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Microwave Theory and Techniques, IEEE Transactions on

Issue 3 • Date Mar 1994

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Displaying Results 1 - 25 of 28
  • HTS microstrip matching networks and filters

    Publication Year: 1994 , Page(s): 523 - 525
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    High-temperature superconducting (HTS) YBCO microstrip bandpass filters and microstrip impedance matching networks were fabricated, tested and compared with the predicted performance. Vector corrected measurements of these circuits were performed at cryogenic temperatures. Comparisons of the insertion loss for the HTS and corresponding Au filters are presented, as well as the predicted noise figure for the low-noise amplifiers using HTS and Au matching networks View full abstract»

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  • Scattering from an infinite cylinder of small radius embedded into a dielectric one

    Publication Year: 1994 , Page(s): 463 - 470
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    In this paper the scattering from an infinite metallic or dielectric cylinder of electrically small radius, embedded into a dielectric cylinder, is considered. The problem is solved by the method of separation of variables, in conjunction with translational addition theorems. Analytical expressions are obtained for the scattered field and the various scattering cross-sections, when the radius of the inner cylinder is electrically small. Both polarizations are considered for normal incidence. Numerical results are given for various values of the parameters and for metallic or dielectric inner cylinder View full abstract»

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  • A multi-relaxation (FD)2-TD method for modeling dispersion in biological tissues

    Publication Year: 1994 , Page(s): 526 - 528
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    Pulse excitation in FD-TD provides multifrequency results with a single run of the code. The introduction of the Frequency Dependent FD-TD ((FD)2-TD) has also recently provided a means to deal with dispersive materials on condition that they had a first order permittivity. The authors present a multirelaxation approach to widen the (FD)2TD applicability to materials with more complex permittivity such as biological tissues View full abstract»

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  • Conversion between the TLM solutions and field solutions

    Publication Year: 1994 , Page(s): 529 - 532
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    The Transmission-Line Matrix (TLM) method uses a network of interconnected transmission lines to simulate electromagnetic wave propagation. Therefore, the TLM solutions are not exactly the field solutions, especially for two-dimensional cases. As a result, conversion between the TLM solutions and field solutions need to be described. This issue is addressed in this paper and boundary (interface) conditions for the two-dimensional (2D) TLM dual mode simulations are formally derived. Also, the correspondence between simulated constitutive parameters and those of the actual medium is formally established View full abstract»

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  • Improved analysis method for multiport microstrip annular-ring power-dividers

    Publication Year: 1994 , Page(s): 376 - 382
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (580 KB)  

    An improved analysis method for multiport microstrip annular-ring power-dividers is presented which is essentially based on the planar circuit theory assuming magnetic walls at conductor edges. The generalized impedance matrix of the power-dividers is evaluated using two approaches, the Green's function approach and the circular harmonic function approach. The concept of effective dimensions is adopted for taking into account fringing fields to compensate the planar circuit theory. The properties of the power-dividers can be controlled by varying the width of the conductor ring in contrast to those of disk structures. Characteristics of a four-port power-divider in the form of microstrip lines calculated with the present approach are in good agreement with experimental data View full abstract»

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  • Scattering of TE-polarized EM wave by discontinuity in grounded dielectric layer

    Publication Year: 1994 , Page(s): 481 - 488
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (708 KB)  

    The two-dimensional problem of EM wave interaction with a dielectric discontinuity in an infinite grounded dielectric layer is studied. An electric field integral equation (EFIE) for TE illumination has been derived based on the Green's function for the electric field produced by induced polarization currents in the discontinuity region. Impressed electric fields consist of either plane waves incident from space above the dielectric layer or surface waves supported by that layer. Method of Moments (MoM) numerical solutions for the induced electric field in the discontinuity region are implemented. The amplitudes of surface waves excited by excess discontinuity-region polarization currents are calculated, as well as the pattern of the scattered field and the associated scattering width. It is observed that the excitation of a surface-wave mode reduces the back scattered radiation for TE-polarized plane wave incidence. The accuracy of the theory is verified by comparison of numerical results with those of existing studies View full abstract»

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  • Integral equation scalar Green's function formulation for computation of cutoff wavenumbers and modal fields in waveguides

    Publication Year: 1994 , Page(s): 532 - 535
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    A scalar formulation for cutoff wavenumber and modal field calculations is presented. Integral equations are used with a scalar Green's function for a two dimensional rectangular resonator for both TE and TM modes. These are transformed into matrix equations by the Galerkin method. The electric TE field is calculated from the scalar potential and is written in the form of a contour integral. The advantage of the scalar formulation is the simple form of the matrix eigenvalue equations which are used in the moment method solution, and the economy in CPU time in the determination of TE cutoff wavenumbers View full abstract»

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  • Coplanar transmission lines on thin substrates for high-speed low-loss propagation

    Publication Year: 1994 , Page(s): 396 - 402
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    We investigate the attenuation and phase velocity characteristics of coplanar strip (CPS) transmission lines designed for high-speed, low-loss propagation at sub-THz frequencies. Photoconductor switches driven by femtosecond optical pulses were used to generate propagating picosecond electrical transients. External electrooptic sampling was used to measure the time-domain impulse-response characteristics with subpicosecond time resolution. The finite-difference transmission-line-matrix (FD-TLM) numerical method was used to model picosecond pulse propagation on identical transmission lines. The experiment and the numeric simulations have clarified nonquasistatic high-frequency effects and were shown to agree over a 500 GHz frequency range. Additionally, analytic quasi-static velocity and characteristic impedance formulas have been verified and their frequency range of validity established for the investigated CPS geometries. Radiation into the substrate is the dominant loss mechanism at frequencies above ~100 GHz for the CPS lines on thick substrates. CPS transmission line fabrication on thin substrates has been proposed as a method for reducing high-frequency loss and increasing the microwave propagation velocity. CPS transmission lines fabricated on 8-μm-thick Si membranes have been studied and demonstrated to possess the desired high-speed, low-loss properties View full abstract»

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  • A multicomposite, multilayered cylindrical dielectric resonator for application in MMIC's

    Publication Year: 1994 , Page(s): 415 - 423
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    A method, based on the mode matching technique, to study various resonant modes of a multicomposite, multilayered cylindrical dielectric resonator is presented. Dielectric sphere and cone resonators placed in practical environments are investigated. The calculated resonant frequencies show very good agreement compared with the numerical results of the finite difference method for the spherical resonator and with the measured values for the conical resonator, respectively. Experimental investigations show that the conical resonator can be coupled to a circular microstrip line, which has small size at high frequencies and may be integrated together with an oscillator View full abstract»

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  • A self-diplexing quasi-optical magic slot balanced mixer

    Publication Year: 1994 , Page(s): 383 - 388
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    Drawing on the principles of operation of the magic tee balanced mixer, a quasi-optical magic slot balanced mixer is proposed. The mixer exploits a diametrically fed annular slot radiator which radiates two orthogonal polarizations which are used as signal and local oscillator input ports. The idea has been tested at microwave frequencies. The measured radiation impedances, radiation patterns and conversion efficiency show that reasonable performance is readily obtained over a 30% bandwidth and that this quasi-optical balanced mixer is suitable for submillimeter wave applications View full abstract»

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  • Finite element analysis of MMIC structures and electronic packages using absorbing boundary conditions

    Publication Year: 1994 , Page(s): 441 - 449
    Cited by:  Papers (23)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (664 KB)  

    In this paper, a three-dimensional finite element method (FEM) is employed in conjunction with first and second-order absorbing boundary conditions (ABC's) to analyze waveguide discontinuities and to derive their scattering parameters. While the application of FEM for the analysis of MMIC structures is not new, to the best of the knowledge of the authors the technique for mesh truncation for microstrip lines using the first and higher-order ABC's, described in this paper, has not been reported elsewhere. The scattering parameters of a microstrip discontinuity are computed in two steps. As a first step, the field distribution of the fundamental mode in a uniform microstrip is obtained by exciting the uniform line with the quasi-static transverse electric field, letting it propagate, and then extracting the dominant mode pattern after the higher order modes have decayed. In step two, the discontinuity problem is solved by exciting the structure by using the fundamental mode obtained in step one. The scattering parameters based on the voltage definition are calculated by using the line integral of electric fields underneath the strip. Numerical solutions for several waveguide discontinuities and electronic packages are obtained and compared with the published data View full abstract»

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  • Switching characteristics of an optically controlled GaAs-MESFET

    Publication Year: 1994 , Page(s): 365 - 375
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    The switching characteristics of an optically controlled Metal Semiconductor Field Effect Transistor (MESFET), popularly known as Optical Field Effect Transistor (OPFET), have been derived analytically. The limitations of the existing model have been overcome in the present model. Calculations are being carried out to examine the effect of illumination on the current-voltage characteristics, drain-to-source capacitance (Cdc), internal gate-to-source capacitance (Cgs), drain-to-source resistance (Rds), the transconductance (gm), the input RC time constant and the cutoff frequency (fT) of a GaAs-MESFET. The variations of these parameters with gate length Lg and the doping concentration Nd have also been studied in dark and illuminated conditions. The results of numerical calculations show that there is an overall decrease in the input RC time constant of the device in the illuminated condition arising from the internal gate-to-source capacitance and the transconductance. The results obtained on the basis of the model show a close agreement with the reported experimental findings. The simple model presented here is fairly accurate and can be used as a basic tool for circuit simulation purposes View full abstract»

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  • Space domain approach for the analysis of printed circuits

    Publication Year: 1994 , Page(s): 450 - 457
    Cited by:  Papers (6)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    A numerical approach to the solution of printed circuit structures of arbitrary shapes, embedded in a single or multilayer dielectric medium is presented. The electromagnetic fields are described in terms of the classical Sommerfeld integrals. The method of moments has been used to solve the derived integral equations for the surface electric and magnetic currents flowing on the conductors and/or the electric field distribution across the apertures. The matrix pencil technique is employed to decompose the current or the voltage waves along the line into their components like the fundamental modes, higher order modes, etc. The finite structures including discontinuities like bends, T junctions, crossovers, etc. are solved for their scattering parameters utilizing this method. The main advantage of this method is the generality which allows a large variety of problems to be covered View full abstract»

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  • A microwave Gaussian-beam launcher with an active aperture-blockage to control the spot-size of the beam

    Publication Year: 1994 , Page(s): 520 - 522
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    A method of controlling the spot-size of a focused microwave Gaussian-beam using an active aperture-blockage is described. The Gaussian-beam launcher consists of an open-ended scalar-horn with a dielectric hyperhemisphere at its aperture. Also included is an AgI-pellet at the aperture-center with a provision to heat it with an external dc source. The scalar-horn plus the dielectric lens launch a Gaussian-beam; and, the AgI pellet when heated, becomes a superionic conductor offering an aperture-blockage. This results in a variation of the spot-size of the emergent-beam. Theoretical results and experimental data are furnished and compared View full abstract»

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  • Synthesis of lumped models from N-port scattering parameter data

    Publication Year: 1994 , Page(s): 535 - 537
    Cited by:  Papers (21)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    A closed form technique is described which allows the synthesis of an N-node lumped network from N-port scattering parameter (S-parameter) data. The synthesis is appropriate for networks where N is very large, for example, high speed digital interconnect networks. The resulting lumped model can be used in SPICE and other simulators. The synthesis is valid for any structure that is small with respect to wavelength. Thus it is also appropriate for synthesizing lumped models of simple discontinuities, such as step junctions and cross junctions. A description of the theory and several examples are provided View full abstract»

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  • Analysis of the scattering by dielectric bodies using the SIE formulation

    Publication Year: 1994 , Page(s): 471 - 480
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    A surface integral equation (SIE) formulation is derived in order to analyze the scattering by a homogeneous dielectric body inside a cavity to which cylindrical waveguides are coupled. Cavity and dielectric body may be arbitrarily shaped; the waveguides may be of arbitrary cross section. Completely closed dielectric-loaded cavities and structures containing metal inserts or magnetic conductors are considered as well. It is shown that the SIE formulation reduces a field problem by one dimension leading to highly efficient algorithms. From numerical results, the influence of surface current expansions is studied. The accuracy of the method is demonstrated by field plots and by the comparison of numerical results to those of other methods View full abstract»

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  • Nonuniform transmission line codirectional couplers for hybrid MIMIC and superconductive applications

    Publication Year: 1994 , Page(s): 407 - 414
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    A new design approach for thin-film codirectional quadrature couplers and their applications is described. An in-depth analysis and semi-empirical design curves are presented for these couplers. Forward-wave coupling is achieved by making use of the difference between even- and odd-mode phase velocities. Modified nonuniform codirectional couplers with a dummy channel for continuously decreasing or increasing taper and employing wiggly, serpentined and smooth coupled edges have been designed and tested. It is found that a wiggly coupler can achieve a 50% length reduction compared to a smooth-edge coupler. A further 60% length reduction compared to a wiggly coupler is achieved by a serpentine coupler. Coupler performance for wiggly and serpentined configurations is computed by choosing a realizable phase velocity function for a given coupler length. Either constant 90° or -90° phase shift is possible with these couplers giving significant design flexibility in some applications. The results for a Ku-band Σ-Δ magic-T circuit employing a 0 dB wiggly coupler and a -3 dB smooth-edge coupler are also presented in the paper View full abstract»

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  • Analysis of a microstrip crossover embedded in a multilayered anisotropic and lossy media

    Publication Year: 1994 , Page(s): 424 - 432
    Cited by:  Papers (5)  |  Patents (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    The equivalent circuit and the scattering parameters of the orthogonal microstrip crossover discontinuity are determined by assuming that the conducting strips are embedded in a multilayered substrate which may contain both anisotropic dielectrics and materials with a nonnegligible conductivity. The equivalent circuit of the crossover is obtained in terms of the complex excess charge densities on the strips. These excess charge densities are computed by means of the Galerkin method in the spectral domain. Comparison is carried out with previously existing results for microstrip crossovers on lossless isotropic substrates and original results are presented for crossovers on anisotropic and lossy substrates View full abstract»

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  • Microwave noncontact examination of disbond and thickness variation in stratified composite media

    Publication Year: 1994 , Page(s): 389 - 395
    Cited by:  Papers (30)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    Numerical and experimental results of a microwave noncontact, nondestructive detection and evaluation of disbonds and thickness variations in stratified composite media are presented. The aperture admittance characteristics of a flange mounted rectangular waveguide radiating into a layered, generally lossy dielectric media backed or unbacked by a conducting sheet is modeled. The theoretical implementation is based on a Fourier transform boundary matching technique to construct the field components in each medium, coupled with a stationary form of the terminating aperture admittance of the waveguide. The model can serve as a reliable test bed for real-time examination of layered composite media. Experimental results for several cases are presented which show good agreement with the theoretical findings. This is a versatile technique for near-field in situ interrogation of stratified composite media which provides for high resolution measurements View full abstract»

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  • 20-GHz 5-dB-gain analog multipliers with AlGaAs/GaAs HBTs

    Publication Year: 1994 , Page(s): 518 - 520
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    From-DC-to-above-20-GHz monolithic Gilbert cell analog multipliers have been developed using AlGaAs/GaAs HBT technology. As a double balanced active mixer, it exhibits very high conversion gain of above +5 dB with extremely high LO-IF isolation of 33 dB for RF/LO inputs up to 20 GHz. It exhibits conversion gain of +9 dB for 5 GHz RF/LO inputs. As a double balanced upconverter, it exhibits positive conversion gain with high LO-RF isolation of 23 dB for RF output up to 8.5 GHz. As a detection mixer in coherent optical heterodyne receivers, it can operate for RF/LO inputs up to 15 GHz under a less than -7.5 dBm LO input condition View full abstract»

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  • Group and phase velocities in the TLM-symmetrical-condensed node mesh

    Publication Year: 1994 , Page(s): 514 - 517
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    This paper presents the analytical expressions of group and phase velocities as a function of frequency in the TLM-symmetrical-condensed node mesh for the three fundamental directions. The direction [1, 1, 1] happens to be more dispersive than the directions [1, 1, 0] and [1, 0, 0], giving the TLM-symmetrical-condensed formulation dispersion characteristics similar to those of the FD-TD algorithm with a Courant number of 1/√3 View full abstract»

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  • Comparison between two sets of basis functions for the current modeling in the Galerkin spectral domain solution for microstrips

    Publication Year: 1994 , Page(s): 505 - 513
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    A frequently used technique for the numerical full wave analysis of planar microwave passive structures is the method of moments (MoM). A very important determinant for the accuracy and efficiency of this technique is the choice of the basis functions used in the approximation of the unknown current components. The application of several types of entire and subsectional domain basis functions has been proposed in the literature. However, little comparison has been made between different types of basis functions. In this paper, a comparison is presented between two sets of frequently used subsectional domain basis functions for the canonical case of the microstrip transmission line. The emphasis in this paper is on the relative accuracy, the convergence and the computational efficiency of both sets of basis functions. The intent of the paper is primarily to be an eye opener for the implications of the choice of the basis functions View full abstract»

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  • A resetting algorithm for transient analysis of coupled transmission line circuits

    Publication Year: 1994 , Page(s): 494 - 500
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    The numerical inversion of the Laplace transform has been used as an important tool for time domain analysis of high speed VLSI interconnects modeled by transmission line networks. In this paper, a resetting algorithm based on the numerical inversion of Laplace transform with Pade approximation is described. The initial conditions of coupled transmission lines required by the resetting algorithm are also derived. The new method results in substantial improvement of the accuracy of the numerical inversion of Laplace transform for solving transmission line networks with long transients. The new method also bridges the gap between two types of circuit simulation techniques, i.e., the numerical inversion of Laplace transform and the numerical integration View full abstract»

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  • Physics-based expressions for the nonlinear capacitances of the MESFET equivalent circuit

    Publication Year: 1994 , Page(s): 403 - 406
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    In this paper, we present a simple physical determination of the nonlinear capacitance parameters (Cgdo and Cgso) of the MESFET equivalent circuit. Semiempirical models such as the Curtice and Statz-Pucel models, in conjunction with these physics-based expressions, are a fast tool for CAD of microwave integrated circuit simulation, saving the designer the tedious and sometimes difficult process of parameter extraction and providing a better estimate of device statistics. Using the equations obtained in this work, a submicron gate length MESFET has been simulated and theoretical results are in good agreement with the experimental measurements View full abstract»

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  • Transient responses of an exponential transmission line and its applications to high-speed backdriving in in-circuit test

    Publication Year: 1994 , Page(s): 458 - 462
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    Step responses of an exponential line terminated with resistive loads are evaluated by means of time-domain scattering parameters. The results are used to illustrate the interaction between a nonuniform line and a nonlinear load. We find that an exponential line could be used to compensate the nonlinear load effects in high-speed backdriving 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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