Electric surface current model for the analysis of microstrip antennas with application to rectangular elements

An approach to the analysis of microstrip antennas which is applicable also to relatively thick substrates using the relevant Green´s function is presented. The Green´s function is derived and closed form expressions for various antenna characteristics which explicitly take into account the presence of the dielectric material are obtained in terms of the electric surface current density. For rectangular microstrip elements near resonance the current distribution is approximated using lossless transmission line analysis, thus enabling the complete evaluation of the characteristics of the element near resonance. The results obtained in this approach for the radiation resistance, surface wave resistance, radiation pattern, directivity, and bandwidth are presented in a detailed set of graphs for a representative set of parameters.