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Microwave Theory and Techniques, IEEE Transactions on

Issue 4 • Date Apr. 1984

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Displaying Results 1 - 25 of 31
  • [Front cover - Apr. 1984 [T-MTT]]

    Page(s): f1 - f2
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    Freely Available from IEEE
  • Multiconductor Transmission Lines In Multilayered Dielectric Media

    Page(s): 439 - 450
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    A method for computing the capacitance matrix and inductance matrix for a multiconductor transmission line in a multilayered dielectric region is presented. The number of conductors and the number of dielectric layers are arbitrary. Some of the conductors may be of finite cross section and others may be infinitesimally thin. The conductors are either above a single ground plane or between two parallel ground planes. The formulation is obtained by rising a free-space Green's function in conjunction with total charge on the conductor-to-dielectric interfaces and polarization charge on the dielectric-to-dielectric interfaces. The solution is effected by the method of moments using pulses for expansion and point matching for testing. Computed results are given for some cases where all conducting lines are of finite cross section and other cases where they are infinitesimally thin. View full abstract»

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  • Patent abstracts

    Page(s): 477 - 480
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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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  • [Back cover - Apr. 1984 [T-MTT]]

    Page(s): b1 - b2
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    Freely Available from IEEE
  • On the Solution of a Microstripline with Two Dielectrics

    Page(s): 333 - 339
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    We present the calculation for, the capacitance and the effective dielectric constant for a microstripline with two different dielectrics. The solution is based on the exact transformation law provided by two successive Schwarz-Christoffel transformations, which is given in terms of the Jacobi Zn function. This function can be easily separated into its real and imaginary parts, allowing the exact determination of the curve which separates the two dielectrics in the transformed plane. Once the curve is obtained, the capacitance of the system is calculated numerically by a finite-difference method. We compare our results with data obtained from Wheeler's approximate ellipse solution, as well as with other analytical solutions. We assume an infinitely wide ground plane and TEM-mode propagation. View full abstract»

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  • A New Method for Calculating TE and TM Cutoff Frequencies of Uniform Waveguides with Lunar or Eccentric Annular Cross Section

    Page(s): 348 - 354
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    Cutoff frequencies are determined for the uniform waveguide with circular outer conductor and eccentric circular inner conductor. The "lunar line" formed by connecting the inner circle to the outer circle is also considered. Both TE and TM modes are treated. The technique used is to combine conformal mapping of the cross section with the powerful method of intermediate problems. This combination of methods has not been applied previously to the calculation of cutoff frequencies. It produces good, rigorous lower bounds for the frequencies. When complementary upper bounds are found by the Ritz method, very small intervals are determined containing the exact frequencies. For the examples considered, the first twenty or so frequencies are bounded very accurately. View full abstract»

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  • Variational Methods for Nonstandard Eigenvalue Problems (Further Comments)

    Page(s): 474 - 476
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    In response to the author's reply to the first Comment on the above paper, it is affirmed that the proof of fallacy and statements contained therein stand unaltered. The author's attempt at clarification shows that his propositions are founded on contradictory suppositions and equivocation. If not for rigor and consistency, what is the excuse for using mathematics? The issues, however, are not merely ones of purity and semantics-although precision in terminology is essential to meaningful communication--but there is also an important practical consideration. View full abstract»

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  • A Complete GaAs MESFET Computer Model for SPICE (Short Papers)

    Page(s): 471 - 473
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    A model for the gallium arsenide MESFET has been implemented into the source code of the well-known circuit simulation program SPICE. Both large-signal and small-signal simulations of MESFET circuits are now possible within the familiar framework and data format of SPICE. The line-by-line modifications made to SPICE to achieve the model implementation will be made available to interested researchers. View full abstract»

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  • Multiple-Post Inductive Obstacles in Rectangular Waveguide

    Page(s): 365 - 373
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    A complete analysis of multiple-post inductive obstacles in rectangular waveguide is presented. A moment method solution with exponential ( ejnTheta) expansion and weighting functions is used in a Galerkin solution. Post currents are expressed as a Fourier series. As many Fourier series terms (ejn Theta) as desired may be included. All higher order (cutoff) mode interactions between posts are taken into account. The solution is rapid and accurate, and errors maybe controlled (specified). Data are given for the triple-post obstacle and for a two-element filter. View full abstract»

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  • Fast-Fourier-Transform Method for Calculation of SAR Distributions in Finely Discretized Inhomogeneous Models of Biological Bodies

    Page(s): 355 - 360
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    The paper describes a novel iterative approach for calculations of specific absorption rate (SAR) distributions in arbitrary, lossy, dielectric bodies. To date, the method has been used for 2-D problems where its accuracy has been confirmed by comparison with the analytic solutions for homogeneous and layered, circular, cylindrical bodies. With computation times that are proportional to N log2N rather than N2 to N3 for the method of moments, the present approach should be extendable to 3-D bodies with N= 104to 105 cells allowing, thereby, details of SAR distributions that are needed for EM hyperthermia, as well as for assessing biological effects. View full abstract»

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  • A Novel Quasi-Optical Frequency Multiplier Design for Millimeter and Submillimeter Wavelengths

    Page(s): 421 - 427
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    This paper describes a novel design for millimeter and sub-millimeter wavelength varactor frequency triplers and quadruplers. The varactor diode is coupled to the pump source via waveguide and stripline impedance matching and filtering structures. Output power at the various harmonics of the pump frequency is fed to quasi-optical filtering and tuning elements. The low-loss quasi-optical structures enable near-optimum control of the impedances seen by the varactor diode at the idler and output frequencies, resulting in efficient high-order harmonic conversion. A minimum efficiency of 4 percent with 30-mW input power has been obtained for a tripler operating between 200 and 280 GHz, with a peak efficiency of 8 percent between 250 and 280 GHz. Another tripler, designed for the 260-350-GHz band, gave a minimum conversion efficiency of 3 percent with 30-mW input power, with a peak efficiency of 5 percent at 340 GHz. View full abstract»

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  • Determination of the Characteristic Impedance by a Step Current Density Approximation (Short Papers)

    Page(s): 450 - 452
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    The step current densities are used to determine the characteristic impedance of a transmission line with rectangular shape of the conductors. Numerical results for different rectangular lines with asymmetrical position of the inner conductor are presented. The comparison of the results for the square and rectangular coaxial lines shows quite good agreement with the known data. View full abstract»

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  • A Planar Quasi-Optical Subharmonically Pumped Mixer Characterized by Isotropic Conversion Loss (Corrections)

    Page(s): 476
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    In the above paper, the antenna patterns in Figs. 8 and 9 were transposed. Fig. 8 is actually the H-plane pattern and Fig. 9 is the E-plane pattern. View full abstract»

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  • Microwave Diffraction Tomography for Biomedical Applications (Comments)

    Page(s): 473 - 474
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    In the above paper, and a subsequent publication, Bolomey et al. suggested a very useful technique of biological tomography which may provide a fast image reconstruction at low cost. In a more recent work, Bolomey also presented some interesting results of a reconstructed image of a pony kidney. The virtue of the suggested technique lies in the rapidity of data collection by modulated scattering Here we would like to point out that more theoretical study is still needed on the interpretation of the reconstructed image. View full abstract»

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  • Analysis of Wave Propagation in Anisotropic Film Waveguides with Bent Optical Axes

    Page(s): 339
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    We present an analytical method for studying the wave propagation in anisotropic planar optical waveguides where the oblique angle between the optical axis and the propagation axis changes arbitrarily in the film surface along the propagation length. The analysis is based on the coupled-mode theory, where the coupling between a guided mode and radiation modes is regarded to be of major importance. We apply a hypothetical boundary method to quantize the continuum of radiation modes, and replace the continuously changing oblique angle by a step approximation. It is shown that these approximations do not degrade the computational accuracy. To exemplify the wave-propagation properties, we deal with a waveguide consisting of LiNbO3 and let the oblique angle change linearly along the propagation length. It is found that the incident guided TE mode leaks its power primarily in a very narrow region centered on the critical oblique angle, and that TE radiation modes play an important role in the power conversion, even though they carry far less power than the TM radiation modes. View full abstract»

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  • Analysis and Design of Branch-Line Hybrids with Coupled Lines

    Page(s): 427 - 432
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    The scattering parameters of four-ports consisting of coupled lines with coupled or uncoupled connecting branches are derived in terms of the even- and odd-mode impedances and the lengths of the lines. These are used to analyze and formulate basic design procedures for the application of these structures as directional couplers including 0° and 90° 3-dB hybrids. The proposed new structures are quite compact at lower frequencies as compared to conventional uncoupled branch-line and rat-race hybrids. The results for the case of the coupled-line four-port with uncoupled branch lines also lead to closed-form expressions for the lengths and impedances of the lines required to nullify the effect of coupling between the main lines of a conventional branch-line coupler for use at higher frequencies. The measured response of the fabricated couplers is in good agreement with the theoretical predictions. View full abstract»

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  • Lumped Capacitance, Open-Circuit End Effects, and Edge-Capacitance of Microstrip-Like Transmission Lines for Microwave and Millimeter-Wave Applications

    Page(s): 433 - 439
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    A detailed analysis of lumped capacitance, open-circuit end effects, and edge-capacitance of finite-length strip conductors embedded in multilayer, isotropic dielectrics without sidewalls is presented. The analysis uses the well-known variational technique, in conjunction with the transverse transmission-line technique. The lumped capacitances of square and rectangular conductor patches in sandwiched microstrip, inverted microstrip, and suspended microstrip are computed. Further, extensive data on the open-circuit end effects and edge-capacitances of finite-length strip conductors in these rnicrostrip-like transmission lines are generated. Using the method presented, the analysis of lumped capacitance, open-circuit end effects, and edge-capacitances of finite-length strip conductors in various microstrip-like structures reduces to the determination of a single admittance parameter. This parameter can be simply obtained from the transmissionline equivalent circuit. View full abstract»

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  • Coupled Microstrips on Double Anisotropic Layers (Short Papers)

    Page(s): 467 - 470
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    A variational expression is presented for the mode capacitances of coupled microstrip lines with double anisotropic layered substrates. It is shown that the even-and odd-mode phase velocities can be made equal when a sapphire layer is deposited on a boron nitride substrate. High coupler directivity can be achieved with appropriate values of both layers' thicknesses. View full abstract»

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  • Characteristics of Transmission Lines with a Single Wire for a Multiwire Circuit Board

    Page(s): 360 - 364
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    This paper presents the characteristic impedance Z0 and the phase velocity vp of transmission lines with a single wire for a multiwire circuit board (MWB) under the quasi-TEM wave approximation. The characteristics are discussed for each of three investigated strictures a: (I)H = h + r, (II)H = h, and (III)H = h - r, where r, h, and H are the radius of the wire, the thickness of the dielectric (adhesive layer), and the distance from the ground plane to the center of the wire, respectively. A charge simulation method is used for the calculation of the parameters. Z0 and vp are presented in graphical form for adhesive relative dielectric constants epsilon* of 1.0, 2.65, and 5.0 as a function of r/h. An approximate formula of Z0 for the structure of case (II) with epsilon* = 5.0 is also presented. View full abstract»

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  • An Efficient 200-290-GHz Frequency Tripler Incorporating a Novel Stripline Structure

    Page(s): 416 - 420
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    This paper describes a broadly tuneable frequency tripler which can provide more than 2-mW output power at any frequency between 200 and 290 GHz. It is derived from an earlier narrow-band prototype design, with the major improvements being the use of a new low-pass filter design implemented using a novel suspended substrate stripline structure, an optimized waveguide transformer, and a lower loss contacting output backshort. View full abstract»

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  • Theory and Numerical Modeling of a Compact Low-Field High-Frequency Gyrotron

    Page(s): 373 - 386
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    The electron-cyclotron maser interaction provides an extremely efficient means of generating high-power radiation in the millimeter and submillimeter regimes. For devices where both high frequencies and low magnetic fields are required, high cyclotron-harmonic interactions must be considered. We present here a finear and nonlinear analysis of a TEm11 whispering-gallery-mode gyrotron. Resonances at the mth and (m +- 1)th cyclotron harmonic are found. The start oscillation condition is calculated from linear theory for a wide range of parameters. Maximum efficiency for different beam and cavity conditions is calculated with a fully relativistic numerical simulation code. High efficiencies, >35 percent, have been found at the mth cyclotron harmonic. The effect on the efficiency of an initial velocity spread in the electron beam has also been considered. View full abstract»

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  • The Displaced Rectangular Waveguide Junction and its Use As an Adjustable Reference Reflection

    Page(s): 387 - 394
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    The reflection from a displaced junction in rectangular waveguide and the equivalent circuit parameters are calculated using modal analysis. The use of weighted Gegenbauer polynomials to describe the field in the plane of displacement is shown to significantly improve the rate of convergence of the solution in comparison to waveguide-type mode functions. Approximate formulas are given for displacements of up to 25 percent of the waveguide dimensions. An E-plane displaced junction is suggested for use as an adjustable reference reflection. View full abstract»

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  • Determination of the Admittance of a General Waveguide-Coaxial Line Junction (Short Paper)

    Page(s): 465 - 467
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    An analytical approximate method to determine the admittance of a general coaxial-waveguide junction is presented. The accuracy of the method is verified experimentally for the case of rectangular waveguide. View full abstract»

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  • Perturbation for Open Analysis and Design Equations and Closed-Ring Microstrip Resonators

    Page(s): 405 - 410
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    Simple closed-form expressions for the resonant frequency and electromagnetic field distribution for various modes of the open- and closed-ring microstrip resonators are derived by utilizing the perturbation analysis of the equivalent curved waveguide model. These results are shown to be in good agreement with the exactly computed values obtained by the solution of the eigenvalue equation for the equivalent waveguide model and the experimental data. The effect of gap capacitance on the eigenvalues of the open-ring resonator is also examined. View full abstract»

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  • Characteristics of Metal-Insulator-Semiconductor Coplanar Waveguides for Monolithic Microwave Circuits

    Page(s): 410 - 416
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    Using a full-wave mode-matching technique, an extensive analysis is presented of the slow-wave factor, attenuation, and characteristic impedance of a metal-insulator semiconductor coplanar waveguide (MISCPW) as functions of the various structural parameters. Design criteria are given for low-attenuation slow-wave propagation. By a proper optimization of the structure, performances comparable with or even better than those of alternative structures proposed in the literature are theoretically predicted. 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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