A Circularly Polarized Patch Antenna with Parasitic Strips

In this paper, a circularly polarized (CP) patch antenna with simple structure, stable in-band performance, and good out-of-band radiation suppression is presented. The radiator of the proposed CP patch antenna is a rectangular patch with four rounded corners. A slot having one circular end and one open end, as well as four T-shaped slots with open end are etched in the radiator to excite two CP resonant modes, leading the desirable 3-dB axial ratio (AR) bandwidth. Using two parasitic strips, a new zeros both for the curve of impedance matching and axial ratio are generated to broaden the -10 dB impedance matching (IB) bandwidth and 3-dB AR bandwidth. The simulated IB bandwidth with S-11 < -10 dB is around 12.1% (3.43 - 3.87 GHz), the simulated 3-dB AR bandwidth is around 9.1% (3.38 - 3.7 GHz), and the in-band gain is larger than 6.0 dB.