Moment method analysis of an aperture coupled microstrip antenna with multilayer superstrate

Microstrip patch antennas are often required to operate in non-homogeneous layered structured. The ideal feed of system for this type of antenna is an aperture coupled arrangement which required no physical contact between the antenna and feed. The microstrip feedline on the lower surface of the bottom substrate is coupled electromagnetically through a small aperture in the ground plane to the patch on the upper surface of the upper substrate. This paper presents a moment method analysis of this structure to determine the input impedance and far field radiation pattern. Results are in good agreement with measured results