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Microwave Theory and Techniques, IEEE Transactions on

Issue 7  Part 1-2 • Date July 1994

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Displaying Results 1 - 25 of 50
  • Evaluation of quasi-static matrix parameters for multiconductor transmission lines using Galerkin's method

    Page(s): 1223 - 1228
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (646 KB)  

    Quasi-static matrix parameters for multiconductor transmission lines are numerically evaluated by solving a set of integral equations for the bound charges using Galerkin's technique, with a piecewise constant approximation for the charge distribution. Several hints are given as how to improve the efficiency and accuracy of computations.<> View full abstract»

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  • Comments on "Useful Bessel function identities and integrals" [with reply]

    Page(s): 1283 - 1284
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    The original paper [see ibid., vol, 41, p 1468-71, 1993] is claimed to contain nothing new either in substance or in application. It would appear that one of the reasons for the publication is that the integrals derived therein are not found in common references. Furthermore, the proof given in the paper is in the nature of a verification and hence hinges upon knowing the correct answers beforehand. It is not difficult to establish direct proofs. The original authors give their reply to these comments.<> View full abstract»

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  • Analysis of radiation from an open-ended coaxial line into stratified dielectrics

    Page(s): 1261 - 1267
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    Radiation from an open-ended coaxial transmission line into an N-layer dielectric medium is studied in application to nondestructive evaluation of materials. Explicit formulations for two cases of layered media, one terminated into an infinite half-space and the other into a conducting sheet are addressed in general form. In the theoretical derivations it is assumed that only the fundamental TEM mode propagates inside the coaxial line. The terminating admittance of the line is then formulated using the continuity of the power flow across the aperture. The admittance expressions for specific cases of two-layer dielectric composite with generally lossy dielectric properties, and a two-layer composite backed by a conducting sheet are presented and inspected explicitly. The numerical results of the aperture admittance formulation are discussed and compared with the available infinite half-space model which had been experimentally verified View full abstract»

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  • Design of superconductive multiplexers using single-mode and dual-mode filters

    Page(s): 1411 - 1418
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    The objective of this short paper is twofold: 1) to present experimental and computer-simulated results for a number of single-mode and dual-mode high-temperature superconductor (HTS) filters; and 2) to present the measured performance of an integrated 3-channel circulator-coupled multiplexer employing dual-mode HTS thin film filters. The CAD algorithm used to design the HTS filters is also described. The results presented demonstrate the feasibility of building C-band compact-size superconductive multiplexers View full abstract»

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  • GaAs MESFET active resonant circuit for microwave filter applications

    Page(s): 1419 - 1423
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    Inverting and noninverting active integrator circuits are compensated for the effect of finite output conductance of the GaAs MESFET by the addition of capacitors and then used to realize an active tuned circuit resonating at 1.5 GHz with fully controllable Q-factor. The active tuned circuit is promising for implementing high-order IF filters at low-microwave frequencies View full abstract»

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  • Frequency-independent equivalent circuit model for microstrip open-end and gap discontinuities

    Page(s): 1268 - 1272
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    The development of user friendly software for microwave integrated circuits will become possible with the adoption of lumped equivalent circuits for interconnect discontinuities. Frequency independent equivalent lumped circuit models are proposed in this paper, wherein resistors are introduced to account for radiation and surface wave losses at microstrip discontinuities. Simple algebraic expressions are obtained for the elements of lumped equivalent circuits for the microstrip open-end and gap discontinuities. These expressions are highly accurate as they are obtained from the full-wave solution in conjunction with physical interpretation and curve fitting techniques. These equivalent circuits include resistor, inductor, and capacitor elements View full abstract»

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  • Calculation of the dispersive characteristics of open dielectric structures by the finite-difference time-domain method

    Page(s): 1207 - 1212
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    An enhanced three-dimensional Finite-Difference Time-Domain (FDTD) technique is applied to the characterization of the fundamental and higher order modes of single and coupled image guide structures. The basic FDTD algorithm is modified to include multidimensional changes of permittivity and an irregular mesh is used for computational efficiency. In this paper FDTD calculations are compared with experimental and theoretical results found in the literature and good agreement is found View full abstract»

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  • A broadband free-space millimeter-wave vector transmission measurement system

    Page(s): 1131 - 1139
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    We report both broadband monolithic transmitter and receiver IC's for MM-wave electromagnetic measurements. The IC's use a nonlinear transmission line (NLTL) and a sampling circuit as a picosecond pulse generator and detector. The pulses are radiated and received by planar monolithic bow-tie antennas, collimated with silicon substrate lenses and off-axis parabolic reflectors. Through Fourier transformation of the received pulse, accurate 30-250 GHz free space gain-frequency and phase-frequency measurements are demonstrated. Systems design considerations are discussed, and a variety of MM-wave broadband transmission measurements are demonstrated View full abstract»

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  • Design of coupling irises between circular cavities by modal analysis

    Page(s): 1307 - 1313
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    Single and dual iris coupling between circular waveguide cavities is studied using a rigorous mode-matching approach. Single, dual, and triple mode coupling irises are considered. It is seen that triple mode coupling can be achieved and controlled employing only a dual iris configuration. The analysis is performed by means of the generalized S-matrix technique; frequency dependence and finite thickness are accurately taken into account, and extensions to other types of coupling, i.e., coupling to an external input waveguide are straightforward. Measured results on dual and triple mode irises show close agreement with computations View full abstract»

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  • Design of six-port stripline ferrite junction circulators

    Page(s): 1272 - 1275
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    Circulation conditions for a six-port stripline ferrite junction circulator have been formulated. For external magnetic field biased above FMR it results in wider transmission frequency bandwidth compared to normal three-port devices. We surmize that six-port circulators can also be used as high power devices similar to the three-port counterpart View full abstract»

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  • The determination of the noise, gain and scattering parameters of microwave transistors (HEMT's) using only automatic noise figure test-set

    Page(s): 1105 - 1113
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (852 KB)  

    A method for the complete characterization of microwave transistors in terms of noise, gain and scattering parameters using only a computer-controlled noise figure measuring set-up is presented. The selection of the optimum measuring conditions, all steps of the experimental procedure, the data collection and the processing needed to derive all the parameters are completely controlled by original (unpublished) software and do not require the presence of an (unskilled) operator. This is novel with respect to other approaches to the same problem. Experimental results regarding the characterization of 32 samples of HEMT's from four manufacturers in the 8-12 GHz frequency range are reported View full abstract»

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  • Multiterminal distributed resistors as microwave attenuators

    Page(s): 1140 - 1148
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    This paper presents an approach to the design of multiterminal planar resistors of arbitrary shape, utilized as microwave attenuators. It indicates how to convert the results of two-dimensional field computations into the nodal description of the circuit, required by commercially available microwave CAD packages. The paper introduces the concept of self-dual geometry, which, in conjunction with symmetry, defines a class of distributed attenuators lending themselves to substantial simplifications in design. A general property of resistive networks is demonstrated, based on which the effects of incremental changes in the multiterminal resistor shape (including trimming) can be intuitively assessed. Some of the proposed ideas are exemplified by the design and test of an extremely compact multiple value attenuation pad, providing (by minimal adjustment) 1-dB steps between 0 and 5 dB View full abstract»

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  • Efficient design methodology for microwave frequency multiplexers using infinite-array prototype circuits

    Page(s): 1337 - 1346
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1032 KB)  

    Frequency multiplexers of the manifold type, in which individual channel filters connect to a main trunk line without the use of isolating directional circuit components, are noted for their compactness, achieved through controlled signal interactions among channel circuits. A major drawback often associated with manifold designs is the potentially large number of network variables that must be handled simultaneously. The new multiplexer design approach being presented utilizes infinite-array prototype circuits based on logarithmic-periodic principles which, in turn, allow a significant reduction in the simultaneous-variable count. The technique is not confined to manifold architectures and can accommodate both contiguous and noncontiguous channels with a wide variety of frequency band allocations. The versatility of the approach is illustrated by two experimental contiguous-band five-channel multiplexer circuits that operate at C- and X-band frequencies, with one circuit designed for equal fractional bandwidths of 20%, and the other for constant absolute bandwidths of 800 MHz. These examples are believed to represent the first practical and successful utilizations of logarithmic periodicity in microwave multiport network design View full abstract»

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  • Waveguide diplexer and multiplexer design

    Page(s): 1393 - 1396
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    A new computer-aided procedure of designing waveguide manifold multiplexers, which combines a rigorous numerical analysis of electromagnetic characteristics of the key elements of the structure and a simple circuit engineering design technique, is proposed. This procedure enables one to obtain the required multiplexer characteristics without any experimental corrections at the minimum computer time expense. Typical design results are given to demonstrate the efficiency of the method View full abstract»

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  • Multilayer suspended stripline and coplanar line filters

    Page(s): 1403 - 1407
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    Using metallization patterns on both sides of a suspended stripline substrate or adding an additional dielectric and conductor layer to coplanar line circuits, additional degrees of freedom arise for filter design like an extended range of impedances, tightly coupled line structures or increased end coupling between lines of different metallization layers. In this way, very compact filter circuits with improved performances may be realized as it is shown for different types of filters using this technique, even including active elements to realize strongly frequency selective amplifiers or active filters View full abstract»

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  • Concerning the use of high-temperature superconductivity in planar microwave filters

    Page(s): 1287 - 1294
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    The fundamentals of high-temperature superconductivity (HTS), as they apply to planar microwave filters, are briefly outlined. It is seen that some problems which are not usually prominent in the design of planar microwave filters come to the fore in the HTS case, and some of these problems are discussed. These problems include: preventing fields from impinging on normal conductor housings or radiating, reducing forward-coupling effects in order to permit the use of smaller substrates, coupling between the desired circuit mode and undesired housing waveguide-type modes, and estimating the maximum power that an HTS filter can handle without significant nonlinear effects View full abstract»

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  • Guided waves along a metal grating on the surface of a grounded dielectric slab

    Page(s): 1190 - 1197
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    The propagation of guided waves along a metal grating lying on a grounded dielectric substrate is studied. Hitherto, investigation of the properties of such waves has been restricted to directions of propagation perpendicular to or nearly parallel to the strips of grating. Averaged boundary conditions for the fields at the grating are used here to simplify the analysis, and are expected to yield accurate results for grating periods that are sufficiently small compared to a wavelength. Comparisons made with more exact computations in the literature are shown to be good. The results have potential application for microwave and millimeter wave waveguides, slotted microstrip antennas, and circuit elements View full abstract»

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  • Microstrip filter design using direct EM field simulation

    Page(s): 1353 - 1359
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    For the first time, we present minimax filter design with electromagnetic (EM) simulations driven directly by a gradient-based optimizer. Challenges of efficiency, discretization of geometrical dimensions, and continuity of optimization variables are overcome by a three-stage attack: 1) efficient on-line response interpolation with respect to geometrical dimensions of microstrip structures simulated with fixed grid sizes; 2) smooth and accurate gradient evaluation for use in conjunction with the proposed interpolation; and 3) storing the results of expensive EM simulations in a dynamically updated database. Simulation of a lowpass microstrip filter illustrates the conventional use of EM simulation for design validation. Design optimization of a double folded stub bandstop filter and of a millimeter-wave 26-40 GHz interdigital capacitor bandpass microstrip filter illustrates the new technique View full abstract»

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  • A simple convolution procedure for calculating currents induced in the human body for exposure to electromagnetic pulses

    Page(s): 1172 - 1175
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    The finite-difference time-domain (FDTD) and frequency dependent finite difference time-domain (FD)2TD methods have been previously used to calculate internal electric (E) fields and induced currents for exposure of the anatomically based model of the human body to electromagnetic pulses (EMPs) and continuous wave (CW) sinusoids. The limitation of these methods is that a complete, computer resource intensive, simulation must be done for each different waveform of interest. The authors describe a simple and efficient technique based on convolution theory which provides the response of the body to any incident waveform (EMP or CW) from a single simulation with an incident impulse waveform. This allows the impulse response to be stored, and the response of the body to any desired waveform to be efficiently computed on a small computer or PC View full abstract»

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  • Ka-band slot-fed higher order-mode low-loss Fabry-Perot filters

    Page(s): 1423 - 1426
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    Low-loss bandpass filters consisting of Fabry-Perot resonators excited by slots which couple to higher order resonator modes are demonstrated. For close reflector spacings, the slots efficiently couple power from rectangular waveguide to the TEM400 and TEM300 modes of the resonator. At Ka-band the filters have insertion losses less than 1 dB in general and less than 0.5 dB in some cases. The unloaded Q values of the filters range from 1500 to 3000. The filters are mechanically tunable over a 25% bandwidth View full abstract»

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  • Computer-aided analysis and design of a planar multilayer Marchand balun

    Page(s): 1429 - 1434
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    Analytical expressions for the scattering (S) parameters for a planar multilayer Marchand balun, constructed of broadside-coupled microstriplines, are derived for the first time, based on the coupled-line quasi-TEM normal mode parameters. New design equations and a new design procedure for the balun based on the derived S-parameters and a circuit synthesis technique are presented. Calculated results for a GaAs microwave monolithic integrated circuit balun designed by this procedure are compared to a general full-wave planar analysis, and good performance and agreement are obtained View full abstract»

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  • Linear fractional curve fitting for measurement of high Q factors

    Page(s): 1149 - 1153
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    A procedure is described for a precision measurement of the unloaded Q factor and of the coupling coefficient for microwave resonators. The complex reflection coefficient data are processed by the linear fractional curve-fitting routine on a personal computer View full abstract»

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  • On the dispersion in TLM and FDTD

    Page(s): 1275 - 1279
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    The dispersion relations of a two-dimensional TLM mesh and a three-dimensional TLM mesh with condensed symmetric nodes are calculated. For the calculation of the TLM dispersion relations, we use a generalized method which can be applied to any TLM node described by square scattering and propagation matrices of equal dimension. Introducing the FDTD Hilbert space representation, it is shown that the method is closely related to the method of calculating FDTD dispersion relations View full abstract»

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  • A new rigorous method for the determination of iris dimensions in dual-mode cavity filters

    Page(s): 1314 - 1320
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    A variational method based on the mode expansion is used in order to determine the accurate physical dimensions of coupling irises in dual-mode cavity filters. By considering the concept of localized and accessible modes, a series of convergence tests are carried out in order to optimize the number and nature of modes which should be included in the numerical calculations. As a consequence, the size of matrices involved and the corresponding computation time are reduced dramatically. This approach, validated by corresponding experimental data, allows us to achieve a considerable reduction of the fabrication time of this type of filter. Actually, the filter can be tuned immediately without any correction of the calculated irises View full abstract»

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  • A compact, high power notch filter with adjustable F0 and bandwidth

    Page(s): 1397 - 1403
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (664 KB)  

    The network described is a notch filter, synthesized as a capacitively-coupled short circuited shunt stub design. A well-known equivalence between open circuited, quarter wavelength high-impedance stubs, and capacitively coupled short-circuited stubs of lower impedance, is used iteratively to achieve a design with some innovative features: The shunt stubs are all the same impedance; typically; 50 Ω. The series 90 degree coupling lines are also the same impedance (again typically 50 Ω). Dimensions and components may thus be easily selected for high-power and low-loss operation. The coupling capacitors (which are in series with the stubs) are adjustable without compromising Q. Re-entrant stubs are used which allow a mixed lumped-distributed stub response and easy adjustment of stub lengths. A rugged coaxial construction is adopted with nothing cantilevered or unsupported. These features result in a design which is quite compact, tunable over a wide range of center frequencies, allows for adjustable bandwidth and thus selectivity, while intrinsically exhibiting high-power capability, low passband loss, and suitability for operation in demanding environments View full abstract»

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Aims & Scope

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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