3 W CW simultaneously with 22% conversion efficiency was achieved at 35 GHz from a double-drift GaAs IMPATT diode. At 44 GHz, 2 W and 18% efficiency were obtained. The design of the amplifier circuits which utilize these devices is discussed. The circuit design is based on a 3-step closed form algorithm. The first step is a passive circuit characterization with automatic network analyzer. In the second step a computer is used to generate diode device lines, and the third step is load line synthesis for predictable operation. The resulting performance and its sensitivity on the mechanical tolerances is described. 2 W over a 2-GHz bandwidth was achieved simultaneously with minimum gain of 9 dB.

Two high power communication amplifiers operating in the Extremely High Frequency (EHF) spectrum are described. Both amplifiers are based on silicon double-drift IMPATT diodes for power generation. The first amplifier operates in the high gain, narrowband injection-locking mode and represents a first step toward low cost manufacturing of this type of amplifier. It is capable of 6.2 W and 31 dB gain at 36.79 GHz, with 250 MHz injection-locking bandwidth. The second amplifier operates in the low gain, wideband negative resistance mode in which there is no power output in the absence of an input signal. A state-of-the-art power output in excess of 3.5 W was achieved from 43.5 to 44.5 GHz with a nominal 3 dB gain. This amplifier is in its advanced development stage.

A 130 GHz GaAs Schottky-barrier diode oscillator operated in the MITATT mode is described. Preliminary results show that the noise performance of a MITATT source is indeed lower than that of an IMPATT source. With further improvement, MITATT diode oscil-lators can be useful for medium power, low noise applications above 100 GHz.

InP Gunn devices are playing an important role in the development of millimeter-wave components as active devices which perform well throughout the millimeter-wave range. Efficient CW oscillators have been developed covering the 35-140 GHz range. InP Gunn diodes are also being used extensively for low noise and medium power amplification. Amplifiers have been constructed for operation up to 95 GHz.

Focal-plane sensor arrays promise to enhance the performance of quasi-optical millimeter-wave imaging systems. We have developed two kinds of quasi-optical mixers for use in such arrays. Both mixers are planar and can be fabricated on high-dielectric-constant substrates by photolithography. Mixer models tested at X-band showed conversion losses as low as 6.5 dB ± 3 dB, and preliminary tests at 35 GHz indicate these devices will work well at millimeter wavelengths.

An open resonator formed by a flat and a spherical reflector, which with suitable scaling would be appropriate for operation at near-millimeter wavelengths, has been constructed and tested. For ease of fabrication and study, we have performed preliminary experiments in the microwave range of 8.0 to 12.5 GHz on a prototype resonator, but scaling to higher frequencies is quite straightforward. Partial reflectors were constructed of metal strip gratings which have an inductive amplitude reflection coefficient of magnitude about 0.985 at 10.0 GHz. By tuning the frequency of the incident plane-polarized radiation, the Gaussian TEMcimn cavity resonances have been observed in both transmission and reflection. The center frequencies and line widths of several of these resonances have been measured. A confocal resonator of this type would be appropriate as a scanning interferometer for high-resolution spectral analysis of the radiation of a millimeter wave source, and resonators with curved metal grid reflectors could be used for millimeter wave laser oscillators.

The use of harmonic mixers in spectrum analyzers and millimeter-wave frequency phase lock loops provides a simple technique for frequency translation to IF frequencies that are more easily dealt with using low cost post amplifiers and associated circuitry. This paper describes a simple low cost times 3 millimeter-wave harmonic mixer that can be easily scaled to any order of multiplication using printed circuit techniques.

Various low-cost, compact integrated circuit components were developed at millimeter-wave frequencies with state-of-the-art performance. These components include mixers, Gunn VCOs, IMPATT oscillators, frequency doublers, PIN attenuators, PIN switches, couplers and filters. Using these components as building blocks, many RF subsystems can be assembled for system applications.

The operation of a millimeter-wave harmonic gyrotron is described in which the interaction is between large-orbit axis-encircling electrons and cylindrical cavity TEn11 modes. Gyrotron cavities operating on this principle are well matched to low current, moderate energy, rf-accelerated electron beams (- 100 mA, - 250 keV). Efficiencies up to 15% have been measured for moderate harmonic interactions and multi-kW power levels have been attained at the eleventh harmonic of the cyclotron frequency. The concept allows the magnetic field of the gyrotron to be reduced by an order of magnitude, thereby making a submillimeter-wave gyrotron feasible. However, mode competition problems must be considered for high-harmonic, submillimeter wave operation. We have been successful in suppressing mode competition by destroying unwanted modes. The beam current required for oscillation is highly dependent on the electron perpendicular energy. The energy requirement can be reduced by dielectric loading of the gyrotron cavity. We have also begun testing a 30 dB gain, twelfth-harmonic gyro-klystron amplifier.

The considerations and tradeoffs for applying millimeter wave sensors to tactical missile guidance requirements are discussed. These sensors can operate in the active (radar) and passive (radiometric) modes for achieving a high degree of countermeasure immunity. The missile with its millimeter wave seeker is typically required to operate in an antonomous, lock-on-after-launch mode. This implies precise acquisition and track capabilities in the RF head as well as the signal processor such that competing clutter can be rejected and likely target candidates detected and classified.

The U.S. Navy has supported the development of microwave radiometric (MICRAD) imaging for a variety of applications, especially in the millimeter-wave portion of the electromagnetic spectrum. Potential applications of MICRAD imaging include navigation aid for aircraft, map-matching position fixing, terminal homing, and attitude reference sensing. This paper will focus on MICRAD applications to imaging systems, and map-matching correlation systems.

Active millimeter wave (MMW) sensing technology is playing an increasing role throughout the DoD research and development community in the area of Self Contained Munitions (SCM's), autonomous missiles and armament primarily intended for air and surface launched standoff antiarmor weapon systems. Each type of SCM, which requires fire-and-forget search, detection, discrimination and warhead aiming sensing functions, places varied operational, packaging and performance specifications on its MMW sensor subsystem. This paper attempts to portray the rationale for implementation of active MMW sensing devices into SCM's, along with a description of the spectrum of SCM sensor operational parameters. A treatise of active MMW sensor technologies required for ultimate successful weaponization will include discussions in the areas of signal processing and MMW RF hardware. Ultimately, as active MMW technology matures, the critical trade between complexity, cost and effectiveness must be analyzed for each SCM type. A qualitative discussion in this area will be covered as well, yielding insight into future MMW development areas which require increased heavy emphasis in order to meet the stringent requirements on SCM active MMW sensing subsystems.

Since the reflectivity characteristics from target and clutter are considerably different at millimeter wave frequencies, one should not consider the same signal processing philosophies as it's used at lower frequencies. To derive the full advantage of improved resolution capability at such high frequencies the target and clutter signature and their statistical properties should be considered in the design of the operation millimeter wave radar seekers. We are proposing a statistical signal processing approach which can be incorporated in the design of constant false alarm processor of an airborne millimeter wave seeker. This scheme consists of three distinct functional units, (I) An adaptive filter for noise elimination and decorrelation of signal and clutter, (II) A pattern classifier for identifying the type of clutter statistical distribution and (III) A CFAR processor. This scheme enables an airborne millimeter wave radar to process more information during every scan while maintaining a constant false alarm rate by fixing a threshold adaptive to the type of clutter that is encountered.

Millimeter wave upconverter assemblies covering the frequency ranges of V, E, and W Bands are described. These upconverter assemblies are used to extend the output capabilitl of existing X and Ku Band sweepers to the millimeter wave ranges, and are capable of providing power across the full waveguide bandwidth. Maximum output powers generated are 4 mW, 1.5 mW and 0.5 mW for V, E, and W lands respectively.

Frequency management problems, scarcity of orbital position assignment, and resistance to interfering signals are projected to become serious problems for satellite communication (SATCOM) systems operating below about 15 GHz. International frequency allocations in the 15-50 GHz range permit SATCOM system operation with increased frequency bandwidth and hence may eliminate significant frequency management problems. This paper addresses some of the salient factors that influence SATCOM systems operating over the range 7-50 GHz. Propagation losses, frequency variation of a terminal's EIRP, spatial discrimination, and band-width available for spread spectrum AJ are presented as a guide to choosing the operating frequency of an EHF SATCOM system.

Several communications satellites now being developed for future commercial and military systems will have the ability to provide electronically controllable antenna patterns for maximum capability and flexibility. The multiple beam antennas which provide this coverage contain one key element known as a beam forming network (BFN). Critical components employing ferrite device technology have recently been developed for use in wide variety of beam forming networks in the millimeter wave region. These components have the required insertion loss, switching energy, size, weight and reliability necessary in satellite applications.

During the past three years, interest in satellite communications in the frequency bands above Ku-band has expanded dramatically. As a result, a number of key technology developments, targeted to meet specific next generation spaceborne needs, were undertaken. The state-of-the-art in solid state power transmitters and low noise receivers, including critical passive component technology, is presented. This includes filters as well as a series of rugged high performance ferrite components such as isolators, circulators and latching switches.

A study/measurements program comparing predicted MMW intensities to measured intensities at receiver locations after multiple reflections through urban intersections has been completed. MMW instrumentation equipment belonging to the Institute for Telecommunication Sciences was taken to downtown Boulder, Colorado to perform double bounce transmission measurements around corners through selected downtown intersections. A transmitter beam was directed obliquely toward the building fronts on one side of a street in such a way that the specularly reflected ray would pass through the intersection and be reflected (for the 2nd bounce) by the building fronts along the observable side of the intersecting avenue and to the receiver. For each initial angle of incidence of the transmitter beam an azimuth intensity profile was made by the narrow beam receiver. It was observed that 9.6 GHz was distinctly superior to either 28.8 or 57.6 GHz for achieving general non line-of-sight street level urban area communications.

A summary is given for terrestrial applications of millimeter-wave communication systems. Consideration is given to the role of atmospheric attenuation in making an appropriate choice of frequency band, and to systems that take advantage of attenuation effects to limit intercept range. Examples are given for several types of recently-developed systems, including cases operating at various frequency bands,between 36 and 70 GHz. An extensive reference list is included.

Highly accurate continuous spectra of the absorption coefficient and refractive index of some potentially useful materials have been made over the 60-420 GHz range. Measurements have been made on some common ceramic, semiconductor, crystalline and glass materials. The absorption coefficient of low loss materials increases with frequency which implies that microwave data cannot be used for the design of millimeter wave dielectric waveguides, devices, windows and quasi-optical elements. The data in this paper show the millimeter wave frequency dependence of tan δ, the real and imaginary parts of the dielectric permittivity and the optical constants, namely, the refractive index and absorption coefficient. The measurements have been made in a plane-wave Michelson interferometer operating as a polarizing, dispersive Fourier transform spectrometer. The accuracy and reproducability of the refractive index is six significant figures.

This paper describes briefly the standards and measurement systems that are maintained at NBS to provide calibration service in the ranges 26 to 40 GHz, 55 to 65 GHz, and at 95 GHz. The measurement systems range in degree of automation from manually tuned reflectometer and attenuation measurement systems to automated single and dual six-ports. Plans to complete the coverage of the range from 26 GHz to 75 GHz and to extend the range beyond 100 GHz are discussed.

Calculations are made of rain-induced cross polarization and attenuation on horizontal paths, at wave-lengths between 1.36 and 30.0 millimeters, and rainfall rates between 5 and 40 millimeters per hour. On a one kilometer path, cross-polarization ratio vs wavelength exhibits a maximum in the region between 5 and 10 millimeters, the location in this region varying with rainfall rate.

The Georgia Institute of Technology Engineering Experiment Station is developing a pulsed, coherent, high-power 95 GHz instrumentation radar employing an extended interac-tion amplifier (EIA) transmitter. The system (HIPCOR-95) is intended to provide milli-meter wave instrumentation support to future reconnaissance, surveillance, and target acquisition programs. This paper describes the new technology which supports the develop-ment of such a radar and the characteristics and operating parameters of the system.

Extended Interaction Oscillator and Amplifiers (EIO/A) have proven to be reliable high power sources of millimeter waves.1 Their unique capabilities have been demonstrated in various modulator configurations. Proper selection and tailoring of the modulator will define the capability of the EIO/A to meet the requirements of the radar system. This paper describes the basic characteristics of the EIO/A, the typical modulator configurations developed to drive the EIO/A, and comparative results attained by each method.

An airborne imaging 92/183 GHz radiometer was recently flown onboard NASA's Convair 990 research aircraft during the February 1983 Bering Sea Marginal Ice Zone Experiment (MIZEX-WEST). The 92 GHz portion of the radiometer was used to gather ice signature data and to generate real-time millimeter wave images of the marginal ice zone. Dry atmospheric con-ditions in the Arctic resulted in good surface ice signature data for the 183 GHz double sideband (DSB) channel situated ±8.75 GHz away from the water vapor absorption line. The radiometer's beam scanner imaged the marginal ice zone over a ±45 degrees swath angle about the aircraft nadir position. The aircraft altitude was 30,000 feet (9.20 km) maximum and 3,000 feet (0.92 km) minimum during the various data runs. Calculations of the minimum detectable target (ice) size for the radiometer as a function of aircraft altitude were performed. In addition, the change in the atmospheric attenuation at 92 GHz under varying weather conditions was incorporated into the target size calculations. A radiometric image of surface ice at 92 GHz in the marginal ice zone is included.