Research on circularly polarized small disk coupled square ring microstrip antenna for GPS application

A circularly polarized (CP) small Disk coupled square ring microstrip antenna is presented in this paper. The CP radiation of the presented antenna is achieved by using two disks under the square ring fed by two probes with 90-degree phase shift. The resonant frequency of the antenna is at 1.575GHz, Which is lowered by about 23.4% as compared to that of the normal patch antenna. The axial ratio (AR) of the antenna is lower than 3dB and the maximum gain is more than 3dB at the resonant frequency, and the isolation between the two disks is lower than -18dB during the operating band. The measured results of the fabricated antenna agree well with the simulated results.