The past 30 years have witnessed the introduction and phenomenal improvement of digital communications services. Several characteristics emerge when looking at the trends. First, capacity and capability of communications networks are growing rapidly. Next, local and personal access to digital services is expanding. Finally, ordinary 4 kHz analog voice lines are now providing 28.8 kbps digital services in the home. Only 15 years ago, this data rate was 300 bps, a growth factor of 96 in 15 years or 36 percent per year. In addition, clever data compression techniques have reduced the data rates required for speech and video, and we now have the ability to provide video conferencing on computers using existing terrestrial networks. As the world makes greater use of wireless communications, hundreds of satellites are orbiting in space to provide fixed and mobile services. Because of the large number of satellites, the geostationary orbit is heavily used. More sophisticated satellites could be designed, but a simpler solution is to move to higher frequencies offered by millimeter wave bands. Dozens of US companies are currently developing systems that will provide high data services to the world.

First operation of a new generation of MW level, 110 GHz generator on the DIII-D fusion experimental device has been achieved. THe desire for high power, cw millimeter (mm) wave sources to support fusion research and development is just now beginning to be realized. Plasma heating and current drive with directed mm waves rely on the strong absorption achieved when the wave frequency matches the natural 'cyclotron' frequency of electrons in a magnetic field, or its harmonics. Recent progress in fusion experiments highlights the need for control of the interior details of the hot plasma, and mm wave systems are ideally suited for this role. A brief status of fusion research is given, and the importance of mm waves in the future directions for fusion research is described. The vacuum transmission components necessary for transmitting, monitoring, and launching high power 110 GHz waves into a plasma have been developed at General Atomics and will be described. High power mm waves have a number of attractive technological features for fusion applications compared with other candidate plasma heating and current drive technologies. Millimeter waves can be transmitted with high power density over large distances with low losses by utilizing corrugated waveguides, so the generators can be sited remotely, facilitating maintenance and saving valuable space near the fusion device.

An ultra low phase noise 89-GHz frequency source module based on MMIC technology is developed. This source module consists of a 5.5625-GHz fundamental-mode dielectric resonator oscillator and a diode doubler using GaAs-based HBT MMIC technology, a 11--to-22 GHz doubler, a 22-to-88 GHz quadrupler, and W-based output amplifiers fabricated using GaAs HEMT MMIC technology. The module is packaged in a miniature and hermetically sealed housing, and has good phase noise performance due to the low 1/f noise of the GaAs-based HBT devices and the high-Q off-chip dielectric resonator. At 89 GHz, the measured phase noise results are - 112 and -125 dBc/Hz and 1-kHz and 1-MHz offset, respectively. These results represent state-of-the-art performance for the MMIC based W-band source module.

In recent years research in the development of InP-based HEMTs for millimeter wave and submillimeter wave power applications has increased dramatically. This has led to the development of InP-based power HEMTs with state-of-the-art performance. A review of the development of InP-based HEMTs for millimeter wave and submillimeter wave power applications is presented in this work.

A high performance 38 GHz monolithic pseudomorphic high electron mobility transistor (PHEMT) power amplifier has been developed for commercial millimeter-wave radio systems. This highly integrated MMIC chip has three power PHEMT stages and achieved 25 dBm 1-dB compressed output power with 19 dB power gain using 6V drain-source bias. The MMIC process utilized an optimized power PHEMT structure and has demonstrated high yield with excellent reproducibility making it suitable for high volume commercial applications.

We have developed an ultra-low noise 94 GHz MMIC amplifier using InGaAs/InAlAs/InP transistor technology. The MMIC designs incorporate a single transistor stage with input and output matching networks as well as gate and drain bias networks. Two MMICs have been incorporated into a single housing providing 10 dB of gain. At room temperature, the integrated amplifier has a measured noise of 365 K at 94 GHz. Cryogenic measurements have been performed using a direct detection total power radiometer with all amplification provided by MMIC amplifiers. The noise figure for the entire radiometer has been measured to be 78 K. The noise figure for the cryogenic InP MMIC 2-stage amplifier unit has been measured to be 51 K with a low power consumption of 0.84 mW per stage. The stability of the radiometer with a 4 GHz bandwidth, is characterized by a power spectrum with a '1/f knee' frequency of 45 Hz.

In this paper we present a design procedure of high frequency amplifiers that uses the gain peaking technique to extend their bandwidth. Namely, the performance of single inverters with and without gain peaking elements, was compared theoretically. Then, we derived simple analytical formulae that we have used together with powerful computer aided design tools to estimate the peaking inductances added to GaAs wideband monolithic direct coupled amplifiers to extend their frequency bands. It is shown that the gain peaking technique is effective for extending the bandwidth, for two circuit blocks in cascade a gain between 12 and 16 dB from dc up to 12-GHz was predicted by the simulation results.

For portable communication terminals, power amplifiers on monolithic technology are needed. In this paper the design and test of a 60 GHz monolithic power amplifier is presented. The amplifier uses PMHFET monolithic technology with 0.15 micrometers mushroom gate length and microstrip structures. The chip size is 3mm X 1.5mm. For the amplifier design, a PMHFET nonlinear model based on continuous DC and AC measurements up to V-band was obtained. Models for some of the microstrip discontinuities were obtained from EM simulations. An output power greater than 100mW at 62GHz with more than 10dB gain was achieved. A power added efficiency of 16 percent was measured with V_DS equals 2.5V.

Multi-atmosphere CO₂ lasers can provide continuous gain over bands 20 to 30 cm^-1 wide in each R and P branch of the 00⁰ yields 10⁰ and 00⁰1 yields 02⁰0 bands, covering approximately 60 percent of the 9.2-10.8 micrometers region. By contrast, the spectrum of a typical low pressure CO₂ lasers is 99 percent empty. We describe design studies and the construction of a 20-atmosphere laser that will operate on a single longitudinal model and prove mode-to-mode tunability, thus effecting a useful compromise between the narrow-line capability of a low pressure laser and the broad tunability of a multi-atmosphere laser. One important application of this laser is to pump double-Raman processes in methyl fluoride which will shift the narrow linewidth and tunability to the 150 to 650 micrometers region of the far IR.

We report 24 new laser lines from ¹³CH₃OH methanol when pumped by a cw-CO₂ laser. The majority of the lines are pumped by the 10R and 10SR bands of the CO₂ laser. Two are pumped by the 9HP hot-band CO₂ line. We measured 21 laser frequencies in this molecule; 18 from new lines and three from previously reported lines. We also remeasured and corrected the frequency of the 9P(44) pumped line as 3 378 404.87 MHz. Assignment of two lines: 10SR(17) - 77.5758 cm^-1 and 10R(50) - 119.3020 cm^-1, and predictions for other potential FIR laser lines with these two pumps are also included in this work.

Difluoromethane (¹²CH₂F₂) together with its ¹³C isotopomer is a well known efficient laser medium for the generation of far-infrared laser lines. Both isotopers have produced nearly 200 laser lines with wavelengths in the range between 95.6 and 1448.1 micrometers . We report here the discovery of 13 new far-IR laser lines from ¹²CH₂F₂ and seven new lines from ¹³CH₂F₂. MOst of the new lines were pumped by high J-lines of the 9R branch of a cw-CO₂ laser. Wavelengths range from 97.6 to 616.18 micrometers . Frequency, pump offset, relative polarization, and relative intensity were measured for most of the new lines.

Until recently hydrazine had 35 known far-IR laser lines when optically pumped by a ¹²C¹⁶O₂ cw-laser. We have discovered 127 new lines pumped by regular, sequence, and hot band lines of a ¹²C¹⁶O₂ cw-laser. One hundred and one of these new lines have wavelengths less than 200 micrometers , the shortest wavelength line is 49.2 micrometers . Of the 162 known lines, 139 have been frequency measured. We list the pump line, pump offset, FIR wavelength and frequency, optimum pressure, relative intensity, and relative polarization for each line. Preliminary work has also identified 12 new lines when hydrazine is pumped by an N₂O laser.

In this work, precise frequencies were measured for two important far IR (FIR) laser transitions in methanol optically pumped by the 9P(16) CO₂ laser line at an offset of +64 MHz from the line center, using IR - millimeter wave double resonance technique. The two measured FIR frequencies are at 525,427.902 and 477,790.879 MHz, with an estimated precision of +/- kHz. In addition another frequency was measured at 573,025.151 MHz, and this line corresponds to an absorption transition whose lower level is the upper pumped level. The measurements provide valuable confirmation for the assignments of the IR as well as the FIR transitions. In addition, we also measured accurate frequencies for several transitions in the ground vibrational state in the range 109-127 GHz.

We have developed a technique of achieving continuous-wave far-IR lasing in NH₃ using a line-tunable mid-IR NH₃ laser which is optically pumped by a CO₂ laser. In the sequential pumping, a number of far-IR laser lines is obtainable from a single CO₂ laser pump line. Continuous-wave laser action on 10 far-IR lines of ¹⁵NH₃, including 4 new ones, has been observed in the wavelength range from 60 to 400 micrometers .

The direct and concise method of the Transverse Transmission Line (TTL) is applied for the unilateral, antipodal and bilateral finlines asymmetric in the plane-E, with semiconductor substrates, including the conductor thickness. The effective dielectric constant, the attenuation constant, and the characteristic impedance are developed. Some of these structures are applied to devices as coupler and impedance transformer. In the TTL method, the Maxwell's equations in Fourier transform domain, are used to obtain the electromagnetic fields in terms of the transversal electromagnetic fields. By applying the boundary conditions and using the moment method and the Parseval's theorem, an homogeneous equations system is obtained with two variables. The complex propagation constant is obtained by setting the determinant of the system matrix equal to zero. The effective dielectric constant is determined by means of the relation between the phase constant and the wave number of the free space. For evaluating the characteristic impedance, the definition that relates the transmitted power and the voltage across the slots is used. Computer programs are developed in FORTRAN 77 language, and the results in 2D and 3D are obtained using a Pentium microcomputer, of the effective dielectric constant, the attenuation constant, and the characteristic impedance with parameters such as the operating frequency, the thickness of the semiconductor substrate and its conductivity, and the slots widths and their location. These results are compared with references and the agreement is quite good.

Recent advances in millimeter-wave monolithic integrated circuit technology have resulted in a significant reduction in the size and cost of active microwave circuits over the past several years. More accurate deice and circuit models, efficient user-friendly design tools, improved manufacturing processes, cost-effective packaging and high-volume testing have all contributed to this success. The Ferrite Development Consortium, sponsored by the Defense Advanced Research Projects Agency has effectively applied may of these same techniques to reduce the size and cost of planar circulators. This paper will review recent activities being conducted in this program related to millimeter-wave microstrip circulators.

Various design techniques used for beam waveguide feed systems are characterized. These include the use of gaussian beam, Geometrical Optics and physical optics systems. Also introduced is a new technique based upon a conjugate phase matching focal plane technique. Advantages, disadvantages and range of applicability of each technique is given. In addition, comparisons of computed and measured results from each type of design are presented.

In this paper, a micro-slot coupled structure in up to 4- layered region is investigated. Many characteristics of conventional lines are easily explained through this study. For example, the coplanar waveguide can be considered as a stripline tuning with a wider slot. Microstrip and suspended lines are also easily modeled by this structure. However, as a multilayer structure, one can get many design flexibilities, such as wide achievable impedance ranges and more tunable parameters.

A numerical approach based on the 3D finite-difference method and the analytical results of the fields in waveguides is developed for the analysis of the characteristics of waveguide three-port junctions. The basic two wave equations described by two transverse field components with respect to the direction of the power propagation are derived from the Maxwell Equations in cylindrical coordinates. For the junctions filled with air, there is only one field component in each equation, and generally solving the equation relative to electric field is enough for the obtain of the property of the junction. Two typical cases were analyzed by the approach and the results agree well with the earlier experimental and theoretical results.

An experimental 8mm-wave multi-functional transmission system has been set up for the transmission of color TV, telephony, and data in a bi-directional manner. In this paper, the design and performance of this system is presented with regard to detailed system considerations and description. A series of measurements and experiments have been carried out to measure the practical transmission performance, and to observe the transmission quality. At a given bit error rate, the deterioration of signal-to-noise ratio in a nonlinear band-limited channel have been predicted with a MSK modulation. The link availability of this system at different data rates are given in reference to the rainfall distribution of Hong Kong. The experimental results show that the transmission range > 1km for TV signal under clear-air conditions, transmit-receive isolation > 50dB, low bit error rate at a serial data communication, and high quality of TV programs transmission can be observed.

The mm- and submillimeter wave spectrum of a glass at low temperatures is often dominated by the dynamics of two level systems (TLS). These E and M properties are reviewed here. Next the low-temperature far-IR absorption measurements on a number of alkaline earth: rare earth fluoride mixed crystals with the fluorite structure are described, compared to the glass results, and found to display a similar frequency distribution of TLS. At higher far IR frequencies a characteristic temperature dependence associated with excited state transitions of the TLS is observed for both mixed crystals and glasses, suggesting a fundamental connection between the TLS in these very different systems.

The National Institute of Standards and Technology is developing a Fabry-Perot resonator to measure the permittivity at 60 GHz. The system is designed to operate in a semi-confocal configuration with the ability to adapt the system for high-temperature measurements. This talk will focus on design of the system, mode identification, and measurements of permittivity for three low-loss materials.

Transmittance of 'Gore-Tex' woven radome membranes with various diameter of threads and thickness of the laminate has been studied as a continuous function of frequency over the range 90-900 GHz by utilizing Fourier transform spectroscopy. For the first time the transmittance has been measured with various angles of incidence of the incident wave. Strong diffractive scattering has been found above the frequency with wavelength comparable with period of the fabrics. Gore-Tex woven membrane materials are suitable for radome applications up to 1000 GHz.

This paper discusses the development of an open-path millimeter-wave spectroscopy system in the 225-315 GHz atmospheric window. The new system is primarily a monostatic swept-frequency radar consisting of a mm-wave sweeper, hot- electron-bolometer or Schottky detector, and trihedral reflector. The heart of the system is a Russian backward- wave oscillator (BWO) tube that is tunable over 225-350 GHz. A mm-wave sweeper has been built with the BWO tube to sweep the entire frequency range within 1 s. The chemical plume to be detected is situated between the transmitter/receiver and the reflector. Millimeter-wave absorption spectra of chemicals in the plume are determined by measuring swept- frequency radar signals with and without the plume in the beam path. Because of power supply noise and thermal instabilities within the BWO structure over time, the BWO frequencies fluctuate between sweeps and thus cause errors in baseline subtraction. To reduce this frequency-jitter problem, a quasi-optical Fabry-Perot cavity is used in conjunction with the radar for on-line calibration of sweep traces, allowing excellent baseline subtraction and signal averaging. Initial results of the new system are given for open-path detection of chemicals.

In this paper, an optoelectronic sampler is described. The device is made with microstrip propagation lines and ultra- rapid photoconductive switches which are integrated in the same substrate. The sampler is used to measure the output electrical signal provided by an ultra-fast detector. The detector electrical pulse lasts from 20 ps to 100 ps and is sampled every 4 ps. The total record length is 400 ps.

The spectral performance of bandpass grid filters centered at terahertz frequencies is presented. The filters are composed of a periodic array of cross-shaped apertures in an evaporated metal film on a thin dielectric substrate. A commercial Fourier-transform spectrometer is used to measure spectral transmittance. Results are presented for filters using gold films of different thickness. The peak transmittance is correlated with the DC surface resistance R_s of the film, which is probed using an in situ test structure on the fabricated filters. This is true even though the gold films all have a thickness several times the classical skin depth at the resonant frequency. Measurements of R_s and peak transmittance at 77 K show an equivalent correlation, indicating that some of the loss is due to the finite conductivity of the gold film. The dielectric substrate causes a downward shift in the center frequency of the filter proportional to the dielectric constant and thickness of the substrate. The center frequency shifts rapidly with increasing dielectric thickness and reaches an asymptotic value reduced from the freestanding case by the square root of the mean dielectric constant. Measurements are compared to a finite-difference time domain model, which accurately predicts the center frequency, but does not account for losses. The performance of these filters, along with their simple fabrication, makes them useful frequency- selective elements at far-IR wavelengths.

Theoretical analysis indicates that resonant infrared photoconductors can achieve unit quantum efficiency at resonant frequencies. This concept, which is based on establishing a resonant absorption cavity internal to the detector element, offers numerous other enhancements and advantages over conventional detectors. Here, we present an overview of the operation of the device and outline the fabrication process of a Ge:Ga far-IR photoconductor. The preliminary test results performed on a prototype Ge:Ga detector show the expected resonant fringes with enhanced response. The summary of the results and the status of the project will be discussed.

In this paper we consider preformatting at the transmitter side to minimize the intersymbol interference introduced by the delay spread caused by Rician fading channels on differentially detected MSK signals. We propose a new phase compensation scheme that alters the phase of the transmitted signal in such a way that the phase shift of the diffuse component is such that it causes only a minimum increase in the intersymbol interference of the detected signals.

We report an RF optical InP-based PIN-HEMT photoreceiver operating across a measured 36-46 GHz frequency band fabricated on the same wafer using selective area regrowth with molecular beam epitaxy. The photoreceiver design consists of a 20 micron circular InGaAs/InP photodiode integrated with a wide band 0.15 micron gate length InGaAs/InAlAs/InP low noise amplifier optimized for 44 GHz operation. The heterodyne technique of beating the frequency of two lasers was used to generate an RF modulated light signal at 1.3 micron wavelength. The output of the photoreceiver was measured on a spectrum analyzer and was found to be -24 to -27 dBm across a 36-46 GHz band.

We have included in our two-gap model of superconductivity in the cuprates the effect of pair breaking caused by magnetic impurity scattering. This model explains many of the observed features of the cuprates including the temperature and frequency dependence of the surface resistance and penetration depth, the anomalous temperature dependence of the upper critical magnetic field, and the zero bias anomalies observed between cuprates and normal metal contacts. This model can also explain many of the phase coherence experiments in YBaCuO on the basis of magnetic scattering at an interface or grain boundary due to strain-induced oxygen loss. We have recently extended this model to calculate the electromagnetic properties and the density of states in the presence of magnetic scattering. The latter results will be presented here.

We describe two projects aimed at applying the great temperature sensitivity of superconducting thin films when biased at heir critical temperature to high sensitivity radiometry in the 10-50 micrometers wavelength region. The first is a standards-grade system for installation in the NIST low-background infrared calibration facility. It employs thin-film Nb thermometers, and has an operating temperature of 9 K. This system's absorber is a large aperture Cu cone with a blackened interior, to which a thermometer chip is thermally grounded. The absorber and a thermal isolation platform are each thermally stabilized with separate active feedback loops that sense the resistance of their respective thermometers. Temperature control at the level of 1.4 nK has been achieved with this system. Power sensitivity is presently limited by 1/f noise to approximately 10 pW, approximately a factor of 4 better than the current system based on Ge thermistors. The second system is intended for high-sensitivity imaging arrays, and employs YBCO films on free-standing zirconia membranes. The operating temperature is 89 K for pure YBCO devices and in the range of 70-85 K for Co-doped YBCO devices, depending on doping level. The best measured performance on these devices is an optical noise-equivalent power of 1.1 pW/Hz^1/2, with an associated 3-dB rolloff frequency of 130 Hz for the pure YBCO devices and 0.6 pW/Hz^1/2 and 31 Hz for the Co-doped devices. These values represent the best performance, by approximately a factor of two in NEP and an order-of- magnitude in speed, ever reported for superconducting infrared bolometers operating at liquid-nitrogen temperature.

In this paper the design of single side band mixers to convert C to V band signals is presented. A step by step design technique, based on harmonic balance simulations is described. The mixer devices are Schottky diodes compatible with a GaAs MESFET technology. The mixers were optimized for minimum conversion loss over the widest possible bandwidth when used as both up or downconverters in order to be used on a large number of applications. The experiments show, for both applications, a minimum conversion loss in the range of 8 to 9dB and a 3dB bandwidth larger than 6GHz.

In this paper the design of a multifunction MMIC for millimeter wave mobile communication systems is presented. The MMIC is a single balanced mixer that can work as both up and down converter between C and V band and as a BPSK modulator. A step by step design technique is described, based on harmonic balance simulations. The mixer devices are Schottky diodes, and all the components are integrated in a MMIC chip using GaAs MESFET technology. The mixers were optimized to have a similar performance as both up or down converter, between C and V bands and a bandwidth greater than 4 GHz. The experiments show, for both applications a minimum conversion loss in the range of 6 to 8 dB and a -3dB bandwidth larger than 7 GHz.

We present measured data for three W-band singly-balanced mixers utilizing both GaAs pseudo-morphic HEMT and InP HBT device technologies, and critically compare their LO power requirements, and conversion loss and noise figure performance. Of the three distinct single-balanced mixers which were investigated, i.e. the GaAs HEMT and InP HBT Schottky-diode rat-race mixers and the dual quadrature resistive GaAs HEMT mixer, the InP HBT diode mixer exhibited the best noise figure at low intermediate frequencies and achieved good conversion loss performance with low LO drive requirements.

Three kinds of metal-insulator-metal diodes, W-Ni, W-Co, and W-Fe diodes, have been used as mixer-generators of far-IR radiation. The dependencies of the generated far-IR power on the dc bias voltage applied to the didoes have been investigated. Observed bias dependencies can be predicted by analyzing their current-voltage characteristics.

In our present work a computer simulation using the AFOSR code 'MAGIC' has verified the analytical simulations previously presented. The object is to eliminate the low- frequency oscillations that degrade the high-frequency operation of plasma-filled microwave tubes by adding a transverse ion flow or 'flush' to the plasma included. The computer simulation shows a rapidly growing low-frequency oscillation that is strongly damped and even terminated for increasing values of flush rate.

Experimental measurements made on a single Spindt-type molybdenum field emitter are correlated with a simple analytic model of the electron distribution. The measurements were made by using a nanofabricated detector whose position relative to the emitted was determined using laser interferometry. Methods used to correlate theory with experiment are explained, and the dependence of the beam profile on tip sharpness, gate diameter, anode distance, and tip work function are examined. It is shown how the analytic model may be extended to find the trajectories needed for particle simulations. Analysis has shown that the rms spread angle is approximately 20 degrees.

Recent advances in MMW solid-state technology, combined with state-of-the-art quasi-optical feed elements, have made possible upgrades to an instrumentation radar in the W-band. Mixer diodes capable of cryogenic operation have led to a reduction in the receiver noise figure, and a Gunn-effect diode amplifier has boosted transmit power. Application of Gaussian beam optics has provided a reduction in transmit and receive losses, while increasing transmit/receive isolation and power handling capability. In all, an improvement of almost two orders of magnitude is ought, yielding the capability to provide metric tracking and range-Doppler imaging on a variety of important targets.

Radiation patterns are presented for planar equiangular spiral antennas at wavelengths of approximately 10 micrometers . These antennas are fabricated using integrated-circuit processes on silicon substrates and are coupled through dielectric lenses. Patterns are presented over a full 2D scan for orthogonal linear polarizations, and for left- circular (LCP) and right-circular (RCP) polarizations. The antennas respond preferentially to left-circularly polarized radiation, as expected for the left-handed sense of the spiral arms. Cross-polarization ratios as large as 10 dB in circular polarization are obtained, corresponding to an axial ratio of 1.2. No difference in response between horizontally and vertically polarized radiation is observed, as expected for circularly polarized antennas. Directivities as large as 14 dB in left-circular polarization have been obtained. The cross-polarized directivity is considerably lower than the co-polarized directivity. All patterns are approximately circularly symmetric about the (theta) equals 0 axis. The cross-polarization ratio and pattern symmetry strongly depend on the alignment of the antenna and detector response is antenna coupled, even at radiation wavelength of the same order of magnitude as the resolution limit of the optical lithography used to define the antenna geometry.

This paper presents the latest result of applying the microstrip's leaky mode for a millimeter-wave active integrated antenna design. In contrast to the use of the first higher-order leaky mode, the second higher-order leaky mode, the second higher-order leaky mode of even symmetry is employed in the new approach, which allows larger dimension for leaky-wave antenna design and thereby reduces its performance sensitivity to the photolithographic tolerance. The new active integrated antenna operating at frequency about 34 GHz comprises of a microstrip and a coplanar waveguide stacked on top of each other, named as the millimeter wave micro-CPW integrated antenna. The feed is through the CPW that would be connected to the active uniplanar millimeter-wave (M)MIC's. Our experimental and theoretical investigations on the new integrated antenna show good input matching characteristics for such a highly directed leaky-wave antenna with the first-pass success.

Amid the areas of application that the military has identified to transfer its technologies to is that of the law enforcement where they are interested in the application of different types of imaging sensors, particularly the millimeter wave sensors, to the detection of weapons concealed underneath clothing. In order to detect concealed weapons underneath clothing, it is important for the sensor to (1) have a good heavy clothing penetration, (2) operate at a reasonable long range and (3) display data in a near real time. Because these three prerequisites cannot be accomplished simultaneously, we introduce in this work a signal processing stage referred to as the Automated Statistical Characterization and Partitioning of Environments procedure (A'SCAPE), to be located between the data collection and the data display stages of the sensor in order to enhance the collected data before it is displayed. In this paper advantages and inconveniences of passive millimeter-wave sensors are discussed, A'SCAPE is described and an illustrating example is presented.

Frequency multipliers using symmetrical characteristics diodes have been found useful for odd order frequency multiplication. In this paper, a planar 60 GHz frequency tripler based on new high power multi stack quantum barrier varactor is reported. Measurements show a low series resistance of 1.3 (Omega) and high breakdown voltage of 22 volts which permit a high conversion efficiency and output power. Using a 10 stack diode we have designed and fabricated a 60 GHz planar tripler. This type of multiplier is very attractive for application in automotive anti- collision avoidance radar's, indoor communication systems and other mm-wave systems.

Based on the semi-classical density matrix equations, optimized operation of optically pumped NH₃ MIR laser emission at 12.08 micrometers and 12.81 micrometers was studied theoretically and experimentally. The effect of pump power, gas pressure and buffer gas N₂ on MIR output power were discussed in detail.

The spectral characteristics of mini-optically pumped NH₃ cavity laser emission at 67.2 micrometers was studied. It was found that the spectrum of 67.2 micrometers emission was duality. With low power CO₂-9R(30) pumping condition, the spectrum appeared to be two wide FIR laser lines, which were the result of competition of multi-Raman processes. With high power pumping conditions, the spectrum extended to be a very wide band, which was he result of the combination of the competition and interaction enhancement of Raman processes. The wide band spectral characteristics of 67.2 micrometers would be significant to the tuning of NH₃ OPFIRL.

A pulsed radiation power of approximately 1 W was reached for the first time, with the aid of a ZnGeP₂ crystal, at the difference frequency of CO₂ lasers radiation in the submillimeter spectral range.

Stimulated emission of far-IR radiation from uniaxially compressed p-Ge in strong electric fields is shown to be due to population inversion of strain split acceptor levels. The peak corresponding to the optical transitions between split- off and ground acceptor states is found in the spectrum of stimulated emission. The strong frequency tuning by stress due to pressure dependence of the energy splitting of these states is obtained. The inversion takes place as the split- off acceptor state is in the valence band continuum.

A type of E-plane double-Y junction, or YY-junction, circulator has been developed based on the nonradiative dielectric waveguide in Ka band. The operating principle of the circulator was analyzed by the theories of the polarization wave and the eigen network. The structure of the YY-junction is beneficial to enlarge the bandwidth with the structure-minimized. Experimental results show that this circulator is of good performance. The central frequency is 34.5GHz, the 1.5dB insertion loss and 20dB isolation bandwidth is about 1.3GHz.

Microwave oscillations have been observed for the first time from the spacer-cladded GaAs/AlAs multiple-quantum-well resonant tunneling structures stabilized by a microstrip resonator system, which is compatible with use of MBE technology methods, provides a proper circuit conditions at high frequencies appearing to be rather promising for applications in millimeter and submillimeter wavelength range.

The IV curves and the direct detector response of HTS bicrystal grain-boundary Josephson junctions have been measured under submm-wave irradiation at frequencies 350-750 GHz. The Josephson oscillation spectrum has been measured using the Hilbert transformation of detection response dependence. The Josephson oscillation linewidth and corresponding value of effective noise is compared to the estimates from the dc measurements of noise rounding of IV curve. To separate sources of noise the direct measurements of junction's output noise has been performed at 1.5 GHz and low frequencies 0.5-20 kHz.

The noise generator based on the backward wave oscillator (BWO) in 370-535 GHz frequency range has been constructed. The noise spectrum width can be varied from 1 GHz to entire BWO range of operation. The maximum noise temperature is not less than i09 K.

It was originally analytically solved the problem of field distribution of a narrow-directed MM-wave beam behind obstacle. Experiments proved anticipated field levels that are 40 dB higher than the levels of omni-directed decimeter (DM) radiation. It was proposed and verified in series of measurements the model of forming of interference structure of MMW beam field in a shadow of vegetation, versus vertical receiver movement. Taking into account MMW beam peculiarities, it was demonstrated the advantages of frequency re-use increasing efficiency in digital cellular network in comparison with existing DM systems, in application to mobile telecommunications and fixed wireless access.

In this paper, a band filter system improving fuzzy infrared heat image is presented. So long as pre-memory target proper temperature spectrum, the electric filter system will act on image contour preaccentuator.

An original planar n-GaAs diode with n-n⁺ junction has been constructed to detect radiation in the range from millimeter wavelength. The operational principle of this detector is based on free carrier heating in semiconductor by incident power. The analytical formulae for the voltage arising in the planar diode under microwave and laser radiation obtained by solving phenomenological carrier transport and Poisson equations shows no frequency dependence of the detected voltage up to 1 millimeter wavelength. The frequency dependence of detected voltage in high frequency range results from the frequency dependence of the momentum relaxation time of hot carriers. Experimental results of microwave and laser radiation measurements have shown a good agrement with theoretical suggestions.

For high-resolution radar, target recognition is performed by using 1D range profile.In this method, a radar target is described as composed of several kinds of scattering centers with different geometric shapes and structures. However, 1D range profile is so extremely sensitive to aspect angle that a useful target recognition procedure is very unlikely to evolve from it. Here, a study is performed ion the fractal characterization of 1D range profiles of high-resolution polarimetric radar targets at four kinds of polarimetric states and a new concept of the fractal matrix is proposed.

An antenna structure my be conveniently fabricated using corrugated dielectric wave guides. Here trapped dielectric corrugated antenna has been designed and phase constants are computed. By computing phase and decay constants for various corrugation thickness, corrugation period, corrugation height, the radiation pattern can be plotted.

Millimeter wave WLAN is promising for broadband office communications, however, to realize it, the millimeter wave indoor propagation has to be carefully studied for it gives predominate influences on the system performance. This paper briefly presents the predicted results of millimeter wave indoor propagation by ray tracing approach, the path loss of 1, 2, 10, 30 and 60 GHz propagation in a typical Chinese universities building are compared, the increase of pass loss with frequency is statistically studied and reported.

An integrated quasioptical receiver circuit comprising planar complementary log-periodic antenna, SIS mixer with microstrip matching transformers and parallel array of unshunted SIS junctions operating as a local oscillator has been designed, fabricated and tested. The array of parallel SIS junctions united in a microstrip transmission line can be described as a Josephson transmission line (JTL) with single flux quanta synchronously moving along the array of quantum interferometers. The JTL with 20 junctions each 4 micrometers in diameter has critical current 4.5 mA, normal resistance 0.3 (Omega) and a self-detection step at about 1.1 mV. The step width is over 1.5 mA in current scale and 50 (mu) V in voltage scale that corresponds to about 1 (mu) W oscillation power and 25 GHz tuning range with 550 GHz central frequency. A current applied along the top electrode of the JTL allows to vary the output power of such oscillator. The advantages of such oscillator in comparison with Flux-FLow Oscillator are higher impedance of microstrip line about 10 (Omega) that makes easier matching to SIS mixer, lower losses at frequencies about the energy gap for Nb, narrow linewidth and the possibility to tune output power. THe SIS junction IV curve shows current steps at about 1.2 mV that corresponds to the matching circuit central frequency about 600 GHz that is close to JTL central frequency.

A new millimeter wave resonant method for determination of absorption cross-section of vegetation stalks is given. The method is developed for study of vegetation stalks absorption cross-section as a function of their moisture content, or kR parameter (k is a wave number, R is a stalk radius) in millimeter wavelengths band. Modes E01 of a cylinder resonator are employed for such measurements. Dielectric permittivity and loss tangent of a sample can be found by measuring a frequency shift and Qfactor changes of the resonator. Absorption cross-section of a sample is then calculated using a formula obtained in our theoretical study. This formula can be written analytically as a result of rigorous solution of the related diffraction problem (scattering of a plane electromagnetic wave by cylinder with complex dielectric permittivity if stalk radius is less then 0.5 mm for the wavelength of 8 mm). Results of this investigation may be used in creating electrodynamical models of media containing cylindrical stalks of plants, in direct measurements of some canopy parameters, transmission properties measurements of vegetation canopies etc. Key words: absorption cross-section, measurement, canopy, stalk, resonator, millimeter waves

Special interest in the region of measuring technique of MM and subMM wavelength bands consists in carrying out devices for rapid frequency measuring and estimating of harmonical UHF signals intensity in wide frequency band 60-600 GHz. Power minimum level of these signals is equal 106 -iO W and its dynamicd range of input levels is equal about 60 dB. The measuring thne provided by this technique is equal not more 1 sec. In a number of works [1-3] of the recent time physics and technical bases and applied aspects of the Josephson effect concerned to problem of electromagnetic UHF radiation frequency measuring is examined. In these works a mechanism of the Josephson junction interaction with external electromagnetic UHF signals and relations, are given which simply connect the frequency of its oscillation with the voltage on the Josephson junction. The procedure of the harmonica! signal frequency measuring functionally may be reduced to the estimating of "special features" of the volt-ampere characteristic (VAC) or inverted VAC of the Josephson junction, which displays in the form of a step break of the characteristics under the strict coincidence of the external UHF frequencies and own oscillations of the junction under non-stationary mode as a result of its interaction. Thus for measuring harmonical and poliharmonical signals on the basis of the non-stationary Josefson effect it is necessary to identify the special feature of the VAC or *VAC and their deflection and to determine coordinates of the central point of the special feature or the *VAC deflections asymmetry center.

The frequency and power measurements technique using ac Josephson effect is founded on deviation of the voltagecurrent curve of irradiated Josephson junction from its autonomous voltage-current (V-I) curve [1]. Generally this technique, in case of harmonic incident radiation, may be characterized in the following manner: -to measure frequency of the hannonic microwave signal inadiating the Josephson junction and to estimate its intensity using functional processing of the voltage-current curves, one should identify the "Special feature existence" zone on the voltage-current curves. The "Special feature existence" zone results the junction's response to the incident radiation. As this takes place, it is necessary to define the coordinate of a central point of the "Special feature existence" zone on the curve and to estimate the deviation of the V-I curve of irradiated Josephson junction from its autonomous V-I curve. The practical implementation of this technique place at one's disposal a number of algorithms, which enable to realize frequency measurements and intensity estimation with a particular accuracy for incident radiation. This paper presents two rational algorithms to determine the aggregate of their merits and disadvantages and to choose more optimal one.

A complication of the tasks solving by the modem radliolocation, radionavigation and communication systems connected with the demand promotion to the resolution and accuracy of coordinates definition and increase in the volumes of transmitted information in satellite communication systems has resulted in boisterous mastering of millimeter wave bands. Success in microwave technology reached in 80' allowed such leading instrument developing companies as Hewlett Packard; EIP, lB millimeter etc. to set up an output of mm- and submm-wave bands devices and systems. It has streamlined Scientific Technological Progress in several spheres, since millimeter, through infra-red frequency range was closed to researchers for a long period of time because of the absence of necessary equipment. At present microwave devices of the short-wave part of mm- wave band and of submm- wave bands are used not only in radiolocation and communications. Unique diagnostic systems based on the analysis of the radiation parameters of different microwave sources were created. They have their application in medicine, thermonuclear energetics, radioastronomy, biology, nuclear physics, the physics of the solid state body, geology, etc. The above circumstances caused the beginning of the measuring microwave technology researches in 60 to 600 GHz frequency range: generators, power and frequency meters, spectrum analyzers. The task of working out equipment and techniques of the effective control as well as frequency and intensity measurements of the microwave signals in the investigated range is of the special interest. Here are some examples. The creation of a thermonuclear reactor in ITER project is considered to be the project of the century in the energetics sphere. One of the basic engineering tasks in the course of project realization is the creation of the diagnostic equipment realizing in real time spectrum analysis of thermonuclear plasma radiation at the so called cyclotron hannonics. Such analysis allow to get the picture of temperature distribution along the plasma cord diameter in accordance with dynamics of thermonuclear process development. Modem raclioastronomic research gives scientists the unique information on the world tructure. It is also necessary to analyze Space microwave radiation providing exclusive sensitivity of the equipment. In both cases equipment is required to be superwide band, to have high sensitivity and ability to operate at more than 300 GHz frequencies. Today all these requirements are met by the devices using the ac Josephson effect. The Josephson junctions are used as an active transforming element in such devices. At the end of 20 century the sphere of their utilization embraces medicine, communications, radiophysics, space exploration, ecology, military use, etc. The State Research Center "Fonon" ( SRC "Fonon") of the State Committee on Science and Technology of Ukraine was founded in 1991. The main aim of its creation was to concentrate the scientific and financial efforts for development and production of unique devices based on the results of fundamental study in physics of high T superconductivity. First of all we were interested in technological research on the obtaining of low impedance Josephson junctions out of the High T thin films. Using such junctions in combination with our original techniques developed in our Center we have succeed in creating the following new generation equipment: industrial set-up of the frequency meter in the range of 60 ... 600 GHz; experimental set-up of the spectrum analyzer operating in the range of 50 250 GHz; experimental model of radiometric receiver in 180...260 GHz range. All the above devices are based on the using ac Josephson effect for the receiving and processing mm- and submm- microwave signals.

The nonlinear self-consistent theory of two-stream superheterodyne free electron lasers (FEL) with pumping of retarded electromagnetic wave (Dopplertron-type) is developed. The main attention is devoted to the comparative analysis of single sectional and klystron-type schemes of Dopplertron and H-ubitron FELs. These systems are based on application of two-stream instability as a work effect simultaneously with three-waves parametric interaction mechanism which is traditional for FEL. One- and three- sectional of superheterodyne FELs (SFEL) are researched. The first section of klystron scheme plays grouping role, second one is transit space and the third plays demodulator role. It is found out that single sectional SFEL and three- sectional SFEL klystron-type have approximately same gain factors. Therefore a klystron-SFEL is a very promising design because of them great simplicity. In this connection it is shown possibility of creation of FEL-amplifiers which have approximately 30-40 dB amplification levels in mm-IR ranges.

An experimental transmission system at 8mm-wave was built up to perform a multi-channel transmission of audio and video signals in frequency reuse, due to space separation and polarization isolation. The features of such an 8mm-wave communication systems is described in details with respect to system construction and performance. Based on carrier-to- noise ratio and the signal level available, the attenuation margin and link availability are evaluated in terms of path length and specific rainfall distribution at Hong Kong. The quality of the demodulated video and audio signals is used for the analysis of co-channel interference and multipath effects. The experiment results show that the polarization isolation is more than 18.5dB, space isolation is more than 24.1dB, and a good quality in transmission of TV programs is observed in frequency reuse situation under a uncritical condition. Finally, a simplified scheme of the application of this system in wharf container dispatching and management is proposed.

Despite the numerous advantages of microwave passive devices using high temperature superconductors, use of all-HTSC microwave devices has been limited to weak power signal processing due to the limitations in power handung capabilities of the materials. Moreover, practical applications of the HTSC microwave devices have been focused on frequencies below 10 GHz. These technical barriers can be overcome by understanding the detailed high frequency electrodynamic properties of high temperature superconductors. Our experiments, carried out on samples with various degrees of quality over a broad dynamic range of microwave power, frequency, external magnetic fields and temperatures, suggests that for the improvement of the power handling capability and an increase of the frequency application range, the devices made of HTSC materials should have fewer Josephson junctions and increased materials homogeneity.

The state of the art and sub-mm EPR instrumentation is discussed in terms of radiation generation, propagation and detection as well as existing magnets. Possibilities of improving currently prevailing techniques are suggested. Examples are given illustrating the capabilities of the mm and sub-mm EPR spectrometer presently in operation at the NHMFL.

A source of high-intensity, picosecond-to-nanosecond far-IR pulses has been developed at the UCSB Center for Free- Electron Laser Studies. The microsecond-long, far-IR output of the UCSB free-electron laser is sliced into shorter pulses using laser-activated semiconductor reflection switches. We have observed pulse durations as short as 20 ps at 22 cm^-1. An overview of the design and performance of the pulse-slicer system is given.

We will discuss the unique high field millimeter-wave spectroscopic capabilities which we have developed at the National High Magnetic Field Laboratory. The main purpose of this effort is to investigate the electrodynamic response of novel conducting materials in very strong magnetic fields. The paper is organized as follows: we begin by discussing the motivation for these studies, followed by an overview of the experimental techniques; the remainder of the paper focuses on a number of recent experimental studies.

The development of low-temperature-grown GaAs photomixers enables the construction of a microwave to submillimeter- wave source capable of large frequency sweeps. By utilizing semiconductor diode lasers to drive the photomixer, this source is all solid-state and compact, and has small power consumption. Frequency stabilization of the semiconductor diode lasers allows this source to be phase-locked to an external microwave reference. Two 805 nm extended-cavity- diode lasers are mixed in a low-temperature-grown GaAs photoconductive photomixer. The difference-frequency mixing product is radiated by a planar spiral antenna and collimated by a Si lens. This output is phase-locked to a microwave reference by downconverting it in a whisker- contacted Schottky-barrier diode harmonic mixer and using the output to offset-phase-lock one laser to the other. The photomixer output power is 300 nW at 200 GHz and 10 nW at 1.6 THz, as measured by a 4 K InSb bolometer calibrated with a methanol laser and a power meter at 526 and 812 GHz.

A versatile, passive 95 GHz imaging testbed is reported. Naturally occurring W-band black body radiation provides the input. One or more radiometers are mechanically scanned in a raster pattern over the focal plane. Output signals of the radiometers are amplified, sampled and integrated before A/D conversion. The passive millimeter wave (PMMW) image is formed from the resulting 2D array of focal plane data. Images from 192 by 254 to 64 by 64 pixels have been achieved, frame time being proportional to the image size. Simple image processing may be required, depending on image parameters. The test bed easily accommodates a variety of receivers, from single channel to multichannel arrays. Both superheat and tuned radio frequency radiometers have been tested. The testbed is suitable for both fixed and mobile operation. Experimental results are reported for laboratory studies and for field tests in the Big Bend and Davis Mountains regions of southern Texas. The testbed has proven to be a compact, economic and versatile method of demonstrating and exploring PMMW imaging.

Investigations of the non-ohmic properties of conducting materials are a powerful tool in the elucidation of transport mechanisms. Phase-resolved microwave harmonic mixing is a very sensitive method for the detection of nonlinearities which avoids many of the disadvantages of other methods. A nonlinear current-voltage characteristic gives rise to a dc-current proportional to the deviation from linearity when microwave radiation of frequency (omega) and its second harmonic 2 (omega) are applied to a sample. We report on investigations of the nonlinear behavior of thin films of YBCO and TIBCCO at incident microwave power levels ranging from 0.4W to 40W. In films of high quality a mixing signal appears only in the temperature region of the superconducting transition. In contrast films of poor quality exhibit nonlinear behavior between 4.2K and room temperature. The dependence of the mixing signal on the incident power level was studied too. The mixing results are compared to those of harmonic generation experiments done by other groups. The possible mechanisms for the nonlinear behavior are discussed.

We present mm-wave transmission as a complementary technique to characterize the properties of superconducting thin films, obtaining information on both the real and imaginary part of the dielectric function. Examples are given to illustrate the strength of the technique to measure the response of di-electric materials and stratified systems. We demonstrate the BCS-behavior of a conventional superconductor NbN, and show furthermore the unconventional behavior in both the absorptive and reactive part of the conductivity of a 20 nm thick DyBa₂Cu₃O_7-(delta ) film.