Showing papers in "IEEE Transactions on Microwave Theory and Techniques in 1994"

FASTHENRY: a multipole-accelerated 3-D inductance extraction program

Abstract: A mesh analysis equation formulation technique combined with a multipole-accelerated Generalized Minimal Residual (GMRES) matrix solution algorithm is used to compute the 3-D frequency dependent inductances and resistances in nearly order n time and memory where n is the number of volume-filaments. The mathematical formulation and numerical solution are discussed, including two types of preconditioners for the GMRES algorithm. Results from examples are given to demonstrate that the multipole acceleration can reduce required computation time and memory by more than an order of magnitude for realistic integrated circuit packaging problems. >

Conversions between S, Z, Y, H, ABCD, and T parameters which are valid for complex source and load impedances

Abstract: This paper provides tables which contain the conversion between the various common two-port parameters, Z, Y, H, ABCD, S, and T. The conversions are valid for complex normalizing impedances. An example is provided which verifies the conversions to and from S parameters. >

Space mapping technique for electromagnetic optimization

Abstract: We offer space mapping (SM), a fundamental new theory to circuit optimization utilizing a parameter space transformation. This technique is demonstrated by the optimization of a microstrip structure for which a convenient analytical/empirical model is assumed to be unavailable. For illustration, we focus upon a three-section microstrip impedance transformer and a double folded stub microstrip filter and explore various design characteristics utilizing an electromagnetic (EM) field simulator. We propose two distinct EM models: coarse for fast computations, and the corresponding fine for a few more accurate and well-targeted simulations. The coarse model, useful when circuit-theoretic models are not readily available, permits rapid exploration of different starting points, solution robustness, local minima, parameter sensitivities, yield-driven design and other design characteristics within a practical time frame. The computationally intensive fine model is used to verify the space-mapped designs obtained exploiting the coarse model, as well as in the SM process itself. >

FD-TD modeling of digital signal propagation in 3-D circuits with passive and active loads

Abstract: Most existing computer-aided circuit design tools are limited when digital clock speeds exceed several hundred MHz. These tools may not deal effectively with the physics of UHF and microwave electromagnetic wave energy transport along metal surfaces such as ground planes or in the air away from metal paths that are common at or above this frequency range. In this paper, we discuss full-wave modeling of electronic circuits in three dimensions using the finite-difference time-domain (FD-TD) solution of Maxwell's equations. Parameters such as stripline complex line impedance, propagation constant, capacitance per unit length and inductance per unit length can be easily computed as a function of frequency. We also discuss FD-TD Maxwell's equations computational modeling of lumped-circuit loads and sources in 3-D, including resistors and resistive voltage sources, capacitors, inductors, diodes, and transistors. We believe that this approach will be useful in simulating the large-signal behavior of very high-speed nonlinear analog and digital devices in the context of the full-wave time-dependent electromagnetic field. >

Active integrated antennas

Abstract: This paper provide a review of the active integrated antenna (AIA) technologies. After a brief introduction on the definition and some historical remarks, the paper concentrates on the research effort on the past decades or so. The AlAs are reviewed in its various functions. First, an oscillator-type AIA is presented, followed by very interesting aspects of coupled oscillator arrays for phase control. Use of an AIA concept for efficient RF front ends is described with examples on high-power amplifier AlAs. Next, a phase-conjugation-based retrodirective array is reviewed. Finally, AIA systems for receiving, transmitting, and duplexing are reviewed.

Dielectric properties of single crystals of Al/sub 2/O/sub 3/, LaAlO/sub 3/, NdGaO/sub 3/, SrTiO/sub 3/, and MgO at cryogenic temperatures

Abstract: A dielectric resonator technique has been used for measurements of the permittivity and dielectric loss tangent of single-crystal dielectric substrates in the temperature range 20-300 K at microwave frequencies. Application of superconducting films made it possible to determine dielectric loss tangents of about 5/spl times/10/sup -7/ at 20 K. Two permittivity tensor components for uniaxially anisotropic samples were measured. Generally, single-crystal samples made of the same material by different manufacturers or by different processes save significantly different losses, although they have essentially the same permittivities. The permittivity of one crystalline ferroelectric substrate, SrTiO/sub 3/, strongly depends on temperature. This temperature dependence can affect the performance of ferroelectric thin-film microwave devices, such as electronically tunable phase shifters, mixers, delay lines and filters. >

Electromagnetic dyadic Green's function in spherically multilayered media

Abstract: A spectral-domain dyadic Green's function constructed for defining the electromagnetic fields in spherically multilayered media is considered by assuming that distribution and location of current sources are arbitrary. The scattering dyadic Green's function in each layer is constructed in terms of the spherical vector wave functions by applying the method of scattering superposition. The coefficients of the scattering dyadic Green's functions, based on the coupling recurrence equations satisfied by the coefficient matrix, are derived and expressed in terms of the equivalent reflection and transmission coefficients. The general solution has been applied to specific geometries, e,g., two-, three- and four-layered media that are frequently employed to model the practical problems, and the coefficients of the scattering dyadic Green's functions are presented. >

General noise analysis of nonlinear microwave circuits by the piecewise harmonic-balance technique

Abstract: This paper presents a self-consistent set of algorithms for the numerical computation of noise effects in forced and autonomous nonlinear microwave circuits. The analysis relies upon the piecewise harmonic-balance method, and thus retains all the peculiar advantages of this technique, including general-purposeness in the widest sense. The noise simulation capabilities include any kind of forced or autonomous nonlinear circuit operated in a time-periodic large-signal steady state, as well as microwave mixers of arbitrary topology. The limitations of the traditional frequency-conversion approach to noise analysis are overcome. The analysis takes into account the thermal noise generated in the passive subnetwork, the noise contributions of linear and nonlinear active devices, and the noise injected by sinusoidal driving sources of known statistical properties. The nonlinear noise models of two representative families of microwave devices (FET's/HEMT's and Schottky-barrier diodes) are discussed in detail, and several applications are illustrated. >

Accurate simulation of GaAs MESFET's intermodulation distortion using a new drain-source current model

Abstract: An accurate characterization of the nonlinear distortion caused by the Ids(Vgs,Vds) current in a MESFET, does not allow the common approach of splitting this nonlinear equivalent circuit element in two voltage dependent nonlinear current sources, Gm(Vgs) and Gds(Vds). By an improved laboratory characterization procedure, it was possible to extract the cross terms of the Ids(Vgs,Vds) Taylor series expansion. Measurements and Volterra series simulations, made at 2 GHz, have shown that they can give an important contribution to the prediction and understanding of MESFET's intermodulation load-pull behavior. >

Microstrip to waveguide transition compatible with MM-wave integrated circuits

Abstract: Microstrip to waveguide transitions used presently typically require a relatively complex waveguide mount extending on both sides of the planar circuit. Additionally, the planar substrate has to be cut into specific forms limiting the flexibility of the planar circuit design and complexity. In this paper, a new type of transition is described based on the principle of slot coupled antennas radiating into the waveguide. In this way, the extension of the planar circuit is not restricted, and at the same time, the involved antenna element can be used to hermetically seal the microwave/MM-wave input. >

Oscillator array dynamics with broadband N-port coupling networks

Abstract: This paper considers the analysis of an oscillator array with an arbitrary coupling network, described in terms of N-port circuit parameters. A Kurokawa analysis is used to transform the frequency domain network description into a set of equations for the oscillator amplitude and phase dynamics. The results reduce to previous work with "loosely" coupled Van der Pol oscillators, provided that the coupling network satisfies a broadband condition: the Q-factor of the coupling network must be much smaller than that of the oscillator. The theory is verified using a new coupling structure and a six-element patch oscillator array operating at 4 GHz, which produced a 70/spl deg/ scanning range using a phase-shifterless technique. >

A very small dielectric planar filter for portable telephones

Abstract: A high performance, high-dielectric stripline filter with the size of 4.5 mm/spl times/3.2 mm/spl times/2.0 mm has been developed. The filter consists of planar resonators and its structure is made of high permittivity multilayer ceramic in the Bi-Ca-Nb-O system. The performance is distinctive with its attenuation pole. An equivalent lumped circuit is derived to explain the behavior of the attenuation pole quantitatively. A precise design procedure is also described. >

A field theoretical derivation of TLM

Abstract: A field theoretical foundation of the TLM method is presented in this paper. In the derivation of the condensed symmetric TLM node, the Method of Moments is applied to Maxwell's equations to obtain discretized field equations. It is shown that the traditional mapping between wave amplitudes and electric and magnetic field components incorporates serious problems. Therefore, a new mapping between the wave amplitudes and the electric and magnetic field components is introduced. Applying the new mapping to the discretized field equations, the fundamental equations of the three-dimensional TLM method with condensed symmetric node are derived from Maxwell's equations. >

Linearized modulator for suboctave-bandpass optical analog links

Abstract: The spurious-free dynamic range of a suboctave externally modulated optical analog link can be improved (to >140 dB Hz/sup 4/5/) with modest received optical power and little noise figure penalty by using a simple linearized modulator. Its design consists of two standard Mach-Zehnder interferometric modulators in series, and so can operate at microwave frequencies. This paper develops standardized measures of linearized modulator performance, and uses them to evaluate the modulator; link examples are also given. A simple experiment verifies the basic theoretical predictions. >

Some important properties of waveguide junction generalized scattering matrices in the context of the mode matching technique

Abstract: Some important properties for the generalized scattering matrix [S] of waveguide step discontinuities, in the context of the mode matching technique, are derived by considering the conservation of the complex power and self reaction across the discontinuities. Apart from their theoretical significance, these properties are useful for the numerical verification of the mode matching technique when designing waveguide circuits. The properties are shown to apply in the general case of junctions between lossless inhomogeneously filled waveguides, and they are proven to remain valid irrespective of the number of modes retained in the field expansions. During the process of deriving these properties, the mode matching technique for a waveguide step discontinuity is revisited and some subtle theoretical issues are resolved. In this framework, the selection of the appropriate testing modes for enforcing the field continuity conditions across the discontinuity is rigorously justified. In addition, two distinct mode matching formulations corresponding to the two possible orthogonality relations among the eigenmodes of lossless waveguides are proven to be equivalent. Finally, it is shown that the correct application of the held boundary conditions across the step discontinuity implies requirements on the number of modes used to represent the fields, in each waveguide, which are compatible with the relative convergence criterion. >

CPW-fed active slot antennas

Abstract: We have combined microwave oscillator design with theoretical characterization of planar antennas to build active slot-oscillators. The design is uniplanar, does not require via holes and is compatible with monolithic transistor technology. The coplanar waveguide (CPW) fed antenna impedance is calculated using the space domain integral equation technique (SDIE), a full wave method of moments approach. Slot-oscillators were built at 7 GHz and 20 GHz and the predicted oscillation frequencies agree well with experiments. The 20 GHz medium power oscillator has an output power of 17 mW and a DC to RF efficiency of 14%. The design is easily scaled to millimeter-wave frequencies and can be extended to power combining arrays. >

Two-junction tuning circuits for submillimeter SIS mixers

Abstract: The capacitance of superconducting tunnel junctions can seriously degrade the performance of quasiparticle (SIS) mixers operating in the submillimeter band, so it is essential to provide a circuit for tuning out this capacitance at the operating frequency. In this article, we present two new tuning circuits for SIS mixers which use a pair of SIS junctions connected by an inductance. Compared to previously proposed tuning circuits, ours have a broader bandwidth, are easier to scale to higher frequencies, and may be easier to fabricate. We have constructed quasi-optical mixers which employ these tuning circuits, using Nb/Al-Oxide/Nb SIS junctions defined by optical lithography. The performance of these devices is excellent, giving receiver noise temperatures of 113 K (DSB) at 490 GHz and 230 K DSB at 612 GHz. In addition to demonstrating the effectiveness of our tuning circuit, these results show that quasi-optical mixers can be competitive with or superior to waveguide mixers at submillimeter wavelengths. The mixers continue to perform well at frequencies up to 672 GHz, which is about 95% of the Nb gap frequency. >

Analysis and design of quadruple-ridged waveguides

Abstract: In a previous paper, a unified approach has been proposed for the analysis and design of single- and double-ridged waveguides by a magnetic field integral equation (MFIE) formulation (see ibid., vol. 41, no. 11, p. 1965-71, Nov. 1993). This paper presents a continuing work with emphasis on the design of quadruple-ridged waveguides. The characteristics of square, circular and diagonal quadruple-ridged waveguides, including cutoff frequencies, attenuation, impedance and modal field distributions, are for the first time systematically analysed and reported. Distinct to being in a single- or double-ridged waveguide, the fundamental-mode in a quadruple-ridged waveguide has a cutoff frequency very close to that of the second-lowest mode, thus the natural single mode bandwidth is very small. However, when the second-lowest mode is effectively suppressed or not excited, a very wide bandwidth (6:1) can be achieved. This unique property, plus the capabilities of dual-polarization, high power, and low impedance, makes the quadruple-ridged waveguides well-suited to many antenna and microwave applications. >

Intercomparison of permittivity measurements using the transmission/reflection method in 7-mm coaxial transmission lines

Abstract: Broadband permittivity measurements made by eleven organizations using the transmission/reflection (T/R) method are compared to high-accuracy cavity resonator results. T/R accuracy is less than 10% for /spl epsiv//sub r//sup '/ >

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

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

Design of superconductive multiplexers using single-mode and dual-mode filters

Abstract: The objective of this short paper is twofold: 1) to present experimental and computer-simulated results for a number of single-mode and dual-mode high-temperature superconductor (HTS) filters; and 2) to present the measured performance of an integrated 3-channel circulator-coupled multiplexer employing dual-mode HTS thin film filters. The CAD algorithm used to design the HTS filters is also described. The results presented demonstrate the feasibility of building C-band compact-size superconductive multiplexers. >

A new aperture admittance model for open-ended waveguides

Abstract: A new model for the aperture admittance of open-ended waveguide structures radiating into a homogeneous, lossy dielectric is presented. The model is based on the physical and mathematical properties of the driving point admittance of passive, stable one-port networks. The model parameters, which depend upon the geometry of the waveguide and aperture, are determined from a relatively small number of computed admittances. This computed data is obtained by a full-wave moment method solution and, hence, includes the effects of radiation and energy storage in the near field and the evanescent waveguide modes. The accuracy of the numerical method is demonstrated by comparison with measured values. As an example, the model parameters are determined for the coaxial-line geometry. The accuracy of the model, for both the direct and inverse problem, is verified and a rigorous sensitivity and uncertainty analysis is performed. The new model has important applications in the field of dielectric spectroscopy. >

Simple CAD procedure for microwave filters and multiplexers

Abstract: The design of microwave filters and multiplexers requires a common step before actual hardware implementation, namely, the identification of a number of specific ideal electrical components with actual waveguide discontinuities. In the past, this step was accomplished semi-analytically using approximate single-mode discontinuity models. The complete filter or multiplexer could then be assembled, but additional final tuning or optimization with a large number of parameters was generally required. In this paper, we propose an alternative technique for the design of microwave filters or multiplexers that directly uses a full-wave electromagnetic simulator and that effectively decomposes the complex design task into a series of simple sub-tasks with clearly identified objectives. The procedure described only involves a limited number of actual physical parameters at each step so that it is computationally very efficient and rapidly convergent. >

FET model parameter extraction based on optimization with multiplane data-fitting and bidirectional search-a new concept

Abstract: A new optimization formulation is presented for efficient FET model parameter extraction, in which data-fitting is carried out in multi reference planes instead of only one, and the objective function is minimized by a bidirectional search technique. As an example of application, all parameters of a commonly used 15-element small-signal FET equivalent circuit model are clearly identified from only one set of measured S-parameters. A self-consistent generation of starting values can be involved regarding the FET in the passive pinch-off operating mode. Moreover, applying multi-bias data-fitting, which is performed without increasing the number of ordinary optimization variables, yields a robust determination of both the overall bias-independent parasitics and the bias-dependent intrinsic elements. For demonstration results are presented for a 0.5-/spl mu/m MESFET. >

Review of printed Marchand and double Y baluns: characteristics and application

Abstract: A review of printed baluns is presented. This is divided into two main groups; Marchand baluns (band pass networks) and double Y baluns (all pass networks). For each of these groups of baluns, three different realizations are given: microstrip-slot line, CPW-slot line and CPW/sub FGP/-CPS and their theoretical and experimental characteristics are compared. Simple expressions for the design of Marchand baluns with Chebyshev response, which replace the complicated synthesis proposed by Cloete are derived. Superior broadbandwidth features of double Y baluns are demonstrated in the design of two uniplanar double balanced mixers. Both the double Y mixer and the CPW/sub FGP/-CPS mixer have a frequency bandwidth 1:6, whilst maintaining other performance similar to that achieved with classical double balanced mixers. >

Analysis and design of microstrip-to-waveguide transitions

Abstract: A wide band, low insertion loss transition from shielded microstrip line to rectangular waveguide is analyzed by the mode matching method and the cascading procedure using generalized scattering matrices. The transition consists of a discontinuity between a ridge waveguide and the microstrip line and a ridge waveguide impedance transformer. The microstrip eigennodes, including complex modes, are obtained by mode matching method with LSE and LSM mode expansion. The element values of the equivalent circuit for a ridge waveguide step junction is determined from its S-parameters. Computed results of a 17-22 GHz transition agree well with available experimental results. This rigorous approach provides a useful tool for the optimum design of microstrip to air filled waveguide or dielectric filled waveguide transitions. >

Microwave inverse scattering /spl minus/ local shape function imaging for improved resolution of strong scatterers

Abstract: Local shape function imaging uses far-field microwave scattering data to reconstruct the presence or absence of small metal cylinders throughout space, in order to model arbitrary metallic objects. The reconstructed images represent the scattering amplitude at discrete locations in space with multiple scattering effects incorporated. Super-resolution is demonstrated for monochromatic image reconstructions. Even better reconstructions are obtained with multiple frequency data. The speed of computation is increased with a fast forward solver algorithm. Also, measured data is used in the local shape function imaging algorithm and the resolution is improved over diffraction tomography. >

Dielectric measurements using a rational function model

Abstract: A recently proposed rational function model for the aperture admittance of 50 ohm Teflon filled coaxial lines in contact with a homogeneous dielectric is experimentally validated. A calibration technique of the automatic network analyzer utilizing standard terminations and time domain gating is used. Uncertainties in the dielectric properties of reference liquids do not enter the calibration procedure. Experimental results for water and methanol are compared with estimated values. A model expression for the sensitivity of the probe is validated. The sensitivities of two coaxial line probes for the measurements made are determined. Results obtained using the new model are compared with those of other workers. >

Linear fractional curve fitting for measurement of high Q factors

Abstract: A procedure is described for a precision measurement of the unloaded Q factor and of the coupling coefficient for microwave resonators. The complex reflection coefficient data are processed by the linear fractional curve-fitting routine on a personal computer. >

Analysis of rectangular waveguide-gratings for amplifier applications

Abstract: A slow-wave structure composed of a grating inside a rectangular waveguide is analyzed. This type of slow-wave structure is examined for use in a low-voltage amplifier application with a sheet electron beam. Dispersion curves, mode field profiles, and taper designs for the waveguide-grating are presented. The amplifier application places stringent requirements on the taper sections that match the smooth waveguide to the waveguide-grating with minimal reflection. >