Analysis and design of a novel noncontacting waveguide backshort

A new noncontacting waveguide backshort has recently been developed for millimeter- and submillimeter-wave frequencies. The design consists of a metal bar with rectangular holes cut into it, which is covered with a dielectric layer to form a snug fit with the broadwalls of a waveguide. It is mechanically rugged and can be readily fabricated for frequencies from 1-1000 GHz. This paper presents a technique for the theoretical characterization of the backshort, using an approach that combines the mode-matching method and a set of coupled space-domain integral equations. The convergence characteristics of the analysis are included, along with a set of general design guidelines     

Novel tunable waveguide backshort for millimeter and submillimeterwavelengths

A new tunable waveguide backshort with low loss and reliable performance has been designed. Based on a fixed short and dielectric phase shifter, it has a simple structure which is easy to design and fabricate. These properties make it a sound alternative for millimeter- and submillimeter-wave applications. A W-band (75-110 GHz) backshort has been designed and tested showing excellent performance with a return loss of less than 0.21 dB     

Quasi-optical waveguide modeling method and microcompact scatteringrange for the millimeter and submillimeter wave bands

The possibility of using the quasi-optical waveguide modeling (QWM) method in the near millimeter and submillimeter ranges of the electromagnetic spectrum for a study of the backward and forward scattering amplitude and phase characteristics of physical objects or scaled models is discussed in the paper. The method is realized with the aid of a quasi-optical waveguide microcompact range (MCR). The microwave part of MCR is based on the regular section of a hollow dielectric waveguide (HDW) and corresponding quasi-optical components. The results of measurements of backward and forward scattering characteristics for a number of standard objects in the 4-mm wavelength band are presented     

A modified conical cavity for submillimeter wave applications

The conical cavity has been modified for use in electron beam devices. In this new cavity resonator a short radial line section couples the beam hole with the conical region providing a suitable interaction gap. Operated in a higher order TM0p0mode the cavity size is large compared to wavelength making it attractive for millimeter or submillimeter applications. In this mode, both Q0and Rshuntare large. For analysis, the modified conical cavity can be considered as a composite consisting of a circular waveguide at cutoff, a radial waveguide, and a shorted "quasi-wedge" guide. Resonant frequencies are found by impedance matching at a transverse plane in the cavity. UnloadedQand Rshuntare found by calculating total energy stored and power loss along with an equivalent voltage across the gap. An experimental cavity was tested. This cavity was scaled forXand Ku bands and operated in TM0p0modes from p=5 to p=9. Measured results agreed well with theory. At the p=9 mode, the radial dimension of the cavity was 4.2 λ. Design curves are presented for the modified conical cavity without beam hole.     

Quarter wave plates for submillimeter wavelengths

A review is given of different types of quarter wave plates as presently used in the optical and microwave spectral range, with a view to their application in the sub-mm wave-length range. Two types of quarter wave plates have been constructed and results of measurements at 640μm are given.     

Heterodyne measurements of submillimeter laser spectrometer frequencies

The frequencies of 46 CW laser lines commonly used for submillimeter spectroscopy, with wavelengths between 0.1 and 0.7 mm, have been measured by heterodyne methods. All the fines are optically pumped by a CO2laser, with threshold pump powers of 3 W or less. The precision of measurement, limited by the laser linewidth, is typically ± 1 part per million.     

Single barrier varactors for submillimeter wave power generation

Theoretical work on single barrier varactor (SBV) diodes indicates that the efficiency of a tripler with a SBV diode has a maximum for a considerably smaller capacitance variation than previously thought. SBV diodes based on GaAs, InGaAs and InAs have been fabricated and their DC properties have been tested. Detailed modeling of the carrier transport properties of the SBV device is carried out in two steps. First, the semiconductor transport equations are solved simultaneously, using a finite difference scheme in one dimension. Second, the calculated I -V and C-V characteristics are used by a multiplier simulator to calculate the optimum impedances and output powers at the frequencies of interest. The authors have developed an analysis technique which complements the harmonic balance technique. Simulations for a case study of a 750-GHz multiplier show that InAs diodes perform favorably compared to GaAs diodes     

New CW lines from a submillimeter waveguide laser

Sixty-one new CW laser lines with wavelengths between 0.1 and 1.5 mm have been observed with a waveguide laser optically pumped by a CO2laser.     

A transmission line for plasma scattering measurements with a submillimeter wave gyrotron

A transmission system has been designed to produce a high intensity (～100 W) and high quality (well-collimated and high purity) beam in the submillimeter wave range (f=354 GHz). Calculations using the Huygens equation for scalar diffraction show that this system can produce a high quality beam. The final goal is to apply it to scattering measurements of density fluctuations driven by instability and wave propagation during ion cyclotron resonance heating in the Compact Helical System (CHS) in the National Institute for Fusion Science at Nagoya. It will provide a high S/N ratio and high spatial and wave number resolution.     

Josephson-Junction driven submillimeter wave microstrip resonator

A microstrip resonator driven by a resistively shunted Josephson junction has been used for submillimeter-wave surface resistance measurements to about 400 GHz. A simple, analytical analysis of the resonator-induced structure in the junction's I-V characteristic gives the resonator surface resistance in the range of 2-160 mΩ with an accuracy of better than 30%     

Dielectric ribbon waveguide: an optimum configuration forultra-low-loss millimeter/submillimeter dielectric waveguide

Dielectric ribbon waveguide supporting the _eHE₁₁ dominant model can be made to yield an attenuation constant for this mode of less than 20 dB/km in the millimeter/submillimeter-wavelength range. The waveguide is made with a high-dielectric-constant, low-loss material such as alumina or sapphire. It takes the form of thin dielectric ribbon surrounded by lossless dry air. A detailed theoretical analysis of the attenuation and field extent characteristics for the low-loss dominant _eHE₁₁ mode along a ribbon dielectric waveguide was performed using the exact finite-element technique as well as two approximate techniques. Analytical predictions were then verified by measurements on ribbon guides made with rexolite using the highly sensitive cavity resonator method. Excellent agreement was found     

A millimeter wave dielectric waveguide antenna

This paper describes the theoretical and experimental results of a novel leaky-wave antenna incorporating a homogeneous dielectric transmission line and radiating aperture into a single structure. The primary objective of this investigation is to demonstrate the ability to control aperture radiation by simply cutting slots into a metal-free dielectric transmission line. Experimental line source antennas with identical periodic slots were designed to operate in the 35 GHz frequency region. The successful performance of these antennas resulted in the design of a dielectric line source antenna with a symmetrical amplitude taper which provided a lower sidelobe level. The design represents a significant breakthrough in achieving affordable, low-loss, lightweight antennas in the millimeter wave region. The most significant applications for this type of antenna include radar surveillance and tactical missile-seeker terminal guidance.     

Optically pumped submillimeter wave semiconductor lasers

An optically pumped multiple quantum well (MQW) submillimeter wave (SMMW) laser is proposed and designed. The laser can potentially generate significant power in the far-infrared regime. It is based on pumping of a series of InGaAs-GaAs quantum wells with a CO₂ laser. The excited electrons created by the pumping process tunnel into the upper of two subband states in an AlGaAs-GaAs quantum well grown in series with the absorption wells, and thereby give rise to a population inversion between these two states which are tuned to the SMMW frequency desired. The authors present the key concepts of the new device and some designed device structures     

Quasi-optical ferrite devices for millimeter and submillimeter wave bands

Main features of the development of quasi-optical ferrite devices, using Faraday effect, are considered. Properties of a polarizing divider and a ferrite rotator of a polarization plane are analysed with standpoint of minimum losses. A matching method, based on an utilization of the rotator element in a form of the multilayers ferrite structure, which can be adjusted independently for right-handed and left-handed cyrcularly polarized waves, is suggested. It is shown, that this method allows to obtain a total matching in a quasi-optical transmission line. Results of an investigation of quasi-optical ferrite devices for the oversized round waveguide withH ₁₁ mode are presented.     

A new method for complex spectral measurement in millimeter and submillimeter wave range

New method for measuring complex transmission or reflection coefficients has been proposed and demonstrated using a simple setup. High measurement quality was achieved: phase sensitivity ～ 0.005 rad., amplitude reproduceability ～ 1%, dynamic range to ～ 10⁷ ÷ 10⁸ (previously 10⁴), phase shift range to be measured 10⁵. It is effective for BWT-Spectroscopy due to the absence of any mechanical adjustments during electronic frequency scan.     

A monolithic active conical horn antenna array for millimeter and submillimeter wave applications

In this paper, a novel active integrated conical horn array is presented. Specifically, a 95 GHz quasioptically fed mixer integrated with an annular slot ring antenna was used as the basic element of the proposed active system. For efficient reception, a low cost micro-machined conical horn array was fabricated and placed on the top of active elements. A modified nonorthogonal finite-difference time-domain (FDTD) approach was applied for analyzing the basic conical horn antenna and a hybrid matrix manipulation technique for efficient antenna array modeling. The proposed active conical horn antenna array was fabricated and measured. Numerical simulations have verified the design at its distributed stages presenting very good agreement with the experimental data.     

A novel PBG coplanar waveguide

A novel coplanar waveguide with photonic bandgap structure is proposed and is implemented by etching holes in the ground plane with an open connected with the gap between strip line and ground plane. Simulation and measurement results show the existence of a bandgap     

A novel theory for dielectric-inset waveguide leaky-wave antennas

A type of leaky-wave antenna that is particularly suitable for applications in the millimeter-wave range is analyzed. The objective of this work is to provide a practical and accurate theory for the design of this class of antennas. The analysis procedure is based on the development of a novel, multimode transverse equivalent network representation. All mutual coupling effects are rigorously taken into account. A single dispersion relation is derived via a transverse resonance procedure, and the complex dispersion behavior of the antenna is obtained through its numerical solution. Useful approximate initial design formulas are given, and a detailed parametric analysis is carried out, showing the effects of changes of all the structural parameters. The results obtained indicate that the structure, in addition to being mechanically simple to realize, exhibits a very flexible electrical behavior. The theory developed, therefore, is a powerful tool for the design and optimization of this class of antennas