New procedure for design of microstrip patch antennas using method of moments

This paper will investigate and discuss the design of microstrip patch antennas, using the theoretical method developed by Abd-Alhameed and Excell (1996). The method is capable of accurately predicting currents, impedance and resonant frequency for any arbitrary surface patch antenna. The patch can be fed either by a microstrip transmission line contacting an edge of the patch, or by a coaxial probe extending through the ground plane and contacting the patch. The surface-patch dipole modes are used to model the microstrip patch. The patch surface is modelled by rectangular and triangular patches, while the strips, corresponding to their dominant current, are modelled by the same surface patches or by segments which include the discontinuity at the edges. The losses that are considered for the microstrip patch antenna, based on the surface patch model, are calculated by applying a similar method to that used for the thin wire antenna. A finite size model of the dielectric substrate is assumed. The moment method solution for the dielectric geometry is implemented by using rectangular volume cells. The method can be used for any arbitrary field distribution within the dielectric, but for the case of a microstrip antenna on a thin substrate it is sufficient to use only the dominant field component, normal to the ground plane. This approximation is also extended to the fringing fields, since this saves computing time and gives adequate results. Various copper patches have been tested experimentally. The results of the measurement are in good agreement with the computed ones