This PDF file contains the front matter associated with SPIE Proceedings Volume 10276, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Quasi-optical power-combining arrays overcome some limitations of traditional power combining schemes, and are expected to facilitate development of compact and reliable millimeter-wave systems. This paper presents an overview of 1993 quasi-optical power combining technology, focusing on approaches for direct DC-to-RF conversion and beam amplification. Arrays for frequency up- and down-conversion, and beam control are briefly reviewed, and possible applications and future research efforts are identified.

Millimeter wave MMIC component technology has made dramatic progress over the last ten years largely due to funding stimulation received under the ARPA Tri-Service MIMIC program. In several smart weapon systems, MMIC components are now specified as the baseline approach for millimeter wave radar transceiver hardware. Availability of this new frontier in microelectronics has also enabled realization of sensor fusion for multispectral capability to defeat many forms of known countermeasures. The current frequency range for these MMIC-based components is approximately 30 to 100 GHz. In several cases, it has been demonstrated that the MMIC component performance has exceeded that available from hybrid microstrip circuits using selected discrete devices. However, challenges still remain in chip producibility enhancement and cost reduction since many of the essential device structure candidates are themselves emerging technologies with a limited wafer fabrication history and accumulated test databases. It is concluded that smart weapons of the future will rely heavily on advanced microelectronics to satisfy performance requirements as well as meeting stringent packaging and power source constraints.

After a short introduction to millimeter wavelength (MMW) radar, this paper presents a current survey and assessment of MMW technology, especially as it relates to radar applications; discusses some important recent research in MMW propagation modeling, clutter characterization, and multipath prediction; presents some examples of recent and on-going MMW radar hardware development programs in the military, phenomenology/instrumentation, and commercial areas; and concludes with a brief discussion of possible future directions for millimeter wavelength radar.

Fresnel zone plate antennas have seen extensive research in recent years. Both transmission and reflection types have been analyzed and tested, and found to give excellent performance. Parameters such as far-field patterns, gain, efficiency, frequency dependence, aberrations, scan capability, focal region properties, and off-axis performance have been examined. While most zone plates are planar, curved (spherical or paraboloidal) versions have been found to offer certain advantages, such as sharpness of focus or larger field of view. In general, millimeter-wave results are emphasized.

InP Gunn diodes provide low-cost, efficient, reliable solutions to power generation and amplification problems throughout the millimeter-wave range. InP has replaced GaAs as the material of choice for most millimeter wave Gunn diodes. It offers a significant efficiency advantage and has extended the frequency range of practical Gunn oscillators beyond 140 GHz. Device performance in applications ranging from 35 to 140 GHz will be described, including local oscillators, VCOs, power amplifiers, and power combiners. CW output powers exceed 500 mW at 35 GHz, 150 mW at 94 GHz and 50 mW at 140 GHz, while conversion efficiencies exceed 15%, 6%, and 2.5%, respectively.

Recent improvements in material structure, device layout, fabrication process, and device matching have resulted in simultaneous improvements in power output, power gain, and power-added efficiency from large size GaAs-based pseudomorphic AlGaAs/hiGaAs HEMTs at millimeter-wave frequencies. Consequently efficient watt level building blocks are now available to build solid state power amplifiers capable of 1 to 20 watt power output for next generation military and civilian systems. This paper describes a state-of-the-art 0.15 pm power HEMT technology suitable for applications in this frequency range. Examples of MIC and MMIC power amplifier circuits are given to illustrate the achievable power performance. Preliminary study of the power HEMT reliability is also discussed.

Ever since microwave tubes were first invented in the 1930’s¹ they have been integral parts of all systems requiring high power in the microwave range ( from approximately 1 GHz to 300 GHz). Applications of microwave tubes include radars, electronic countermeasures, communications, materials processing, heating, particle accelerators, and energy transfer. With a few exceptions, the development of millimeter wave (MM-wave) tubes operating from 30 to 300 GHz has in general been sequential to the development of their lower frequency counterparts. Therefore, it is quite common for MMwave tubes to be scaled versions of the lower frequency tubes. Although a variety of MM-wave tubes have been invented, and developed throughout the electron vacuum tube history, only a few basic tube types have received continued interest in the industry due to technical and economical factors such as fabrication complexity, reliability, cost and market demand.

Progress in the application of ultrafast optics to microwave and millimeter-wave technology using picosecond photoconductors and photoresistors is reviewed. Generation, control and characterization of both pulsed and CW high frequency waves are presented. An optical-microwave inter-mixing technique has been applied to phase lock a free running microwave oscillator to the picosecond laser pulses. A time-domain network analyzer which uses optoelectronic techniques for on-wafer monolithic microwave and millimeter-wave integrated circuit measurements is described.

Recent millimeter-wave three-terminal semiconductor device performance improvement enables monolithic millimeter-wave integrated circuits to be a viable option for many applications through 100 GHz. The low cost of the MMIC circuits, a result of circuit design and fabrication technique improvements, provides a path to low cost millimeter-wave systems for new commercial and military applications. Key technical advances that make the fabrication of high-performance monolithic millimeter-wave integrated circuits possible will be described. System applications and the present state of the art in monolithic millimeter-wave integrated circuits will also be discussed.

This paper provides an overview of techniques for modeling and simulation of millimeter-wave components with the Transmission Line Modeling (TLM) method. It is divided into three parts: Theoretical and algorithmic foundations, computer implementation and validation, and design/optimisation.

As the requirement for microwave engineering has been quickly changing, the research community must also change. Rather than observing the entire microwave research, this paper picks up a subjective view in the form of challenge to the electromagnetics for new requirement for microwaves. This challenge comes from quickly changing environment prompted by a renewed interest in "radio" engineering combined with defense cut. The classical electromagnetic theory must change to be able to provide constructive roles toward the modem radio engineering. Some of the features needed toward this goal is to capture interdisciplinary areas from the electromagnetics point of view. They include close couple to microelectronics, visualization, and system applications. Several subjective views and examples will be presented.