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Microwave Theory and Techniques, IEEE Transactions on

Issue 8 • Date Aug. 2002

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Displaying Results 1 - 25 of 28
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  • Comments on "Biological effects of radio-frequency/microwave radiation" [with reply]

    Page(s): 2032 - 2033
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (155 KB)  

    The original paper [see ibid., vol. 48, p. 1537-43, Sept. 2000] is important in that it summarizes 50 years of research on the thermal effects of microwave radiation in the human body and the penetration of a plane-wave incident on a planar surface of that body. The author would like to see the above paper supplemented with at least a reference to the possible biological effects of the axial electric current and electric field induced in the human body near its resonant length. The authors' reply is given. View full abstract»

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  • An improved algorithm of constructing potentials from Cauchy data and its application in synthesis of nonuniform transmission lines

    Page(s): 2025 - 2028
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB) |  | HTML iconHTML  

    It is required to construct a potential function from Cauchy data in the synthesis of arbitrarily terminated nonuniform transmission lines. An improved algorithm for this problem is discussed in this paper. With the proposed algorithm, not only is computation time reduced, but the possible divergence of the potential function that sometimes occur when adopting the successive approximation method is also avoided. It has been applied successfully to designs of nonuniform transmission-line filters or tapers through solving inverse problems. View full abstract»

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  • Separation of the nonlinear source-pull from the nonlinear system behavior

    Page(s): 1890 - 1894
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (238 KB) |  | HTML iconHTML  

    In this paper, we describe a measurement technique to identify a nonlinear system in the presence of nonlinear source-pull. Models identified with continuous-wave measurement data are not generalizable when nonlinear source-pull is present. This is demonstrated on measured data and compared with the performance of the proposed technique. The method is based on two-tone signals with very close frequencies that excite the system at the fundamental and harmonic frequencies. By varying the phase relation between the beat components, the system's nonlinear behavior is separated from the nonlinear source-pull. Note that such excitations can be generated using commercially available synthesizers with single-sideband in-phase-quadrature modulation options. View full abstract»

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  • Out-of-band emissions of digital transmissions using Kahn EER technique

    Page(s): 1979 - 1983
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (266 KB) |  | HTML iconHTML  

    The Kahn envelope elimination and restoration (EER) technique allows for linear RF power amplification by combining nonlinear, but efficient, RF and AF power amplifiers (PAs). In order to use the EER technique for digital signals, a coordinate transform from the original Cartesian in-phase and quadrature mode into a polar mode has to take place, yielding an envelope (or amplitude) and a PM RF signal. This coordinate transform is extremely nonlinear and thereby broadens the spectra of the original signals. In the final PA stage, both signals are recombined. However, since this recombination process is imperfect, out-of-band (OOB) emissions come up, also known as adjacent channel power or spectral regrowth. In this paper, the impact of the broadening of the amplitude and phase signals on OOB emissions is investigated with respect to imperfect restoration due to signal delays and limited bandwidth of the amplitude path. It is shown that the amount of OOB emissions can significantly be reduced if the modulation scheme shows a "hole" at the origin in its vector diagram. View full abstract»

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  • 2-D analysis of leakage in printed-circuit lines using discrete complex-images technique

    Page(s): 1895 - 1900
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (299 KB) |  | HTML iconHTML  

    The mixed-potential integral equation is combined with the discrete complex-images technique to analyze the complete spectrum of multilayered printed transmission lines. A relevant contribution of the present two-dimensional approach is its ability to study both the bound and leaky regimes in a very simple, systematic, and efficient way. Since the analysis is carried out in the spatial domain, this method makes it possible to analyze the leakage phenomenon for structures with nonzero-thickness conductors. Efficient quasi-analytical techniques are employed to solve the integral equation. View full abstract»

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  • A novel algorithm based on the domain-decomposition method for the full-wave analysis of 3-D electromagnetic problems

    Page(s): 2011 - 2017
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB) |  | HTML iconHTML  

    A novel technique based on the domain-decomposition method and frequency-domain finite-difference method is presented for the full-wave analysis of three-dimensional electromagnetic problems. In this method, the original domain is decomposed into sub-domains, Maxwell's equations are then solved in each sub-domain independently, and the global solution is achieved finally by an iterative procedure. It greatly reduces the computational complexity and the memory requirement compared with the conventional finite-difference method and method of moments, etc. To reduce CPU time, some techniques, such as the relaxation iterative algorithm, overlapped domain decomposition, and multimesh resolution are also investigated and adopted to accelerate the algorithm. The validity of this algorithm is verified by numerical examples, including the analysis of a multilayered aperture-coupled patch antenna, the scattering characteristic analysis of conducting pillars, and the S-parameters extraction of the air-bridge discontinuity. View full abstract»

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  • Hierarchical multilevel potential preconditioner for fast finite-element analysis of microwave devices

    Page(s): 1984 - 1989
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (302 KB) |  | HTML iconHTML  

    A robust hierarchical multilevel preconditioning technique is presented for the fast finite-element analysis of microwave devices. The proposed preconditioner is based on a hierarchical multilevel scheme for the vector-scalar potential finite-element formulation of electromagnetic problems. Numerical experiments from the application of the new preconditioner to the finite-element analysis of microwave devices are used to demonstrate its superior numerical convergence and efficient memory usage. View full abstract»

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  • Electric-magnetic-electric slow-wave microstrip line and bandpass filter of compressed size

    Page(s): 1996 - 2004
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (438 KB) |  | HTML iconHTML  

    This paper presents a novel integrated microstrip low-loss slow-wave line. The new microstrip replaces the conventional metal strip by composite metals paralleling the electric surface and magnetic surface (MS). The MS made of an array of coupled inductors shows a high-impedance state in the stopband, below which the propagation properties can be well controlled by varying the dimensions of the electric surface and MS. The dispersion curves obtained by matrix-pencil analyses closely correspond to those obtained by scattering-parameter extraction. Theoretical results, as confirmed experimentally, indicate that an increase of over 60% in the slow-wave factor can be achieved without sacrificing propagation losses, using the proposed structure. This electric-magnetic-electric (EME) microstrip is insensitive to the alignment position of the periodical structure, and can be constructed using conventional printed-circuit-board fabrication processes and integrated with other microwave components in a multilayered circuit. A compact EME bandpass filter (BPF) with suppressed harmonic responses is presented. The length of the filter is reduced by 26%, and the measured insertion loss and fractional bandwidth is comparable to that of a conventional microstrip BPF on the same substrate. View full abstract»

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  • Accuracy control in the optimization of microwave devices by finite-element methods

    Page(s): 1901 - 1911
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB) |  | HTML iconHTML  

    Automatically optimizing the design of a microwave device can be prohibitively time-consuming when a numerical electromagnetic-field analysis is necessary at each iteration. However, the time taken for the field analysis depends on the accuracy required, and in the early stage of the optimization relatively inaccurate solutions are adequate. This idea is exploited in a scheme that combines a quasi-Newton constrained optimizer with a two-dimensional p-adaptive finite-element method for finding scattering parameters. The scheme has been tested on three H-plane rectangular waveguide devices: a T-junction, a miter bend with a dielectric column, and a two-cavity iris-coupled filter. Time savings of more than an order of magnitude were obtained, compared to the standard approach of requiring equally high accuracy throughout the optimization. View full abstract»

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  • High-Q factor three-dimensional inductors

    Page(s): 1942 - 1949
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (405 KB) |  | HTML iconHTML  

    In this paper, the great flexibility of three-dimensional (3-D) monolithic-microwave integrated-circuit technology is used to improve the performance of on-chip inductors. A novel topology for high-Q factor spiral inductor that can be implemented in a single or multilevel configuration is proposed. Several inductors were fabricated on either silicon substrate (ρ = 30 Ω · cm) or semi-insulating gallium-arsenide substrate demonstrating, more particularly, for GaAs technology, the interest of the multilevel configuration. A 1.38-nH double-level 3-D inductor formed on an Si substrate exhibits a very high peak Q factor of 52.8 at 13.6 GHz and a self-resonant frequency as high as 24.7 GHz. Our 4.9-nH double-level GaAs 3-D inductor achieves a peak Q factor of 35.9 at 4.7 GHz and a self-resonant frequency of 8 GHz. For each technology, the performance limits of the proposed inductors in terms of quality factor are discussed. Guidelines for the optimum design of 3-D inductors are provided for Si and GaAs technologies. View full abstract»

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  • Synthesis of coupled-resonators group-delay equalizers

    Page(s): 1960 - 1968
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (329 KB) |  | HTML iconHTML  

    A systematic synthesis and design procedure for coupled-resonators cavity group-delay equalizers is presented. The procedure consists of solving the approximation problem by optimization and performing cascade synthesis. The error function for the optimization is computed from the given filter's group delay and the zeros and poles of the input impedance of the equalizer. Convergence of the optimization is fast and insensitive to the initial guess even when the number of resonators is large. Two examples, together with experimental results, are presented; comparisons between the externally equalized and self-equalized filters are made. The effect of the isolation of the cascading devices (circulator or 3-dB hybrid) on the ripple of the final group-delay response is also extensively investigated. The good agreement between the theoretical simulation and the experimental results demonstrates the powerful nature and effectiveness of the proposed design procedure. View full abstract»

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  • Analysis of transient interaction of electromagnetic pulse with an air layer in a dielectric medium using wavelet-based implicit TDIE formulation

    Page(s): 2018 - 2022
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (668 KB) |  | HTML iconHTML  

    The interaction of transient electromagnetic pulse with an air layer in a dielectric medium is formulated in terms of a time-domain integral equation and solved numerically via the method of moments. Previous related works pointed to the inherent inadequacy of the marching-on-in-time method in this case, but suggested no remedy. This paper explains why an implicit modeling scheme would work effectively in this case. It is also noted that the use of an implicit scheme would normally involve a solution of a very large and dense matrix equation. To alleviate this drawback of the implicit scheme, the use of a wavelet-based impedance-matrix-compression technique, which has facilitated in the very recent past solutions of time-domain problems with greater efficiency, is described. View full abstract»

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  • Converting baluns into broad-band impedance-transforming 180° hybrids

    Page(s): 1990 - 1995
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB) |  | HTML iconHTML  

    A technique for converting baluns into 180° hybrids by adding an in-phase power splitter is presented in this paper. Incorporating the broad-band antiphase and in-phase power splitting characteristics of the balun and power splitter results in a 180° hybrid with broad-band characteristics. This technique also provides a means of achieving perfect matching and output isolation for three-port lossless baluns. Applying this technique to a Marchand balun will result in a broad-band impedance-transforming 180° hybrid. Simple design equations based on the scattering matrix are presented. These theoretical results are validated by an experimental 180° hybrid using a coupled line Marchand balun. It achieves amplitude balance of 0.5 dB and phase balance of less than 5° from 1.2 to 3.2 GHz. View full abstract»

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  • The reentrant wide-band directional filter

    Page(s): 2028 - 2031
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (266 KB) |  | HTML iconHTML  

    A new type of a wide-band microwave filter is described and named the reentrant directional filter, in which resonance occurs in the form of a traveling wave rather than in the conventional form of a standing wave. This device is the network, which has the constant input impedance and is manufactured as the directional coupler's free construction. An analysis of the reentrant directional filter shows it to have advantages in the case of wide-bands when compared to previously used directional filters. This filter finds application in multiplexers, as well as in matched bandpass (band-stop) filters by using planar multilayer transmission-line technology. Experimental results verify the theoretical approach. View full abstract»

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  • Adaptive synthesis and design of resonator filters with source/load-multiresonator coupling

    Page(s): 1969 - 1978
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (310 KB) |  | HTML iconHTML  

    The paper presents a universal and comprehensive synthesis technique of coupled resonator filters with source/load-multiresonator coupling. The approach is based on repeated analyses of a circuit with the desired topology; no similarity transformation is needed. Restrictions imposed by the implementation on the coupling coefficients such as signs and orders of magnitudes are straightforwardly handled within this technique. The technique is then used to synthesize and design filters with full or almost full coupling matrices by selecting, among the infinite number of solutions, the matrix that corresponds to the actual implementation. In such cases, analytical techniques and those based on similarity transformations cannot be used since they provide no mechanism to constrain individual coupling coefficients in order to discriminate between two full coupling matrices, which are both solutions to the synthesis problem. Using the technique described in this paper, a filter designer can extract the coupling matrix of a filter of arbitrary order and topology while enforcing relevant constraints. There is no need to master all the different existing similarity-transformation-based techniques and the topologies to which they are applicable. For the first time, detailed investigations of parasitic coupling effects, for either compensation or utilization, are made possible. The method is applied to the synthesis of a variety of filters, some of which are then designed and built and their response measured. View full abstract»

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  • A novel amplifying antenna array using patch-antenna couplers-design and measurement

    Page(s): 1919 - 1926
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB) |  | HTML iconHTML  

    This paper proposes a novel amplifying antenna array using the patch-antenna coupler formed by placing one or two open-ended microstrip lines (coupled lines) near and along the nonradiating edge(s) of a patch antenna. An X-band five-element array with broadside 25-dB Chebyshev radiation is demonstrated. When the input signal is fed to the center element, with most of the power radiating from the antenna, part of it is tapped to the coupled lines, amplified by an FET amplifier, and fed to the next antenna element. This process is repeated after all the antenna elements are fed with suitable power. The amplitude distribution of the fields radiated from the antennas is controlled by the coupling coefficient from the patch to the coupled line, which, in turn, is governed by the coupling length and gap between the patch and line. The measured return loss of the designed five-element array is -27 dB at the center frequency of 10 GHz with 2% 10-dB bandwidth. The radiation pattern possesses a transmitting gain of 15.9 dB, a half-power beamwidth of 17°, and a sidelobe level of -22 dB. View full abstract»

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  • Investigation of static and quasi-static fields inherent to the pulsed FDTD method

    Page(s): 2022 - 2025
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (271 KB) |  | HTML iconHTML  

    Demonstrates that trailing dc offsets, which can affect E- or H-fields in finite-difference time-domain simulations, are physically correct static solutions of Maxwell's equations instead of being numerically induced artifacts. It is shown that they are present on the grid when sources are used, which generates nondecaying charges. Static solutions are investigated by exciting electric and magnetic dipoles models with suitable waveforms. View full abstract»

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  • Radiation from a microstrip amplifier

    Page(s): 2005 - 2010
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB) |  | HTML iconHTML  

    A full-wave method is presented to investigate radiation from a microstrip amplifier. The spectral-domain dyadic Green's function, which takes into account both radiation and surface waves, is used to formulate an integral equation. The method of moments is then employed to find the current densities in microstrips and, subsequently, the scattering parameters of the amplifier. The radiated space and surface waves that are launched from the amplifier can be further expressed in terms of the dyadic Green's function and current densities. To verify the numerical results of scattering parameters and far-field radiation patterns, a UHF-band microstrip amplifier matching with single stubs has been implemented and measured. The comparison between simulation and measurement shows excellent agreement. View full abstract»

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  • Construction of solutions to electromagnetic problems in terms of two collinear vector potentials

    Page(s): 1950 - 1959
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB) |  | HTML iconHTML  

    In this paper, the construction of solutions to transient electromagnetic (EM) problems in terms of two collinear vector potentials (VPs) is subjected to a careful theoretical study and numerical verification. The analysis concerns a general isotropic medium that can be inhomogeneous, lossy, and may contain sources. It is also assumed that the medium has instantaneous response, i.e., its EM properties are frequency independent. First, the completeness of the solution in terms of the two VPs in homogeneous and inhomogeneous media is addressed. Second, the behavior of the VPs at interfaces and edges is considered. Finally, a number of simple, but relevant numerical tests are performed to verify the theoretical model. This paper is part of the effort to establish the theoretical background of a novel efficient approach to the analysis of transient EM propagation based on the VPs. View full abstract»

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  • 5.8-GHz circularly polarized rectifying antenna for wireless microwave power transmission

    Page(s): 1870 - 1876
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (319 KB) |  | HTML iconHTML  

    This paper reports a new circularly polarized (CP) high-gain high-efficiency rectifying antenna (rectenna). The CP rectenna can be rotated and still maintain a constant dc output voltage. The high-gain antenna has an advantage of reducing the total number of rectenna elements to cover a fixed area. The rectenna is etched on Rogers Duroid 5870 substrate with εr=2.33 and 10 mil thickness. A high-gain dual-rhombic-loop antenna and a reflecting plane are used to achieve a CP antenna gain of 10.7 dB and a 2:1 voltage standing-wave ratio bandwidth of 10%. The rectenna's pattern has an elliptical cross section with orthogonal beamwidths of 40° and 60°. The rectenna circuit has a coplanar stripline band-reject filter that suppresses the re-radiated harmonics by 20 dB. A highly efficient Schottky diode is used for RF-to-dc conversion with an efficiency of approximately 80% for an input power level of 100 mW and a load resistance of 250 Ω. View full abstract»

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  • Short-open calibration technique for field theory-based parameter extraction of lumped elements of planar integrated circuits

    Page(s): 1861 - 1869
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (305 KB) |  | HTML iconHTML  

    A generalized short-open calibration (SOC) technique is developed toward complete field theory-based deembedding and lumped-element extraction of equivalent-circuit models for planar integrated circuits from admittance-type method of moments (MoM) simulations. With reference to the modal expansion modeling of a rectangular waveguide discontinuity, our investigation at first is to show the physical reason why there exist two aspects of numerical error in a deterministic MoM regarding a microstrip step discontinuity as the showcase in this study. In this SOC scheme, the identified two error sources are put together as a single error term or box for each feed line and then characterized by defining and evaluating two self-consistent calibration standards in the MoM, namely, short and open elements. As such, the core circuit model of the step discontinuity is effectively extracted by removing out two error terms. Subsequently, geometry- and frequency-dependent characteristics of the SOC technique are studied and discussed to demonstrate its effectiveness and accurateness as compared with the conventional transmission-line deembedding technique. After a series of validations by static analysis and measured results, the SOC scheme is used to model symmetrical and asymmetrical microstrip step discontinuities in terms of their equivalent dynamic circuit model over a wide frequency range. View full abstract»

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  • A tunable all-pass MMIC active phase shifter

    Page(s): 1885 - 1889
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (261 KB) |  | HTML iconHTML  

    This paper describes a novel structure for a monolithic-microwave integrated-circuit active phase shifter based on a bridge all-pass network. The design procedure has been developed, leading to a fixed-frequency circuit with large tunable phase variation, associated to a low-gain ripple, and requiring nearly no design optimization. Simulated results predicted an analog tunable 180° phase variation, at 5-GHz operation frequency. The circuit was implemented using GEC-Marconi pseudomorphic high electron-mobility transistor H40 technology, and measured results validated the proposed design method and circuit structure. View full abstract»

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  • Improved analysis of nonreciprocal remanence ferrite phase shifter in grooved waveguide

    Page(s): 1912 - 1918
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (306 KB)  

    In this paper, the nodal finite-element method is used to analyze the differential phase shift of a nonreciprocal remanence ferrite phase shifter in a grooved waveguide. Instead of the former twin-slab model, an improved analytical model is adopted, where the effect of every part of a ferrite toroid on the differential phase shift has been considered. This analysis may replace the correcting factor with good agreement with the experimental data. Furthermore, this analysis is employed to investigate the effect of corner chamfering on the figure-of-merit (differential phase shift per decibel insertion loss) of a ferrite phase shifter. The numerical results are found to agree with the experiments in the literatures. 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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