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Microwave Theory and Techniques, IEEE Transactions on

Issue 10 • Date Oct. 1984

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Displaying Results 1 - 25 of 29
  • [Front cover - Oct. 1984 [T-MTT]]

    Page(s): f1 - f2
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    Freely Available from IEEE
  • Technology Summaries for Microwave Theory and Techniques - 1983

    Page(s): 1372 - 1378
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    This paper consists of compendia of advances for the calendar year 1983 in four selected technical areas of interest to the microwave community. These four areas are Hybrid MIC's, Microwave and Millimeter-Wave Solid-State Devices, Microwave Field Theory, and Microwave Systems. View full abstract»

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  • Patent abstracts

    Page(s): 1422 - 1425
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    These patent abstracts of recently issued patents of interest to microwave engineers are intended to provide the minimum information necessary for readers to detennine if they are interested in examining the patent in more detail. Complete copies of patents are available for a small fee by writing: U.S. Patent and Trademark Office, Box 9, Washington, DC, USA. View full abstract»

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  • IEEE Conference Records [advertisement]

    Page(s): 1426
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    Freely Available from IEEE
  • [Back cover - Oct. 1984 [T-MTT]]

    Page(s): b1 - b2
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    Freely Available from IEEE
  • High-Temperature Microwave Characterization of Dielectric Rods

    Page(s): 1328 - 1335
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    A technique for the simultaneous heating and characterization of dielectric rods using a single microwave source is described. The rod is heated in a rectangular cavity excited by an iris. A variational model for the impedances of homogeneous rods used in the characterization procedure is discussed. It is accurate regardless of the diameter of the rod, even at resonance. Experimental results of Beta-Al2O3 are presented. View full abstract»

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  • Phase Shifts in Single- and Dual-Gate GaAs MESFET's for 2-4-GHz Quadrature Phase Shifters

    Page(s): 1280 - 1288
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    The variation of transmission phase for single- and dual-gate GaAs MESFET's with bias change and its probable effects on the performance of an active phase shifter have been studied for the frequency range 2 to 4 GHz. from measured S-parameter values for single- and dual-gate transistors, the element values of the equivalent circuits were fitted by using the computer-aided design program SUPER COMPACT. For the normal full-gate voltage range 0 to -2 V at VDS= 4 V, the single-gate MESFET varies in transmission phase from 142° to 149° at 2 GHz, and from 109° to 119° at 4 GHz. However, with drain voltage varied from 0.3 to 4 V and a constant gate-voltage bias of 0 V, the phase shifts are much larger, 105° to 145° at 2 GHz and 78° to 112° at 4 GHz. this suggests that large phase shifts may be expected in a dual-gate device and this is found to be so. With VDS= 4 Vand VGS1= - 1.0 V, variation of control (second) gate bias from 0 to - 1.75 V for the NE463 GaAs MESFET produces a transmission phase variation from 95° to 132° at 2 GHz and 41° to 88° at 4 GHz. Such phase shifts cause both amplitude and phase errors in phase-shifter circuits of the kind where signals from two FET channels are combined in quadrature with their gate voltages controlled to provide 0° to 90° phase control with constant amplitude. For the single-gate FET examined, the expected amplitude and phase errors are 0.30 dB and 6° at 2 GHz, and 0.36 dB and 10° at 4 GHz. If dual-gate FET's are used in similar circuits, the distribution of errors is different. For NE463 devices, the corresponding figures are 0.56 dB and 2° at 2 GHz and 1.2 dB and 3° at 4 GHz. the advantage of the dual-gate configuration is that the input impedance conditions are more constant than for the single-gate configuration. View full abstract»

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  • Generation of High-Frequency Radiation by Quasi-Optical Gyrotron at Harmonics of the Cyclotron Frequency

    Page(s): 1398 - 1401
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    A quasi-optical gyrotron can operate, in principle, at high harmonics of the electron-cyclotron frequency, as well as at the fundamental. Lower harmonics are suppressed by exploiting their larger diffraction losses. The radiation-field amplitude is kept below the breakdown value by taking advantage of the focusing properties of the quasi-optical resonator. Cavity design parameters and starting currents are presented which characterize the operation of the quasi-optical gyrotron at the eighth harmonic of gyrofrequency. View full abstract»

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  • Electromagnetic Waves in Toroidal Vessels of Arbitrary Cross Section Filled with Radially Inhomogeneous Dielectric Medium

    Page(s): 1336 - 1341
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    In this paper, analytical solutions of Maxwell's equations in cylindrical coordinates are presented for toroidal resonators filled with homogeneous or inhomogeneous unmagnetized plasma or another dielectric medium. It is shown that the electromagnetic boundary conditions valid on a conducting toroidal surface of arbitrary meridional cross section can be satisfied by the general solution since the general solution contains an infinite set of arbitrary constants. A method is given to show how these constants and the eigenfrequency of the resonator can be calculated for a given cross section of the toroidal vessel. View full abstract»

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  • Finite-Element Analysis of Dielectric-Loaded Waveguides

    Page(s): 1275 - 1279
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    A finite-element analysis in which nonphysical spurious solutions do not appear has been established to solve the electromagnetic field problem of the closed waveguide filled with various anisotropic media. This method is based on the approximate extremization of a functional, whose Euler equation is the three-component curlcurl equation derived from the Maxwell equations, with a new conforming element. Specific examples are given and the results are compared with those obtained by exact solutions and longitudinal two-component finite-element solutions. Very close agreement was found and all nonzero eigenvalues have been proved to have one-to-one correspondence to the propagating modes of the waveguide. View full abstract»

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  • Correction Due to a Finite Permittivity for a Ring Resonator in Free Space

    Page(s): 1288 - 1293
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    To better determine the resonant fields of a dielectric resonator with high permittivity epsilonr, the asymptotic theory with1/√epsilon3 as a small parameter is extended by adding higher order terms in 1/√epsilon r in the fields, the resonant wavenumber, and radiation Q. Extensive data are shown for the Phi independent "nonconfined" mode of a ring resonator, which radiates as a magnetic dipole. Some results are added for the "magnetic quadruple" mode. View full abstract»

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  • Effect of Doping Profile Variation on GaAs Hybrid and Double-Read IMPATT Diode Performance at 60 and 94 GHz

    Page(s): 1342 - 1352
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    Doping profile parameters were varied in a computer optimization of hybrid and double-read GaAs IMPATT diodes at 60 and 94 GHz. The energy-momentum transport model was used to simulate each structure. Optimum results for the various structures that were studied are presented and compared. View full abstract»

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  • Stability of Multifrequency Negative-Resistance Oscillators

    Page(s): 1310 - 1318
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    A general criterion is derived for the stablity of a negative-resistance oscillator with respect to small perturbations in the operating point. The derivation applies when the oscillator output consists of an arbitrary number of related frequency components, including possible nonharmonic components. Examples are given of the application of the stability criterion to coaxial IMPATT oscillator circuits, with experimental verification of the frequency and output power at theoretically determined stable operating points. View full abstract»

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  • Microwave Point Contact Diode Responsivity Improvement through Surface Effects in Vacuum (Short Papers)

    Page(s): 1384 - 1387
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    Desorption of air atoms from point contact diode surfaces via exposure to vacuum can give rise to significant changes in electronic characteristics. In the example considered, exposure of an X-band detector to a modest vacuum gives rise to a responsivity increase of about 80 percent for video and heterodyne detection. Experiments indicate that vacuum desorption of minority surface impurities increases the barrier height and decreases tunneling probability, thus increasing diode nonlinearity and making the diodes more nearly "ideal." The resulting relative increase of the thermionic emission current should decrease the effective shot-noise temperature, thus increasing the signal-to-noise ratio (SNR) even further. View full abstract»

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  • E-Plane Integrated Circuit Filters with Improved Stopband Attenuation (Short Papers)

    Page(s): 1391 - 1394
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    Improved stopband attenuation is achieved by thick strips, by reduced waveguide sidewall dimensions, and by double planar integrated circuits. In contrast to thick strips which may cause high passband insertion losses and filters with reduced waveguide dimensions which require additional tapers, double planar E-plane integrated circuit filters combine the advantages of low costs, high stopband, and low passband insertion losses. Computer-aided design of a four-resonator Ka -band double metal insert filter achieves a calculated stopband attenuation between 40 and 60 GHz of more than 50 dB, the calculated minimum passband insertion loss is 0.43 dB (measured 1.8 dB). Higher order mode excitation and finite thicknesses of the inserts are included in the calculations. View full abstract»

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  • A Comparison of IMPATT Oscillator Power and Frequency Above 100 GHz with Results Derived from Theoretical Models

    Page(s): 1394 - 1398
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    A comparison is made of experimentally determined IMPATT oscillator frequency and power characteristics in the 90-140-GHz band with values obtained from detailed theoretical models. The results show encouraging agreement and demonstrate the potential of the modeling approach for oscillator design. View full abstract»

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  • Theory and Numerical Simulation of a TE111 Gyroresonant Accelerator

    Page(s): 1293 - 1301
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    The production of spiral relativistic electron beams in a TE111 gyroresonant accelerator cavity for injection into a compact high-harmonic gyrotron is studied. Parametric studies are performed to determine the effects of variations in the background magnetic field amplitude, the RF amplitude in the cavity, and the initial beam voltage on the output beam.The effects of velocity spread and a finite radial extent of the input beam are also discussed. Power curves for obtaining optimum operating regimes for the TE /sub111/ accelerator are provided. View full abstract»

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  • Theory and Analysis of GaAs MESFET Mixers (Short Papers)

    Page(s): 1402 - 1406
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    A generalized analysis of the GaAs MESFET mixer is presented. Its advantage is that many of the simplifying assumptions in previous approaches have been substantially eliminated. Using this approach, the nonlinearities of any number of elements in the FET equivalent circuit may be included, any number of Iocal oscillator (LO) harmonics and mixing products may he considered, unusual mixers such as subharmonic mixers, upconverters, and mixers with high IF frequencies can be analyzed. The theory has been verified experimentally. Two mixers are described: one exhibits 11.5-dB conversion gain with + 9-dBm LO power, 5.6-dB minimum noise figure and + 15-dBm third-order intermodulation intercept, and another which exhibits 500-MHz bandwidth, 6-dB minimum gain, 5.5-dB maximum noise figure, and + 12-dBm third-order intercept at + 6-dBm LO power. View full abstract»

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  • Effects of Doping Profile on GaAs, Double-Drift IMPATT Diodes at 33 and 44 GHz Using the Energy-Momentum Transport Model

    Page(s): 1353 - 1361
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    Experimentally determined doping profiles for double-read GaAs IMPATT diodes operating at 33 and 44 GHz are used as starting points for a computer optimization. A computer simulation including energy and momentum relaxation effects was used to simulate these devices as the lengths of the drift regions and the integrated charge in the doping spikes were varied. The effects of these doping profile variations on diode performance are presented. View full abstract»

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  • Scattering at a Junction of Two Waveguides with Different Surface Impedances

    Page(s): 1319 - 1328
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    We consider junction of two cylindrical waveguides and derive the scattering matrix when a single mode is incident in one of the two waveguides. We are interested primarily in the case of two corrugated waveguides with different longitudinal impedances, but the analysis applies also to waveguides with nonzero transverse impedances. It is shown that, under certain general conditions the infinite set of equations specifying the junction scattering coefficients can be solved exactly by the residue-calculus method. Very simple expressions are then obtained between the scattering coefficients and the propagation constants gamman and yi of the modes in the two waveguides. These expressions, obtained previously only in special cases, are direct consequences of certain simple relations derived here for the coupling coefficients between the modes of the two waveguides. In those cases in which the scattering coefficients cannot be determined exactly, we determine them approximately by a perturbation analysis. View full abstract»

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  • Analysis of Slotted, Dielectrically Loaded, Ridged Waveguide

    Page(s): 1302 - 1310
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    This paper considers a symmetrical double-ridged waveguide with an axial dielectric slab inserted into it. Series expansions are used to describe the waveguide fields. The method of moments is employed to provide a system of linear equations from which the propagation constant and the coefficients of the series expansions are obtained. from these quantities, the field distributions and power flow are determined and a characteristic impedance based on a power-voltage definition is computed. The calculated propagation constants are compared with measured values. View full abstract»

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  • Effect of Inner Conductor Offset in a Coplanar Waveguide

    Page(s): 1387 - 1390
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    This paper reports on the effect of structural offset in a coplanar waveguide on the characteristic impedance and fine loss. This effect can be an appreciable factor in designing highy precise circuits, such as MIC's using coplanar waveguide, or a coplanar-type standing-wave detector. The electric field over the cross section of the line is analyzed by assuming a TEM mode of wave propagation, and solving a two-dimensional Laplace's equation by means of the successive over-relaxation method. In the analysis, an approximate solution based on symmetry is employed. Also, measurements are made, to confirm the results thus obtained. View full abstract»

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  • The Interdigitated Three-Strip Coupler (Short Papers)

    Page(s): 1418 - 1422
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    A general design procedure for three-strip interdigitated couplers with arbitrary coupling values is presented. These results are then applied, for various coupling values, to both stripline and microstrip media to check the physical realizability. The dimensions of the coupler can be substantially affected by allowing a small degree of impedance mismatching. View full abstract»

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  • A New Microstrip Dispersion Model (Short Papers)

    Page(s): 1379 - 1384
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    A new unified analysis technique is presented for dispersion in microstrip at high frequencies. The technique exploits the fact that the dispersion in microstrips is due to coupling between a surface-wave mode and the LSE mode of an appropriate model of the microstrip. The analysis uses an effective dielectric constant (EDC) approach to evaluate the mode coupling in the LSE model. Unlike previously reported models, all the parameters of the model are exactly determined from the quasistatic parameters of the microstrip, which takes the fringing field into account. Approximate closed-form equations are derived for the prediction of microstrip dispersion. The results agree within 1.50 percent with the experimental and previously published data over a wide useful range of microstrip dimensions and substrate permittivities. View full abstract»

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  • Modes in Anisotropic Rectangular Waveguides: An Accurate and Simple Perturbation Approach (Short Papers)

    Page(s): 1415 - 1418
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    We present a simple and accurate perturbation method for obtaining the propagation characteristics of anisotropic rectangular waveguides described by a diagonal dielectric constant tensor. Comparison with the results of finite-element technique shows an excellent agreement. View full abstract»

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The IEEE Transactions on Microwave Theory and Techniques focuses on that part of engineering and theory associated with microwave/millimeter-wave components, devices, circuits, and systems involving the generation, modulation, demodulation, control, transmission, and detection of microwave signals. This includes scientific, technical, and industrial, activities. Microwave theory and techniques relates to electromagnetic waves usually in the frequency region between a few MHz and a THz; other spectral regions and wave types are included within the scope of the Society whenever basic microwave theory and techniques can yield useful results. Generally, this occurs in the theory of wave propagation in structures with dimensions comparable to a wavelength, and in the related techniques for analysis and design..

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