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Microwave Theory and Techniques, IEEE Transactions on

Issue 3 • Date Mar 1999

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Displaying Results 1 - 23 of 23
  • Analysis and design of circular ridged waveguide components

    Publication Year: 1999 , Page(s): 330 - 335
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    A fast and efficient radial mode-matching technique (RMMT) is applied to the analysis and design of components in circular ridge waveguide technology. Five different structures are investigated with respect to their performance as filters and polarizers. For fast computation, pie-shaped metal ridges and septa are assumed to better fit the cylindrical coordinate system. In practice, the pie-shaped structures are approximated by rectangular cross-section metal inserts. The validity of this approximation is investigated by comparing with measurements and finite-element analysis. It is found that for thin etchable inserts, the measured filter response is in excellent agreement with the theoretical prediction and that for polarizers, the axial ratio response is not particularly sensitive to the ridge shape. Differences between computed and measured results occur only at return loss and isolation levels beyond 25 dB. A central processing unit time comparison with HFSS (4.0) results in a 10-min versus 3-h advantage in favor of the RMMT View full abstract»

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  • Potential distributions through an annular aperture with a floating inner conductor

    Publication Year: 1999 , Page(s): 372 - 374
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    The potential distributions through an annular aperture in a thick conducting plane are considered when an inner conductor is electrically floating. The charge conservation is used to relate the potential in terms of the total charge on an inner conductor. Numerical calculations are performed to illustrate the behavior of potential distribution, capacitances, and polarizabilities in terms of the aperture geometry and incident field View full abstract»

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  • FET noise-parameter determination using a novel technique based on 50-Ω noise-figure measurements

    Publication Year: 1999 , Page(s): 315 - 324
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    A novel method for measuring the four noise parameters of a field-effect transistor (FET) is presented. It is based on the determination of its intrinsic noise matrix elements [C11INT, C22INT, Re(C12 INT), Im(C12INT)] by fitting the measured device noise figure for a matched source reflection coefficient (F50) at a number of frequency points, thus, a tuner is not required. In contrast to previous works, no restrictive assumptions are made on the intrinsic noise sources. The receiver full-noise calibration is easily performed by using a set of coaxial and on-wafer standards that are commonly available in a microwave laboratory, thus, an expensive broad-band tuner is not required for calibration either. On-wafer experimental verification up to 26 GHz is presented and a comparison with other F50-based and tuner-based methods is given. As an application, the dependence of the FET intrinsic noise sources as a function of the bias drain-current and gate-length is obtained View full abstract»

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  • Waveguide characterization of chiral material: experiments

    Publication Year: 1999 , Page(s): 297 - 301
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    This paper is devoted to waveguide experiments on chiral materials: the constitutive parameters are extracted from the measured response of two chiral slabs of different length. Practical aspects of the implementation are discussed. This includes the injection molding technique used to manufacture the chiral material. Preliminary investigations are performed to qualitatively assess the material properties. These are quantitatively confirmed by the extracted constitutive parameters. The measurements are validated by experiments on a reference material View full abstract»

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  • Uncertainty analysis of the transmission-type measurement of Q-factor

    Publication Year: 1999 , Page(s): 367 - 371
    Cited by:  Papers (34)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    The transmission-type measurement of the Q-factor of a microwave resonator is analyzed with a goal of establishing uncertainty limits on the unloaded Q-factor. The three major sources of systematic errors which are discussed are: the instrumentation inaccuracy, the inequality of the input and output coupling coefficient, and the effect of coupling losses. It is shown that, for tightly coupled resonators, the uncertainty of the transmission-type method is significantly increased View full abstract»

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  • Improving amplifier stability through resistive loading below the operating frequency

    Publication Year: 1999 , Page(s): 359 - 362
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    A new design method for a stable RF amplifier using a broadband-matched 3-dB coupled line is proposed in this paper. The proposed broad-band matching circuit consists of lossless matching circuits at operating frequency band and resistive matching circuits at frequencies below the operating band. This design method improves the stability of the amplifier and is suitable for the design of a power amplifier and multistage amplifier. When applying this proposed method to a design of a two-stage power amplifier for personal communication systems, measured results show 18.0dB gain and 9 W (39.5 dBm) output power View full abstract»

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  • A nonuniform FDTD technique for efficient analysis of propagation characteristics of optical-fiber waveguides

    Publication Year: 1999 , Page(s): 345 - 349
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    In this paper, we present a highly efficient one-dimensional cylindrical nonuniform finite-difference time-domain (1-D CNUFDTD) method, which utilizes the unsplit anisotropic perfectly matched layer (APML) for mesh truncation along the radial direction to analyze axisymmetric optical-fiber waveguides. As a first step, we validate the proposed FDTD algorithm by analyzing a uniform dielectric waveguide of circular cross section and show that the results are in excellent agreement with the conventional mode theory solutions. Next, we apply the algorithm to analyze propagation characteristics of a number of commonly used optical-fiber waveguides, i.e., step-index multimode, graded-index multimode, and single-mode step-index configurations View full abstract»

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  • Suggestions for revised definitions of noise quantities, including quantum effects

    Publication Year: 1999 , Page(s): 325 - 329
    Cited by:  Papers (42)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (124 KB)  

    Recent advances in millimeter- and submillimeter-wavelength receivers and the development of low-noise optical amplifiers focus attention on inconsistencies and ambiguities in the standard definitions of noise quantities and the procedures for measuring them. The difficulty is caused by the zero-point (quantum) noise hf/2 W/Hz, which is present even at absolute zero temperature, and also by the nonlinear dependence at low temperature of the thermal noise power of a resistor on its physical temperature, as given by the Planck law. Until recently, these effects were insignificant in all but the most exotic experiments, and the familiar Rayleigh-Jeans noise formula P=kT W/Hz could safely be used in most situations, Now, particularly in low-noise millimeter-wave and photonic devices, the quantum noise is prominent and the nonlinearity of the Planck law can no longer be neglected. The IEEE Standard Dictionary of Electrical and Electronics Terms gives several definitions of the noise temperature of a resistor or a port, which include: 1) the physical temperature of the resistor and 2) its available noise power density divided by Boltzmann's constant-definitions which are incompatible because of the nature of the Planck radiation law. In addition, there is no indication of whether the zero-point noise should be included as part of the noise temperature. Revised definitions of the common noise quantities are suggested, which resolve the shortcomings of the present definitions. The revised definitions have only a small effect on most RF and microwave measurements, but they provide a common consistent noise terminology from dc to light frequencies View full abstract»

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  • Input impedance characteristics of coaxial slot antennas for interstitial microwave hyperthermia

    Publication Year: 1999 , Page(s): 302 - 307
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    In this paper, a transmission-line type of input impedance model originally developed by King et al. (1983) for the insulated dipole antenna embedded in a homogeneous dissipative medium is extended to the case of insulated coaxial slot antenna. Physical construction of the latter indicates the presence of additional current path(s) inside the feed line, which shall lead to the shortening of its resonance length. This effect is taken into account in the impedance model and verified by experiments. Furthermore, a simple strategy for optimizing the applicator's impedance-matching performance is also described and verified. Excellent agreements observed between theoretical and measured S11 data indicate that these models can be relied upon when designing an efficient applicator for interstitial microwave hyperthermia View full abstract»

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  • Full-wave analysis of coaxial mounting structure

    Publication Year: 1999 , Page(s): 265 - 270
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    An efficient full-wave spectral-domain analysis based on the integral equation method is developed for a coaxial mounting structure of a general form. Using this method, the algorithm for complex input gap impedance of such structures has been derived and the calculated data are presented. The method may be useful for designing active and passive devices mounted in a coaxial line View full abstract»

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  • Ultra-low absorption measurement in dielectrics in millimeter- and submillimeter-wave range

    Publication Year: 1999 , Page(s): 284 - 289
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    A measurement of ultra-low absorption of microwave radiation in dielectrics is reported. Two Fabry-Perot resonators with ⩾600000 quality factors, fully general-purpose interface bus programmable millimeter-wave frequency synthesizer with 10-15-mW continuous wave (CW) power level, 100-Hz frequency resolution from 78 to 118 GHz, and corresponding hardware and software for signal processing were used. The ±500-Hz accuracy of resonance curve width measurements was reached. This high accuracy allowed loss tangent measurement as small as 10-6-10-7 in dielectric samples with a thickness of ~0.5 mm. A convenient method of measurements of almost arbitrary plane parallel samples has been developed and described. Practical applications such as development and control of thin low-loss resonant windows of powerful (~1-MW CW) gyrotrons used in thermonuclear experiments, precise reflection coefficient of metals measurements, as well as other applications are discussed. The existence of such technique up to frequencies exceeding 1 THz makes measurements described at the whole millimeter- and submillimeter-wave bands affordable View full abstract»

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  • A modal analysis of TEM mode in circular-rectangular coaxial waveguides

    Publication Year: 1999 , Page(s): 356 - 359
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (172 KB)  

    A modal analysis of transverse electromagnetic (TEM) mode in a circular-rectangular coaxial waveguide is presented in this paper. The analysis is based on the modal-expansion technique. Analytic expressions for the characteristic impedance and attenuation coefficient are derived from the solution of the TEM mode. The calculated results are compared with those of the finite-element method, as well as published data. Excellent agreement is observed View full abstract»

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  • An anisotropic PML for use with biaxial media

    Publication Year: 1999 , Page(s): 374 - 377
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB)  

    This paper presents the conditions required for an anisotropic perfectly matched layer for material exhibiting a biaxial permittivity tensor. Such materials are common in optical devices. This derivation does not treat arbitrary orientations, but should be general enough for many common situations. The effectiveness of this absorbing boundary condition is considered using the finite-element method View full abstract»

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  • Waveguide characterization of chiral material: theory

    Publication Year: 1999 , Page(s): 290 - 296
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    A new procedure to extract all three constitutive parameters of chiral material from waveguide measurements is presented. Two chiral slabs of different length must be measured. Their scattering parameters are inverted in a largely analytical way, complemented by a simple and fast convergent numerical algorithm. Tests with synthetic scattering data show the method to be very accurate and stable View full abstract»

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  • Study of the effect of various parameters on nonlinear transmission-line (NLTL) performance

    Publication Year: 1999 , Page(s): 350 - 353
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    Nonlinear transmission-line (NLTL) shock-wave generator performance in the presence of frequency-dependent losses is reported. The skin effect is studied using the harmonic-balance technique with the aid of the HP-MDS design database language. Measured results of a 48-section NLTL excited by a 26.6-dBm sinusoidal signal from the literature are compared with simulation with good agreement. Experimental performance of an eight-section GaAs monolithic-microwave integrated circuit NLTL is reported for 26-dBm drive conditions. Schottky diode capacitance-voltage (C-V) characteristics are computed using the Silvaco physical simulator for different doping profiles. Doping profiles are used as a parameter in NLTL design and their effect on NLTL performance is investigated. S-parameter measurements are performed for the GEC Marconi Materials Technology GaAs Schottky diode family from which the C-V characteristics are extracted and used to validate simulation. The problem of variable dynamic range is addressed and variable diode areas are used to enhance matching View full abstract»

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  • Inverse scattering using the finite-element method and a nonlinear optimization technique

    Publication Year: 1999 , Page(s): 336 - 344
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    A new spatial-domain technique for the reconstruction of the complex permittivity profile of unknown scatterers is proposed in this paper. The technique is based on a combination of the finite-element method (FEM) and the Polak-Ribiere nonlinear conjugate gradient optimization algorithm. The direct scattering problem is explicitly dealt with by means of the differential formulation and it is solved by applying the FEM. The inversion methodology is oriented to minimizing a cost function, which consists of a standard error term and regularization term. A sensitivity analysis, which is carried out by an elaborate finite-element procedure, results in the determination of the direction required for correcting the profile. Significant reduction of the computation time is obtained by introducing the adjoint state vector methodology. The efficiency of the presented inversion technique is validated by applying it to the inversion of synthetic scattered far-field measurements, which are corrupted by additive noise View full abstract»

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  • The dispersive boundary condition applied to nonuniform orthogonal meshes

    Publication Year: 1999 , Page(s): 257 - 264
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    The dispersive boundary condition (DBC) is a versatile boundary condition in that it can be used for radiation problems as well as for guided-wave problems. The DBC is applied to nonuniform meshes and various implementations are reported. Stability issues are discussed and numerical results are presented for a microstrip line and for a point source radiator. Error analysis is carried out in the time and frequency domains View full abstract»

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  • New calibration method in electrooptic probing due to wavelength control and Fabry-Perot resonance

    Publication Year: 1999 , Page(s): 308 - 314
    Cited by:  Papers (3)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    The use of the Fabry-Perot resonance in direct internal electrooptic probing reveals a new calibration method. Substrate resonances modulated by the Pockels effect results in a direct amplitude modulated electrooptic signal. The relation between this signal amplitude and wavelength-derivative of the reflected average probe-beam intensity describes the absolute potential on the device-under-test (DUT). A fibered electrooptic probing system has been developed containing a fiber reinjection probing head. A confocal arrangement optimizes the spatial resolution on the DUT while respecting the Fabry-Perot resonance limit. The direct AM electrooptic probing under wavelength optimization has been demonstrated experimentally by two-dimensional scanning of a monolithic-microwave integrated-circuit section View full abstract»

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  • An optimal circular-waveguide dual-mode filter without tuning screws

    Publication Year: 1999 , Page(s): 271 - 276
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    A novel circular-waveguide dual-mode (CWDM) filter structure is proposed. The coupling between the degenerate modes in the same cavity is provided by an off-centered circular iris built in at the middle of the resonant cavities. Considering the facts of: (1) simplicity of the mechanical process; (2) a potentially high Q; (3) a wide spurious-free frequency band; and (4) the effectiveness of electromagnetic (EM) modeling, the structure can be considered as an optimal coupling structure for CWDM filters when a precise EM design is required. A rigorous mathematical proof is given for explaining its working mechanism. The detailed formulations for designing the new coupling structure is also discussed. To validate the new structure, a narrow-bandwidth four-pole Ku-band elliptic filter is designed, manufactured and tested. Very good agreement is obtained between the calculated and measured responses View full abstract»

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  • A simplified derivation of the capacitance of a two-wire transmission line

    Publication Year: 1999 , Page(s): 365 - 366
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (64 KB)  

    This paper demonstrates that it is much easier to determine capacitance in a two-wire transmission line by tracing a known line of force than by the methods which customarily have been used to solve this problem View full abstract»

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  • A technique for improving the accuracy of the nonuniform finite-difference time-domain algorithm

    Publication Year: 1999 , Page(s): 353 - 356
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    This paper deals with the problem of improving the accuracy of the nonuniform finite-difference time-domain (NUFDTD) algorithm, which is known to contain higher discretization errors than the conventional uniform FDTD. The improvement is achieved by effectively canceling out the numerical reflections that typically occur due to dispersion in the nonuniform mesh. The modified nonuniform algorithm is applied to a generic coaxial discontinuity problem and to that of near-to-far-field transformation. The proposed method is simple, does not require any interpolations or extrapolations, provides higher accuracy than the conventional NUFDTD algorithm, and is stable View full abstract»

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  • Channel temperature measurement using pulse-gate method [power amplifier FET]

    Publication Year: 1999 , Page(s): 362 - 365
    Cited by:  Papers (1)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    In this paper, we report on an approach of measuring power amplifier field-effect transistor (FET) channel temperature under real-world operating conditions. The principle of this approach is to compare the magnitude of power amplifier gain at both DC and pulse bias conditions. By utilizing the temperature-dependent gain characteristic of the power amplifier FET and applying pulse-gate control, the gain would gradually decrease with the rising temperature of the hot plate. The channel temperature is then determined when the decreasing gain reaches the level of the base line, which is measured under the specified DC bias and radiofrequency conditions View full abstract»

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  • Effectiveness analysis of lossy dielectric shields for a three-layered human model

    Publication Year: 1999 , Page(s): 277 - 283
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    In this paper, we discuss the shielding effects of lossy dielectric materials located in front of a human model. Using the method of moments, we investigated the shielding effects by calculating the “whole average specific absorption rate (SAR)” and the “local SAR” for a three-layered elliptical model of the human body, which simulates the skin, fat, and muscle tissues. According to the results, in the low-frequency range of 200-800 MHz, the multiple reflection between the shield and human model gives rise to an increase in the whole average SAR when a low-loss material shield is placed in front of the human model. On the other hand, the local SAR increased not only at the skin layer, but also at the muscle layer. At higher frequencies, the SAR became a continuously decreasing function of frequency 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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