Showing papers on "Microstrip published in 1990"

Application of the three-dimensional finite-difference time-domain method to the analysis of planar microstrip circuits

Abstract: A direct three-dimensional finite-difference time-domain (FDTD) method is applied to the full-wave analysis of various microstrip structures. The method is shown to be an efficient tool for modeling complicated microstrip circuit components and microstrip antennas. From the time-domain results the input impedance of a line-fed rectangular patch antenna and the frequency-dependent scattering parameters of a low-pass filter and a branch-line coupler are calculated. These circuits were fabricated and the measurements made on them are compared with the FDTD results and shown to be in good agreement. >

Propagation modes and dispersion characteristics of coplanar waveguides

Abstract: The coplanar waveguide (CPW) structure is subdivided into five classes based on substrate thickness, backside metallization, and ground plane width. Radiation and guided modes are studied in each class, and their effects on loss and dispersion are described. For coplanar waveguides, dispersion due to interaction with surface wave parallel-plate modes in the substrate strongly depends on the ground-to-ground spacing (W+2G). If this spacing is small compared to dielectric wavelength and substrate thickness, both dispersion and radiation losses are minimized. In finite ground plane cases, small ground-to-ground spacing compared to substrate thickness is necessary to avoid the excitation of the microstrip mode and to minimize the deviation of the CPW mode from the odd mode of the ideal line. Limitations on the reduction of (W+2G) come from conductor loss, which imposes a minimum width requirement on the center conductor. If substrate thickness is to be kept large compared with this dimension, it is inevitable that, at high frequencies, the operation of the CPW will not be below the cutoff frequency of surface wave modes. However, the interaction of the CPW mode with surface wave modes is negligible for integrated circuit applications when ground-to-ground spacing is small compared with dielectric wavelength. >

Full-wave analysis of conductor losses on MMIC transmission lines

Abstract: A mode-matching analysis of lossy planar transmission lines is presented. This method uses a modified mode-matching technique developed for travelling-wave FET analysis. The metallic layers are treated in the same way as the remaining waveguide subregions, with each of them characterized by its complex dielectric constant. This leads to a fully self-consistent description of the conductor losses. In contrast to the usual perturbation methods, it includes metallic loss by a self-consistent description without any skin-effect approximation. The analysis holds for arbitrarily high losses and also for metallization dimensions smaller than the skin depth. The approach is validated by comparison with previous experimental and theoretical work. Monolithic microwave integrated circuit (MMIC) microstrip and coplanar lines are investigated. The variation in propagation characteristics for typical metallization thickness is studied and the consequences with regard to MMIC design are discussed. For the coplanar waveguides (CPWs) significant deviations compared to the conventional assumption of lossless zero-thickness strips are found. >

Microwave Engineering Using Microstrip Circuits

Abstract: Transmission line theory two-port parameters microstrip transmission lines - basic theory microstrip transmission lines - further considerations discontinuities the Smith chart and its uses hybrid-line couplers parallel-coupled lines and directional couplers filters miscellaneous components active circuit characterization microstrip circuits and subsystems microstrip experiments.

Modeling and simulation of interconnection delays and crosstalks in high-speed integrated circuits

Abstract: A computer model for n parallel microstrip lines is developed for circuit simulation. This model for the lossy transmission line system can be readily implemented into circuit simulators and can accurately simulate the delay and crosstalk effects of interconnects in high-speed integrated circuits. Modal analysis is applied to decouple the n-coupled-line system into n independent lines, and the characteristic solutions of telegraph equations are represented by a set of simple time-varying equivalent circuits. The model has been implemented in a general-purpose circuit simulator, iSMILE, which is compatible with SPICE. Simulation results on propagation delay times and crosstalk are presented for high-speed GaAs HEMT (high-electron-mobility transistor) integrated circuits. >

Radiation from cylindrical leaky waves

Abstract: Formulas are derived for the far-infrared radiation pattern of cylindrical leaky waves propagating on a planar surface. The formulas can be used to predict the radiation pattern of a general class of leaky-wave antennas, consisting of a finite-size source which excites a radially propagating leaky wave on some planar surface. Leaky-wave antennas consisting of antenna elements embedded in dielectric layers (microstrip elements) fall into this category. Using the equivalence principle, formulas are derived for both transverse electric (TE) and transverse magnetic (TM) leaky waves with arbitrary propagation constants. The formulas allow for radiation from cylindrical apertures of arbitrary size, so that the effect of truncating the supporting planar surface with an absorbing material can be determined. Particular attention is devoted to the case of a leaky wave for which the real and imaginary parts of the complex propagation constant are equal, since this type of wave has been shown to be responsible for broadside radiation in certain leaky-wave antennas comprised of dielectric layers. >

Input impedance and radiation pattern of cylindrical-rectangular and wraparound microstrip antennas

Abstract: The radiation from a cylindrical microstrip antenna excited by a probe is analyzed. Both the cylindrical-rectangular and the wraparound elements are discussed. The current distribution on the patch is rigorously formulated using a cylindrically stratified medium approach. A set of vector integral equations is derived which governs the current distribution on the patch. The set of equations is then solved using a moment method. The input impedance and the radiation pattern are derived both exactly and in the small substrate thickness limit. >

Oscillator design and computer simulation

Abstract: This second edition of the number one guide to oscillator design presents a comprehensive, unified approach to oscillator design that can be used with a wide range of active devices and resonator types. Resonator types covered include: L-C, crystal, SAW, dielectric resonator, coaxial line, stripline and microstrip. This text covers modern CAD synthesis and analysis techniques and is valuable to experienced engineers as well as to those new to oscillator design. The books topics include: Analysis fundamentals, oscillator fundamentals, limiting and starting, biasing, noise, computer simulation and examples and case studies.

Equivalent capacitances of coplanar waveguide discontinuities and interdigitated capacitors using a three-dimensional finite difference method

Abstract: Equivalent capacitances of coplanar waveguide discontinuities on multilayered substrates are calculated using a three-dimensional finite-different method. The application of the method is demonstrated for open ends and gaps in microstrip and coplanar waveguides, as well as for more complicated structures such as interdigitated capacitors. The main advantage of the method is its flexibility in treating multilayered substrates and different conductor configurations. It can therefore be applied to more complicated structures such as interdigitated capacitors, air bridges, and waveguide transitions. The effect of conductor metallization thickness and shielding walls is also taken into account. Good agreement between the calculated data and measurements up to 25 GHz in the case of coplanar structures indicates the validity of the static analysis even for high frequencies. >

Electromagnetic scattering and radiation from finite microstrip structures

Abstract: Two techniques are presented for the analysis of electromagnetic radiation and scattering from finite microstrip structures. The two techniques are based on two different formulations, viz. the volume-surface and surface-surface formulations. In the volume-surface formulation the finite-sized dielectric is replaced by an equivalent volume polarization current whereas the conducting plates are replaced by equivalent surface currents. For the surface-surface formulation the surface covering the dielectric volume is replaced by equivalent electric and magnetic currents and the conducting plates by surface electric currents. Both techniques can be utilized for the analysis of arbitrarily shaped finite microstrip structures. The techniques are quite accurate, and they are utilized to validate each other. Typical numerical results are presented to demonstrate the agreement between these two solution techniques. >

The current distribution and AC resistance of a microstrip structure

Abstract: The AC resistance of the strip in a microstrip structure is compared with that of an isolated strip for better understanding of the conductor loss mechanism. An analysis is presented of the AC resistance in a microstrip structure for any metallization thickness by deriving the current distribution over the strip cross section. The analysis uses the separation of variables technique and the Green's function method. It shows that the skin current of the strip is concentrated toward the ground plane in a microstrip structure. In the extreme case, the AC resistance of the strip can be twice as high as the AC resistance of the same isolated strip. The imperfect ground plane also adds to the total conductor loss of a microstrip line. For a wide strip over a lossy ground plane at high frequency, the ground plane surface current distribution is concentrated directly under the strip, and the ground plane AC resistance can be as large as the strip AC resistance. Therefore, the total AC resistance at the microstrip line can be four times as high as that of an isolated strip conductor. >

High speed CMOS driver circuit

Abstract: A high-speed CMOS driver circuit which compensates for the intervening transmission line effects resulting from the existence of a printed circuit board, or a ceramic or silicon substrate between the coupled CMOS devices, thus preventing significant signal degradation. Several techniques are employed to increase circuit speed. Firstly, P-channel and N-channel output drivers are sized so that the characteristics impedance of each of the devices matches the characteristic impedance of its associated transmission line (whether it be on a printed circuit board or on a ceramic or silicon substrate). A printed circuit board transmission line may be of either the microstrip or stripline variety. Secondly, since P-channel and N-channel output drivers must be capable of delivering relatively high current, it is therefore highly desirable to eliminate or greatly reduce any crowbar current that could flow during the brief transition state when both N-channel and P-channel devices are on. Several preferred circuit designs are identified for the reduction or elimination of this crowbar current.

Design considerations for low sidelobe microstrip arrays

Abstract: The factors affecting the realizable sidelobe performance of microstrip arrays are discussed and quantified. These include excitation amplitude and phase accuracies, mutual coupling, diffraction effects, positioning errors, and errors due to imperfect element matching and feed network isolation. It is shown that low-sidelobe microstrip arrays require a very tight tolerance on the resonant frequencies of the elements, and the elimination of spurious radiation from the feed network. Cross-polarization and surface wave effects are discussed. An experimental 16-element microstrip array prototype incorporated these considerations into the design, and achieved a -35 dB relative sidelobe level. >

A rigorous dispersive characterization of microstrip cross and T junctions

Abstract: A full-wave spectral-domain analysis is applied to the characterization of multiport microstrip discontinuities. This method uses the moment method to find the currents in the microstrip circuits and subsequently the scattering parameters of the junctions. In this approach, all the physical effects are considered, including radiation and surface waves. The numerical results for a T- and a cross-junction are presented and agree well with the quasi-static values at low frequencies. The S-parameters of a T-junction are further compared with the measured results, with excellent agreement. The utilization of a shaped T-junction as a broadband equal-power divider is also discussed. >

Comments on "A new model for calculating the input impedance of coax-fed circular microstrip antennas with and without air gaps" [with reply]

Abstract: For original paper by Abboud et al. see IEEE Trans. Antennas Propagat., vol.38, p.1882-5 (1990). In the original paper, the resonance frequency of coax-fed circular microstrip antennas with and without air gaps has been modeled (in its Section III) by incorporating and rearranging some results previously reported by others. The present author, while working with the formulas of that Section III noticed a discrepancy in (8) and (9). This has been investigated thoroughly and the observations are presented. A brief reply is given by Damiano et al.

An integral equation approach to the analysis of finite microstrip antennas: volume/surface formulation

Abstract: An E-field integral equation for the analysis of finite printed circuit antennas with multiple dielectric regions is developed. In this analysis, the ground plane is considered to be finite. The dielectric substrates may be either lossless or lossy, and they may be inhomogeneous but must be finite. The equivalence principle is used to replace all conducting bodies by equivalent surface electric currents and all dielectrics by equivalent volume polarization currents. The respective boundary conditions on the dielectrics and the conductors are utilized to solve for the electric current on the entire structure. Typical results are presented to illustrate the potential of this method. >

Multilayer MMIC using a 3 mu m*3-layer dielectric film structure

Abstract: Very small multilayer MMICs (monolithic microwave integrated circuits) using miniature microstrip lines on a thin dielectric film are described Their configuration, loss characteristic, and dielectric materials (silicon oxynitride and polyinide) are discussed Other effective thin-film transmission lines, line crossovers, and vertical connections are also discussed Multiport Wilkinson dividers, 90 degrees and 180 degrees hybrids, and distributed amplifiers are implemented in an area of less than 1 mm/sup 2/ >

Radiation and scattering from structures involving finite-size dielectric regions

Abstract: A full-wave approach is presented for calculating the scattered fields produced by structures that involve finite-size dielectric regions. The dielectric is first approximated by an array of interlocking thin-wall sections; the electric field boundary conditions are then applied through the use of appropriate surface impedances. Rooftop basis functions, chosen to represent the surface current, are appropriately placed on the thin-wall sections in such a way as to accurately represent the polarization current while preventing fictitious charge within the dielectric. Rooftop currents are also used to represent the current on any conductor that may be present. The matrix elements are calculated, depending upon the distance between the source and field locations, through a scheme that employs Taylor series expansions and point source approximations. The technique is applied to scattering from dielectric cubes and composite dielectric-conductor structures, and to radiation from microstrip structures. Numerical convergence and agreement with the literature are demonstrated. >

A monolithic or hybrid broadband compensated balun

Abstract: A compact microstrip balun structure, capable of multioctave performance, has been devised for monolithic or hybrid circuit applications. The structure requires no suspended substrate techniques and can be designed to occupy only a small amount of circuit area, thus allowing it to be easily integrated with a variety of monolithic circuit designs such as mixers, multipliers, and class B push-pull amplifiers. If a matching network is incorporated with the balun structure, a 10:1 operational bandwidth can be achieved. >

Method of packaging microwave semiconductor components and integrated circuits

Abstract: Integration and packaging of monolithic microwave integrated circuits (MMIC) components is facilitated by using a motherboard comprising high resistivity silicon, which having a thermal conductivity three times that of gallium arsenide. Ultra high purity, uncompensated silicon preferably is used. Anisotropic etching of recesses in the motherboard facilitates precise placement of the MMICs in the recesses, enabling use of automated die and wire bonding techniques to reduce required assembly time substantially. Using a silicon motherboard also ultimately enables incorporation of required control circuitry. The silicon motherboard also transmits RF energy well, a useful characteristic particularly in C-band and X-band applications in which microstrip is used, though other transmission media function well at even higher frequencies.

Resonant frequency of a rectangular microstrip patch on several uniaxial substrates

Abstract: A full-wave analysis for determining the resonant frequency of a rectangular microstrip patch on multiple uniaxial anisotropic layers with or without an anisotropic overlay is presented. Two independent methods are used to derive the immittance matrix for the patch, from which the resonant frequency is determined. They are the Hertz vector potentials and the modified spectral domain immittance approach. Numerical results of the resonant frequency are given for several patch configurations, including cases of a patch on a single anisotropic layer, a patch on a double layer with one layer anisotropic and one layer isotropic, a suspended patch resonator with anisotropic substrate, a patch with anisotropic overlay and a patch on two anisotropic substrates with an anisotropic overlay. Changes in the resonant frequency of up to 58% are reported as n/sub x//n/sub y/ is changed from 1.0 (for isotropic substrates) to 2.0. >

An asymptotic closed-form microstrip surface Green's function for the efficient moment method analysis of mutual coupling in microstrip antennas

Abstract: A relatively simple closed-form asymptotic representation for the single-layer microstrip dyadic surface Green's function is developed. The large parameter in this asymptotic development is proportional to the lateral separation between the source and field points along the air-dielectric interface. This asymptotic solution remains surprisingly accurate even for very small (a few tenths of a free-space wavelength) lateral separation of the source and field points. Thus, using the present asymptotic approximation of the Green's function can lead to a very efficient moment method (MM) solution for the currents on an array of microstrip antenna patches and feed lines. Numerical results based on the efficient MM analysis using the present closed-form asymptotic approximation to the microstrip surface Green's function are given for the mutual coupling between a pair of printed dipoles on a single-layer grounded dielectric slab. The accuracy of the latter calculation is confirmed by comparison with numerical results based on a MM analysis which employs an exact integral representation for the microstrip Green's function. >

Accurate design of microstrip directional couplers with capacitive compensation

Abstract: An accurate design is presented for microstrip directional couplers with high directivity using capacitive compensation. The method utilizes symmetry analysis and equivalency principals to develop closed-form solutions of the compensating capacitance and a new odd mode characteristics impedance necessary to realize an ideal microstrip directional coupler. The design approach is valid for any degree of coupling, thereby overcoming limitations of previous approaches to this design concept. >

Analysis of stacked microstrip patches with a mixed potential integral equation

Abstract: A method based on the mixed potential integral equation for the analysis of flat microstrip antennas in a double-layer substrate is presented. The method is used to compute the input impedance of a stacked patch configuration. This structure permits a larger bandwidth and may also provide dual-frequency operation. The Green's functions are discussed in detail, and numerical results are obtained for the propagation constant of the dominant surface wave. Theoretical and experimental results are compared for a dual-frequency and a broadband stacked patch antenna. Theoretical results for the input impedance are in good agreement with measurements. The difference between theoretical and experimental results for the resonant frequency is less than 4.5% in all cases. >

On slot-coupled microstrip antennas and their applications to CP operation-theory and experiment

Abstract: A simple theory based on the cavity model is developed to analyze microstrip antennas excited by a slot in the ground plane. By using an equivalent magnetic current source at the feed, the electric field under the patch is obtained in terms of a set of cavity modes. In particular, the loci of the slot feed location for achieving the circular polarization and the input impedance are computed and found to be in excellent agreement with the experimentally measured results. Simple but surprisingly accurate formulas for slot-fed circularly polarized microstrip antennas are derived and compared with those for probe-fed counterparts. >

Magnetostatic-forward-volume-wave-based guided-wave magneto-optic Bragg cells and applications to communications and signal processing

Abstract: Realization of magnetostatic forward volume wave (MSFVW)-based guided-wave magneto-optic (MO) Bragg cells and their applications to communications and signal processing are reported. Bragg diffraction of guided-optical waves from the MSFVW in a noncollinear coplanar geometry is analyzed. The design of microstrip line transducers that facilitate wideband MO Bragg diffraction with electronically tunable microwave carrier frequencies (2.0 to 12.0 GHz) are briefly discussed. Experimental results obtained with the resulting Bragg cells in both pure and bismuth-doped yttrium-iron-garnet (YIG) waveguides and a comparison to the theoretical predictions are presented. Applications of the Bragg cells to light beam modulation, scanning/switching, and RF spectral analysis are presented in detail. >

Guidelines for design of electromagnetically coupled microstrip patch antennas on two-layer substrates

Abstract: Graphical guidelines for design of electromagnetically coupled square and circular microstrip antennas are given. Substrates composed of two different dielectric layers are considered. The analysis is extended to electrically thick substrates. Given the required resonant frequency and the bandwidth, material parameters are selected. Patch dimension and the optimal position of the feed line are obtained from the provided graphs. The design data were computed by applying the method of moments in the spectral domain to solve the integral equation for the currents on the patch and portion of the microstrip feed line. The integral equation was formulated using the appropriate dyadic Green function for the grounded multilayered slab. >

Capacitance of a strip capacitor

Abstract: The boundary element method (BEM) is used to calculate the capacitance of a strip capacitor which includes the edge effect, and an empirical formula is derived for the capacitance. The empirical formula can be applied to the capacitance of microstrip lines by using a method of electric images. The capacitance values of microstrip lines calculated by the formula agree well with results of other analytical expressions and with measured data. >

Response of a planar microstrip line excited by an external electromagnetic field

Abstract: The voltages and currents induced by external electromagnetic fields on a planar microstrip line have been studied with the use of a distributed-source transmission-line model. The frequency response of the microstrip line has been analyzed by simulating the illuminating field with a plane wave arbitrarily incident on the line. The influence of the microstrip geometrical and electrical characteristics on the voltages and currents induced on the line has been examined, and indications for reducing the circuit susceptibility have been obtained. The model adopted can be used for studying the response of the line to any type of external field arbitrarily varying in space time. Numerical results show that for lines loaded with the characteristic impedance at both terminals, voltage amplitudes on the order of some millivolts and currents of some hundreds of microamperes can be induced at f=3 GHz by an incident plane wave with an electric-field intensity of 1 V/m and for various angles of incidence. The voltages and currents induced on a microstrip circuit can be reduced by using substrates of sufficiently high permittivity. >

Experimental Investigation of Dual-Mode Microstrip Ring Resonators

Abstract: The general behavior of microstrip ring resonators has been known for some time. In particular, the possibility of exciting two degenerate resonances on a single ring has already been established. In the technical literature, however, one can not find (to the authors knowledge) a complete and detailed description of actual microwave filters implemented by explicitly using the dual-mode nature of the microstrip ring. In this paper we present computer simulations and measured results describing a dual-mode filter cell implemented by using a single microstrip ring resonator. The microstrip dual-mode filter presented allows the implementation of two transmission poles and two transmission zeros using only one dual-mode ring resonator. This result is of particular interest because it has already been demonstrated experimentally that a similar behavior can be also obtained with circular-waveguide resonators. The presence or the absence of the transmission zeros is explained in simple terms. In addition, a procedure is presented to predict the position in frequency of the transmission zeros.