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Microwave Theory and Techniques, IEEE Transactions on

Issue 1 • Date Jan. 1971

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Displaying Results 1 - 25 of 34
  • [Front cover - Jan. 1971]

    Page(s): f1 - f2
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    Freely Available from IEEE
  • Table of contents - Jan. 1971

    Page(s): 1
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    Freely Available from IEEE
  • Rectangular Waveguides with Impedance Walls

    Page(s): 2 - 8
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    The propagation of guided waves in a rectangular geometry having impedance boundary conditions is investigated. An impedance compatibility relation is derived that must be satisfied in order that a separable modal solution exists for a given impedance configuration. Several new rectangular waveguides are developed; among them are 1) a tall rectangular waveguide operating in a dominant H/sub 10/ mode with no H/sub 0N/ modes; 2) a rectangular waveguide with two parallel anisotropic impedance surfaces; 3) a rectangular waveguide with two parallel walls having isotropic impedance surfaces, the other two walls being anisotropic; 4) a rectangular waveguide supporting only E modes; and 5) rectangular coaxial systems containing impedance surfaces. The modal structure of rectangular waveguides with impedance boundary conditions offers advantages over the conventional waveguide. The potential of oversizing for low-loss and high-power applications is enhanced because of the additional modal control provided by the impedance surfaces. Other applications are suggested. View full abstract»

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  • Vector Variational Solutions of Inhomogeneously Loaded Cylindrical Waveguide Structures

    Page(s): 9 - 18
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    A vector variational formulation of the Maxwell curl equations in terms of all six electromagnetic field components is developed for circular waveguides symmetrically loaded with dialectric. A guide-wall boundary integral term, which renders the electric Dirichlet boundary conditions natural, is included in the variational expression. It is, therefore, unnecessary for the trial electromagnetic field functions to satisfy any guide-wall boundary conditions. This greatly extends the class of problems for which the vector variational-solution procedure is applicable and permits simple expansion functions for the trial fields, thus facilitating integral calculations. Solution results for several hybrid-mode circulator-waveguide structures are presented and compared with available experimental data. View full abstract»

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  • Hybrid-Mode Analysis of Microstrip by Finite-Element Methods

    Page(s): 19 - 25
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    A numerical analysis is presented in terms of finite elements of hybrid-mode propagation in closed microstrip. Two modes with zero frequency cutoff are described; one is a quasi-TEM mode and the other a surface mode. Also investigated is a third mode which corresponds to the lowest order waveguide mode in the absence of the strip. View full abstract»

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  • A Comb-Line Elliptic Filter

    Page(s): 26 - 29
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    The design of a new type of elliptic filter, particularly suitable for narrow-band low-loss applications at VHF and UHF, is presented. The filter is derived from a lumped-element bandpass prototype by replacing the lumped inductors, which are normally the main contributory factors to the loss, by a comparatively low-loss distributed network. The latter consists of an n-wire digital line short-circuited at one end, the length of which is i/8 or less. An experimental elliptic filter of fifth order was constructed at 136.6 MHz with a pass bandwidth of 5 MHz, having 60-dB points at /spl plusmn/ 7 MHz from midband. The measured insertion loss of 1.1 dB is lower than that of a comparable lumped-element filter by a factor of at least 3,5:1. It compares favorably also with a comb-line filter, both in terms of loss and physical size. View full abstract»

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  • A Frequency Dependent Solution for Microstrip Transmission Lines

    Page(s): 30 - 39
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    Theoretical and experimental results of "open" microstrip propagation on both a pure dielectric and a demagnetized ferrite substrate are presented. The theory enables one to obtain the frequency dependence of phase velocity and characteristic impedance, and also to obtain the electromagnetic field quantities around the microstrip line. It utilizes a Fourier transform method in which the hybrid-mode solutions for a "fictitious" surface current at the substrate-air interface are summed in such a way as to represent the fields caused by a current distribution that is finite only over the region occupied by the conducting strip and is assumed equal to that for the quasi-static case. View full abstract»

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  • An E Vector Variational Formulation of the Maxwell Equations for Cylindrical Waveguide Problems

    Page(s): 40 - 46
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    A vector variational formulation of the Maxwell equations applicable to cylindrical waveguide problems is developed in terms of the electric E field. This three-component vector formulation allows an approximate solution of loaded waveguide structures which cannot be described in terms of a single-field component or potential function. The three-component formulation is more economical than corresponding six-component formulations for a given order of approximation because the solution matrices which result are reduced in size (/spl sim/1/2) and contain fewer zero elements. The E-field variational integral is expanded in terms of the field components for inhomogeneously loaded parallel-plate and rectangular waveguide geometries to illustrate a computer-assisted vector variational solution procedure. View full abstract»

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  • A New Technique for the Analysis of the Dispersion Characteristics of Microstrip Lines

    Page(s): 47 - 56
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    Dispersion characteristics of shielded microstrip lines are investigated using a new technique. The method utilizes the well-known singular integral equation approach for deriving an alternate form of eigenvalue equation with superior convergence properties. It is shown that accurate numerical results may be obtained from this eigenvalue equation using only a 2x2 matrix equation. In comparison, the conventional formulation of the problem requires the use of matrices that are much larger in size. Aside from the numerical efficiency, the simplicity of the method makes it possible to conveniently extract higher order modal solutions for the propagation constants that affect the high-frequency application of microstrip lines. Even though the derivation of the determinantal equation requires some intricate mathematical manipulations, the user may bypass these completely and use the final eigenvalue equation which is programmable on the computer. View full abstract»

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  • Nonreciprocal Wave Propagation in Semiconductor Loaded Waveguides in the Presence of a Transverse Magnetic Field

    Page(s): 57 - 65
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    Approximate solutions for the complex propagation constant in semiconductor loaded waveguides are obtained by expansion of the fields in terms of a finite number of the empty waveguide modes. Solutions are obtained for the case of partial loading in the narrow dimension of the guide, which explicitly exhibit the non-reciprocal effects observed in the presence of a transverse magnetic field. Coupling between the TE/sub 10/ and TM/sub 11/ empty waveguide modes is shown to explain qualitatively the observed experimental effects. Good quantitative agreement with experiments using Si samples is obtained. View full abstract»

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  • Application of Ferrite to Electromagnetic Wave Absorber and its Characteristics

    Page(s): 65 - 72
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    An electromagnetic wave absorber utilizing ferrite or rubber ferrite composed of ferrite powder and rubber is described. In our investigation, the existence of a matching frequency f/sub m/ and a matching thickness t/sub m/ has been found. The terms f/sub m/ and t/sub m/ mean that the ferrite which is backed with a conducting plate can be a perfect absorber only under the conditions that the frequency of the incident wave is f/sub m/ and that the thickness of the ferrite is t/sub m/.Each ferrite has two matching frequencies f/sub m1/, f/sub m2/, (f/sub m1<f/sub m2/) and two matching thicknesses t/sub m1/, t/sub m2/, respectively. The f/sub m1/ of solid ferrite cannot be beyond 2 GHz. Through the development of rubber ferrite, the upper limit of f/sub m1/ can be overcome and f/sub m2/ ranges from 4 to 12 GHz. The matching thickness t/sub m1/ is a simple function of Snoek's value S and ranges from 4 to 10 mm regardless of f/sub m1/. The superiority of ferrite or rubber ferrite to lossy dielectric material as an absorber has been noticed in the frequency range under 7.5 GHz. The characteristics of matched load at 77/spl deg/K was investigated with success. View full abstract»

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  • Propagation in One-Dimensional Random Media

    Page(s): 73 - 80
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    Propagation in one-dimensional random media is studied using matrix methods. This work applies, for example, to plane wave propagation in layered-media TEM transmission lines with random spacing, etc., where the spurious mode is a reflected wave. The imperfection is assumed to have a white spectrum. Similar techniques have previously been applied to multimode waveguide where the spurious mode is a forward wave. The present work is of interest because it yields exact computable results for certain transmission statistics in a simple way. These may be of help in comparing various approximate perturbation theories and in finding out what happens to signals in very long random transmission media where perturbation theory fails. Specifically, we compute the expected value and the variance of the complex loss (input/output) for lossless (i.e., zero heat loss) and Iossy random media. In the lossless case only we compute the expected reciprocal input resistance and conductance, which Zakai has previously shown to be computable using a different approach. The imperfection (e.g., dielectric constant /spl epsiv/(x) of a continuous random medium, capacitance C(x) of a TEM line) is assumed to consist of a dc component and a white ac component. The more practical case of a flat low-pass spectrum for the ac component is considered, and the region of applicability of the present results to this problem is indicated. Similar methods may be used to calculate the covariance of the (complex) loss and higher moments of the loss and of the reciprocal input resistance and conductance for zero heat loss, although these calculations are not carried out here. The covariance would be required in order to study signal distortion in such a random medium. View full abstract»

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  • A New Method of Synthesizing Matched Broad-Band TEM-Mode Three-Ports

    Page(s): 81 - 88
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    A new method of synthesizing matched broad-band TEM-mode three-ports is presented. The three-ports consist of n sections in cascade with each section composed of two coupled lossless transmission lines of electrical length /spl theta/ and an intermediate resistor. The main object is to analyze and design broad-band unsymmetrical structures with the symmetrical three-port as a special and important case. The analysis of the three-port is performed by means of a more convenient four-port analysis. An even-odd-mode method is used and a new definition of the odd mode is introduced. This new definition considerably simplfies the treatment of unsymmetrical three-and four-ports with one half of the network identical to the other apart from an impedance scaling factor. The analysis yields two uncoupled two-ports in each mode. The even-mode networks are identical with cascaded quarter-wave impedance transformers while the odd-mode networks contain all the resistors. A new technique for their design is presented and a computer program for complete synthesis of hybrid three-ports has been worked out. Several experimental stripline three-ports were built. A three-section unsymmetrical (k=1.7) matched three-port showed a measured isolation better than 20 dB and a maximum VSWR of 1.3 from 5 to 12 GHz. The total loss of a four-section equal-power divider was 0.2dB, maximum VSWR 1.25, and minimum isolation 23 dB over the frequency range 2.5-12.0 GHz. View full abstract»

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  • Operating Criteria for Active Microwave Inductors (Correspondence)

    Page(s): 89 - 91
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    A method is given whereby the range of frequencies of operation of an inverted common collector transistor circuit (synthesized inductance) is found experimentally as a function of bias current. A complementary relationship is shown to exist between this method and that which gives the frequency range by determining the maximum reflected negative resistance characteristics. View full abstract»

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  • Grid-separated microwave triode oscillators - analysis and design (Correspondence)

    Page(s): 91 - 93
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    A grid-separated microwave triode oscillator which uses a common capacitance as the feedback element is examined. This particular design lends itself to a straightforward theoretical analysis which is shown to be in good agreement with experimental results at 2.5 GHz. View full abstract»

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  • Contribution to the Problem of Orthogonality Relations for Magnetoplasma-Filled Waveguides (Correspondence)

    Page(s): 93 - 94
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    The orthogonality properties of the modes of a magnetoplasma waveguide involve a set of adjoint modes. We show how to obtain these adjoint modes without calculus in some particular cases. View full abstract»

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  • Balanced Transmission-Line Measurements Using Coaxial Equipment (Correspondence)

    Page(s): 94 - 96
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    The availability of commercial precision coaxial hybrids makes measurements on balanced two-conductor transmission lines as easy and as practical as on an unbalanced coaxial system. These hybrids, when used as a balun, transform an unbalanced coaxial system to a balanced shielded system and because of the nature of the balanced shielded system permit the measurement of the characteristics of loads connected thereto by the use of commercial coaxial test equipment. This technique has been successfully used from 600 MHz to 5 GHz, and with presently available components can be used at HF and VHF as well. The theory upon which the measurement technique is based is outlined and some results of an experimental verification included. View full abstract»

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  • The Generation of Pulse-Modulated Signals at C Band and Beyond (Correspondence)

    Page(s): 96 - 99
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    A method is presented to generate pulse-modulated signals at C band and beyond where the pulse duration may be in the order of a nanosecond. The generation technique involves the use of a TEM-mode pulse-forming network having a time-limited impulse response and a source of step-modulated RF energy. View full abstract»

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  • Design of a Tapered Transition in a Circular Waveguide (Correspondence)

    Page(s): 99 - 100
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    This correspondence describes a successful design procedure for transitions in circular waveguide. The design procedure is discussed and a universal design curve developed. As an example, one point on a 12-in taper from WRC 283 (2.81-in ID) to WRC 621 (1.28-in ID) is calculated. Test results for the 12-in taper in the 5.925-to 6.425-GHz common carrier band are given. View full abstract»

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  • 1-M W Four-Port E-Plane Junction Circulator (Correspondence)

    Page(s): 100 - 103
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    An S-band four-port E-plane waveguide junction circulator has been developed that has a power-handling capability of 1-MW peak and 1-kW average. Improved ferrite materials and dielectric matching techniques have resulted in a device having a high-power insertion loss of 0.5 dB and a biasing magnetic field of 400 G. The E-plane configuration lends itself to a compact lightweight circulator design having a high-power capability greater than the H-plane configuration, since RF breakdown problems are alleviated by locating the ferrite in the region of minimum RF electric field. The final device requires approximately one-tenth the amount of ferrite and permanent magnet material used in comparable differential phase-shift circulators. The size and weight are reduced by a factor of approximately 5. View full abstract»

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  • A 360/spl deg/ Reflection-Type Diode Phase Modulator (Correspondence)

    Page(s): 103 - 105
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    A 360/spl deg/ phase modulator using two series-tuned varactors in a parallel connection is described. The design minimizes the change in total phase shfit with frequency and gives a small attenuation ripple. The modulator is centered at 2 GHz and gives a total phase shift at 360/spl deg/ at the center frequency, an attenuation ripple of 1.3 dB over a 10-percent bandwidth and a 7/spl deg/ decrease of phase shift at the band edges. View full abstract»

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  • A Comparison of Two Nonreciprocal Latching Phaser Configurations (Corresondence)

    Page(s): 105 - 107
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    The microwave and switching characteristics of the rectangular-toroid Iatching-ferrite-phaser configuration are compared and contrasted with those of the circumferentially magnetized circular rod in rectangular waveguide. View full abstract»

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  • Rays, Modes, and Equivalent Networks (Correspondence)

    Page(s): 107 - 109
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    This correspondence describes certain analogies between ray-optical and modal (equivalent-network) procedures employed in the study of a variety of propagation, guiding, and scattering phenomena. View full abstract»

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  • Input Impedance Behavior of Stripline Circulator (Correspondence)

    Page(s): 109 - 110
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    The input impedance of the Bosma model for a stripline circulator has been computed for light coupling in below-resonance operation. The result agrees with the two-tank circuit model proposed by Fay and Comstock and with experimental measurements. View full abstract»

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  • Eigenvalues for a Spherical Cavity with an Impedance Wall (Correspondence)

    Page(s): 110 - 111
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    The boundary value solution for the resonance frequencies of a spherical cavity with an impedance wall is presented for the TE and TM cases. It is found that in the TE case with a capacitive cavity surface, a new mode exists and corresponds to the fundamental mode. This is in contrast to the perfectly conducting spherical cavity where a TM mode is the lowest order mode. 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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