Advances in millimeter and submillimeter technology have created new opportunities in basic and applied research. The improvements in the generation of radiation in this region of the spectrum and the further developement of techniques and components enhances possibilities in resonance spectroscopy of solids, gases, and plasmas as well as application in atmospherics, materials processing, radiometery, astronomy, and others.

Applications of millimeter-wave radar, imaging, and communication technology requires cost- effective implementation of intelligent scanning antenna systems. Recent ideas based on switched-beam, traveling wave, and coupled-oscillator or injection-locking techniques show promise for reducing complexity and cost of conventional phased-array systems. This paper focuses on coupled-oscillator techniques and remaining technical challenges for practical implementation of these ideas.

A wide range of applications for high-power millimeter waves are reviewed. Some, such as magnetic fusion, are already reduced to practice, while others require varying degrees of development in one or more areas for their potential to be realized. Sensing trace amounts of contaminants in the atmosphere requires a relatively small amount of development, while the requirements of wider applications like material processing are not even completely known yet. Futuristic applications, such as the launching of satellites utilizing high-power millimeter waves, require significant commitment to be realized.

Microwave FM reflectometry is largely used in thermonuclear fusion experiments to measure the electron density profile. The presence of density fluctuations has a strong influence on the reliability of the data. Large disturbances on the beat signal appear when its frequency is near to the fluctuation frequency. This effect has been observed also in our reflectometric diagnostic even if the modulating frequency used is the highest commercially available (80.0 GHz/msec). In order to reduce the fluctuations effect we have investigated the feasibility of operating the Impatt sources at a higher sweep rate (4000 GHz/msec). To do that we have measured the frequency response and the power response at different sweep speed for our W band sources observing reliable performances and good stability when not limited by thermal management problems. An extensive time resolved spectrum analysis has been done to discover nonlinear effects due to current crowding or local hot spot in the diode. On the basis of this characterization we have designed a high speed current driver tailored to the Impatt sources and able to work well above the requested response time, embodying DC bias control and protection circuit. The driver, based on low cost commercial components, implements microwave frequency range and offset control through a digital interface providing large flexibility on the diagnostic setup.

Methanol has a rich torsion-vibration-rotation spectrum extending from the millimeter and submillimeter regions all the way through the far-infrared (FIR) and up to the near IR. High- resolution studies of the lower vibrational modes have revealed numerous perturbations arising from Fermi, Coriolis, and asymmetry resonances. A remarkable number of the perturbed energy level systems contribute to the extensive FIR laser emission observed from methanol isotopomers optically pumped by CO₂ lasers. FIR laser lines involving perturbed IR levels have been invaluable aids in assigning the FIR and IR spectra and thereby locating the specific energy channels through which the CO-stretching, CH₃-rocking and OH-bending vibrational modes interact with eachother, frequently via torsion-mediated coupling.

The methanol spectrum has been the subject of extensive studies in the microwave, far- infrared, and infrared regions of the electromagnetic spectrum for more than 50 years. The complexity of the spectrum, and the very high quality of the current data lead us to present in a single book all the available spectroscopic information in the regions of broadest interest. Our atlas, currently in press, presents a list of approximately 35,000 assigned transitions from the microwave to the mid-infrared region. The line positions are reported with the current achievable accuracy, and approximate peak intensities are given in this work for the first time. Many new assignments of absorption transitions are presented in this atlas for the first time. The optically pumped methanol laser is introduced, and a list of all the 576 currently known optically pumped FIR laser lines with their quantum number assignments, so far as they are known, are included. The energies of almost 7000 levels, calculated by the Rydberg-Rits combination principle, and the Taylor expansion coefficients for the energy levels are presented. The complete plot of the absorption spectrum from 28 to 1258 cm^-1 is given.

Methanol and its isotopic species have been systematically investigated as sources of far- infrared (FIR) laser emission utilizing a newly designed optically pumped FIR laser system. The system combines several different FIR laser cavity designs with the extended line coverage available from a recently developed high-resolution CO₂ laser of high efficiency. New FIR laser lines have been observed pumped by fundamental band CO₂ lines of high J, sequence band lines, and hot-band CO₂ transitions. The new FIR laser lines extend over a broad spectral region, and contribute significantly to the frequency coverage of the optically pumped FIR laser. Many new short-wavelength lines have been observed for normal CH₃OH using a 2-m-long Fabry-Perot FIR laser cavity. Accurate heterodyne measurements have been made of the FIR laser frequencies and the CO₂ laser pump offsets for many of the new lines.

Laser emission near 100 micrometers from intervalence band transitions of p-type Ge in E (perpendicular) B fields is reported. Our idea is to substitute a Voigt configured permanent magnet for the traditional superconducting one. We compare the results using this new design with our results using a Faraday-configured superconducting magnet. Emission is observed at much lower electric-field pulse magnitude in Voigt configuration. The use of a variable temperature cryostat has allowed detailed temperature dependence of the emission to be studied down to 1.7 K. The emission-strength peaks around 2 K, and a rapid decrease below 2 K has been observed. Heating limits the rep rate, but we have observed emission up to 30 Hz with our permanent magnet. Observation of submm emission from a Voigt-configured p-Ge laser using a permanent magnet represents a breakthrough in practicality because it considerably simplifies the device and eliminates the necessity of liquid helium, in principle.

The millimeter wave cross-correlation spectral technique has been reviewed. The principle and fundamental structure of the spectrometer are presented. A method for measuring complex permittivity based on this technique was proposed. The improvement of the resolution was done by using a phase-locked mm-wave source.

In this paper we report the results of an extensive study on the far-infrared photoconductivity of high purity n-type GaAs. The crystal, which was grown at Max Plank Institute using liquid- phase epitaxy, exhibited the fine structures of the excited state transitions of the residual shallow level impurities. The major peak in the spectral response belongs to the 1s-2p transition, with its responsivity about thirty five times higher than the continuum. At 3.4K detector temperature, 625 mV bias, and 100 Hz chopping frequency the detector responsivity at 35.4 cm^-1 (279 micrometers ) was measured to be 0.017 A/W. Under these same conditions, the NEP was 5.9 X 10^-14 W/(root)Hz. The dark current at 25 mV bias was 5.6 X 10^-14 A.

Shielded multilayered structures are commonly used in MIC circuits up to 140 GHz. This paper describes an original method to accurately calculate the complex propagation constant of shielded multilayered structures with minimal computational effort. The method combines singular value decomposition and poles location technique. In order to construct the complete spectrum of the multilayered structure, the poles detected are used to ensure that no modes are missed. It is shown that this accurate method elimiates difficulties related to poles and steep gradients in finding the complex propagation constant of the multilayered structure. Numerical results are compared first to those calculated by zero detection method and second to data obtained by singular integral equation.

The transverse transmission line method is used to study the effective dielectric constant, the attenuation constant, and the characteristc impedance for the odd-mode and the even-mode excitation of the edge-coupled slotlines, unilateral fin lines and bilateral asymmetric and antipodal finlines with semiconductor substrates. By applying the boundary conditions to the tangential electric fields, the fields in all dielectric regions are determined as functions of the electric fields in the slots. Applying the boundary conditions to the magnetic fields at the dielectric interface, an inhomogeneous equations system is obtained, in which the current densities in the fins are related to the electric fields in the slots. Using Galerkin's method and Parseval's theorem, it is possible to obtain the characteristic equation for determining the complex propagation constant. The effective dielectric constant is determined by means of the relation between the phase constant and the wave number of the free space and the characteristic impedance is determined. Computer programs are developed and the results given by them provide the analysis of the variation of the effective dielectric constant, the attenuation constant and the characteristic impedance. These results are compared with references in which the substrate is a lossless material and the agreement is quite good.

Some models which predict the microwave properties of superconducting microstrip lines, radial stubs, coplanar lines and coplanar waveguides are presented. These models take into account the dispersion which occurs in superconducting lines when the frequency of operation becomes close to the gap frequency of the superconductros (700 GHz for niobium). The effects of fringing fields are also taken into consideration. These models are also valid for high-temperature superconductors. They have been developed in the specific case of elements for which the characteristic dimension (the dielectric thickness for microstrip lines, the spacing between conductors for coplanar elements) is of the same order of magnitude as the typical length of penetration of the magnetic field in the metal. The length of penetration is the skin depth for normal metals and the London penetration depth for superconductors. The consequence of this particular topology is that the propagation of signals in such a transmission line is slow-wave and its microwave properties are modified. These models are also valid for classical line configurations (dielectric thickness much higher than penetration length).

Dynamic characteristic impedances of the broadside-coupled coplanar waveguide (CPW) are calculated using the spectral-domain approach. It is found that variation of the mode characteristics impedances can be substantial over the dominant-mode frequency range, indicating the need for dynamic characteristic impedances for accurate designs of broadside- coupled CPW circuits at high frequencies.

This paper reports the development of an ultra-wide slotline antenna. The antenna is fed using a broad-band coplanar waveguide-to-slotline transition. A return loss of better than 10 dB over a very wide bandwidth of 0.5 to 6 GHz has been measured. Typical measured gain is 8 dBi at 5 GHz. As the antenna can easily be scaled for operations at millimeter and submillimeter wavelengths, its achieved extremely wide bandwidth demonstrates the potential for ultra-wide- band applications in these regimes.

This paper reports the effects of elevated temperatures on high-frequency/high-speed devices, particularly GaAs metal semiconductor field effect transistors (MESFETs) and high-electron mobility transistors (HEMTs). A novel high-temperature electronic technique (HTET) that was employed to stabilize the performance of these devices at high temperatures will also be discussed. The HTET substantially reduced the leakage currents in the substrate, improved the output resistance and breakdown voltage. The HTET also aids in obtaining comparable gain, at elevated temperatures, to the gain obtained at room temperature. The high temperature effects on high-frequency/high-speed FETs and HTET have also been simulated using LIBRA. The simulation results show strong correlation with the experimental data.

New planar transmission lines employing multilayer structures are examined for possible applications in microwave and millimeter-wave integrated circuits. Detailed investigations are presented through numerical results calculated using the spectral domain technique. The newly proposed transmission lines have many attractive features such as large impedance ranges, flexibility and the ability to realize complicated, densely packed integrated circuits, as well as miniaturization through the use of thin dielectric layers.

A new type of wavefront dividing reflection interferometer for the far infrared is discussed. The interferometer uses two sets of interpenetrating rings, one fixed and the other movable for the production of an interferogram. The advantage of this interferometer compared to the lamellar grating is higher modulation of shorter wavelengths. This modulation advantage is also applicable to transmission-reflection beamsplitters in a Mach-Zehnder interferometer. A two mirror wavefront dividing interferometer may be constructed so small that it fits in the deqar of a He-cooled detector. Using this interferometer, asymmetric Fourier transform spectroscopy may be conducted, yielding simultaneously the optical constants n and k with a sample and a reference interferogram.

We describe the design principles of an electron spin resonance spectrometer operating at 250GHz, which uses quasioptics to propagate the far-infrared radiation instead of conventional waveguide techniques. We include examples that illustrate the sensitivity and flexibility of the spectrometer. We also include a quasi-optical analysis of the expected performance of a novel reflection mode spectrometer.

Transmission, absorption coefficient, refractive index, real and imaginary parts of dielectric permittivity and loss tangent spectra of polytetrafluorethylene (teflon), Gore-Tex and another teflon based radome memebrane materials are presented as a continuous function of frequency over the range 60-2,400 GHz (5 mm-0.125 mm in wavelength). The new data are better resolved and cover a much wider frequency range. The transmission reduces significantly with increasing frequency for most radomes. The absorption coefficient or loss tangent values increase almost exponentially with increasing frequency for all these radome materials. The refractive index or the real part of permittivity values are alomst similar to teflon since these radomes are teflon based.

A plasma filling of a microwave tube cancels space-charge effects and has other benefits. Unfortunately, ion plasma oscillations can generate noise, frequency shifts, and even terminate beam current. A possible solution is to have a transverse ion flow, which convects the ion instability away before it can grow to disruptive levels. Keywords, stabilization, plasma-filled tubes, instability control.

A nonlinear multimode frequency-domain analysis of the gyrotron is used to study the effect of excentricity of the electron beam on its performance. The guiding center of the electron beam which is usually at the center of the cavity is now shifted by a distance (Delta) _c. Variations in the gyrotron output power, efficiency, and oscillation frequency pulling because of the electron beam excentricity have been calculated for a simple cavity gyrotron with oscillation frequency of 35 GHz. This paper also introduces the ability of varying the electron beam radius to limit the variations due to the electron beam excentricity.

Passive imaging technology has been recognized and reduced to practice for sensing targets in the battlefield environment for several decades. Most imaging is done at optical and infrared wavelengths which require favorable weather conditions. This paper describes what is on the horizon for a new imaging technology 'passive millimeter wave (PMMW) imaging' that can operate in all weather conditions. It will introduce the reader to the unique world of PMMW imaging by describing the technical approach underway at the Wright Laboratory Armament Directorate, Advanced Guidance Division, Eglin AFB, Florida. A PMMW analytical model has been developed and a data collection/phenomenology testbed is being built to validate this model. This will be a mobile test facility that will provide the needed ground truth for an Airborne PMMW Captive Flight Test program in the FY97/98 timeframe. The thrust of this analytical model is the treatment of theoretical equations that allow low altitude imaging in and out of the millimeter wave spectral 'window' frequencies. PMMW sensors at 35, 60 (non- window), and 95 GHz are being fabricated and will be collocated on the same platform to validate this model. This testbed will be the hardware used to begin a radiometric imaging program that will serve not only military needs for advanced munition sensor development, but commercial and academic endeavors as well.

We report on the first heterodyne measurements with a diffusion-cooled hot-electron bolometer mixer in the submillimeter wave band, using a waveguide mixer cooled to 2.2 K. The best receiver noise temperature at a local oscillator frequency of 533 GHz and an intermediate frequency of 1.4 GHz was 650 K (double sideband). The 3 dB IF roll-off frequency was around 1.7 to 1.9 GHz, with a weak dependence on the device bias conditions.

We present the noise properties of a mixer with the NbN-MgO-NbN quasiparticle tunnel junctions. Our work is based on experiment in the 120-180 GHz range with the NbN tunnel junctions in the mixer. Mixer printed circuit is totally made of NbN. The mixer operates at 5.4 K temperature unacceptable with Nb junctions. The minimum DSB receiver noise temperature is about 65 K at 162 GHz and approaches the Nb SIS mixer performance in mm band. It has been found that the noise sources in the NbN junctions are comparable to the Nb junctions and that the receiver noise with the NbN SIS mixer may be only few times more than the quantum limit of noise in the frequency range below the gap frequency. Output noise of the SIS mixer has been found constant in a wide frequency band and within an important range of the local oscillator amplitudes.

Recent astronomical observations of neutral carbon at 492 GHz have shown that its distribution is widespread in interstellar molecular coulds. Studies of the distribution and excitation of neutral carbon are of key importance in understanding the chemistry of such regions. Observations of CI at 809 GHz to complement those at 492 GHz would be of great importance in such studies. We are currently building as SIS receiver for the frequency band 800-900 GHz for use in observing submillimeter spectral lines, including CI. The receiver will be operated on the TIRGO infrared telescope, situated on the summit of the Gornergrat, Switzerland (altitude 10,390 ft). It is anticipated that this receiver will be mounted on the TIRGO telescope towards the end of 1996, or the beginning of 1997.

We have made a submillimeter-wave telescope for a Japanese sounding rocket, -520-17, which is dedicated for an observation of cold dust in Orion molecular cloud region. The submillimeter-wave telescope was launched on January 23, 1995. The telescope include an off-axis Gregorian telescope with aperture of 30cm, focal plane bolometer array, cryogenic cooling system down to 0.3K, and a star sensor using charge modulation device. A very low emissivity optical arrangement of less than 1% is achieved using pure aluminum mirror, off axis reflector and cold optics. Single moded conical feed horn is effectively coupled with bolometers with efficiency of more than 90%. The focal plane array consists of 12-element bolometers, six for 250 micrometers observation and six for 500 micrometers observation. NEPs of the bolometers are 5 X 10^-17 W/(root)Hz which is read out by AC bridge read-out circuit. Total system gives sensitivities of about 10^-12 W/cm² (DOT) sr for diffuse objects or 2Jy for compact objects at 500 micrometers over 100deg² region with a beam size of 10arcmin. This observation should give unique data on cold dust distribution, which is believed to dominate the dust mass distributional, over Orion Molecular Cloud region. Also discussed in the last section is a development of array detectors for future space mission in far-infrared and submillimeter-wave region.

A millimeter-wave (mm-wave) sensor in the frequency range of 225-315 GHz is being developed for continuous emission monitoring for airborne effluents from industrial sites with applicability to environmental compliance monitoring and process control. Detection of chemical species is based on measuring the molecular rotational energy transitions at mm- wave frequencies. The mm-wave technique offers better transmission properties than do optics in harsh industrial environemnts such as those with smoke, dust, aerosols, and steam, as well as in adverse atmospheric conditions. Laboratory million-meter with this technology. Proof of principle of the open-path system has been tested by releasing and detecting innocuous chemicals in the open air. The system uses a monostatic radar configuration with transmitter and receiver on one side of the plume to be measured an a corner cube on the other side. A wide-band swept-frequency mm-wave signal is transmitted through the plume, and the return signal from the corner cube is detected by a hot-electron-bolometer. Aborption spectra of the plume gases are measured by comparing the return signal processing technique based on deconvolution, we have shown a high specificity of detection for resolving individual chemicals from a mixture. This technology is applicable for real-time measurement of a suite of airborne gases and vapors emitted from vents and stacks of process industries. A prototype sensor is being developed for wide-area monitoring of industrial sites and in-place monitoring of stack gases.

The systematic research and engineering efforts for new class of vacuum tube devices such as diffraction radiation generators are in progress in the IRE of the National Academy of Sciences of Ukraine. For its operation DRG is based on excitation of open resonator (OR) by the Smith-Pursell radiation initiated when electron flow is rectinearly moving near diffracted grating (DG) arranged on one of the OR mirrors. By now a collection of small-sized highly stable through all mm band DRG, packetized in optimum magnet systems with air clearance of 32 mm is available. The supply power is less then 500 W. The magnetic field for accompanying of electron flow is 0,4-0,7 T. The mass of optimum magnet syustem of rare- earth elements is about 2-8 kg. The device is cooling by the water system.

In a strict mathetical setting of the electrodynamic task about the free oscillations of waveguide dielectric resonantors (WDR) with the ferrite longitudinally magnetized disk has been solved. An analysis of the data obtained was carried out. It is shown that in the spectrum of the free resonance frequencies EH_mnp +/- and HE_mnp +/- kinds of oscillations can exist separately. The results of numerical calculations for the EH₀₁₁ and HE₁₁₁ +/- oscillations are given here.

The effect of superhigh Q was revealed theoretically in investigation of coupling of electromagnetic oscillations in open waveguide resonators in the vicinity of singular points (so- called Morse critical points MCP) of the dispersion equation. The effect is connected with anomalous behavior of the diffraction Q factor, which tends to infinity near the MCP. An experimental study of the effect of superhigh Q oscillations in an open resonator (OR) of a diffraction radiation generator (DRG) has been considered in the paper. It has been found that if an interaction between oscillations and competitive dispersion modes on diffraction grating of the generator leads to realization of the phenomenon of compensation of dispersions. As the result, dispersion curves have such sections where the frequency of the generator does not depend on small changes of an external control parameter (an accelerating voltate or a distance between the mirrors of OR). At these sections the frequency of DRG remain constant and this fact caused the effect of superhigh Q.

A novel optically pumped submillimeter laser system with a thin gold-coated glass waveguide and a 'dual color' laser outcuopled mirror has been developed. The system is based on the improvement of the laser cvavity efficiencies at IR and submillimeter wavelength. The thin gold-coated glass waveguide is fabricated by a specific technique, the 'dual color' outcoupled mirror is made up of a multilayer dielectric coating and a gold coating. The new type of submillimeter laser system has the advantages of having a lower IR pump loss, a lower submillimeter transmission loss and a higher submillimeter laser coupling output. The output laser lines in the spectral range from 118.8 micrometers to 1253.7 micrometers in wavelength have been obtained. The transverse intensity profiles of the submillimeter laser are a near Gaussian beam. The manufacturing technique and results are presented in this paper.

The strong photoeffect was discovered experimentally in specially doped InSe crystals at temperatrue 4.2 K as a result of laser radiation action at fixed wavelengths of 337 and 195 microns. Also some of the kinetic, galvanomagnetic and optical anomalies had been observed. They are explained by appearance of the gap E in the conduction band continuum of degenerated 2D semiconductor charge density waves state. The long wave threshold of photocurrent was found to depend strongly on a magnitude of electric current (J) through the crystal. A rough estimation gives a value dE/dJ approximately 0.4 meV/mA. We had carried out experiments in order to study instabilities of InSe electrical properties in temperature range 4.2-300 K by quasi stationary conditions. Abrupt electrical resistivity increases about 5 times were observed by us at temperatures 5, 10, 14, 27, 31, 170, and 200 K.

The experimental investigations of solid state structures in strong electric and magnetic fields, when the strongly anisotropic distribution of hot carriers are realized due to strong interaction of charge carriers with optical phonons in the momentum space are presented. The study was stimulated by the theoretically based possibility to realize the electron resonant dynamic bunching in the momentum space under appropriate conditions and also by the creation of the submillimeter p-Ge lasers. These investigations are directed to the development of solid state analogues of vacuum electronics devices. The effect of electrons redistribution between valleys and the essential nonequidistance of Landau levels have been observed in n-Ge crystals in the electric field above 1kV/cm. This has shown the prospects of laser effect in n-Ge, n-Si, diamond. The efficiency of laser effect in these materials has to be significantly greater than in p-Ge. The emergence of collective effects like the hot electron resonant bunching effect in the momentum space at a ballistic transport of electrons up to optical phonons energy in GaAs/AlGaAs heterostructures is discussed. In GaAs/AlGaAs heterostructures the complex structure of photovoltaic response dependent on frequency and polarization of the incident radiation has been observed. This effect reveals a possibliity to elaborate solid state detectors to analyse the parameters of millimeter and submillimeter waves.

A nontraditional method of synthesis of metal grating angular and frequency bandpass filters based on the analysis of spectrum of complex eigen frequencies of resonators forming a filter is described. Two types of filters, the resonators of which are formed by two infinite metallic strip periodic gratings in H- or E-plane, are considered. It was shown that filters of the first type has spurious passbands, they are more difficult in manufacturing and suggestion method has an advantage over traditional approach in high frequency range.

The purpose of this paper is investigation of propagation peculiarities of the surface electromagnetic waves (SEW) on the lateral surface of a superlattice (SL) that consists of alternating layers of ferrimagnet insulator and semiconductor. Most particular attention is payed to those collective surface modes which arise from the coupling between magnetoplasmons, magnons and fluctuating electromagnetic fields. Previous ivnestigations of mixed SEW in infrared region were made for a two layered sandwich structures antiferromagnet/semiconductor in the absence of external static magnetic field. Investigation of SEW on the lateral surface of SL in the presence of external magnetic field requires a generalization of the results for more general case of dielectric and magnetic permeability tensors in phenomenological theory of SL. The method of effective homogenous anisotropic medium is used in this work to find permeability tensors of the ferrite/semiconductor SL. This method can be used if the period of SL is less than the light wavelength. In the presence of an external static magnetic field each medium is described by a gyrotropic tensor. The effective medium description allows to express the dielectric and magnetic premeability tensors of the SL in terms of individual layers permeabilities. Using these tensors, the dispersion relation for SEW localized at the interface between lateral surface of the semi-infinite SL and an isotropic dielectric (or vacuum) are obtained. In the case of Voigt configuration some new resonance and cut-off frequencies are found.

In this paper, the multilayer waveguides with nonlinear cladding medium are analyzed by the so-called transversal equivalent network method. In this method, the electromagnetic field problem of the nonlinear dielectric waveguides is equivalent to network problem by using the transmission line theory, the governing Eigen-equation is then obtained by the transversal resonance technique. The main features of these waveguides for TE case characterized by the relation between propagating power in the waveguide and wavenumber and the distribution of electromagnetic field, are numerically simulated. The method developed in this paper and the results so obtained are valuable for the design and applications of the multilayer dielectric waveguides with nonlinear medium.

It was analyzed and synthesized based on the theory of the two-port cascade network in this paper, the discontinuity of the joint between the standard metal waveguide and the flexible waveguide was also considered. A corrugated rectangular flexible waveguide at Ka-band was optimally designed as a periodical structured, the results of the experiments meet the theory well.

Dielectric leaky wave antennas are finding growing attentions. A dielectric insulated inset waveguide trapped leaky wave corrugated antenna has been designed which is light weighted rigidly fixed on the top metal plane and on side metal walls. This antenna is mechanically simple to realize so that it is particularly suitable at millimeter wave applications. However, since the metallic side walls are touching the dielectric slab, the conductor loss will be more as comparted to insulated dielectric guide antenna.

Scattering of multilayer mediums containing anisotropic material is analyzed with Fourier transformation techniques and matrix methods. A closed-form representation of the electromagnetic field over the anisotropic region are presented. Numerical results are presented and it agrees with the experiments. It can be used as a quasi-optical Faraday rotator for use as either an isolator or circulator.

Experiments with helical electron beams (HEB) of powerful gyrotrons displayed the existense of intense nonstationary processes in HEB. The version of numerical simulation of HEBs is proposed which is based on the method of large particles. Some results of the analysis are given with account of the electrons reflected from the magnetic mirror and locked in the adiabatic trap. First of all, among the traced effects is intense bombardment of the cathode by the trapped electrons. Also, the formation of quasistationary states with their parameters (velocity spread, pitch-factor) essentially different from those given by the static theory was detected.

While investigating the scattering from vegetation canopy it is necessary to know the scattering-law of electromagnetic waves on some single elements. Some principal problems that arise while studying the electromagnetic wave scattering from single leaf have been formulated in this paper. Two problems can be considered here: the influence of the moisture content and the shap of the leaf upon the scattering characteristic. This study represents some results of the experimental investigation of diffraction properties of vegetation canopy and its elements. These experimental components of the study included measurements of back- scattering cross sections, distribution of electromagnetic field in the near zone and radiation pattern. The measurement has been carried out in the millimeter range.

Theoretical and experimental analysis of factors limiting the quality of images being obtained by means of active coherence millimeter wave quasioptical imaging systems is carried out. Advantages of millimeter wave imaging based either on the artificial destruction of the quasimonochromatic radiation spatial coherence or on the proper choice of a temporal frequency spectrum composition of the spatially coherent radiation were theoretically and experimentally revealed. Two types of receiver arrays were applied to realize millimeter wave imaging.

Calculations have been made of molecular absorption coefficients and spectral contrasts of radio brightness temperatures in millimeter waveband caused by atmospheric impurity gases. We have defined optimal frequencies and angles of impurity gas remote sensing when the contrasts of radio brightness temperatures for impurity and pure atmosphere become measurable and take maximum values. The main attention has been paid to the radiometric monitoring of sulfur dioxide and ozone. We have studied the possibilities of the radio emission reception in wide resonant bands of impurity gases. In some parts of the millimeter band there exists a strong nonlinear dependence of the atmosphere radio emission on frequency. Because of this, even in the case of a pure atmosphere there is at any time a difference signal between channels positioned at the center and wings of the spectral line. Some methods and algorithms of their account have been proposed. A description is given of the spectral radiometer designed for the frequency band of sulfur dioxide 131 GHz with a sensitivity of 0.1 K. Preliminary results are presented of the atmosphere radio emission investigation in the frequency band of sulfur dioxide 131 GHz near industrial objects.

Mode jumping, by sudden frequency and power changes in Gunn-varactor voltage controlled oscillators, VCO's, is analyzed theoretically. This uses a double radial line equivalent circuit for VCO with metallized discs on microwave integrated circuit across a reduced height waveguide. Theoretical predictions are demonstrated in numerous experimental verifications. Finally, a simple method is proposed to avoid mode jumping in such a VCO, which is no longer unpredictable: in increasing the length of the short circuit plunger, L_SC, the VCO should only be tuned for L_SC values corresponding to the descending curves of the tuning range versus L_SC graphs. These are identified as the stable VCO operation modes.

Vacuum microelectronics is an emerging technology which relies heavily on solid state microfabrication techniques and the phenomenon of field emission. A whole new class of high frequency devices may become available by combining state-of-the-art fabrication techniques with the superiority of vacuum as a transport medium for electrons. An experiment has been designed to enhance understanding of stable operation of single tips as well as multiple arrays of field emitters and to provide correlation with theory and simulation. The quality of performance of an electron gun has two major factors: energy distribution, and the intensity of the electron beam. The energy distribution is to be measured by manipulating a microfabricated detector within an UHV environment. The detector is in the form of a Faraday cup with multiple apertures. The location of the detector is determined via laser interferometry.

Considerable progress has been made in the development and demonstration of millimeter wave MMIC technology up to frequencies approaching 100 GHz. The recently completed multiyear, ARPA-sponsored, MIMIC program provided a considerable amount of funding and government-contractor team energy to advance the state-of-art with a number of important GaAs-based transceiver building blocks. Unfortuanely, producibility of millimeter wave MMIC transceiver modules has not been similarly addressed to provide a truly low cost, marketable product. This paper considers the module producibility problem and its various technological implications.