COMMUNICATIONS IN NUMERICAL METHODS IN ENGINEERING Commun. Numer. Meth. Engng 2004; 20:489–500 (DOI: 10.1002/cnm.683) Numerical analysis of rectangular microstrip patch over ground plane with rectangular aperture T. Fortaki ∗;† , D. Khedrouche, F. Bouttout and A. Benghalia Electronics Department; University of Constantine; 25000 Constantine; Algeria SUMMARY In this paper, a rigorous full-wave analysis of rectangular microstrip patches over ground planes with rectangular apertures in substrates containing isotropic and anisotropic materials is presented. The dyadic Green’s functions of the problem are eciently determined in the vector Fourier transform domain. The integral equations for the unknown patch current and aperture eld are solved numerically by applying the Galerkin method of moments. The TM set of modes issued from the magnetic wall cavity model are used to expand the unknown current on the patch. Also, the same basis functions are used for approximating the aperture eld in accordance with the concept of complementary electromagnetic structures. The validity of the solution is tested by comparison of the computed results with experimental data. Numerical results show that changes in aperture length can drastically shift the resonant frequency. The aperture width, on the other hand, can be used for a ne adjustment of the operating frequency. Other results also indicate that dielectric anisotropy eect is especially signicant when the size of the aperture is similar to that of the patch. Copyright ? 2004 John Wiley & Sons, Ltd. KEY WORDS: patch; ground plane with aperture; anisotropy; full-wave analysis 1. INTRODUCTION In microstrip antenna designs, it is important to ascertain the resonant frequency of the an- tenna accurately because microstrip antennas have narrow bandwidths and can only operate eectively in the vicinity of the resonant frequency. As such, a theory to help ascertain the resonant frequency is helpful in antenna designs [1]. Numerous advantages have been obtained by feeding a radiating element through an aperture cut into a microstrip line ground plane [2]. Such advantages include weak parasitic radiation in the useful direction with respect to conventionally fed antennas and optimal performance for both the feeding network and antenna element. In addition, the presence of aperture on the ground plane adds new design parameters that can be used to tune the antenna impedance and resonance frequency, without modifying the radiating patch itself. A rectangular coupling aperture introduces two physical parameters—its length and width. Since the presence of ∗ Correspondence to: T. Fortaki, Electronics Department, University of Constantine, 25000 Constantine, Algeria. † E-mail: t.fortaki@caramail.com Received 20 December 2002 Copyright ? 2004 John Wiley & Sons, Ltd. Accepted 27 November 2003