Abstract: The paper deals with the dynamic analysis of microstrip structures. It is shown that the mixed-potential integral equation for stratified media, which was introduced in a previous publication, provides a rigorous and powerful approach. The Green's functions belonging to the kernel of the integral equation are expressed as Sommerfeld integrals, in which surface wave effects are automatically included. A two-dimensional moment's method using subsectional basis functions has been chosen. Thus, microstrip patches of any shape can be analysed at any frequency and for any substrate. Practical numerical aspects are carefully discussed, and special numerical devices are introduced to reduce computation time without loss of accuracy. Complete results for a rectangular patch and for a slotted patch are given and compared with measured values. Radiation patterns corresponding to the ideal situation of a substrate with infinite transverse dimensions are presented for a rectangular patch.

Abstract: This paper addresses the problem of anisotropy in substrate materials for microwave integrated-circuit applications. It is shown that in modeling the circuit characteristics, a serious error is incurred which becomes larger with increasing frequency when the substrate anisotropy is neglected. Quasi-static, dynamic, and empirical methods employed to obtain the propagation characteristics of microstrip, coplanar waveguides, and slotlines on anisotropic substrates are presented. Numerical solutions such as the method of moments and the transmission-line matrix technique are outlined. The modified Wiener-Hopf, the Fourier series techniques, and the method of lines are also discussed. A critique of the aforementioned methods and suggestions for future research directions are presented. The paper includes new results as well as a review of established methods.

Abstract: Two novel configurations for increasing the impedance bandwidth of the microstrip patch antennas are described. One of these configurations uses two additional resonators which are gap-coupled to the nonradiating edges of a rectangular patch, whereas in the second case, four additional resonators are gap-coupled to the four edges of a rectangular patch. Green's function approach and segmentation method are used for analysis. The experimental results are in reasonable agreement with analysis and impedance bandwidths of 480 MHz and 815 MHz are obtained for the three resonators and five resonators configurations, respectively (in S -band with substrate \epsilon_{r} = 2.55 and thickness = 0.318 cm).

Abstract: A theoretical approach for the representation of microstrip discontinuities by equivalent circuits with frequency-dependent parameters is presented. The model accounts accurately for the substrate presence and associated surface-wave effects, strip finite thickness, and radiation losses. The method can also be applied for the solution of microstrip components in the millimeter frequency range.

Abstract: A variable phase shifter based on the slow-wave effect for operation in the millimeter wave region, comprising a GaAs substrate for mechanical support; an n + doped semiconductor layer disposed on the GaAs substrate for operation as a first ground plane; an n doped semiconductor layer disposed on the n + semiconductor layer with a thickness to permit only one mode at millimeter wave frequencies to propagate, while suppressing higher order millimeter wave modes; and a Schottky metal microstrip with first and second ends disposed on top of the n doped semiconductor layer. Means are provided in the form of ohmic contacts for electrically connecting the n + semiconductor layer to ground electrical potential. These ohmic contacts are disposed on top of the n doped layer, but are provided with a very large surface area contact to the n doped layer in order to significantly reduce the resistance between the ohmic contact and to the n + semiconductor layer. Means are included for providing an electrical bias voltage between the Schottky metal microstrip and the n + doped layer. The propagating phase velocity of millimeter waves propagating along the Schottky metal microstrip can be varied in accordance with the bias voltage to obtain a desired phase shift between the first and second ends of the metal microstrip. In one embodiment, a metallic second ground plane is disposed on the other face of the semiconductor substrate. In a preferred embodiment, the n doped semiconductor layer is approximately 2 microns or less in thickness.

Abstract: : The combination of microstrip and dielectric structures has been found to offer possibilities for improvements upon purely microstrip planar antennas which are limited particularly at millimetre wavelengths by dissipative losses and by radiation from complex feed networks. All the structures considered retain microstrip radiating elements and in the first case a dielectric feed line was used in a travelling-wave array which enabled feeder losses to be reduced. However field compatibility problems with all-dielectric feeder networks caused excessive radiation losses. The same compatibility problems with conventional rectangular waveguide prevent the full potential of this array from being realized but is still preferable to all-dielectric feeder networks. The retention of microstrip feed networks allows much improved integration possibilities and this was realized by combining a microstrip patch with an overlaid dielectric sphere. When combined in the form of parallel connected arrays with a sparse feed network the result is much lower levels of corrupting radiation than have previously been achieved and the provision of space within the aperture for electronic components such as phase shifters.

Abstract: An approach to the analysis of microstrip antennas on cylindrical bodies is presented. The printed radiator is replaced by as assumed surface current distribution, and the fields are solved taking into account the presence of the dielectric layer and the metallic cylinder. Calculation takes place in the Fourier domain. The far field, calculated asymptotically from this solution, is used to get the radiation patterns of the wraparound antenna for any dielectric and the half-wavelength patch for \epsilon_{r} = 1 .

Abstract: Three new configurations for increasing the impedance bandwidth of the microstrip patch antennas are described. In these configurations, additional resonators are directly coupled through short sections of microstrip line to the radiating edges, nonradiating edges, and all the four edges of the rectangular patch antennas, respectively. Green's function approach and segmentation method are used for the analysis. The experimental results are in reasonable agreement with the analysis and impedance bandwidths of 548 MHz, 605 MHz, and 810 MHz are obtained for these three configurations, respectively in S -band (substrate thickness = 0.318 cm and \epsilon_{r} = 2.55 ). The variation in the radiation pattern over this impedance bandwidth is discussed.

Abstract: A general multiple coupled line model compatible with standard CAD programs, such as SPICE, is presented. It is shown that the model can be used to help analyze and design coupled line (e.g., microstrip) circuits with linear, as well as nonlinear/time varying terminations, and to help study the pulse propagation characteristics in high-speed digital circuits.

Abstract: A study of an arbitrarily-shaped planar circuit is reported. The theoretical background is presented and then a numerical method of analysis is introduced. Experiments show good agreement between the theoretical calculations and the measurements. The examples of applications concern stripline circuits but the method may be also applied to waveguides.

Abstract: In a microstrip antenna, the resonant frequency of a particular mode is determined by the shape and size of the conducting patch, the relative permittivity of the substrate and, to some extent, the thickness of the substrate. If the resonant frequency is to be changed, a new antenna is usually needed. Recently, Lee and Dahele have shown that the resonant frequencies of microstrip antennas can be changed by introducing an adjustable airgap between the substrate and the ground plane. In addition to providing a means for tuning the resonant frequencies, the airgap also has the effect of increasing the bandwidth of the antenna. The purpose of the paper is to present a comprehensive report on our research on microstrip antennas with airgaps. First, experimental results obtained by introducing an airgap in (i) circular-discs, (ii) annular-rings and (iii) dual-frequency stacked-disc microstrip antennas are presented. Secondly, the theories that have been developed are described. Thirdly, comparison between theoretical and experimental results is given.

Abstract: The design and experimental measurement of a dual-band, monolithic microstrip antenna is presented. The structure utilises a short-circuited length of microstrip transmission line to provide reactive loading and, thereby, retains the low-profile characteristic of a normal microstrip patch radiator.

Abstract: The planar-circuit approach to the analysis and design of microwave integrated circuits (MIC's), with specific reference to microstrip circuits, is reviewed. The planar approach overcomes the limitations inherent to the more conventional transmission-line approach. As the operating frequency is increased and/or Iow-impedence levels are required, in fact, the transverse dimensions of the circuit elements become comparable with the wavelength and/or the longitudinal dimensions. In such cases, one-dimensional analyses give inaccurate or even erroneous results. The analysis of planar elements is formulated in terms of an N-port circuit and results in a generalized impedance-matrix description. Analysis techniques for simple geometries, such as the resonant mode expansion, and for more complicated planar configurations, such as the segmentation method, are discussed along with planar models for accounting for fringing fields effects and radiation loss.

Abstract: H-shaped and rectangular ring microstrip antennas have been compared with the commonly used rectangular patch antenna. It has been found that the H-shaped patch antenna is smaller in size (about half), and is broadbeam but with narrow bandwidth. On the other hand, for larger bandwidth and/or narrow beamwidth applications a rectangular ring antenna is better than a rectangular patch antenna. Because of size reduction the H-shaped patch looks attractive for UHF applications.

Abstract: A general multiple coupled line model compatible with standard CAD programs, such as SPICE, is presented. It is shown that the model can be used to help analyze and design coupled line (e.g., microstrip) circuits with linear, as well as non-linear/ time varying terminations, and to help study the pulse propagation characteristics in high speed digital and optical circuits.

Abstract: Electrically thick (and hence wideband) microstrip patch antenna elements are difficult to excite without adversely affecting their performance. A novel feeding technique is presented which circumvents the difficulties. A simple design theory is presented and a practical example is described which operates between 11 and 12 GHz.

Abstract: A numerical analysis is presented for a multiconductor transmission line in multilayered Iossy, dielectric regions where the ground plane is of finite extent. The transmission fines are infinitely long and vary in cross section from finite to infinitesimally thin. The Green's function for such a two-dimensional transmission line involves an arbitrary constant. If the ground plane is infinite, the method of images could be used where this constant cancels out. However, in the case of a finite ground plane, the constant has to be evaluated. Here a numerical method is presented where the constant could be eliminated rather than evaluated by imposing the condition for the total charge to be zero. The transmission lines, dielectric regions, and the ground plane can have arbitrary cross sections.

Abstract: A waveguide-to-coax-to-microstrip transition includes a rectangular waveguide portion having a ridged impedance transformer attached to the lower wide wall. The waveguide portion is closed off by a conductive wall through an aperture in which the center conductor of a coaxial transmission-line passes. A ridge extension isolated from all four walls of the rectangular waveguide couples the ridge to the center-conductor of the coax. For broadbanding, a glass plate is located between the ridge extension and the upper wide wall. The strip conductor of a microstrip transmission-line is connected to the center conductor of the coaxial transmission-line. The plane of the dielectric plate of the microstrip may be oriented parallel to the narrow wall of the rectangular waveguide to achieve high packing density.

Abstract: A first planar printed circuit board and a second planar printed circuit board are assembled to intersect each other at right angles to each other. Each board includes a microstrip realization of a drooping dipole antenna. The realization comprises, for each planar board, two vertical parallel feed lines with a radiating element extending from each feed line. Each of the feed lines is fed 90° out of phase with the other feed line on the same board.

Abstract: Several matrix formulations for the microstrip step-discontinuity problem are compared. Although they are theoretically identical, one of them has an advantage in numerical labor, relative, and absolute convergence. Results of this method are checked with other published data and with those independently obtained by the modified residue calculus technique.

Abstract: An integrated superconducting microstrip is shown to be a convenient, flexible, and well-characterized matching element for a super-conductor-insulator- superconductor (S1S) quasi-particle heterodyne mixer. The resonant interaction (Fiske modes) between the Josephson oscillations of a voltage-biased junction and the microstrip provides a convenient method for determining the electrical length of the microstrip line. An open-circuited microstrip stub that reflects a parallel inductance across the junction is used to broaden the bandwidth of the RF match of a 36-40-GHz S1S- mixer. Measurements with Pb-alloy junctions in a full-height waveguide mixer with fixed mechanical tuning give an instantaneous bandwidth of '10 to 15 percent with a mixer noise temperature T /sub M/ (DSB) = 10+- 2.5 K.

Abstract: Equations for the design and analysis of Iossless radial-line stubs are available in the literature. However, when actually fabricated in microstrip or stripline, these stubs possess finite conductor loss. This attenuation must be included if these components are to be properly integrated with other lossy transmission-line elements as part of a microwave computer-aided design program, such as Super-Compact®. New equations for open-circuited radial-line stubs, which include the effects of conductor loss are presented.

Abstract: Several matrix formulations for the microstrip step discontinuity problem are compared. Although they are theoretically identical, one of them has a decided advantage in numerical labor, relative and absolute convergence. Results by this method are checked with other published data and with those independently derived by the modified residue calculus technique.

Abstract: A probe apparatus is provided for on-wafer testing of an electrical circuit, the probe apparatus comprising a base plate formed from an electrically conductive material, the base plate including top and bottom surfaces; a substrate formed from a dielectric material, the substrate including top and bottom surfaces, the top surface of the substrate being electrically connected to the bottom surface of the base plate; at least one microstrip transmission line secured to the bottom surface of the substrate, the microstrip line including a first end and a second end; a coaxial connector including a center conductor in electrical contact with the first end of the microstrip transmission line; and a needle probe electrically connected to the second end of the microstrip transmission line, the needle probe extending in a direction substantially away from the base plate.

Abstract: A high frequency connector for interconnecting a microstrip circuit and an external circuit. That portion of a center conductor which is adjacent to the microstrip circuit is deviated from the axis of the connector and resiliently supported, thereby eliminating an intermediary element for interconnection to promote easy and positive interconnection. The connector is desirably applicable to TEM mode waves lying in the frequency band of 0.3-30 GHz.

Abstract: This paper presents closed-form expressions that model the electrical characteristics of finlines and suspended-substrate microstrip fines over a wide range of structural parameters for millimeter-wave applications. The expressions for finlines are within +-0.8 percent for the cutoff wavelength and within +-2 percent for the phase constant and the characteristic impedance (based on the power-voltage definition for a small slot (d/b <= 0.2)) of spectral-domain results. The expressions for suspended and inverted microstrips me within +-1 percent. The equations are vital to CAD of millimeter-wave planar circuits using these media.

Abstract: Bandwidth enhancement methods for electromagnetically coupled microstrip dipoles are discussed. It is demonstrated that if parasitic metallic strips are incorporated in the structure either co-planar and parallel to the embedded microstrip transmission line open end, or between the transmission line and the microstrip dipole, then substantial bandwidth enhancement results. Experimental verification of this model is introduced for a bandwidth definition based on the frequency range which satisfies a voltage standing-wave ratio (VSWR) \bar{E} - and \bar{H} -plane patterns verify the theoretical model which accounts for radiation from the microstrip dipole, the parasitics, and the transmission line.

Abstract: A transmission line model for microstrip configurations, for which separation of variables is possible, is presented. For this, the patch is modelled as a transmission line joining the radiating apertures. Each section of the transmission line is replaced by a π-network. The effect of apertures in the direction perpendicular to the direction of propagation is included through the complex eigenvalues. The effect of mutual coupling between the radiating edges can be described using variational technique and finally incorporated in the equivalent circuit of the structure. Application of the transmission line method appears to be large. Some patch shapes have been analysed and others indicated.