A method for the FDTD analysis of quasi-optical MESFET arrays is presented in this paper. To analyze active devices such as MESFETs, this method creates a set of field-state central finite difference equations; and all the field and state variables are solved simultaneously at the same FDTD time step. It will be shown in this paper that this formulation is simple and straightforward. The analysis of quasi-optical MESFET oscillator arrays have been performed to show the application of this method. Excellent agreements have been obtained between the results from this simulation method, from commercial softwares, and from experimental measurements to show the validity of this method.

In this paper we present a full-wave algorithm for the design and the optimization of quasi-optical frequency multipliers and discuss its implementation in a specialized computer code, able to simulate the non-linear device, the planar antenna and the embedding layered structure as a whole. The analysis of the multiplier is performed under the simplifying approximation of an infinite array excited by an uniform plane wave incident from the broadside direction. The array parameters are deduced from a full-wave analysis, based on the Method of Moments, while the solution of the non-linear circuit is found by the Harmonic Balance method. This analysis algorithm is integrated into an optimization routine, which adjusts the antenna geometry and the layered structure, in order to maximize the overall conversion efficiency of the multiplier. As an example, we discuss the design of quasi- optical frequency tripler, operating at 430.5 GHz, based on Hetero-structure Barrier Varactors (HBVs). We present the characterization of the non-linear devices, the design and the fabrication of the antenna array and the optimization of the measurement setup, using the external filters and dielectric slabs.

We had recently demonstrated a room temperature operated widely tunable THz-wave generation (frequency: 0.9 - 2.1 THz, wavelength: 140 - 310 micrometer) introducing a Si prism coupler onto a LiNbO₃ crystal which was pumped by a Q- switched Nd:YAG laser. The process involved is an optical parametric oscillation (OPO) utilizing the polariton mode scattering of LiNbO₃. This tunable THz-wave source was applied to the problem of differential imaging. In a proof-of- concept experiment, we optically tagged objects embedded in a shade and measured the difference between transmittance at two wavelengths. The image of a tagged object was emphasized in comparison with that of an untagged objects. Differential THz imaging has not been reported previously, to our knowledge, mainly because of the lack of convenient tunable THz-wave sources. It seems possible to use dual-wavelength differential transmittance spectroscopy in the THz-wave region to monitor the gases in the industry.

The far-infrared Cherenkov-type difference frequency generation (CDFG) in a planar optical waveguide is analyzed theoretically. The general expression for the CDFG angular distribution is given. The novel doubly resonant cavity is proposed. The CDFG efficiency enhancement due to resonant both at the optical and FIR frequencies is estimated to be a factor a few thousands.

One of the critical challenges facing the progress of millimeter and submillimeter-wave systems is the development of compact, efficient and reliable local oscillators that can generate low-noise and adequate output power levels. Recent theoretical and experimental results have established that fundamental-mode operation of InP Gunn devices could be obtained over much of the D-Band (110 GHz - 170 GHz). Based on these results, second-harmonic power generation could provide the needed local oscillators up to the highest frequency in the millimeter-wave region. This paper reports rigorous computer simulations that estimate the performance of second- harmonic InP Gunn oscillators at frequencies above 200 GHz. The simulation model, based on the ensemble Monte-Carlo technique, has been developed and validated experimentally. It accounts for heat dissipation and incorporates device-circuit interaction through the harmonic-balance technique. Results based on this model predict output power levels of 28 mW at 200 GHz and 7 mW at 310 GHz.

We report on the generation of tunable ultra-narrowband microwave radiation using a frequency locked superlattice oscillator fabricated in a planar design. As active device, a wide-miniband GaAs/AlAs superlattice was used, showing, at room temperature, self-sustained current oscillation giving rise to microwave generation at a natural frequency near 5 GHz and ultraharmonics up to the 7^th order; the linewidth of the harmonics was near 1 MHz. We observed a drastic reduction of the linewidths to less than 10 Hz by frequency locking the oscillator (approximately 100 (mu) W) with a weak narrowband driving field (approximately 0.1 (mu) W). The oscillator was tunable within a locking range of 1 percent of the natural frequency. Besides harmonic also subharmonic locking was observed.

We report new optically pumped Far-infrared (FIR) laser lines from the in-plane CH₃-rocking absorption band of ¹³CD₃OD. A wave guide CO₂ laser of wide tunability (290 MHz) and a Fabry-Perot cavity were used as pump source and FIR laser, respectively. The new laser lines were characterized in wavelength, optimum pressure, offset of absorption transition, relative polarization, and relative intensity. The offset of the absorption transition was also measured for some previously reported FIR laser lines.

The eigenmodes of a resonator with misaligned rooftop mirrors are circular right or left polarized waves which have different resonant frequencies. We discuss effects of the frequency pulling and polarization behavior of the output of the methanol model laser with a three-level homogeneously broadened amplifying medium with rooftop misaligned resonator as a function of the pump intensity and the parameters of the resonator. We show the possibility of a constant in time output of the rooftop laser with its each linearly polarized component modulated in time with a frequency equal to the beat frequency of the Stark -- splitted components of the laser- active transition line. The electric strength vector of the output radiation in this case rotates in time with the beat frequency.

Diode-pumped solid state (DPSS) lasers employing diode arrays and optical crystals suffer from excessive weight, low conversion efficiency, and high fabrication cost. This paper reveals a unique design of coherent, high performance InGaAsP/InP strained-layer quantum-well (QW) semiconductor laser capable of delivering CW power output greater than 500 mw at 1.55 microns. It is important to mention that InGaAsP/InP strained-layer double-quantum-well (DQW) laser diodes are capable of yielding even higher optical power output with improved differential quantum efficiency (DQE) and with lower threshold current at 20 deg C. Compact packaging, minimum power consumption, eye-safe operation and minimum cost are the major benefits of this laser design.

The p-Ge hot hole laser is as yet the only solid state tunable laser with a strong emission in the THz frequency range. Monte Carlo simulations have shown that modelocking of the laser on the intervalence band transition should be possible by gain modulation through the application of an appropriate rf electric field. Recently we did observe for the first time the generation of 200 picosecond pulses in the high frequency (approximately equals 100 cm^-1) emission range. Now also pulses as short as 100 ps have been observed in the low frequency regime (approximately equals 50 cm^-1). A detailed study of the wavelength dependent optical output of the laser has been started now for (normal) pulsed -- as well as for active mode locked operation. Results on pulse shape and small signal gain in the low frequency (equals low magnetic field) regime are given.

FIR Lasers have been widely used in a various field of physics. HCN Lasers are the most popular Laser in this region for their relatively high power output where other sources of radiation are weak. HCN Laser works at wavelength of 337 micrometer and 311 micrometer. An optimum operation condition for a pulse and continuous wave HCN Laser is obtained.

Microfabricated field emitter arrays have attracted interest for a variety of applications. The most prominent of these applications are flat panel displays, microwave amplifiers, x- ray tubes, electron beam probes, ionizers for vacuum pressure gauges, mass spectrometers, and electronic charge management on spacecraft. From a commercial point of view, the most exciting application has been flat panel displays, while high frequency applications are the most challenging with respect to cathode performance. Displays require attention to issues related to economic high-volume production, very low-voltage operation, and a very high level of uniformity over large areas with a low emission current loading. Microwave and other high frequency applications require small areas, with high tip packing density and the highest possible current loading per tip. Ionization and charge management applications require moderate emission performance, but present special problems with regard to stability and lifetime in relatively harsh environments. Designing an emitter array to meet the requirements of any of these applications involves dealing with lithography issues concerning emitter size and packing density; materials issues as they relate to fabrication processes; stability and lifetime issues with regard to hostile environments, and electronic properties such as dielectric constant, resistivity, and work function of the emitter tip; and the cost of large-scale production.

Nonlinear transmission lines (NLTLs) provide a nonlinear, dispersive medium for soliton propagation. Taking advantage of the soliton propagation effects, electrical impulse compression and harmonic generation can be achieved in NLTL circuits. In this paper, characteristics of solitons propagating along NLTLs have been investigated and simulated by the finite-difference time-domain (FDTD) technique. Unique nonlinear interactions among solitons propagating along nonlinear transmission lines are observed in our model. A novel NLTL millimeter-wave tripler has been developed which is realized by periodically loading back-to-back diodes in a high-impedance transmission line. Our simulation results show that this NLTL tripler has higher conversion efficiency than conventional NLTL triplers.

A quasi-optical diode-grid frequency tripler array was analyzed by the Finite-Difference Time-Domain (FDTD) method in this paper. A nonlinear algorithm was successfully developed in order to deal with the nonlinear characteristic of a varactor. The results obtained for a test case showed excellent agreement between the FDTD and a direct mathematical method. The detailed analysis of a frequency tripler array employing back-to-back AlGaAs/GaAs heterojunction varactor was given.

We report on the design and Chip-on-Board integration of a monolithic microwave LNA (low noise amplifier) with a monolithic microwave mixer for a mobile L band receiver front- end. GaAs MESFET process with 0.5 micrometer gate length devices was used for the MMICs fabrication. Both MMICs were tested on-wafer and mounted on a soft substrate microstrip carrier (Chip on Board). Experiments are presented.

We constructed a new reflective-type polarimeter system at 35 - 250 GHz for the 45 m telescope at Nobeyama Radio Observatory (NRO). Using the system, we can measure both linear polarization and circular polarization for our needs. The new system has two key points. First is that we can tune the center frequency of the polarimeter in the available frequency range, second is that insertion loss is low (0.15 plus or minus 0.03 dB at 86 GHz). These characteristics extended achievable scientific aims. In this paper, we present the design and the performance of the system. Using the system, we measured linear polarizations of some astronomical objects at 86 GHz, with SiO (nu) equals 0,1 and 2 at J equals 2 - 1 and ²⁹SiO (nu) equals 0 J equals 2 - 1 simultaneously. As a result, the observation revealed SiO (nu) equals 0 J equals 2 - 1 of VY Canis Majoris is highly linearly polarized, the degree of linear polarization is up to 64%, in spite of SiO J equals 2 - 1 (nu) equals 1 is not highly linearly polarized. The highly linearly polarized feature is a strong evidence that ²⁸SiO J equals 2 - 1 transition at the ground vibrational state originate through maser action. This is the first detection of the cosmic maser emission of SiO (nu) equals 0 J equals 2 - 1 transition.

Electrically controlled phase shifter and optically controlled modulator have been developed and manufactured on basis of dielectric image guides (DIGs) in 37 to 120 GHz frequency band. Phase shift is possible in the 360 degree range, with 2 degree accuracy, while direct losses are approximately 1.5 dB. Modulator is narrowband, approximately 300 MHz, with 25 B modulation depth, and approximately 10^-5 sec time constant.

The analysis of tapered microstrip lines on anisotropic layers with height variations is performed by using a combination of Green's function, the moment method and transmission line theory. The characteristic impedance and the phase constant along the microstrip tapered line are obtained, allowing the determination of the input parameters of microwave integrated circuits, such as microstrip tapers with linear, exponential, parabolic and cosine-squared variations on the strip width.

The fabrication of air-filled rectangular metal-pipe waveguide using a lithographically-based technique has recently been reported. This type of waveguide, together with other passive components such as antennas, couplers, mixers and filters may offer a realistic route to terahertz frequency integrated circuits in view of the compatibility of the fabrication technique with those of standard semiconductor processing. In this contribution, we report the fabrication of a range of waveguide components for operation at frequencies of up to 300 GHz. These measurements represent the highest frequency characterization study so far reported for a micromachined passive structure of this type and provide proof of TE₁₀ propagation with the expected cut-off frequency. Numerous measurements have been taken using G-band (WR-F) guide which show an attenuation loss of approximately 0.6 dB per guide wavelength at 200 GHz. This low value of attneuation shows that these micromachined waveguide are viable components for use in integrated circuits at terahertz frequencies. The insertion loss repeatability (due to mismatch effects at the ports of the waveguides) has been measured and has been shown to be better than plus or minus 0.5 dB. Preliminary results are presented for J-band (WR-3) waveguide which clearly shows the cut off frequency.

In the development of nonlinear optical switching mechanisms, it would be very desirable to have a computer simulation of the electromagnetic pulse propagating in the nonlinear fiber. This would be helpful in understanding the underlying electromagnetics, and would also be helpful in designing new switching configurations. One method which has been widely used in electromagnetic simulation is the finite-difference time-domain (FDTD) method. Its effectiveness in optical fiber simulation is restricted by the fact that the short wavelengths of light dictate dense sampling, which becomes a logistical problem in three dimensional simulation. Techniques are described which allow 3D simulation of small sections of nonlinear optical fibers. The results of these simulations are used to predict behavior over longer distances.

This work presents an implementation procedure for the E-plane printed-probe coupler. This coupler can be obtained with an array of printed capacitive elements, mounted on the E plane of a waveguide. The design of a multiprobe directional coupler starts by the performance analysis of a single probe, with variable depth and width. Using the tridimensional TLM (Transmission Line Matrix Method), a database of results with probes of fixed width and variable depth and fixed depth and variable width is generated. Using these results and a simple design procedure a multi-element array was designed, where the coupling coefficient of each element is proportional to the coefficients of the Chebyshev polynomial. Using these results, a simulation of the 5-element Chebyshev array was performed using the three-dimensional TLM. The simulation difficulties are discussed and the results are shown.

The Transverse Transmission Line (TTL) Method in the Fourier transform domain is used to project and analyze unilateral power dividers with three-ports in millimeter wave. It's presented by the first time. In addition, broadband power dividers have been analyzed using series connections of two fin lines, having essential applications to divide power and to work like an impedance transformer.

Computer programs are developed in FORTRAN 77 and Matlab for Windows languages, given the results in 3-D of the dispersion and of the coupling, as functions of the frequency, conductivity and permittivity for the unilateral fin lines coupler asymmetric in E-plane, on semiconductor substrate. The characteristic impedance and complex propagation constant, for the odd and even-modes excitation are obtained by Transverse Transmission Line method -- TTL. These programs are easily used in graduate and undergraduate courses with good efficiency.

An electromagnetic application is developed to obtain the effective dielectric constant, the attenuation constant and the characteristic impedance of the arbitrary bilateral fin lines with semiconductor substrate and conductor thickness, simultaneity at the first time. Also the concise Transverse Transmission Line -- TTL full wave method is used, in the analysis. New results of the complex propagation and of the characteristic impedance as function of the frequency and different dimensions and conductivity of the substrate, are obtained in 3-D.

Superconductive hot-electron bolometer (HEB) mixers have been built and tested in the frequency range from 1.1 THz to 2.5 THz. The mixer device is a 0.15 - 0.3 micrometer microbridge made from a 10 nm thick Nb film. This device employs diffusion as a cooling mechanism for hot electrons. The double sideband noise temperature was measured to be less than or equal to 3000 K at 2.5 THz and the mixer IF bandwidth is expected to be at least 10 GHz for a 0.1 micrometer long device. The local oscillator (LO) power dissipated in the HEB microbridge was 20 - 100 nW. Further improvement of the mixer characteristics can be potentially achieved by using Al microbridges. The advantages and parameters of such devices are evaluated. The HEB mixer is a primary candidate for ground based, airborne and spaceborne heterodyne instruments at THz frequencies. HEB receivers are planned for use on the NASA Stratospheric Observatory for Infrared Astronomy (SOFIA) and the ESA Far Infrared and Submillimeter Space Telescope (FIRST). The prospects of a submicron-size YBa₂Cu₃O_7-(delta ) (YBCO) HEB are discussed. The expected LO power of 1 - 10 (mu) W and SSB noise temperature of approximately equals 2000 K may make this mixer attractive for various remote sensing applications.

Numerical simulation using a variable finite difference technique has been performed to study the transient behavior of extrinsic photoconductors and the steady state behavior of blocked impurity band detectors. Comprehensive modeling of transient behavior shows that carrier sweep-out causes a two component response to illumination changes in extrinsic photoconductors. Simulations for large signals on low photon backgrounds indicate that the background flux plays an important role in transient response, even when the signal is many orders of magnitude larger than background. Modeling of blocked impurity band detectors illustrates the field variations that determine device performance. When blocking layer doping exceeds a critical value, a field gradient develops at the blocker/absorber interface due to the ionization of neutral acceptors. In practice, this would reduce the efficiency of transport in the blocking layer and decrease device responsivity.

Experimental results together with computer simulations, provide evidence to support the premise that quantum barrier devices can indeed yield sufficient improvements over conventional Schottky diodes, as to warrant their further study, especially for low-power millimeter and sub-millimeter wave receivers and where local oscillator power is at a premium.

A novel concept of the hot-electron bolometer using a microrefrigeration by SIN tunnel junctions for direct cooling the electrons of the absorber has been proposed. We have analyzed the most attractive case of cooling starting from 300 mK that can be achieved in a simple cryostat with ³He pumping. Electronic cooling to 50 - 100 mK has shown considerable decrease of the electron-phonon thermal conductance G_e-ph but small decrease of G_(Sigma ) equals G_e-ph + G_cool in comparison with G_e-ph before cooling. The maximum decrease of G_Sigma by a factor of 1.8 has been achieved at temperatures around 200 mK. The analysis shows that the noise equivalent power (NEP) can be decreased using direct electronic cooling. The thermal noise component of NEP is decreased by a factor of 3 for electronic cooling from 300 to 100 mK mainly due to decrease of the electron temperature (and small decrease of G_(Sigma )). Tunnel junction noise and amplifier noise components of NEP can also be improved by a factor of 4 due to increase of the power responsivity. For general noise analysis we used analytical expressions for main noise components and I-V curve of SIN tunnel junctions. The optimal bias currents were found for short noise component and amplifier noise component.

Using high temperature grain boundary Josephson junctions (GBJJs) made of YBa₂Cu₃O_7-(delta ) (YBCO) deposited across silicon bicrystal boundary, we successfully demonstrated direct detection at wavelength as short as 118.8 micrometer (frequency of 2.525THz) and the operation temperature up to 70 K. Radiation from a far infrared (FIR) laser was coupled to the junction, via a TPX plano convex lens and a high resistivity Si hyperhemispherical lens. The response at wavelength of 183.4 micrometer was obtained for the YBCO GBJJs on MgO bicrystal substrates. Also, investigated are the effects of response on external DC magnetic fields and polarization of electromagnetic waves as well as the harmonic mixing properties.

Sensitive and robust heterodyne mixers are needed for future atmospheric remote sensing missions. This data from satellites such as NASA's Earth Observing System (EOS) lends great insight into molecular interactions in our environment. The Microwave Limb Sounder (MLS) on EOS will detect radiation emitted from 0₃, ClO, and OH molecules which are critical to our understanding of ozone depletion and greenhouse warming. The heterodyne mixers on MLS must exhibit sufficient spectral sensitivity, wide bandwidth, low noise, and minimal LO power requirements. Planar GaAs Schottky diodes currently are the most promising technology for space-borne radiometers where cryogenic cooling is not desirable. In this work we present progress on a novel wafer bonding technology, MASTER, used to integrate submillimeter wavelength planar GaAs Schottky mixer diodes with quartz microstrip circuitry. Problems associated with wafer expansion after bonding, open- circuited devices, and Ti/Pt/Au metallization removal have been solved and device yield is significantly improved. FTIR measurements of the bonding adhesive's properties at submillimeter wavelengths are discussed. We have fabricated 640 GHz subharmonic mixers for EOS-MLS which nearly match state-of-the-art performance at this frequency with DSB T_mix equals 2396 K and L_mix equals 10.98 dB using 4.67 mW of LO power. RF testing of a new higher yield batch of MASTER mixers is in progress.

We discuss two types of resonant techniques for measuring the electrodynamic properties of conductors in the millimeter and sub-millimeter wave spectral ranges. Using a series of backward wave oscillator sources, we can obtain essentially complete coverage of the frequency range 30 - 1000 GHz. At 100 GHz and below, cylindrical cavity resonators operating the in their TE₀₁₁ mode are employed to measure both components of the complex surface impedance of bulk samples. Above approximately 100 GHz, a Fabry-Perot resonator, consisting of a sapphire plate with a conducting sample placed against one side, is used. Both thin film and bulk samples may be measured with this technique. We focus on measurement on thin film samples, where the complex conductivity can be obtained directly from the transmission spectra.

This article presents general principle and the first application of magneto-optical methods for the direct measurement of the complex magnetic permeability in the mm- wave range. The computer controlled quasi-optical spectrometer, which was used for the magneto-optical measurements in the frequency range 70 - 120 GHz, is described. The proof-of-principle experiments were conducted with a soft microwave Nickel Ferrite and with a hard Sr- Hexaferrite permanent ceramic magnet. The potential of magneto-optical methods for the accurate measurement of complex magnetic permeability in the mm-wave range was demonstrated. It was shown that the transverse magneto-optical effect can provide the reliable measurement of the initial permeability. The results of the mm-wave magneto-optical measurements are presented and discussed.

A new FAst Scan Submillimeter Spectroscopic Technique (FASSST) is described. It uses voltage tunable Backward Wave Oscillators (BWOs) as primary sources of radiation. In contrast to the more traditional phase or frequency lock techniques, it uses fast scan (approximately 10⁵ Doppler limited resolution elements/sec) and optical calibration methods. Its attributes include (1) absolute frequency calibration to approximately 1/10 of a Doppler limited linewidth (less than 0.1 MHz), (2) high sensitivity, (3) the ability to measure many thousands of lines/sec, and (4) simplicity. This system is made possible by (1) the excellent short term spectral purity of the broadly (approximately 100 GHz) tunable BWOs, (2) a very low noise, rapidly scannable high voltage power supply, (3) fast data acquisition, and (4) software capable of automated calibration and spectral line measurement.

The characteristics of higher order modes in microstrip patch resonators with several dielectric anisotropic layers are presented. The analysis is developed by using a combination of the moment method and the Hertz vector potentials, in the Fourier domain. Curves for the complex resonant frequency against the structural parameters, emphasizing the effect of the dielectric anisotropy of the dielectric layers, are presented for the dominant and several higher order modes.

This paper discusses the development and field testing of a remote chemical detection system that is based on millimeter- wave (mm-wave) spectroscopy. The mm-wave system is a monostatic swept-frequency radar that consists of a mm-wave sweeper, a hot-electron-bolometer detector, and a trihedral reflector. The chemical plume to be detected is situated between the transmitter/detector and the reflector. Millimeter-wave absorption spectra of chemicals in the plume are determined by measuring the swept-frequency radar return signals with and without the plume in the beam path. The problem of pressure broadening, which hampered open-path spectroscopy in the past, has been mitigated in this work by designing a fast sweeping source over a broad frequency range. The heart of the system is a Russian backward-wave oscillator (BWO) tube that can be tuned over 225 - 315 GHz. A mm-wave sweeper that includes the BWO tube was built to sweep the entire frequency range within 10 ms. The radar system was field-tested at the DOE Nevada Test Site at a standoff distance of 60 m. Methyl chloride was released from a wind tunnel that produced a 2-m diameter plume at is exit point. The mm-wave system detected methyl chloride plumes down to a concentration of 12 ppm. The measurement results agree well with model-fitted data.

This paper deals with an original approach for the design and realization of high performance micromachined millimeter wave passive circuits on silicon. Full wave finite element 3D and 2D simulations techniques has been done to design the structures. First, because of the silicon anisotropic properties, we have designed a low loss tapered transition between the 50 (Omega) silicon input/output lines and the micromachined circuit. In order to minimize ohmic losses, new technological processes have been implemented. A 6 mm length micromachined coplanar transmission line, embedded between two tapers and probe pads, and featuring an overall insertion loss of less than 0.8 dB at up to 67 GHz has been achieved. From this technology, we have realized a high quality factor cavity in the 35 GHz range through an appropriate coupling between a micromachined coplanar line and a dielectric resonator acting on it whispering gallery modes. This original structure features a loaded Q of about 2000.

The measurement of the surface impedance of a sample at microwave frequencies is usually done by placing the sample inside a microwave cavity. The resulting change of the quality factor and of the resonance frequency of the cavity can be used to determine the complex surface impedance of the sample. Instead of measuring the whole lorentzian curve a fast method using automatic frequency control (AFC) can be used where only the transmitted signal amplitude and the resonance frequency are measured. This method is very useful whenever the surface impedance depends strongly on temperature as for example in the case of a superconducting transition and when the temperature stabilization of the small cavity is a severe problem. However this method can only be used with a microwave source which exhibits nearly no dependence of the output power on the frequency and which has a very good frequency stabilization. Such sources are available only for frequencies up to 60 GHz. Problems with backward wave oscillators (BWO) at higher frequencies can be avoided by using a new computer controlled frequency (CCF) method. This method offers the advantage of a full control over the output frequency of the source and the ability to measure very fast and with high accuracy all the parameters necessary for the determination of the surface impedance.

After a brief presentation of the first vector measurements ever performed up to the THz with coherent sources, which were using BWOs and an interferometric technique, the possibility to use solid-state components is described. It involves frequency multiplication in Schottky harmonic generators as sources, and frequency downconversion in Schottky harmonic mixers as detectors. Instead of an interferometric setup, or instead of a second detection in a reference branch parallel to the DUT (Device Under Test) branch, like it is operated in classical millimeter network analyzers, the phase acquisition is purely electronic, which presents several advantages. The configurations of the analyzer without extensions are described. This section contains the choice of the harmonic order, the crosstalk effects and how to cancel them, and the dual-sense detection configuration, in which the microwave propagates, at the same time, in two directions. The interest of the latest configuration is when testing a given Schottky device in both harmonic generation (source) and harmonic mixing (detection) roles at the same time. The 4S-parameter configuration is shown. The 2S-parameter configuration is a simplified arrangement. The principle of phase acquisition does not involve any absolute frequency stabilization, since it is only the difference between two microwave sources which is stabilized. However some experiments need very stable and pure microwaves, which can be done. The analyzer can work at two frequencies at the same time. A description of several possible extensions of the analyzer is included. When a very large dynamic range is needed, one can associate with the analyzer a source which can remain free-running. When associating a Gunn oscillator feeding a multiharmonic harmonic generator, one can cover the frequencies up to 500 GHz. When associating two Gunn oscillators, the first followed by a multiharmonic harmonic generator, the second feeding a harmonic mixer, one can cover frequencies up to 1000 GHz. This setup can also work at two frequencies at the same time.

This paper presents a new calibration method for the six-port network analyzer comprising a single six-port reflectometer. Its main feature is to take into account the imperfections which are present in the switches that commute the system from the reflection to the transmission modes and vice-versa.

Our recent results on Hilbert-transform spectral analysis based on ac Josephson effect are reported. High-quality epitaxial YBa₂Cu₃O_7-x thin-film Josephson junctions have been fabricated on untwinned (110) NdGaO₃ bicrystal substrates to satisfy the operational requirements of Hilbert-transform technique. The design and characteristics of the developed laboratory Hilbert-transform spectrometers are presented. Spectra of Josephson radiation in high-T_c junctions have been measured in the frequency range from 60 to 2250 GHz, and a Lorentzian shape of Josephson radiation has been obtained both for equilibrium (eV very much less than kT) and nonequilibrium (eV very much greater than kT) cases. The first spectral measurements of coherent transition radiation at Test Facility Linear Accelerator at the Deutsches Elektronen-Synchrotron DESY (Hamburg) have been made and the length of electron bunches of 1.2 ps has been determined from these spectra. The comparison of Hilbert-transform spectral analysis with conventional techniques is presented.

A new method of precision measurements of dielectric permittivity and loss tangent of medium and highly absorbing materials over an extended W-band frequency range is developed. A quasi-optical-waveguide spectrometer is designed and constructed. An electronically sweeping backward wave oscillator (BWO) is used as the source of tunable coherent radiation in the frequency range 70 to 118 GHz for the spectrometer. The high output power of BWO, precision waveguide and quasi-optical components and an extra high sensitivity specially constructed liquid helium cooled InSb detector enable adequate energy throughput in transmission for the first time for highly absorbing materials. A simple quasi- optical-waveguide transmission measurement set up of the spectrometer provides the transmittance measurement from which the loss tangent and imaginary part of dielectric permittivity spectra of materials are evaluated very accurately. A quasi- optical-waveguide bridge configuration of the spectrometer provides the measurement of the phase retardation through a specimen from which the real part of dielectric permittivity spectrum are determined with high accuracy. Data for acrylic (medium absorbing), CVD grown low resistivity germanium, General Diode Corp. low resistivity silicon (very absorbing) and thick layer of water are presented and compared.

A new 60 GHz open resonator system has been developed to measure the permittivity and loss tangent of low-loss microwave and millimeter wave hard substrate materials. The system uses a new measurement method namely the cavity-length variation technique to determine the position difference and the profile of the resonance peak with and without the specimen for the calculation of the permittivity and loss tangent. A 20-nanometer length resolution is reached for the variation of the cavity length. This new technique provides an interferogram containing a number of resonance peaks with and without the specimen each having a complete Gaussian or Lorentzian profile. The real part of the dielectric permittivity and loss tangent can now be determined accurately. It is no longer necessary to use a stable, wide- band and tunable frequency source. The accurate data for some hard substrate materials is obtained, excellent agreement is obtained between the new data and the data extrapolated from the Fourier Transform Spectroscopy technique measurements.

A new electron beam source based on a pseudospark discharge was developed. The electron beam has high brightness of about 3 X 10¹¹ A/(m rad)² and can be used for compact free electron lasers. New experiment result is reported, a beam energy of 230 keV, a current of 7 kA and an emittance of 48 mm mrad are obtained.

In this paper the results of measurements of the wave beam parameters into TJ-II transmission lines are presented. Wave pattern of the launching antennas, polarization, power distribution across the wave beam were measured. The measurements were made at low power level on a stand. The smooth horn antenna and the special corrugated antenna were designed for these measurements. Parameters of these antenna are presented as well. A comparison of the experimental data and the results of the calculations is made.

A new technique is reported for micro-machining millimeter and submillimeter-wave rectangular waveguide components using an advanced thick film UV photoresist known as EPON^TM SU-8. The recent introduction of this resist has been of great interest to the millimeter-wave and terahertz micro-machining communities, as it is capable of producing features up to 1 mm in height with very high aspect ratios in only a single UV exposure. It therefore represents a possible low-cost alternative to the LIGA process. S-parameter measurements on the new rectangular waveguides show that they achieve lower loss than those produced using other on-chip fabrication techniques, they have highly accurate dimensions, are physically robust, and cheap and easy to manufacture.

We have characterized the dynamic of carriers in photoconductors which are already located in microwave devices. We particularly examined the trapping time and trap emptying time of Low Temperature grown CdTe. A trapping time of 1.6 ps was found from both optoelectronic cross correlation and Time Resolved Reflectance measurements. Trap emptying time is usually investigated by pump and probe optical transmission technique that gives the dynamic of non linear absorption. We have used instead a new method called Time Resolved Reflectance Close to Brewster's Angle in order to study non linear absorption occurring in photoconductive material already processed in microwave structure. We developed a model to estimate the trap emptying time of LT CdTe. We found a trap emptying time of 0.58 ps which is lower than the trap time 1.6 ps. These parameters make CdTe a good candidate to optical/microwave conversion in high bit rate communications or as a sampling gate in a sample and hold circuits.

This paper presents the analysis and design of millimeter-wave aperture coupled microstrip antenna arrays fed by a dielectric image line (ACMADIL). A theory based on the cavity model of microstrip antenna and the change in modal voltage of image line at aperture was developed to analyze the single element aperture coupled microstrip patch antenna. It was then combined with the array theory to design linear traveling wave microstrip antenna arrays at Ka-band. Experiments show very good results for the arrays.

integrated antennas have the advantages of low cost and can be readily mass produced using standard IC fabrication processes. However, integrated antennas suffer from the surface wave effect at millimeter waves. One of the ways to avoid this problem is to integrate the antennas on a dielectric lens. This structure does not support surface-waves and tend to radiate most of their power into the dielectric side making the pattern unidirectional on high dielectric constant lenses. The dielectric lens also provides mechanical rigidity and thermal stability. There are various dielectric lenses which can be used for receiver application. Among them the extended hemispherical lens is very practical, since it can synthesize other lenses such as hemispherical, hyperhemispherical, or ellipsoidal simply by varying the extension length behind the hemispherical position. In reference five, investigation on such antenna/lens system is presented. In reference 6, slot- ring antennas on dielectric lens is investigated. In many applications the extended hemispherical lens/objective lens antenna system is more attractive, because it can provide higher gain and may be used in imaging system. On the other hand, monopulse direction-finding techniques are currently the most accurate and rapid method for locating a target electronically. This antenna system can also be used as monopulse antenna. However, the treatments on such antenna system are not presented yet. In this paper, the radiation pattern of the antenna system fed by double-slot antenna are computed using ray-tracing and diffraction integration methods. Although the double-slot antenna is used as feed antenna, other antenna such as slot-ring, bow-tie antenna can be used too.

An inclined-plane dual-horn structure is presented that couples energy from free-space to microstrip and back to free- space again. The structure consists of two back-to-back inclined planes that taper down to a common parallel-plate waveguide. The energy is fed from the parallel-plate waveguide to the microstrip using a transition that also serves as a power splitting network. The insertion loss from free-space to microstrip for the passive array is better than -2.5 dB from 30 to 47.5 GHz.

A practical design of a compact integrated Rotman lens is presented, which will be used as a beamformer of multiple beam antenna arrays in wireless indoor communication network. An improved design equations of integrated Rotman lens is derived to calculate the lens contour and a non-circular focal arc is introduced in beam ports to minimize the phase aberrations on the aperture of array. A log-periodic electromagnetic coupling microstrip patch array is adopted as radiation elements. Both theoretical and experimental results show the designed multiple beam antenna has wide band width performance.

Internal beam-shaping reflectors are crucial for getting high powers out of vacuum-sealed gyrotrons. Thermal limitations of the vacuum window as well as external injection of the microwave beam into corrugated waveguides require very specific beam characteristics. Previous beam shaping reflectors have achieved satisfactory results but have shown room for improvement. One cause for error has been inaccuracy in the theoretical modeling of the input to the reflectors. Small inaccuracies in the amplitude and phase distribution of the theoretical patterns for the input beam can cause dramatic effects in the output beam's characteristics. It is possible to use measured data instead of theoretical data for the input to the mirror design. Measured amplitude data of the input to the reflectors has been available; however, both the amplitude and phase information of the beam are required for the design procedure. It is difficult to directly measure the phase distribution at 110 GHz so a phase reconstruction algorithm was developed to determine the phase pattern associated with a propagating beam. The measured amplitude data with its reconstructed phase was then used as the input to the beam- shaping, dual-mirror design. In this paper we discuss the design procedure for the dual-mirror design using measured amplitude data with its reconstructed phase for the input.

The fields refracted by circular symmetric hyperbolic lens illuminated by a linearly polarized wave incident obliquely on the aperture are calculated from the induced surface currents. It is shown that the fields in the axial region are almost same as the fields in the aperture of corrugated horn under balanced hybrid conditions. The image structures for different focal ratio are compared with the classical Airy pattern, deduced by scalar analysis, of optical focusing systems. The coupling between the lens and a corrugated horn at different position on focal plane are also considered.

Nowaday, it becomes necessary to characterize materials on a very large bandwidth for frequencies up to 100 GHz. Photoconducting microdipole antenna benches have already shown their ability to answer such a problem. Before the realization of such benches, a theoretical design of the antennas is necessary for the prediction of their behavior (transient radiated free field duration, frequency bandwidth. . .). For this reason, we propose in this paper, a theoretical approach based on the coupling of different tools: the finite difference time domain method (FDTD), a drift diffusion model for considering photoconducting materials and the geometrical optic for the lens modeling. After the description of the software, some results will give the capabilities of such an approach.

A more accurate analysis and design for HTc superconducting microstrip patch antenna is presented in this work. The concise Transverse Transmission Line (TTL) method in the Fourier Transform Domain (FTD) along with the Transmission Line Model are applied. Sine the TTL is a full wave method and very much suitable on microwave and millimeter-wave components study, it gives accurate effective dielectric constant which contributes definitively to obtain all others antenna parameters with higher precision such as length, efficiency, bandwidth, quality factor, radiation patterns.

The development of a far-infrared imaging system based on ultrafast THz time-domain spectroscopy has opened a new field of applications of femtosecond technology. This new 'T-ray' imaging technique allows to look through or inside a variety of materials and to obtain chemical image contrast based on spectroscopic information. Using the flight-of-time information present in THz pulses reflected from compound samples we demonstrate the principle of tomographic T-Ray imaging. THz pulses are reflected from refractive index discontinuities inside an object, and the time delays of these pulses are used to determine the positions of the discontinuities along the propagation direction. This allows a 3-dimensional tomographic reconstruction of the sample's refractive index profile.

NASDA and CRL are planning to develop a spaceborne SMILES, which is to be installed in the Exposed Facility (EF) on the JEM of the ISS. By observing gases such as ClO, HCl, NO, N₂O, HO₂ and BrO in the stratosphere, JEM/SMILES can trace the chemical reactions concerning the ozone depletion and climate change. Global distribution of those gases will be mapped with a height resolution of about 2 km. JEM/SMILES receives low-intensity signals from those gases with highly sensitive SIS (Superconductor-Insulator-Superconductor) mixers at 640 GHz, which are cooled to 4.2 K by a space-qualified mechanical cooler. The mission target is to demonstrate the effectiveness of the submillimeter-wave limb emission sounding and to establish space applicability of the low-noise SIS mixers and a mechanical 4-K cooler. JEM/SMILES is expected to be launched in 2003, and the experiments will last a year or more.

We present the results of experimental development of an ultrasensitive normal metal hot-electron microbolometer with Andreev mirrors and electronic cooling by superconductor- insulator-normal metal (SIN) tunnel junctions. A value NEP equals 5 (DOT) 10^-18 W/Hz^1/2 for the temperature fluctuations component of noise and the thermal time constant (tau) equals 0.2 microseconds at 300 mK have been estimated for one of the realized devices with thermal conductance G approximately equals 6 (DOT) 10^-12 W/K. At 100 mK, the thermal conductance was decreased to G approximately equals 7 (DOT) 10^-14 W/K, that gives NEP equals 2 (DOT) 10^-19 W/Hz^1/2 for the temperature noise component and a thermal time constant (tau) equals 5 microseconds. Such microbolometer is intended as a detector of millimeter and submillimeter wave radiation for space applications.

Millimeter waves is expected to be used for indoor broadband wireless access for its rich frequency spectrum resources. To implement the indoor MMW wireless system, it is important to know its propagation characteristics in building, which are governed by the transmission properties of construction materials. This paper focuses on the measurements of reflection characteristics and refractive indices of some interior construction materials (such as glass, brick, plaster board, silencing board, etc.) at Ka-band. The free-space reflection method was used to measure the reflection and transmission coefficients. Then the complex refractive indices of various materials could be calculated by using the Fresnel's formula.

We developed a 40 - 50 GHz array receiver which has six feed horns (2 X 3 array) and six superconducting-insulating- superconducting (SIS) mixers. We used tunerless SIS mixers to make the tuning system simple and to achieve the high stability. The receiver system is designed as a sophisticated tool for continuum observation of the Sunyaev-Zel'dovich effect toward clusters of galaxies. The receiver noise temperature is 20 - 30 K. The instantaneous band width is 700 MHz. This system is installed on the focal plane platform of the Nobeyama 45-m telescope. We did a test observation to evaluate the performance of the receiver system. The estimated DSB system noise temperature were 110 - 170 K at 43 GHz. The aperture efficiency and the main-lobe efficiency of this system were 0.4 - 0.6 and 0.5 - 0.9, respectively.

The theory of the multilayer shielded and open microstrip lines considering the superconductor strip on semiconductor regions is presented. The Transverse Transmission Line (TTL) is used in the analysis. The superconductor effect is included with the boundary condition of the surface impedance that is related to the complex conductivity of the material, calculated from the advanced two-fluid model. Applying the moment method the complex propagation constant of the structure, including the phase constant and the attenuation constant, is obtained. Results are presented for the complex propagation constant, versus the frequency and the temperature, of this multilayer superconducting microstrip line.

The integral equations' method proposed in this paper enables one to rigorously solve Maxwell equations for 3D-structures of arbitrary geometrical shape in case of any incident wave. The electromagnetic fields of the reflected and transmitted waves have been found for some new structures. One of them is the semiconductor sensor to detect a microwave electric field. The sensor is constructed as a vibrator made of two microstrip conductors with a semiconductor sample of cuboid form placed between them.

The solution of the plane electromagnetic wave scattering problem by a spherical inclusion embedded into half-space with dielectric losses is obtained. To treat the problem the translation-addition theorems for the basic vector solutions of the Maxwell's equations in spherical, cylindrical and rectangular coordinate systems together with the field series expansion techniques are used. Matching the boundary conditions for the tangential components of the electric and magnetic field at the two half-spaces interface and also at the sphere boundary allows to reduce the above mentioned problem to the infinite set of linear inhomogeneous equations. No restrictions on the half-space losses value as far as the size and complex permittivity of the spherical inclusion and its burial depth are implied. The results could be useful in sea foam-covered areas investigations and in diagnostics of the porous lossy materials.

A full-wave transverse transfer matrix method have been used for analysis of cylindrical and rectangular hollow center waveguides with multilayered coating. The complex modes of leaky-wave character have been investigated in such waveguides with lossy materials filling the covering. The dispersion equations for investigated structures have been introduced and solved in the complex plane region and the propagation and attenuation constants have been obtained. Using this technique the numerical synthesis of the optimal coating profile have been performed. The wide-band, band-path, and narrow-band mode self-filtration, and the possibility of reduction of the dominant mode propagation constant are considered. In this paper the complex permittivities and permeability are neither restricted by any conditions, and nor associated with concrete materials, and the main goal is the synthesis of permittivity and permeability distribution, which are most fitted to our purposes. For example, such coatings may be implemented using composite and artificial materials by means of ion implantation or other technique.

Physical speed restrictions of the passive micron structures are investigated. A possibility of sub-picosecond logic and analog operations execution by the passive circuits for the signals with spatially modulated electromagnetic fields is shown.

At liquid helium temperatures, electronic transitions are observed in doped semiconductors in the far infrared region. High resolution FTIR spectroscopy has been found quite useful to resolve these transitions. At ambient temperature, free charge carriers have high mobility, but near liquid helium temperatures, the electrons or holes are frozen and become loosely bound to the defect centers. Thus the behavior of ionized carriers is explained by pseudo-Bohr or hydrogen like model. In P-doped silicon electronic transitions have been resolved from ground (1s) state of phosphorus impurity to excited state of electronic levels 3p+/- and 2p+/- in the far infrared region. Using Faulkner expressions for binding energies of excited p levels, the dielectric constant of P- doped silicon has been measured at liquid helium temperatures. The precise measurements of FTIR spectroscopy show small variations of frequency of these transitions from 6K to 50K, which results in the corresponding variation in the dielectric constant at these temperatures.

The processes in the cylindrical magnetron with cutting slots in the cavity have been considered. The investigation shows that the space charge in the system is the active nonlinear medium. The equations describing the excitation of oscillations in this medium have been derived (H approximately H_k). The autosoliton solution for the system is obtained. The results allow to take a new look into the mechanism of generation of mm-oscillations in the magnetron with a surface wave.

We experimental show that output characteristics of non- relativistic Diffraction Radiation Generator (DRG) are greatly perfected when we create a local inhomogeneity of focusing magnetostatical field in the interaction space of electronic beam. We conclude that it is perspective to use a thick electron beams in the DRG of SubMM frequency range.

The rare earth element erbium has been incorporated in silicon-germanium strained quantum well structures by ion implantation. A dopant concentration of 10¹⁸/cm³ was obtained through the process of amorphization and solid phase epitaxial regrowth. The incorporated erbium atoms were found to be electronically active producing luminescence at 1.54 micrometer from the characteristic ⁴I_13/2 yields ⁴I_15/2 transition. Photoluminescence spectra of the specimens were found to be entirely dominated by atomically sharp, strong erbium signal without any contribution from band-edge or quantum well emission. The erbium luminescence was found to be temperature dependent, reducing exponentially with temperature with an activation energy of 120 meV. This energy was shown to correspond to the position of the erbium related level from the conduction band.

Combining with acupuncture and moxibustion theory of China, this paper discussed acupuncture and moxibustion effect of millimeter wave multiplied with infrared ray and bass spectrum, and provided a feasible path for applications of millimeter wave in biomedical engineering.

In the present paper topographical methods of image reconstruction of two-dimensional cross-sections of volumetric objects, surfaces or subsurface regions in millimeter wavelengths band are suggested and considered. Experimental images obtained using antennas and waveguiding lines of different types and radiation frequency f approximately equals 33 divided by 38 GHz are represented. Volumetric dielectric objects and plane-parallel ferrite (or dielectric) plates distributed in free space or in homogeneous dielectric medium have been taken as objects under investigation. It is shown that in the frequency band under consideration, the images of investigated objects with characteristic dimension A approximately equals 2 (lambda) divided by 7 (lambda) may be obtained by first-order diffraction tomography method (Born, Rytov or high frequency approximation of the first-order for scattered electromagnetic field).

The long-term potential of terrestrial passive millimeter imaging is contingent upon demonstrating real-time imaging with a system that can be conveniently a deployed at an acceptable cost. For small apertures with modest resolution, imaging can be readily achieved using fully-staring focal plane arrays, but as in the infrared, the high cost per pixel means that scanning (preferably electronic) of a smaller number of detectors across the image is attractive. Aperture synthesis using sparse and filled arrays of antennas offers high sensitivity and resolution from a small number of antennas that can be conformal to vehicle shape, but requires complicated beam-forming technologies. Alteratively, electronic scanning can be accomplished by electronic modulation of a filled antenna. This paper will discuss novel approaches and technology requirements for achieving electronic beam-steering.