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Showing papers in "IEEE Transactions on Microwave Theory and Techniques in 1988"


Journal ArticleDOI
TL;DR: In this article, a method to determine the small-signal equivalent circuit of FETs is proposed, which consists of a direct determination of both the extrinsic and intrinsic small signal parameters in a low-frequency band.
Abstract: A method to determine the small-signal equivalent circuit of FETs is proposed This method consists of a direct determination of both the extrinsic and intrinsic small-signal parameters in a low-frequency band This method is fast and accurate, and the determined equivalent circuit fits the S-parameters well up to 265 GHz >

1,491 citations


Journal ArticleDOI
TL;DR: In this paper, the frequency-dependent characteristics of the microstrip discontinuities have been analyzed using full-wave approaches and the time-domain finite-difference (TD-FD) method is presented.
Abstract: The frequency-dependent characteristics of the microstrip discontinuities have previously been analyzed using full-wave approaches. The time-domain finite-difference (TD-FD) method presented here is an independent approach and is relatively new in its application for obtaining the frequency-domain results for microwave components. The validity of the TD-FD method in modeling circuit components for MMIC CAD applications is established. >

372 citations


Journal ArticleDOI
TL;DR: In this article, the mixed potential integral equation (MPIE) is applied to microstrip structures, which can be used at any frequency ranging from DC to higher-order resonances.
Abstract: The author gives a comprehensive description of the mixed potential integral equation (MPIE) as applied to microstrip structures. This technique uses Green's functions associated with the scalar and vector potential which are calculated by using stratified media theory and are expressed as Sommerfeld integrals. Several methods of moments allowing the study of irregular shapes are described. It is shown that the MPIE includes previously published static and integral equations. Hence, it can be used at any frequency ranging from DC to higher-order resonances. Several practical examples including an L-shaped patch have been numerically analyzed and the results are found to be in good agreement with measurements. >

348 citations


Journal ArticleDOI
TL;DR: A survey of modern nonlinear CAD techniques as applied to the specific field of microwave circuits shows that the various subjects are not just separate items, but rather can be chained in a strictly logical sequence.
Abstract: The authors present a survey of modern nonlinear CAD (computer-aided design) techniques as applied to the specific field of microwave circuits. A number of fundamental aspects of the nonlinear CAD problem, including simulation, optimization, intermodulation, frequency conversion, stability, and noise, are addressed and developed. For each one it is shown that either well-established CAD solutions are available, or at least a solution approach suitable for implementation in a general-purpose CAD environment can be outlined. Also, the discussion shows that the various subjects are not just separate items, but rather can be chained in a strictly logical sequence. Finally, an elementary treatment of vector processing is given, to show that supercomputers can handle the involved large-size numerical problems efficiently. >

314 citations


Journal ArticleDOI
TL;DR: In this article, an analysis of microstrip/slotline transitions is given using a network description through transmission-line models, and the validity of the modeling results is verified experimentally by measuring the transmission coefficient of a cascade of two transitions separated by a slotline in the frequency range from 1 to 16 GHz.
Abstract: An analysis of microstrip/slotline transitions is given using a network description through transmission-line models. Different transitions, such as transitions containing uniform and nonuniform lines as well as soldered and virtually shorted microstrip lines, are treated. Although a transition with a soldered microstrip short offers the largest bandwidth, optimal combinations of different microstrip and slot stub diameters can be found by modeling. In the case of a virtual short through an optimally chosen circular microstrip stub, the bandwidth is typically about 10% below the maximum achievable value of a soldered short. The validity of the modeling results is verified experimentally by measuring the transmission coefficient of a cascade of two transitions separated by a slotline in the frequency range from 1 to 16 GHz. For practical applications, design curves are given for 0.635-mm-thick alumina substrates. >

278 citations


Journal ArticleDOI
TL;DR: A unified hierarchical treatment of circuit models forms the basis of the presentation, and the concepts of design centering, tolerance assignment, and postproduction tuning in relation to yield enhancement and cost reduction suitable for integrated circuits are discussed.
Abstract: The authors review the current state of the art in circuit optimization, emphasizing techniques suitable for modern microwave CAD (computer-aided design). The main thrust in the field is currently the solution of realistic design and modeling problems, addressing such concepts as physical tolerances and model uncertainties. A unified hierarchical treatment of circuit models forms the basis of the presentation. It exposes tolerance phenomena at different parameter/response levels. The concepts of design centering, tolerance assignment, and postproduction tuning in relation to yield enhancement and cost reduction suitable for integrated circuits are discussed. Suitable techniques for optimization oriented worst-case and statistical design are reviewed. A generalized l/sub p/ centering algorithm is proposed and discussed. Multicircuit optimization directed at both CAD and robust device modeling is formalized. Tuning is addressed in some detail, both at the design stage and for production alignment. State-of-the-art gradient-based nonlinear optimization methods are reviewed with emphasis given to recent, but well tested, advances in minimax, l/sub 1/, and l/sub 2/ optimization. >

238 citations


Journal ArticleDOI
TL;DR: In this paper, the high electron mobility transistor's (HEMT's) noise behavior is presented from theoretical and experimental points of view, and a comparison between the noise performance of both MESFETs and HEMTs is carried out.
Abstract: The high electron mobility transistor's (HEMT's) noise behavior is presented from theoretical and experimental points of view. The general method used in the high-frequency noise analysis is described and the different approximations commonly used in the derivation of the noise parameter expressions are discussed. A comparison between the noise performance of both MESFETs and HEMTs is carried out. The measurement techniques providing the noise figure and the other noise parameters are then described and compared. >

235 citations


Journal ArticleDOI
TL;DR: In this paper, integrable lumped-element straight-line, single-loop, and spiral inductors have been derived using numerical solutions of the inductance integral, basic microstrip theory, and network analysis.
Abstract: Lumped elements are considered as very attractive structures for the realisation of MMICs with respect to considerable size-reduction. Improved models for integrable lumped-element straight-line, single-loop, and spiral inductors, as well as for interdigitated and MIM capacitors, have been derived using numerical solutions of the inductance integral, basic microstrip theory, and network analysis. The broad experimental verification shows good agreement between models and experiments, with deviations of 5-10% up to 18 GHz. Besides the practical values and frequency range, losses of the lumped elements are presented. >

224 citations


Journal ArticleDOI
Abstract: A direct time-domain finite-difference method is used to recharacterize the microstrip. Maxwell's equations are discretized both in time and space and a Gaussian pulse is used to excite the microstrip. The frequency-domain data are obtained from the Fourier transform of the calculated time-domain field values. Since this method is completely independent of all the above-mentioned investigations, the results can be considered as an impartial verification of the published results. The comparison of the time-domain results and those from the frequency-domain methods has shown the integrity of the time-domain computations. This method is very general and can be applied to model many other microwave components. >

212 citations


Journal ArticleDOI
TL;DR: In this paper, a dielectric waveguide shorted at both ends was constructed as a cavity resonator, and the attenuation constant of this guided mode was determined by measuring the Q of this cavity.
Abstract: A dielectric waveguide shorted at both ends was constructed as a cavity resonator. By measuring the Q of this cavity, one can determine the attenuation constant of this guided mode on this dielectric structure. The complex permittivity of the dielectric waveguide material can also be derived from the measurements. Measurements were made at Ka-band for dielectric waveguides constructed of nonpolar, low-loss polymers, such as Teflon, polypropylene, polyethylene, polystyrene, and rexolite. >

167 citations


Journal ArticleDOI
TL;DR: In this article, an approach for the time-domain simulation of transients on a dispersive and lossy transmission line terminated with active devices is presented, which combines the scattering matrix of an arbitrary line and the nonlinear causal impedance functions at the loads to derive expressions for the signals at the near and far ends.
Abstract: An approach for the time-domain simulation of transients on a dispersive and lossy transmission line terminated with active devices is presented. The method combines the scattering matrix of an arbitrary line and the nonlinear causal impedance functions at the loads to derive expressions for the signals at the near and far ends. The problems of line losses, dispersion, and nonlinearities are first investigated. A time-domain formulation is then proposed using the scattering-matrix representation. The algorithm assumes that dispersion and loss models for the transmission lines are available and that the frequency dependence is known. Large-signal equivalent circuits for the terminations are assumed to be given. Experimental and computer-simulated results are compared for the lossless dispersionless case, and the effects of losses and dispersion are predicted. >

Journal ArticleDOI
TL;DR: In this article, a broadband monolithic microwave active inductor and its characteristics are discussed, which consists of a cascode FET with a feedback resistor, and operates in a much higher frequency range than a spiral inductor.
Abstract: A broadband monolithic microwave active inductor and its characteristics are discussed. The inductor consists of a cascode FET with a feedback resistor, and operates in a much higher frequency range than a spiral inductor. The size is independent of the inductance value. Miniaturized wideband amplifiers in two frequency bands are realized utilizing these active inductors. >

Journal ArticleDOI
TL;DR: In this article, the equivalent circuit of a via connecting two semi-infinitely long transmission lines through a circular hole in a ground plane is found, and the pi-type equivalent circuit consists of two excess capacitances and an excess inductance.
Abstract: The equivalent circuit of a via connecting two semi-infinitely long transmission lines through a circular hole in a ground plane is found. The pi -type equivalent circuit consists of two excess capacitances and an excess inductance. These are quasistatic quantities and thus are computed statically by the method of moments from integral equations. The integral equations are established by introducing a sheet of magnetic current in the electrostatic case and a layer of magnetic charge in the magnetostatic case. Parametric plots of the excess capacitances, the excess inductance, and the characteristic admittance of the via are given. >

Journal ArticleDOI
TL;DR: In this paper, a computational scheme is proposed that can be applied to the analysis of cascaded waveguide discontinuities of alternating boundary-enlargement and boundary-reduction type.
Abstract: A computational scheme is proposed that can be applied to the analysis of cascaded waveguide discontinuities of alternating boundary-enlargement and boundary-reduction type. Based on the mode-matching technique, the proposed procedure makes use of the admittance matrix characterization of waveguide stubs. With respect to the conventional S-matrix formulation, it leads to a notable reduction of the computational effort, particularly for lossless structures. At the same time, the criterion for avoiding relative convergence problems can be satisfied. The procedure has been used to set up a very accurate and efficiency computer-aided design tool of branch guide couplers (BGCs). These are key elements of beam-forming networks for multicontoured beam satellite antennas and have to be designed with very high accuracy so as to eliminate the necessity for tuning the components realized. Design accuracies better than 0.1 dB in Ka-band are demonstrated by experimental results. >

Journal ArticleDOI
M. Kobayashi1
TL;DR: A dispersion formula for the effective relative permittivity epsilon /sup *//sub eff/(f) of an open microstrip line is derived for computer-aided design (CAD) use.
Abstract: A dispersion formula epsilon /sup *//sub eff/(f)= epsilon /sup */-( epsilon /sup */- epsilon /sup *//sub eff/(0))/(1+(f/f/sub 50/)/sup m/), for the effective relative permittivity epsilon /sup *//sub eff/(f) of an open microstrip line is derived for computer-aided design (CAD) use. The 50% dispersion point (the frequency f/sub 50/ at which epsilon /sup *//sub eff/(f/sub 50/)=( epsilon /sup */+ epsilon /sup *//sub eff/(0))/2)) is used a normalizing frequency in the proposed formula, and an expression for f/sub 50/ is derived. To obtain the best fit of epsilon /sup *//sub eff/(f) to the theoretical numerical model, the power m of the normalized frequency in the proposed formula is expressed as a function of width-to-height ratio w/h for w/h>or=0.7 and as a function of w/h, f/sub 50/, and f for w/h >

Journal ArticleDOI
TL;DR: A new Fourier transform algorithm for almost-periodic functions (the APFT) is developed that is both efficient and accurate and a particularly simple derivation of harmonic Newton using the APFT.
Abstract: A new Fourier transform algorithm for almost-periodic functions (the APFT) is developed. It is both efficient and accurate. Unlike previous attempts to solve this problem, the new algorithm does not constrain the input frequencies and uses the theoretical minimum number of time points. Also presented is a particularly simple derivation of harmonic Newton (the algorithm that results when Newton's method is applied to solve the harmonic balance equations) using the APFT; this derivation uses the same matrix representation used in the derivation of the APFT. Since the APFT includes the DFT (discrete Fourier transform) as a special case, all results are applicable to both the periodic and almost-periodic forms of harmonic Newton. >

Journal ArticleDOI
TL;DR: Finite, boundary, and hybrid element approaches are presented as numerical methods for computing electromagnetic fields inside lossy dielectric objects that have direct application in hyperthermia as a cancer therapy where the EM fields produced inside the patient by external sources are of interest.
Abstract: Finite, boundary, and hybrid element approaches are presented as numerical methods for computing electromagnetic (EM) fields inside lossy dielectric objects. These techniques are implemented as computer algorithms for solving the Maxwell equations in heterogeneous media in three dimensions. Algorithm verification takes the form of comparisons of test cases with analytic solutions. Computed results for each technique are in good agreement with exact solutions, especially in light of the coarse computational grid resolutions used. Implementation was in FORTRAN on a moderate-sized computer (MicroVax II). The basic problem formulation is quite general; however, it has direct application in hyperthermia as a cancer therapy where the EM fields produced inside the patient by external sources are of interest. An example of the application of these numerical methods in a three-dimensional clinical setting is shown. >

Journal ArticleDOI
TL;DR: A powerful software tools for the simulation of nonlinear microwave circuits under single- or multiple-frequency excitation is described, with built-in facilities based on the multidimensional Fourier transform allowing a straightforward and unrestricted treatment of mixer and intermodulation problems.
Abstract: A powerful software tools for the simulation of nonlinear microwave circuits under single- or multiple-frequency excitation is described. The program operates in a truly general-purpose fashion, both circuit topology and active-device equivalent circuits being arbitrarily established by the user at the data entry level. Built-in facilities based on the multidimensional Fourier transform allow a straightforward and unrestricted treatment of mixer and intermodulation problems. The capabilities of the program are illustrated by a number of practical examples. >

Journal ArticleDOI
TL;DR: In this paper, the use of large-signal model in an interactive program for amplifier analysis is shown and the computed load-pull results and IMD (intermodulation distortion) predictions are shown to be in good agreement with measured data at 10 GHz.
Abstract: Equivalent circuit modeling techniques are described for both small-signal and large-signal models of GaAs MESFETs. The use of large-signal model in an interactive program for amplifier analysis is shown. The computed load-pull results and IMD (intermodulation distortion) predictions are shown to be in good agreement with measured data at 10 GHz. >

Journal ArticleDOI
TL;DR: In this paper, explicit design equations for combline and interdigital filters with tapped-line inputs are presented, based on an equivalent circuit for a tapped line input filter, derived from the open-wire-line equivalent circuit given by E.G. Cristal.
Abstract: Explicit design equations for combline and interdigital filters with tapped-line inputs are presented. The equations are based on an equivalent circuit for a tapped-line input filter, derived from the open-wire-line equivalent circuit given by E.G. Cristal (ibid., vol.23, no.12, p.1007-113, 1975). Using the new equivalent circuit, explicit expressions are given for all parameters of the circuit. The design equations are checked by an analysis program. The results are compared to the data given by M. Dishal (ibid., vol.13, no.9, p.696-8, 1965) and E.G. Cristal. >

Journal ArticleDOI
TL;DR: In this article, a simple transmission-line grid model and measured low-frequency parameters for the diodes were used to predict the measured performance over the entire capacitive bias range of the Diodes, as well as over the complete reactive tuning range provided by a reflector behind the grid, and over a wide range of frequencies form 33 GHz to 141 GHz.
Abstract: Monolithic diode grids have been fabricated on 2-cm square gallium-arsenide wafers with 1600 Schottky-barrier varactor diodes. Shorted diodes are detected with a liquid-crystal technique, and the bad diodes are removed with an ultrasonic probe. A small-aperture reflectometer that uses wavefront division interference was developed to measure the reflection coefficient of the grids. A Phase shift of 70 degrees with a 7-dB loss was obtained at 93 GHz when the bias on the diode grid was changed from -3 V to 1 V. A simple transmission-line grid model, together with the measured low-frequency parameters for the diodes, was shown to predict the measured performance over the entire capacitive bias range of the diodes, as well as over the complete reactive tuning range provided by a reflector behind the grid, and over a wide range of frequencies form 33 GHz to 141 GHz. This shows that the transmission-line model and the measured low-frequency diode parameters can be used to design an electronic beam-steering array and to predict its performance. An electronic beam-steering array made of a pair of grids using state-of-the-art diodes with 5- Omega series resistances would have a loss of 1.4 dB at 90 GHz. >

Journal ArticleDOI
TL;DR: In this article, an analytic large-signal model for the GaAs MESFET is presented, which describes the conduction and displacement currents of the FET as a function of instantaneous terminal voltages and their time derivatives.
Abstract: An analytic, large-signal model for the GaAs MESFET is presented. The device model is physics-based and describes the conduction and displacement currents of the FET as a function of instantaneous terminal voltages and their time derivatives. The model allows arbitrary doping profiles in the channel and is thus suitable for the optimization of ion-implanted and buried-channel FETs. It also accounts for charge accumulation in the conducting channel at high electric fields and the associated capacitance in a self-consistent manner. Theoretical predictions of the model are correlated with experimental data on X-band power FETs and excellent agreement is obtained. >

Journal ArticleDOI
TL;DR: It is shown that the finite-difference time-domain method adapted to the needs of S-matrix calculations of microwave two-dimensional circuits is an effective tool of circuit analysis in engineering applications.
Abstract: A version of the finite-difference time-domain method adapted to the needs of S-matrix calculations of microwave two-dimensional circuits is presented. The analysis is conducted by simulating the wave propagation in the circuit terminated by matched loads and excited by a matched pulse source. Various aspects of the method's accuracy are investigated. Practical computer implementation of the method is discussed, and an example of its application to an arbitrarily shaped microstrip circuit is presented. It is shown that the method in the proposed form is an effective tool of circuit analysis in engineering applications. The method is compared to two other methods used for a similar purpose, namely the contour integral method and the transmission-line matrix method. >

Journal ArticleDOI
TL;DR: In this paper, the effects of modal dispersion and the complex surface conductivity of the superconductor are demonstrated, with the conclusion that it is necessary to incorporate both phenomena for accurate modeling of transient propagation in strip transmission lines.
Abstract: The algorithm suitable for the computer-aided design of transmission lines is used to model the propagation of picosecond and subpicosecond electrical signals on superconducting planar transmission lines. Included in the computation of a complex propagation factor are geometry-dependent modal dispersion and the frequency-dependent attenuation and phase velocity which arise as a result of the presence of a superconductor in the structure. The results of calculations are presented along with a comparison to experimental data. The effects of modal dispersion and the complex surface conductivity of the superconductor are demonstrated, with the conclusion that it is necessary to incorporate both phenomena for accurate modeling of transient propagation in strip transmission lines. >

Journal ArticleDOI
TL;DR: In this article, a novel configuration called the uniplanar MMIC is proposed, which consists of coplanar waveguides, slotlines, air bridges, and lumped circuit elements (GaAs FETs, capacitors, inductors, resistors, etc.), which are integrated on a single side of the GaAs substrate.
Abstract: A novel configuration called the uniplanar MMIC is proposed. It consists of coplanar waveguides, slotlines, air bridges, and lumped circuit elements (GaAs FETs, capacitors, inductors, resistors, etc.), which are integrated on a single side of the GaAs substrate. The uniplanar MMIC has no via holes and no thin polished substrates. As an application of the unipolar MMIC configuration, key monolithic circuits for a 26-GHz full MMIC receiver have been designed and fabricated. The circuits developed, namely, 26-GHz low-noise amplifier, a 26-GHz medium-power amplifier, a 6.5-GHz dual-output voltage-controlled oscillator, 6.5/13-GHz and 13/26-GHz frequency doublers, and a 26-GHz/1-GHz FET mixer, provide improved RF performance with a simplified fabrication process. >

Journal ArticleDOI
TL;DR: In this article, a design technique for cryogenically cooled amplifiers is briefly discussed, and examples of realization of L-band, C-band and X-band amplifiers are described.
Abstract: Typical DC characteristics and X-band noise parameters are presented and qualitatively correlated wherever possible with other technological or experimental data. While certain general trends can be identified, further work is needed to explain a number of observed phenomena. A design technique for cryogenically cooled amplifiers is briefly discussed, and examples of realization of L-band, C-band, X-band, and K-band amplifiers are described. The noise temperature of amplifiers with HEMTs in input stages is usually less than half of that for all-FET realizations, setting new records of performance for cryogenically cooled, multistage amplifiers. >

Journal ArticleDOI
TL;DR: In this paper, a system for the accurate measurement of high-frequency periodic time-domain voltage and current waveforms of a nonlinear microwave device is presented, where measurements are performed in the time domain using a high-speed sampling oscilloscope.
Abstract: A system is presented for the accurate measurement of high-frequency periodic time-domain voltage and current waveforms of a nonlinear microwave device. The measurements are performed in the time domain using a high-speed sampling oscilloscope. The results are Fourier-transformed into the frequency domain for error correction and then back into the time domain. An error-correction algorithm is presented that makes it possible to obtain accurate waveforms in spite of nonideal system components. Practical difficulties in measurement-system characterization are also discussed. An accurate circuit model for the measurement fixture is developed and its element values are determined. Measurement results are given showing the waveforms in a microwave transistor operated in the nonlinear region. The errors caused by signal processing are discussed. >

Journal ArticleDOI
TL;DR: In this paper, a slot-coupled microstrip directional coupler and its application to a planar multiport DSC was described. But this coupler can be applied to both loose coupling and tight coupling (e.g. 3 dB).
Abstract: A slot-coupled microstrip directional coupler and its application to a planar multiport directional coupler (MDC) are described. This coupler can be applied to both loose coupling (e.g. 10 dB) and tight coupling (e.g. 3 dB). A four-port planar MDC fabricated by combining these couplers is described. Measured and calculated results are in agreement for both couplers. >

Journal ArticleDOI
TL;DR: In this paper, the transfinite element-method is used in conjunction with the planar waveguide model to analyze MMIC devices, using analytic basis functions together with finite-element approximation functions in a variational technique.
Abstract: A numerical procedure called the transfinite element-method is used in conjunction with the planar waveguide model to analyze MMIC devices. By using analytic basis functions together with finite-element approximation functions in a variational technique, the transfinite-element method determines the fields and scattering parameters for a wide variety of stripline and microstrip devices. With minor modification, the method can be applied to waveguide junctions, treating singular points in the junctions very efficiently. Calculations are shown for a rectangular-waveguide two-slot 20-dB coupler, stripline band-elimination filter, and several microstrip discontinuity problems. Good agreement of the numerical results with published values demonstrates the validity of the procedure. >

Journal ArticleDOI
TL;DR: In this article, a monolithic diode grid was fabricated on 2-cm/sup 2/ gallium-arsenide wafers in a proof-of-principle test of a quasi-optical varactor millimeter-wave frequency multiplier array concept.
Abstract: Monolithic diode grid were fabricated on 2-cm/sup 2/ gallium-arsenide wafers in a proof-of-principle test of a quasi-optical varactor millimeter-wave frequency multiplier array concept. An equivalent circuit model based on a transmission-line analysis of plane wave illumination was applied to predict the array performance. The doubler experiments were performed under far-field illumination conditions. A second-harmonic conversion efficiency of 9.5% and output powers of 0.5 W were achieved at 66 GHz when the diode grid was pumped with a pulsed source at 33 GHz. This grid had 760 Schottky-barrier varactor diodes. The average series resistance was 27 Omega , the minimum capacitance was 18 fF at a reverse breakdown voltage of -3 V. The measurements indicate that the diode grid is a feasible device for generating watt-level powers at millimeter frequencies and that substantial improvement is possible by improving the diode breakdown voltage. >