SPECTERAL DOMAIN ANALYSIS OF RESONANT CHARACTERISTICS AND RADIATION PATTERNS OF A CIRCULAR DISK AND ANNULAR RING MICROSTRIP ANTENNA ON UNIAXIAL SUBSTRATE

A full-wave analysis for determining the resonantfrequency, quality factor and far-zone radiation patterns of a circulardisk and annular ring microstrip patches, printed on a uniaxialanisotropic substrate is presented. Green's functions of the structureare determined in Hankel transform domain (HTD) using Hertzpotential vectors. Galerkin's method, together with parsval's relationin Hankel transform domain is then applied to compute the resonantfrequency and quality factor. The far-zone radiation patterns areexpressed in terms of Hankel transforms of the tangential ¯elds on thesubstrate. Wave equation is solved in cylindrical coordinates for thestructure to estimate the basis function. The numerical results showthat there are substantial deviations in calculated resonant frequencyand quality factor when substrate dielectric anisotropy is considered.Furthermore, signi¯cant variations are seen in the radiation patterns ofthe structures due to substrate anisotropy. The variations of resonantfrequency, quality factor and radiation patterns of the structure, withrespect to anisotropy ratio of the substrate, for several values ofsubstrate thickness and patch radius are presented.QC 2012031