Effects of ground plane size on a square microstrip patch antenna designed on a low-permittivity substrate with an air gap

The effects of ground plane size on the characteristics of a square microstrip patch antenna designed on a low-permittivity substrate with an air gap were investigated. The characteristics studied include return loss, gain, half-power beamwidth (HPBW), and radiation pattern. The gain and HPBW varied periodically with increasing ground plane size, and were out of phase with each other. The relationship of the above parameters with the height of the antenna was also considered. Decreasing the antenna height changed the smallest ground plane size for impedance matching, and also reduced back radiation, which improved the front-to-back level of the microstrip patch antenna.