Low cost stacked circular polarized microstrip antenna

A stacked broadband microstrip antenna with circular polarization, composed of two electromagnetically coupled square patches printed on low-loss polypropylene substrate and separated by an air layer, is investigated. Experimental and theoretical results on the input impedance are presented. The bandwidth of the antenna is about 14.4% for a voltage standing-wave ratio of 1.7. The gain in the whole bandwidth is about 9.5 dB. The cross-polar level in both the E and H planes (due to the TM/sub 11/ mode) is better than 20 dB. In circular polarization, an axial ratio of less than 2 dB was measured in the bandwidth in a range of +or-60 degrees around the maximum radiation direction.<>