Showing papers on "Microstrip published in 1988"

Position-sensitive detector with microstrip anode for electron multiplication with gases☆

Abstract: A position-sensitive detector of a new type has been developed. A microstrip anode replaces the wires generally used for electron multiplication with gases. The microstrips which are fixed on a glass substrate are produced by means of photolithography. The applied electric potential alternates between each strip. With a position-sensitive neutron detector equipped with this new type of anode a counting rate of 2.3 MHz/cm 2 has been measured. The microstrip anode combines the improved qualities of a proportional counter with certain properties of a photomultiplier tube.

Time-domain finite difference approach to the calculation of the frequency-dependent characteristics of microstrip discontinuities

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. >

Comparison of three methods for the measurement of printed antenna efficiency

Abstract: Three methods for the measurement of antenna efficiency are evaluated: (1) the Wheeler cap method, (2) the radiometric method, and (3) the directivity/gain method. Each of these methods was used to measure the efficiency of four different printed antennas (three microstrip patches with various feeds, and an eight-element series-fed microstrip array). These methods and the experimental results which were obtained are discussed. >

Microstrip/slotline transitions: modeling and experimental investigation

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. >

Microstrip transmission line excitation of dielectric resonator antennas

Abstract: A systematic investigation of the excitation of a cylindrical dielectric resonator antenna was undertaken to illustrate the possibility of such a feed structure and to characterise the coupling behaviour and radiation patterns of the system.

CAD models of lumped elements on GaAs up to 18 GHz

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. >

Calculations of the dispersive characteristics of microstrips by the time-domain finite difference method

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. >

Conductor-backed slot line and coplanar waveguide: dangers and full-wave analyses

Abstract: Despite the many attractive features of conductor-backed slotline and coplanar waveguide, there are potential problems that are introduced by the use of conductor backing. These potential problems include leakage of power into surface waves or into the dielectric region between the plates, unexpected crosstalk, significant alteration of the guide wavelength, and unexpected or unwanted coupling to neighboring lines. Two theoretical approaches are presented, one purely numerical and the other in network form and analytical in nature, that agree well with each other and with measurements in a special case. They provide a quantitative description of these potential surprises when the line conductors are either infinite or finite in width. >

Waveguide-to-microstrip transitions for millimeter-wave applications

Abstract: Design and test data are presented for waveguide-to-microstrip probe transitions that cover millimeter-wave frequencies from 26 to 110 GHz. The broadband design provides a good transition for full-waveguide bandwidth (40%). Because of the compact structure, the measured insertion loss contributed by the transition is less than 0.1 dB in Ka-band, less than 0.2 dB in Q-band and V-band, and less than 0.35 dB in W-band. These transitions are useful for the device and circuit characterisation of millimeter-wave MICs and MMICs. >

Magnetic tuning of a microstrip antenna on a ferrite substrate

Abstract: The operating frequency of a microstrip antenna on a ferrite substrate can be tuned by varying the DC magnetic bias field applied to the ferrite. The letter reports experimental work where a 40% tuning range has been obtained, with usable patterns and return loss over this band.

Quasi-static analysis of a microstrip via through a hole in a ground plane

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. >

Microstrip phase scan antenna array

Abstract: A microstrip phase scan antenna array is provided having a columnar array microstrip radiating patches mounted on a dielectric substrate. Each column of the array is fed by a separate variable, reciprocal ferrite rod phase shifter which is mounted on the substrate and is coupled to the column which it controls and to a source of millimeter wave energy by microstrip to dielectric waveguide transitions. Each of the phase shifters is controlled by a helical biasing coil surrounding the ferrite rod. All of the biasing coils are serially interconnected by a single scanning control drive wire and the numbers of turns of the coils are related to each other by an arithmetic progression in which the number of turns of a particular biasing coil differs from the number of turns of the adjacent biasing coil in the sequence of biasing coils controlling the array by a constant amount.

Comparison between computed and measured bandwidth of quarter-wave microstrip radiators

Abstract: A simple theory based on a cavity model is used to analyze a quarter-wavelength flat element, without a dielectric substrate, which is connected to the ground plane in one of its sides by a metallic wall. The bandwidth of the element is computed from this model. Very good agreement is obtained between the computed and the measured bandwidth for elements in the S-band. >

Coplanar corporate feed effects in microstrip patch array design

Abstract: The use of coplanar corporate feeds for microstrip patch arrays leads to constructional simplicity, but also to performance degradations due to feed radiation, in addition to limitations due to feed resistive loss, surface waves, mutual coupling and tolerances. These effects are quantified, and this allows specification of array performance limitations in addition to the recommendation of the use of smooth feed discontinuities, high line impedance, and thin substrates. Improvements due to the use of alternate feed geometries, such as sequentially rotated feeding and subarraying, are also quantified and are shown to be substantial.

Resonance frequency of a rectangular microstrip patch

Abstract: The microstrip-patch resonant frequency problem is formulated in terms of an integral equation using vector Fourier transforms. Using Galerkins's method in solving the integral equation, the resonant frequency of the microstrip patch is studied with both Chebyshev polynomials and sinusoidal functions as basis functions. In the case of the Chebyshev polynomials, the edge singularity is included, but it is not important for convergence. Furthermore, the resonant frequency of the microstrip patch is ascertained with a perturbation calculation. The results for Galerkin's method and experiments are in good agreement. The perturbation calculation agrees asymptotically with Galerkin's method. With the aim of developing a computer-aided design formula, the solutions obtained by Galerkin's method are interpolated with a three-variable polynomial. >

Two-port higher mode circular microstrip antennas

Abstract: For circular microstrip antennas, single-mode design techniques work well for the dominant mode (n=1, where n is the azimuthal dependence of the fields in the antenna), but this is not the case for zero-order (n=0) and higher order (n>1) modes, where a modal expansion is necessary. The design of higher order dominant mode circular microstrip antennas is addressed, with an example and measurements for the n=3 case. Measurements for the n=3 modes show reasonable agreement with theory in the forms of the impedance loci, but the frequency dependence is in error by the order of the bandwidth of the antenna. A design example is given for a roof-mounted circular patch for vehicular communications. The example indicates that an n=3 dominant mode patch can be used as a two-port antenna for diversity applications or with a 90 degrees phase shifter and adder as a single-port antenna for omnidirectional coverage with (essentially) circular polarization. >

Notch antenna with microstrip feed

Abstract: The subject invention provides an improved conformal antenna array assembly having a strip conductor, a ground plane separated from and lying parallel to said strip conductor, said ground plane having a slot therein, said slot extending transverse to said strip conductor, a conductive planar element positioned across said slot and orthogonal to said ground plane, said conductive planar element having curved surfaces extending upwardly and outwardly from said slot. The strip conductor or microstrip and the slot-containing ground plane are separated by a dielectric material.

Analysis of arbitrarily shaped two-dimensional microwave circuits by finite-difference time-domain method

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. >

High performance parallel coupled microstrip filters

Abstract: A construction technique is described that allows microstrip parallel-coupled filters to have greater passband symmetry while largely removing the parasitic passband at twice the center frequency. The filter design extends the odd mode phase length by allowing the coupled lines to overlap with lines outside the resonator proper, i.e. the coupling gap of the resonator is extended out onto the 50- Omega lines. The even-mode length has been set by the distance between the 50- Omega lines. Thus, the reference plane for the even mode has been moved into the resonator. This configuration makes the odd-mode length longer than the even mode and thus compensates for the phase velocity difference between modes. >

Simple model for the input impedance of coax-fed rectangular microstrip patch antenna for CAD

Abstract: We present a simple model for the input impedance of a rectangular microstrip patch antenna. This model is well suited for computer aided design (CAD). It is based on classical methods: (a) the cavity model determining the frequency and the input resistance at resonance, (b) the dynamic permittivity of a rectangular microstrip patch antenna (to take into account the influence of the fringing field at the edges of the rectangular patch antenna) and (c) the resonant parallel RLC circuit with an inductive reactance. This model is valid for electrically thick substrates. The theoretical results are in good agreement with experimental data.

Slot-coupled directional couplers between double-sided substrate microstrip lines and their applications

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. >

New slot-coupled directional couplers between double-sided substrate microstrip lines, and their applications

Abstract: A slot-coupled directional coupler between two microstrip lines that couples through a rectangular slot in the common ground plane has been proposed and fabricated for the 1.5-GHz band. The design method and the experimental results for this directional coupler are described, as well as its application to a planar multiport directional coupler (MDC). The measured 3-dB coupling results agreed well with the calculated results, as do the experimental results for a four-port MDC. A planar MDC configuration consisting of a combination of slot-coupled directional couplers has also been proposed. >

The transfinite element method for modeling MMIC devices

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. >

A generalized method for analyzing shielded thin microstrip discontinuities

Abstract: An integral equation method for the accurate full-wave analysis of shielded thin microstrip discontinuities is described. The integral equation is derived by applying the reciprocity theorem and then solved by the method of moments. In this derivation, a coaxial aperture is modeled with an equivalent magnetic current and is used as the excitation mechanism for generating the microstrip currents. Computational aspects of the method have been explored extensively. A summary of some of the more interesting conclusions is included. >

Design rules for microstrip capacitance

Abstract: A variety of published models relating the geometry and material properties to capacitance for microstrip geometry are reviewed. A combination of H.A. Wheeler's (1977) and M.V. Schneider's (1969) models is found to agree with previously published data as well as new data presented here to better than 3%. The combination is presented in a form suitable for use in a spreadsheet. In addition to being useful for computer simulation of specific designs, the composite model can yield some useful insight to add to the intuition of fabrication and design engineers. >

Active radiating element using FET source integrated with microstrip patch antenna

Abstract: An FET source has been integrated with a microstrip patch antenna to form an active radiating module. The patch antenna serves both as a radiating element and a resonator in the feedback loop for the FET oscillator. Power output of 17mW was achieved at 5.7 GHz.

Analysis of microstrip circuits using three-dimensional full-wave electromagnetic field analysis in the time domain

Abstract: In this method, the circuit is excited by a raised cosine pulse source that includes broadened frequency components. The frequency characteristics are then computed from the Fourier transform of the output transient responses. To evaluate the validity and capability of the method, a side-coupled microstrip filter is analyzed and the frequency characteristics are calculated. A quasistatic analysis of this filter is also presented and the results compared with measurements. The frequency characteristics calculated with the full-wave analysis in the time domain show excellent agreement with the measured values, thus demonstrating the validity and the power of the analytical method. >

High speed III-V electrooptic waveguide modulators at lambda -1.3 mu m

Abstract: Traveling wave GaAs electrooptic waveguide modulators at a wavelength of 1.3 mu m with bandwidth in excess of 20 GHz have been developed and characterized. The design and characteristics of both p-i-n modulators in microstrip configuration and Schottky barrier on n/sup -/-GaAs/semi-insulating (SI) GaAs in the coplanar strip configuration modulators are discussed. It is shown that microwave loss and slowing on n/sup +/ GaAs substrates will limit the bandwidth of the microstrip modulator to less than 10 GHz for a device 8 mm in length. Modulators with bandwidths in excess of 10 GHz are fabricated on SI GaAs substrates. >

Aperture coupled circular polarization antenna

Abstract: A generally planar antenna for generating circularly polarized electromagnetic signals, particularly useful at microwave frequencies. Each antenna element comprises a single excitation aperture (7) cut in a planar conductive ground plane (9). Spaced apart from the ground plane (9) by means of a dielectric layer (11) and covering the excitation aperture (7) is a planar conductive radiating patch (5) having slightly different dimensions along each of two orthogonal axes. The radiating patch (5) may have the shape of a near square or an ellipse. Exciting the aperture (7) with linearly polarized electromagnetic energy causes the radiating patch (5) to generate a circularly polarized electromagnetic signal consisting of two orthogonal components that have substantially the same amplitude and are 90° offset in phase from each other. Several antenna elements can be combined to form a large aperture array. Energy may be applied to the excitation aperture (7) by means of a waveguide (3) feed, microstrip line (15), or stripline (15).

The transfinite element method for modeling MMIC devices

Abstract: A numerical procedure called the transfinite-element method is used in conjunction with the planar waveguide model to analyze monolithic microwave integrated circuit (MMIC) devices. By using analytic basis functions together with finite-element approximation functions in a variational technique, the transfinite-element method can be used to determine the fields and scattering parameters for a wide variety of stripline and microstrip devices. >