity millimeter-wave oscillator by means of a probe extending linearly from the microstrip through an access slot in the cylindrical cavity wall into the zone of optimum electric field strength in the oscillator cavity to effect the translation of a TEM wave from the resonating cavity to the microstrip line at optimum power transfer and without wave mode change. (Author)

This document describes a filter reflection image guide oscillator and a solid state line scanning device. The device includes a brass metal heat sink base on which a dielectric waveguide is mounted. A resonant cavity is defined in the dielectric waveguide and an oscillator diode, Gunn or IMPATT, for example, is located in the resonant cavity. The resonant cavity is enclosed by a metal cover with a post which is made to extend into the resonant cavity to contact one electrode of the oscillator diode. The top surface of the waveguide includes a perturbation surface consisting of parallel and spaced metal stripes which are laterally positioned along the length of the waveguide. The spacing of the metal stripes defines the function performed by the device. By changing the bias voltage of the oscillator diode or with the addition of a varactor with a separate DC bias source, the frequency in the waveguide can be changed and thus line scanning or beam steering is made possible.

A high power solid state source of microwave and millimeter wave signals is provided by an optically triggered body of bulk semiconductor material selected from the Group III-V compounds including GaAs, Cr:GaAs, and Fe:InP and having a relatively long gap length which is in the order of 0.5 to 10.0 mm as well as having a resistivity which is greater than 10 to the 7th power ohm-cm. The device is further dc biased to a field of between 15kV/cm and 35kV/cm. Under such conditions, a very low dc current flows without any oscillatory behavior; however, illumination of the semiconductor body with a fast rising optical pulse having a wavelength suitable for carrier generation causes electrons to be lifted to the conduction band which is accompanied by a rapid reduction of the resistivity. At the same time, the electric field across the gap length decreases to a value just above the oscillation threshold whereupon high power RF oscillations are generated whose frequency is a function of the recombination time of the excited carriers. (Author)

A dual GUNN self-oscillating mixer is shown which can mix signals in the VHF range substantially without handling capacity and with higher input mixed signal power than conventional, owing to boosted power from more than one microwave cavity. The device is comprised of two cavities and connected by a 180 deg phase shift coax line for injection locking, or a cavity wall hole in yet another embodiment. The device handles larger power levels without burning out as compared to conventional type mixer devices such as Schottky barrier diodes having nearly 30 times the burnout susceptibility. (Author)

A radiation measurement means is shown which has the capability of detecting radiation in both the millimeter wave, and the infrared, frequency regions. A basic self-oscillating Gunn diode is enclosed in a donut shaped silicon ring. The presence of infrared energy will create holes and electrons in the silicon material, altering its conductivity, and lower the power of oscillation. The realized drop in oscillating power identifies the infrared. Millimeter wave radiation is detected because an intermediate frequency is generated as the Gunn diode operates as a self-oscillating mixer of the new different frequency with its own oscillating frequency. Thus it is possible to detect signals from both ranges, in a single device. (Author)

A triple Gunn diode self-oscillating mixer system is shown which can mix signals in the VHF range substantially without introducing any noise and with high input signal power handling cavity and with higher output mixed signal power than conventional, owing to boosted power from more than one microwave cavity. The device is comprised of three self-oscillating Gunn diode cavities connected by 180 deg phase shift coax lines for injection locking. The device handles larger power levels without burnout as compared to conventional mixer devices such as Schottky barrier diodes having nearly 30 times less burnout capacity. (Author)

The general object of this invention is to provide a method of making low cost millimeter wave resonators. A more specific object is to provide such a method using an easily machined organic type binder for the dielectric resonator. A specific object of the invention is to provide such a method of making low cost millimeter wave oscillators. It has now been found that the aforementioned objectives can be attained by replacing the metal walled cavities by dielectric resonators made of plastic and heavily loaded with a higher dielectric constant powder of above 3.5. The dielectric resonator so produced is easily machined due to its organic type binder and also has a higher dielectric constant when loaded with a higher dielectric silicon, gallium arsenide, boron nitride, or quartz. The combination of low dielectric constant plastic plus higher dielectric constant material has the property of being easily machinable, while at the same time havng the electromagnetic properties of the refractory higher dielectric constant material.

A microstrip integrated circuit reflection amplifier utilizing packaged diodes and permitting some gain and bandwidth adjustment. A 3 db quadrature coupler has two of its ports connected to substantially identical reflection amplifiers. The reflection diodes are adjustably mounted in brackets perpendicular to the dielectric substrate of the microstrip network and may be moved in and out along the microstrip circuit to provide for some gain correction and bandwidth adjustment. (Author), Supersedes PAT-APPL-266 229-81, AD-D009 094.

A device for connecting plural oscillators to a single output port without the use of power dividers, switches or multiplexing filters. The plural oscillators produce multiple frequencies with only one oscillator operating at a given time. The oscillators are mounted in shunt waveguide cavities along a central waveguide manifold at distances from the central waveguide manifold and waveguide end so as not to affect the operating oscillator. (Author), Supersedes PAT-APPL-097 454-79, AD-D006 993.

The present invention relates generally to voltage-tuned oscillators and, more particularly, to a wide-band varactor-tuned microwave Gunn oscillator. Conventional varactor-tuned microwave Gunn oscillator circuits are of microstrip, stripline, coaxial, or waveguide construction in which the biasing and matching is carried out using distributed-type elements. These distributed-type elements are a combination of transmission lines of various impedances whose lengths are appreciable compared to a wavelength at some frequency within the tuning range, typically a quarter wavelength, or multiples thereof, at the center frequency. In addition, conventional circuits utilize Gunn and varactor chips mounted in conventional microwave packages which introduce undesirable parasitic elements. It is generally recognized that distributed circuit elements and package parasitics critically affect the achievable tuning range of varactor-tuned microwave oscillators by reducing the maximum net reactance variation possible for a given change in varactor capacitance. For wide-band tuning, all parasitics must be minimized and the varactor chip must be tightly coupled to the active device and load with non-dispersive and non-distributed coupling elements.

A dielectric waveguide power limiter for a self-oscillating mixer operating on millimeter-wave frequencies. The limiter includes a high resistivity silicon dielectric waveguide and a Gunn oscillator. A plurality of dielectric resonators each including a high uniaxial anisotropy ferrite sphere embedded therein are positioned between the power input end of the waveguide and the Gunn oscillator. (Author)

A millimeter wave amplifier having broadband characteristics in which a Gunn diode or other two terminal negative resistance device having an integral heat sink is center mounted in a reduced height waveguide. The heat sink is attached to a mechanism for selectively adjusting its penetration into the waveguide cavity. The introduction of the heat sink into the waveguide cavity creates a discontinuity to the propagation of energy which causes localized waveguide modes other than the dominant mode to exist. The adjustable position of the heat sink allows the reactance due to the introduction of these modes to be variable, proper adjustment resulting in the cancellation of the parasitic reactances inherent in the packaged negative resistance device. (Author), Supersedes PAT-APPL-622 285-75, AD-D002 869.

The patent application describes a digitally-tuned parametric amplifier apparatus using a varactor and a Gunn diode to provide a widely variably gain and center frequency range.

Computer simulations are presently being performed in order to optimize device parameters. Both optimum donor density and drift length will be calculated. 70% of the fabricated devices exhibit the precalculated low field characteristics such as DC-resistance and Schottky diode characteristics. Radiofrequency performance in the transit-time independent mode is not yet satisfactory. However, very good efficiencies have been measured in the transit-time mode: At 19 GHz efficiencies between 3.5% and 4% have been measured. In this mode domain formation occurred somewhere underneath the negatively biased gate. This device is an excellent planar Gunn oscillator. The goal is to operate this device at non-transit time related frequencies above the transit time frequency with comparable or higher efficiency. Up to now the tested devices did not exhibit sufficiently large negative conductance in Ka band (26.5 - 40 GHz). Certainly, one reason for measuring low small signal gain is the low characteristic impedance of the stripline test circuit (50 Ohms). Other reasons might be some losses of the FET like cathode contact and the steeply falling electric field distribution in the drift region due to the large donor density. Future devices therefore will be made from lower doped epitaxial layers and will be mounted in specially designed stripline circuits containing impedance transformers and resonators.

The goal of this research is to exploit the novel capability of the focused ion beam to implant dopants whose density is a function of the lateral position. Thus, Field Effect Transistors in Gallium Arsenide and Silicon can be fabricated with a gradient of doping from source to drain. We have fabricated and tested such graded FET's in GaAs and have fabricated Si devices up to the point of focused ion beam implantation. In addition, programs for modeling the devices on the computer have been written. Recently, we have conceived and fabricated a new device: a tunable Gunn oscillator which makes use of doping gradients. To carry out these implantations, we have further developed the performance of our focused ion beam machine.

The emphasis of the investigation is centered on studies of active microwave effects in avalanche diodes, transferred electron diodes, microwave field-effect transistors, and on related microwave circuit, materials growth, and physical electronic techniques. In Section A, a report is made on the microwave solid state devices and circuits. Included are: Amplifier Properties; IMPATT Diode Load Characteristics; Interaction of Distributed IMPATT Oscillators; An IMPATT Diode Characterization; Microwave Transistor Studies; Compound Semiconductor Transistor Study; Computer Experiments in TRAPATT Diodes; and High Performance TEO. In Section B, a report is made on materials and fabrication techniques. The topics discussed are: The Epitaxial Growth of Thin GaAs Layers; Read Structures; and Electric-Current-Controlled Liquid Phase Epitaxial Growth of GaAs.

The report presents a technical assessment of present-day transferred electron (Gunn) devices, microwave avalanche devices, and microwave transistors and attempts to estimate their ultimate performance capabilities.

This report describes the research accomplished during the third biannual period of a three year research program dealing with advanced concepts of microwave generation and control in solids. A report is made on microwave solid state devices and circuits. Included are: GaAs Read Diodes; Amplifier Characteristics; Measurement of IMPATT Diode Amplifier Parameters; Computer Experiments on TRAPATT Diodes; High Power and Efficiency CW Transferred Electron Oscillators; Compound Semiconductor Transistor Study; Automated Network Analyzer; Submicron Gate Field Effect Transistor; IMPATT Diode Load Characteristics; and Interaction of Distributed IMPATT Oscillators. A report is also made on materials and fabrication techniques. The topics discussed are: The Epitaxial Growth of Thin GaAs Layers; Read Structures; and Electric-Current-Controlled LPE Growth of GaAs.

An integrated circuit tunable cavity oscillator is described for extremely high frequency operation in image line waveguide. The oscillator includes a metal base with a cylindrical bore, a dielectric or semiconductor waveguide mounted atop the metal base and having a bore which is continuous with the metal base bore. A Gunn or IMPATT diode is assembled in the metal base bore on top of a drum which is urged upwards toward the waveguide bore by a spring located behind the drum. From above, cavity tuning means including a top disk and a threaded screw cover the waveguide bore and push the diode into the metal base bore to define the cavity height of the coaxial cavity of the oscillator. The waveform, which is set up in the recessed cavity in the metal base, is launched into the waveguide. Thus, a ruggedized, low cost, tunable (by a tuning screw) and low weight oscillator for millimeter wave image line or microstrip operation is obtained. Furthermore, the oscillator diode and cavity defining hardware are easily replaceable.

Various technological problems in the development of GaAs microwave devices are covered in this report. The work reported here includes: epitaxial growth of ultra-thin and high-resistivity films, study of the relationship between device performance and material parameters using IMPATT and LSA Gunn diodes, growth of semi-insulating substrates and characterization techniques, and study of ion implantation as a tool for microwave device fabrication.

The report describes the completion of the studies, initiated in FY 69, carried out to assess the practicability of applying microwave integrated circuits and solid state fundamental oscillators to future sensor subsystems for radar and communications, including data relay. The X-band eight-element phased array was evaluated, a simple MIC module including a printed antenna was constructed and studies were carried out of avalanche diode oscillator modulation characteristics, MIC IMPATT avalanche diode oscillators, MIC antennas, and MIC evaluation techniques.

The report describes the results of a program of investigation concerning the reliability and failure modes of gallium arsenide Gunn and IMPATT diodes. Data is presented concerning the burn-out distribution in time of Gunn diodes. Also, the changes in dc and RF parameters of 700 Gunn and 100 gallium arsenide IMPATT diodes resulting from 24 to 168 hours of dc high temperature burn-in are present. The results of long-term RF burn-in experiments are presented. Optical and electron microscope photographs are presented which are used in the analysis of the manufacturing defects leading to early failure in Gunn diodes. Correction of these defects has lead to an increased 24-hour burn-in yield., See also Semi-Annual report, AD770528.

This is the fourth quarterly report on subject contract whose objectives are to investigate theoretically and experimentally new solid-state phenomena and techniques having application to microwave generation, amplification, and control. Current tasks under this program are the following: High-power Gunn-effect devices; gunn-effect amplifiers; modulation properties of gunn-effect devices; avalanche-diode amplifiers; high-efficiency avalanche diodes; nonlinear operating characteristics of IMPATT diodes; solid-state device fabrication; and, instabilities in germanium., See also AD730636.

This report deals with the progress made during the seventh quarterly period of a solid state microwave oscillator and amplifier research and development program. Included are the results of studies of transferred electron punch-through injection, and avalanche diodes and solid state materials. Discussed first are LSA diodes and circuits, Gunn effect amplifiers and oscillators, a PCM Gunn oscillator, and GaAs materials studies. Next discussed are high average power TRAPATT diode structures and research on high frequency TRAPATT oscillators. Also reported are two studies of punch-through injection (Baritt) diodes, one for high frequency cw operation and the other for low frequency cw operation. Work on relaxing avalanche mode (RAM) oscillators is reported along with a summary of a new study on microwave transistors. The report concludes with a discussion of the progress made on ion implantation, on vacuum epitaxial growth in silicon and on ionization rates in GaAs., See also report dated June 72, AD-748 241.

Contents: Solid state devices and components; Antennas and propagation; Communication circuits and components.

The patent describes a circuit for providing accurate timing pulses to steer an antenna array. A Gunn device coupled at the input of each transmitting element supplies a single pulse at predetermined time intervals to the element enabling time delay steering of the antenna array.

This report covers the fabrication of two solid state 14.4-15.2 GHz radio sets. These were fabricated to demonstrate the feasibility of a low-cost microwave radio set. This equipment has been designed for line-of-sight microwave communications and could fulfill requirements where microwave communications are now too expensive, such as in intra-base and bare-base voice and/or sensor communications operations. (Author)

The research program is concerned with new techniques for microwave signal generation. The emphasis of the investigation is on studies of active microwave effects in bulk semiconductors and on physical electronic phenomena. Specifically the study areas include the domain and Limited Space charge Accumulation (LSA) modes of the Gunn-effect, Impact Avalanche and Transit Time (IMPATT) and Trapped Plasma Avalanche Transit Time (TRAPATT) oscillators and amplifiers and microwave semiconductor materials properties. This research is being undertaken to further the understanding of the physical mechanisms and processes which are involved and to obtain information of use in the design of improved microwave sources. The work accomplished during the tenth quarterly period is discussed in this report. (Author), See also Quarterly progress rept. no. 9, AD-871 992.

Contents: Capacity limits of thin-layer memories; Storage based on the Gunn effect., Unedited rough draft trans. of Nachrichtentechnik (East Germany) v20 n7 p264-268 1970.

The purpose of this work was to develop a GaAs Sheet Gunn (Coplanar) device and circuit capability such that maximum power could be extracted from the device. Electronic tuning of the device over the 4.8 - 5.2 GHz range was also desired. Difficulties in growing N layer on semi-insulating substrates, and premature breakdown in finished devices even under pulsed conditions precluded achievement of the original contract objectives. The contract was redirected towards obtaining high power by means of amplifiers. Theoretical and experimental analysis of the Distributed Unidirectional Microwave Amplifier showed that this device offered one method of achieving the desired microwave power levels. A DUMA test vehicle employing six 0.7 W avalanche diodes demonstrated amplification at the 5-watt level, and showed electronic gain at powers as high as 9 W. (Author)

The objectives are to investigate theoretically and experimentally new solid-state phenomena and techniques having application to microwave generation, amplification and control. Current tasks under the program are: Microwave noise emission from indium antimonide; Instabilities in Germanium; Transverse and magnetic field effects on instabilities in bulk semiconductors; Gunn effect amplifiers; High power gunn effect devices; Large signal analysis of avalanche diodes; Multifrequency operation of avalanche diodes; Multifrequency operation of avalanche diodes; Solid state device construction and evaluation. (Author), See also Quarterly progress rept. no. 10, AD-871 171.

The harmonic content of solid state GaAs Gunn effect oscillators has been experimentally investigated using a lamellar grating far-infrared interferometer. The experiment has shown that power as low in frequency as 6 GHz can be modulated by the grating and that the instrument can be used in this frequency range with appropriate high-pass filters and above 60 GHz without filters. A number of the experimental difficulties encountered and instrumental modifications made to reduce the low frequency operating limit are discussed. A high dc bias mode of operation of a high-purity n-type epitaxial GaAs detector was discovered and its properties were investigated. This sensitive, broad-band detector, which had a response time of about 20 nsec, was used for the harmonic content measurements. In general, only a few harmonics of the X-band Gunn effect devices were observed and these died off rather rapidly. The experimental results were in fairly good agreement with theoretical predictions and indicate that the relative harmonic content increases with n/f. No definite correlation between harmonic content and bias voltage was found. The highest frequency at which power was observed was 82 GHz, a tenth harmonic. Thus the results do not contradict the predicted upper frequency limit of operation for these devices. (Author), See also Volume 1, AD-883 604L and Volume 3, AD-883 608L.

The aim of this project is to study the spurious emissions from transit-time Gunn diodes which affect the electromagnetic compatibility of these devices. Harmonic emission far from the fundamental and noise emission in the vicinity of the fundamental have been studied. Efforts on the harmonic program this year were directed toward the isolation and elimination of extraneous reflections and interferences in the far infrared interferometer. Noise from Gunn effect oscillators has been extensively measured. A major contribution to the noise spectrum is upconverted flicker noise present in the diode current. An analytic treatment of this up-conversion process is given. Good agreement is found between measured and calculated spectra. From a single noise measurement performed on a sample in a standard circuit, one may calculate the sample's noise spectrum in an arbitrary circuit if the loaded Q, power, and voltage pushing are known. Transit-time Gunn diodes are characterized by an equivalent noise temperature of 7500K which is comparable to the noise temperature of klystrons. (Author)

The report summarizes work done over a period of three years on a research program directed to the suppression of undesired emissions from active bulk-solid and epitaxial devices. Major emphasis was placed on the spurious emissions of Gunn devices. Both harmonic emission far from the fundamental and noise emission in the vicinity of the fundamental were studied. The technique of Fourier spectroscopy was newly applied to the study of harmonic emissions over the range 8 - 500 GHz. It was found that for Gunn devices operated in the hybrid and LSA modes harmonic power dropped rapidly with increasing frequency. The highest harmonic observed was the tenth (at 82 GHz) of a high-power pulsed LSA X-band device. (Author), See also Volume 2, AD-883 607L.

This effort is the first program to develop high power solid state microwave oscillators to compete with and eventually replace magnetrons in the 100 to 200 watt range at X and Ku-bands. The Limitated Space-charge Accumulation (LSA) mode in GaAs was developed to a point that produced 100 watts peak and 200 mw average power at X-band and 150 watts peak at Ku-band. (Author)

The field dependent electron drift velocity in GaAs has been calculated on the basis of a Monte Carlo simulation of electron motion in k-space. Three scattering processes have been taken into account. These include interactions with longitudinal polar optical mode phonons, non-polar optical mode phonons and acoustical phonons. Numerical calculations including accuracy estimates have been performed for lattice temperatures in the range 200 - 400 degrees K. The results show the threshold field to be nearly temperature independent. The negative differential mobility increases with decreasing temperature, while the peak to valley ratio is nearly constant. An outline is given of work being done in order to include scattering by neutral and ionized impurities. This will make calculations possible for temperatures down to below liquid nitrogen and impurity concentrations up to 10 to the 17th power/cc. (Author)

The objectives are to investigate theoretically and experimentally new solid-state phenomena and techniques having application to microwave generation, amplification and control. Current tasks under the program are: Microwave radiation from indium antimonide; Instabilities in germanium; Transverse and magnetic field effects on instabilities in bulk semiconductor plasmas; Gunn-effect oscillators and frequency converters; Gunn-effect amplifiers; High-power Gunn-effect devices; Avalanche-diode devices; High-power avalanche diodes; High-efficiency avalanche diodes; Solid-state device construction. (Author), See also Quarterly progress rept. no. 6, AD-855 150.

The continuing study of GaAs LSA devices in circuits with the aid of several computer programs and an analysis has been made, as a function of parameters, using I-V effects representing space-charge accumulation. Refined results for calculation of dc electric field as a function of position are presented for two-frequency LSA. Gunn effect diodes capable of average input powers up to 10 watts with CW output powers up to 120 mW have been studied and a protective 'crowbar' is discussed. Electronic tuning of LSA oscillations with bias and temperature is discussed, along with critical skin depth effects. A technique for estimating the effective thermal resistance of thick devices is presented. Development of the pulse bridge to be used for high electric field magnetoresistance measurements is nearly complete. A simplified model for avalanche resonance pumped semiconductor diodes has been developed in terms of its voltage current relation and its equivalent circuit. Schottky barrier avalanche diodes have been fabricated. Hot electron diffusion theory in Silicon was continued and N+ - P junctions constructed for tests of the theory. Techniques work at obtaining millimeter waves from bulk indium antionide is discussed., See also Quarterly progress rept. no. 7, AD-860 331.

The report traces out the development of the low frequency equivalent circuit of the diode-on-a-post type waveguide LSA oscillator and shows that circuit conditions exist for the low frequency oscillations. The input impedance presented to a diode mounted in a rigid waveguide combined with a three-quarter wavelength choke is analyzed in some detail and it is shown that this structure also can support a low frequency oscillation. Experiments in a coaxial cavity have shown the existence of two modes of oscillation. In the higher frequency mode, thought to be LSA, the effective diode capacitance was 1.6 times the cold capacitance, and N/f for the fundamental frequency of oscillation was less than 200,000 sec/cc. A description is given of a resonant waveguide iris structure combined with a ridge waveguide which produces X band output as only the second harmonic frequency. Preliminary experiments have given 13 watts at 4% efficiency at X band and over 50 watts at 10% at the fundamental frequency. (Author)

Electromagnetic compatibility of GaAs oscillators as a function both of contacting procedures and of active region thickness was investigated by evaluation of their output spectra. Twenty-three devices were measured for spectral output. (Author)

The behavior of several different Gunn oscillators operating into a resistive load is experimentally investigated. The effects of applied bias, load resistance, and temperature on oscillation frequency, power, and efficiency are presented. It is seen that at microwave frequencies circuit resonances influence diode behavior and that complete knowledge of the microwave circuit is required. It is then demonstrated that under certain circumstances, such as for the diodes and circuit employed here, the domain capacitance plays a major role in determining frequency behavior and can lead to wide tuning ranges and mode switching determined by the applied voltage or temperature. Applications of this effect and follow-on work are suggested. (Author)

The negative resistance arising in gallium arsenide transferred electron oscillators has been observed over a broadband in material of doping greater than that associated with Limited Space charge Accumulation (LSA) operation. The behavior was characterized by strong circuit dependence, as with LSA, and by high efficiency of as great as twenty percent in pulsed operation. The transition from transit-time operation to nearly LSA operation has been seen experimentally as a continuous function of circuit tuning. An expected decrease in diode capacitance has been observed during the tuning from domain transit operation to LSA. Some clues to the origin of the high efficiency are discussed. The operation of material with gold-germanium alloyed contacts is compared to that with the superior solution grown epitaxial contacts. (Author)

This research program is concerned with new techniques for microwave signal generation. The emphasis of the investigation is on studies of active microwave effects in bulk semiconductors and on physical electronic phenomena. Specifically the study areas include the domain and Limited Space charge Accumulation (LSA) modes of Gunn effect, Impact Avalanche and Transit Time (IMPATT) diodes, microwave semiconductor materials and fundamentals, and a special study dealing with field emission of electrons from semiconductors into a vacuum. This research is being undertaken to further the understanding of the physical mechanisms and processes which are involved and to obtain information of use in the design of improved microwave sources. (Author), See also Quarterly rept. no. 3, AD-844 679.

The publication contains a simple non-mathematical introduction to the theory of the Gunn oscillator and L.S.A. oscillator. The difficulties that have occurred in the fabrication of devices and materials are discussed. Predictions of the commercial availability of devices in the future are made. (Author)

Research was conducted on Gunn oscillators. Successful hybrid mode operation has been obtained over 0.75 to 5 times transit-time frequency in single diodes of epitaxial GaAs. Research was conducted on avalanche (IMPATT) diodes. The broadband negative resistance properties of a 1.3 ohm-cm, 4.5 micron N-region punch-through avalanche diode have enabled its operation as a microwave generator over a 1 to 10 GHz frequency range with 2 to 10 percent efficiency. Large-signal sample impedances were obtained for both the pure transit-time mode and the low-frequency mode was found to be characterized by the necessary presence of an idler frequency at the second harmonic. Research on gallium arsenide crystal growing is also reported. Work on the solution growth method has shown considerable promise. An elementary theory for the magnetoresistance measurement of the Hall mobility, including the correction for the finite geometry of the practical diodes, is presented, and several practical sources of measurement error are discussed. (Author)

The report contains the results of a program to develop and build an electronically steerable MIC linear array with a single MIC receiver front end and the necessary array feed structure. The linear array consisted of four modules in a single housing bolted to a second housing containing four cylindrical waveguide antennas. Phase shifters for beam steering and polarization diversity were tight-coupled meander line, nonreciprocal ferrite structures flux driven to obtain effectively 4-bit operation. A varactor tuned MIC Gunn oscillator was investigated for use as the local oscillator. A new design approach consisting essentially of lumped tuning elements was used. A mathematical model for this approach was generated and computerized. A new design approach in phase shifter flux drivers using standard commercial components was derived. (Modified author abstract)

A Ka-band amplifier structure with 7.5 GHz bandwidth and 6 dB gain was fabricated. Simple adjustments lead to 15 dB gain with 2.5 GHz bandwidth. Measurements utilize double cosine tapered waveguide matching sections terminated by reduced height waveguide and calibrated sliding shorts. From slotted line measurements of reflection coefficients, two port cavity S parameters may be obtained. Insertion of the diode gives new reflection coefficients from which diode impedance can be separated. The accuracy of the calculated diode and waveguide parameters can be checked by testing calculated reflection gain vs. measured reflectometer gain over the frequency range using various calibrated short positions. Using the diode terminal impedance data, computer optimized matching circuits can be designed for particular gain and bandwidth requirements. (Author)

The research is concerned with the investigation and utilization of various phenomena and techniques for the generation, amplification, detection and control of electromagnetic energy at microwave frequencies. The work is mainly oriented toward an investigation of the basic properties, capabilities and potential of: Avalanche transit-time devices including IMPATTs and TRAPATTs; Transferred-electron devices; Microwave field-effect transistors; Microwave integrated circuits.

A general noise theory has been developed for a nonlinear, self-oscillating device in a parallel G-L-C circuit. Variation of the nonlinear device admittance with both RF voltage and bias voltage is incorporated in the theory and the sources of noise are lumped into two equivalent noise generators: a video noise voltage generator and an RF noise current generator. The present study extends the work of Sweet by including the RF voltage dependence in the theory and by applying the theory to a quenched-mode admittance model of transferred-electron (TE) devices. The noise theory is used to study AM and FM TE oscillator noise as functions of load conductance, bias voltage, cavity tuning and carrier doping density for uniformly doped TE devices. (Modified author abstract), See also report dated May 73, AD-764 259.