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Microwave Theory and Techniques, IEEE Transactions on

Issue 4 • Date Apr 1996

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  • MRTD: new time-domain schemes based on multiresolution analysis

    Publication Year: 1996 , Page(s): 555 - 571
    Cited by:  Papers (236)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1108 KB)  

    The application of multiresolution analysis to Maxwell's equations results in new multiresolution time-domain (MRTD) schemes with unparalleled inherent properties. In particular, the approach allows the development of MRTD schemes which are based on scaling functions only or on a combination of scaling functions and wavelets leading to a variable mesh grading. The dispersion of the MRTD schemes compared to the conventional Yee finite-difference time-domain (FDTD) scheme shows an excellent capability to approximate the exact solution with negligible error for sampling rates approaching the Nyquist limit. Simple microwave structures including dielectric materials are analyzed in order to illustrate the application of the MRTD schemes and to demonstrate the advantages over Yee's FDTD scheme with respect to memory requirements and execution time View full abstract»

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  • Theoretical investigation of a free-electron maser operating with a TEM transmission line

    Publication Year: 1996 , Page(s): 607 - 613
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    The possibility of using the transverse electric magnetic (TEM) transmission line in free-electron masers (FEM) is discussed. It is shown that at the centimeter and long-millimeter wavelengths such transmission lines allow one to combine the advantages of an open cavity and a waveguide-based resonator. A particular case of an FEM-based on the use of a shielded two-wire transmission line is investigated theoretically. A mathematical approach that allows one to calculate transmission-line parameters important to the FEM application is developed. It is based on the use of the integral equation technique and on a new representation of the Green function of the internal region of a circle, which was obtained in this paper. Numerical analysis of effective mode area, wave impedance, and attenuation constant was made for the odd TEM mode, which is excited in FEM operation. The FEM under research at Tel Aviv University was considered as an example. The frequency dependence of gain for an FEM operating in the linear regime was calculated. That the obtained gain value is much higher than the ohmic losses in the transmission line shows the possibility of using the TEM transmission line in this FEM View full abstract»

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  • Electromagnetic dyadic Green's function in cylindrically multilayered media

    Publication Year: 1996 , Page(s): 614 - 621
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (708 KB)  

    A spectral-domain dyadic Green's function for electromagnetic fields in cylindrically multilayered media with circular cross section is derived in terms of matrices of the cylindrical vector wave functions. Some useful concepts, such as the effective plane wave reflection and transmission coefficients, are extended in the present spectral domain eigenfunction expansion. The coupling coefficient matrices of the scattering dyadic Green's functions are given by applying the principle of scattering superposition. The general solution has been applied to the case of axial symmetry (n=0, n is eigenvalue parameter in φ direction) where the scattering coefficients are decoupled between TM and TE waves. Two specific geometries, i.e., two- and three-layered media that are frequently employed to model the practical problems are considered in detail, and the coupling coefficient matrices of their dyadic Green's functions are given, respectively View full abstract»

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  • Electromagnetics in high-Tc superconductors

    Publication Year: 1996 , Page(s): 537 - 542
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    The behavior of electromagnetic fields in high-Tc superconductors (HTSs) is studied in order to examine their effects in classical electromagnetic boundary value problems. It is shown that an HTS can not be simply treated as a low loss conductor and boundary conditions of HTSs cannot be considered as perfect conducting boundaries like conventional treatments. The electromagnetics of HTS are investigated in terms of complex conductivity, surface impedance with applied magnetic fields, and computational electrodynamics using the proposed model View full abstract»

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  • Induced polarization effects in coupling processes of waveguide modes

    Publication Year: 1996 , Page(s): 572 - 584
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (976 KB)  

    An analysis of waveguide problems based on a solution of full vector-wave equations is very important for many applications. To solve such problems, a new coupled-mode method, taking into account the so-called induced polarization effects, is proposed in this paper. The theory is based on the spectral method, which makes it possible to analyze correctly a mode excitation by arbitrary sources with longitudinal components. It also takes into consideration singularities caused by abrupt discontinuities of longitudinal currents. The method may be a powerful tool for investigation of propagating and evanescent modes coupling due to both material and geometric effects View full abstract»

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  • Power leakage, characteristic impedance, and leakage-transition behavior of finite-length stub sections of leaky printed transmission lines

    Publication Year: 1996 , Page(s): 526 - 536
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1004 KB)  

    Power leakage and leakage transition phenomena in finite-length stub sections are studied for slot- as well as strip-type leaky transmission lines. A three-dimensional (3-D) method of moments is used for the rigorous analysis of the stub sections. The results reveal several important characteristics of power leakage in printed circuits that are not obtainable from the two-dimensional (2-D) analyses of ideal infinite-length lines. A new definition of the characteristic impedance for a leaky printed transmission line is proposed, which is shown to correctly model the impedance behavior of the finite-length sections. It is noted that the standard definitions of characteristic impedance, commonly used for nonleaky transmission lines, may not apply to practical circuits when leakage exists. Further, the leakage transition behavior in the finite-length sections, operated around a “mode-transition” region, is explained from the 3-D analysis results. Leakage analyses of ideal infinite-length lines can not model such transition excitation in finite-length circuits View full abstract»

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  • A volume-surface integral equation method for solving Maxwell's equations in electrically inhomogeneous media using tetrahedral grids

    Publication Year: 1996 , Page(s): 543 - 554
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1152 KB)  

    Starting with the solution of Maxwell's equations based on the volume integral equation (VIE) method, the transition to a volume-surface integral equation (VSIE) formulation is described. For the VSIE method, a generalized calculation method is developed to help us directly determine E fields at any interface combination in three-dimensional (3-D) electrically inhomogeneous media. The VSIE implementation described is based on separating the domain of interest into discrete parts using nonuniform tetrahedral grids. Interfaces are described using curved or plane triangles. Applying linear nodal elements, a general 3-D formulation is developed for handling scatter field contributions in the immediate vicinity of grid nodes, and this formulation is applicable to all multiregion junctions. The special case of a smooth interface around a grid node is given naturally by this formulation. Grid nodes are split into pairs of points for E-field calculation, and node normals are assigned to these points. The pairs of points are assigned to the elements adjoining the grid node. For each pair of points, the correct field jumps on the interface are given by a surface integral over the polarization surface charge density View full abstract»

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  • A new empirical large-signal HEMT model

    Publication Year: 1996 , Page(s): 622 - 624
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    We propose an empirical large-signal model of high electron mobility transistors (HEMTs). The bias-dependent data of small-signal equivalent circuit elements are obtained from S-parameters measured at various bias settings. And Cgs, Cgd, gm, and gds, are described as functions of Vgs and Vds. We included our large-signal model in a commercially available circuit simulator as a user-defined model and designed a 30/60-GHz frequency doubler. The fabricated doubler's characteristics agreed well with the design calculations View full abstract»

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  • Efficient method for scattering from a homogeneous, circular, cylindrical shell with an inhomogeneous angular-region

    Publication Year: 1996 , Page(s): 624 - 626
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    The two-dimensional (2-D) scalar problem of a circular, dielectric, cylindrical shell exposed to transverse magnetic (TM) incident field is considered. The shell is considered to be homogeneous everywhere, except in a narrow angular-region where it is allowed to be inhomogeneous. The problem is formulated using the moment method (MM). It is shown that the resulting system of MM equations could be very efficiently solved employing a new theory of diagonally-perturbed circulant matrices. The method presented here could be applied for thin shells as well as shells which are “not-so-thin.” Results of computer simulations are also provided verifying the validity of the method proposed View full abstract»

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  • Conductor-loss limited stripline resonator and filters

    Publication Year: 1996 , Page(s): 626 - 630
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (704 KB)  

    We report on stripline resonators on thin dielectric membranes that show dispersion-free, conductor-loss limited performance at 13.5 GHz, 27.3 GHz, and 39.6 GHz. The unloaded-Q (Qu) of the resonators increases as √f with frequency and is measured to be 386 at 27 GHz. The measured results agree well with a new conformal mapping analysis. The stripline resonators are used in a micromachined state-of-the-art planar interdigitated bandpass filter at K-band frequencies. Excellent agreement has been achieved between the microwave model at 850 MHz and the 20 GHz filter. The micromachined filter exhibits a passband return loss better than -15 dB and a conductor-loss limited 1.7 dB port-to-port insertion loss (including input/output CPW line loss) at 20.3 GHz View full abstract»

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  • A new approach for analysis of resonant structures based on the spatial finite-difference and temporal differential formulation

    Publication Year: 1996 , Page(s): 631 - 635
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    This paper presents a new procedure for analyzing resonant structures using the spatial finite-difference and temporal differential formulation. Unlike the conventional finite-difference time-domain methods, the finite-differences are only enforced in the spatial domain for Maxwell's equations. The time-domain differentials of Maxwell's equations are kept, resulting in a system of first-order differential equations. In consequence, a resonant structure problem can be formulated in the eigenvalue problem form and resonant modes are obtained by solving the corresponding eigenvalue problem directly. It is shown that the coefficients of the matrix for the eigenvalue problem can be simply obtained from the finite-difference time-domain formulation. As a result, an efficient alternative way of using the finite-difference time-domain approach to solve the resonant structure problems is presented. The algorithm is applied to metallic waveguide structures and the numerical results agree well with those from other techniques View full abstract»

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  • Analytical evaluation of the MoM matrix elements

    Publication Year: 1996 , Page(s): 519 - 525
    Cited by:  Papers (33)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    Derivation of the closed-form Green's functions has eliminated the computationally expensive evaluation of the Sommerfeld integrals to obtain the Green's functions in the spatial domain. Therefore, using the closed-form Green's functions in conjunction with the method of moments (MoM) has improved the computational efficiency of the technique significantly. Further improvement can be achieved on the calculation of the matrix elements involved in the MoM, usually double integrals for planar geometries, by eliminating the numerical integration. The contribution of this paper is to present the analytical evaluation of the matrix elements when the closed-form Green's functions are used, and to demonstrate the amount of improvement in computation time View full abstract»

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  • Characterization of three-dimensional open dielectric structures using the finite-difference time-domain method

    Publication Year: 1996 , Page(s): 513 - 518
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    Millimeter and submillimeter wave three-dimensional (3-D) open dielectric structures are characterized using the finite-difference time-domain (FDTD) technique. The use of FDTD method allows for the accurate characterization of these components in a very wide frequency range. The first structure characterized through FDTD for validation purposes is a mm-wave image guide coupler. The derived theoretical results for this structure are compared to experimental data and show good agreement. Following this validation, a sub-mm wave transition from a strip-ridge line to a layered ridge dielectric waveguide (LRDW) in open environment is analyzed, and the effects of parasitic radiation on electrical performance are studied. The transition is found to be very efficient over a wide sub-mm frequency band which makes it useful for a variety of applications. In addition to the transition, a sub-mm wave distributed directional coupler made of the LRDW is extensively studied using the FDTD method as an analysis tool. Furthermore, an iterative procedure based on the FDTD models is used to design a 3-dB coupler with a center frequency of 650 GHz and negligible radiation loss. This successful design shows that the FDTD technique can be used not only as an analysis method, but also as a design tool to provide designs which take into account all high frequency parasitic effects View full abstract»

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  • New approach to the design of active floating inductors in MMIC technology

    Publication Year: 1996 , Page(s): 505 - 512
    Cited by:  Papers (10)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (736 KB)  

    An original method for the determination of all possible inductive circuits as a function of the number of field-effect transistors (FETs) used is described in this paper. The method is of general use in monolithic microwave integrated circuits. Circuits with large inductance, either positive or negative in value, can be obtained along with low loss or even negative resistance View full abstract»

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  • Analysis and synthesis of coplanar coupled lines on substrates of finite thicknesses

    Publication Year: 1996 , Page(s): 636 - 639
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    This paper presents two sets of newly developed CAD-oriented formulas for the evaluation of the quasi-static even and odd-mode characteristics of coplanar coupled lines on substrates of finite thicknesses. The first set of expressions is derived based on the conformal mapping method. Numerical results show that both the even- and odd-mode characteristic impedances and effective dielectric constants computed by these expressions are in good agreement with the results generated by the spectral domain method. The second set of formulas is derived based on a seminumerical approach and can be used to calculate the geometrical parameters of coplanar coupled lines directly from the given electrical parameters, without using an iterative approach. These seminumerical formulas give maximum error in impedance calculation of about 2.0% (c/h<2), over a wide range of impedance and dielectric constant values View full abstract»

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  • Analysis of asymmetrical multilayer ferrite-loaded finlines by the extended spectral domain approach

    Publication Year: 1996 , Page(s): 497 - 504
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (668 KB)  

    The spectral domain approach is extended to analyze the nonreciprocal propagation characteristics of asymmetrical multilayer finlines containing magnetized ferrites. This extended method offers several advantages. It can be applied to nonuniform cross-section geometries, uses only one set of basis functions, and the dyadic Green's function is efficiently derived by a recursive algorithm. Fast convergence is obtained and the accuracy of the method is verified by comparison with available computed and measured data. In comparison with symmetrical structures, the additional design degree of freedom of the asymmetry can be used to obtain wider bandwidth and higher nonreciprocity. Of the various structures considered, a four-layer dual ferrite (DF) structure is seen to be the best choice for realization of nonreciprocal phase shifters with widest bandwidth View full abstract»

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  • Color group approach to symmetrical ferrite devices with polarization effects

    Publication Year: 1996 , Page(s): 630 - 631
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    Applicability of the color group approach to symmetrical ferrite devices with polarization effects is demonstrated. By using the theory of symmetry, the scattering matrices of square and circular waveguides with quadrupole dc magnetic field are derived View full abstract»

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  • Micromachined W-band filters

    Publication Year: 1996 , Page(s): 598 - 606
    Cited by:  Papers (66)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (948 KB)  

    Results are presented for high performance planar W-band filters based on silicon micromachining techniques common in microsensor fabrication. Two types of micromachined planar transmission lines are studied: microshield line and shielded membrane microstrip (SMM) line. In both of these structures, the conducting lines are suspended on thin dielectric membranes. These transmission lines are essentially “floating” in air, possess negligible levels of dielectric loss, and do not suffer from the parasitic effects of radiation and dispersion. A 90 GHz low pass filter and several 95 GHz bandpass filters are tested and display excellent performance which cannot be achieved with traditional substrate supported circuits in CPW or microstrip configurations. A full-wave finite-difference time-domain (FDTD) technique verifies the measured performance of the W-band circuits and provides a basis for comparison between the performances of membrane supported circuits and equivalent substrate supported circuits View full abstract»

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  • The design of tuned front-end GaAs MMIC optical receivers

    Publication Year: 1996 , Page(s): 591 - 597
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (700 KB)  

    Recently, much interest has been shown in the design of very low noise tuned front-end optical receivers for use in lightwave systems. This paper looks at the accurate design of such receivers. Simplified design expressions are presented for a number of tuning configurations with theoretical and measured results being presented. The designs were realized as GaAs monolithic microwave/millimeter-wave integrated circuits (MMIC's) View full abstract»

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  • Coupled-mode formulation of multilayered and multiconductor transmission lines

    Publication Year: 1996 , Page(s): 585 - 590
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    A novel coupled-mode formulation for multilayered and multiconductor transmission lines is developed. In this formulation, the solutions to the original multiconductor system are approximated by a linear combination of eigenmode solutions associated with the isolated single conductor line located in an appropriate reference dielectric medium. The reciprocity theorem is used to derive the coupled-mode equations. The coupling coefficients are expressed in terms of the simple overlap integrals between the eigenmode fields and currents of the individual conductor lines. As a basic application, the dispersion characteristics of two identical coupled-microstrip lines are analyzed using the proposed coupled-mode theory. It is shown that the results are in very close agreement with those obtained by the direct Galerkin's moment method over a broad range of weak to strong coupling 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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