Multiport network model for dual feed gap-coupled square microstrip antennas for circular polarisation

In this paper, Multiport Network (MN) Model has been developed to analyze dual feed planar gap-coupled square microstrip antennas for circularly polarization. Several planar square MSA configurations have been proposed to increase both the axial ratio and impedance bandwidths with higher directivity. Only the one square patch is fed at the two orthogonal points with equal amplitude and 90/spl deg/ phase difference and others are parasitically coupled. In MN model, the dimensions of the patch are extended outwards to account for the fringing fields and the impedance matrix of the square microstrip antenna (SMSA) is obtained from its Green´s function. The segmentation method is used to obtain the input impedance of the SMSA.