A conformal spherical-circular microstrip antenna: Axisymmetric excitation by an electric dipole

Abstract

ABSTRACT: A mathematically accurate method of analysis of a spheri - cal-disk antenna conformally printed on a dielectric-co ¤ ered metallicsphere is presented. The antenna is fed by a radial coaxial probesimulated by an electric dipole. The solution consists of reducing theboundary- ¤ alue problem to the dual-series equations, and further to aregularized infinite-matrix equation. This procedure is based on theanalytical in ¤ ersion of the static part of the problem of a disk in freespace, and results in a stable and fast algorithm with a guaranteedcon ¤ ergence. Numerical data on the basic antenna characteristics arepresented. Q 2000 John Wiley & Sons, Inc. Microwave Opt TechnolLett 26: 176]182, 2000. Key words: spherical disk; conformal antenna; dual-series equations;analytical regularization; directi ¤ ity 1. INTRODUCTION Metallic circular disks printed on dielectric substrates areused frequently in patch antenna technology. Conformalprinted antennas are necessary in automotive and airbornecommunications and radar due to their low profile and lightweight. In this paper, the problem of modeling of aspherical-disk conformal printed antenna is considered as-suming an excitation by a coaxial probe. The probe is mod-eled by a radial electric dipole RED located at the surface.of the metal sphere covered with dielectric. From a theoreti-cal point of view, such a geometry is a canonical one for awide class of conformal patch antennas. Previously, similarproblems have been analyzed by direct applications of themethod of moments 1, 2 . However, convergence of thesewxnumerical approximations is not uniformly guaranteed, espe-cially if narrow resonances are present 3 . Patch antennaswxare essentially resonant devices; hence, this must be kept inmind when developing an accurate simulation software. Wepropose an exact mathematical method based on the analyti-cal inversion of the free-space static problem for a sphericaldisk 4, 5 that has been used previously in the analysis ofwxcavity-backed apertures and reflector antennas 6wx]8 . Thismethod belongs to the broad family of techniques collectivelycalled the method of analytical regularization 9 that arewxremarkable for stable and fast numerical solutions.