Mixed-potential Integral Equation Approach Research Articles

Edge feeding of microstrip ring antennas

We have achieved 50 /spl Omega/ input impedance for edge-fed narrow microstrip square-ring antennas by using the circumferential variation of current on the ring. The reference point for the current distribution has been fixed by loading the ring. The antenna has been modeled as a lossy transmission line to determine the variation of resonant frequency and input impedance with load. This model has been validated using the mixed potential integral equation approach. The agreement between the two approaches is found to be good. The concept and the model used here can be applied to any type of ring antenna including loop antennas.

Modeling DC power-bus structures with vertical discontinuities using a circuit extraction approach based on a mixed-potential integral equation

The DC power-bus is a critical aspect in high-speed digital circuit designs. A circuit extraction approach based on a mixed-potential integral equation is presented herein to model arbitrary multilayer power-bus structures with vertical discontinuities that include decoupling capacitor interconnects. Green's functions in a stratified medium are used and the problem is formulated using a mixed-potential integral equation approach. The final matrix equation is not solved, rather, an equivalent circuit model is extracted from the first-principles formulation. Agreement between modeling and measurements is good, and the utility of the approach is demonstrated for DC power-bus design.

A quasi-one-dimensional integration technique for the analysis of planar microstrip circuits via MPIE/MoM

The mixed-potential integral-equation approach, using spatial-domain closed-form Green's functions, and discretized with the method-of-moments, is a state-of-the-art method for the analysis of planar microstrip circuits. One of its most time-demanding tasks is the evaluation of the impedance matrix terms, which typically requires the numerical computation of two-dimensional integrals. A method based on suitable changes of coordinates and domains is introduced in this paper in order to reduce such integrals to a quasi-one-dimensional numerical integration, with a substantial enhancement in the efficiency of the analysis, without affecting the accuracy of the approach. Results are given demonstrating, for practical accuracy values, an improvement of typically one order of magnitude in simulation times.

RCS Computation of Coax-Loaded Microstrip Patch Antennas of Arbitrary Shape

Abstract A space-domain mixed-potential integral equation approach is applied in conjunction with the method of moments to compute the radar cross-section (RCS) of coax-loaded microslrip patch antennas having arbitrary or irregular shapes. The effects of Lhe substrate—which may be electrically thick and may consist of any number of planar, possibly uniaxially anisotropic dielectric layers, backed by a ground plane—are rigorously incorporated in the analysis by means of the vector and scalar potential Green's functions. The latter are expressed in terms of the voltages and currents on transmission line analogs of the layered medium, associated with TM and TE partial fields. The current distribution on the microstrip patch is approximated using vector basis functions defined over triangular elements and the coax probe current is expanded in terms of piecewise-lincar subdomain basis functions. A simple probe-to-patch attachment mode, compatible with the triangular element model of the microstrip patch, is used to enforce current continuity at the junction, and the coax aperture is modeled by a magnetic enrrent frill. The far zone fields are found by the stationary phase method, and are expressed in terms of the Fourier-transformed basis functions and the transmission line voltages and currents evaluated at the stationary phase point value of the transverse wavenumber. Computed RCS results are presented for several loaded and unloaded microstrip patch antennas of various shapes and are shown to be in agreement with published measured data and with computed results obtained by specialized techniques, which—unlike the method presented here—are not easily extendable to arbitrary shapes.

Analysis of Coaxially Fed Microstrip Antennas of Arbitrary Shape with Thick Substrates

Arbitrarily shaped, coax-fed microstrip patch antennas with substrates that may be electrically thick are studied using a mixed-potential integral equation approach. Vector basis functions defined over triangular elements are used to approximate the current distribution on the conducting patch. Rigorous and simplified models of the probe-to-patch junction, compatible with the triangular element model of the microstrip patch, are implemented and their relative merits are discussed. Two models of the coaxial probe, differing in accuracy and complexity, are also implemented and their ranges of validity are examined. Input impedance data for several microstrip patch antennas of different shapes, computed using different coax feed models, are presented and compared with measured results.

Analysis of arbitrarily shaped coax-fed microstrip antennas with thick substrates

Arbitrarily shaped, coax-fed microstrip patch antennas with thick substrates are studied using a mixed-potential integral equation approach. This incorporates a triangle-element model of the patch and a rigorous treatment of the probe-to-patch junction. Computed input impedance data are shown to agree well with measured results.