Eliminiation of frequency shift between axial ratio bandwidth and ‎impedance bandwidth of circular polarized patch antenna‎

Bandwidth of patch antennas has always been a challenge for designers. One of the simplest methods of ‎increasing its bandwidth and gain is to use a thicker patch antenna substrate. Using this method in a truncated ‎circular polarized patch antenna causes a frequency shift between impedance bandwidth and axial ratio ‎bandwidth. In this paper, we were able to compensate this frequency shift by transforming the square truncated ‎patch antenna into a rectangle truncated patch antenna. Using analytical analysis, the factor the main cause of ‎this frequency shift is shown and then its effect compensated. The performance of the proposed method is ‎successfully verfied by applying it to a truncated patch antenna in UHF frequency band designed with air and ‎FR4 substrate. Before applying this method, the total antenna bandwidth namely the common band between the ‎impedance and the axial ratio bandwidth of the antenna is less than 1% while by applying the proposed method, ‎the bandwidth of the antenna is enhanced by about 5%. The manufacture antenna’s measurement results are in ‎good agreement with the simulation results.‎