Bandwidth Enhanced Circularly Polarized Fabry–Perot Cavity Antenna Using Metal Strips

This paper introduces a novel single feed wideband Tai Chi-shaped circularly polarized (CP) antenna that utilizes a Fabry-Perot cavity (FPC) with a 3D printed structure to increase the antenna gain and axial ratio (AR) bandwidth. Besides, a novel method is proposed for AR bandwidth enhancement. Some simple metal strips are introduced, which could adjust the phase of the particular electric field component. By placing the metal strips at an optimal position, the AR bandwidth of the antenna could be effectively broadened. Note that this method has little effect on the other antenna performance and it does not require additional structural changes. The proposed method to increase the axial ratio bandwidth is very simple and effective. The Tai Chi-shaped antenna consists of two separate small patches and two suspended metal rods. The two small patches are 180° out-of-phase excited which are centro-symmetrically placed to form a larger and complete circular patch. The two small patches and the total split patch generate two minimum AR points, which substantially broadens the AR bandwidth. Adding two layers of FR4 substrate to the antenna constitutes an FPC, and the antenna peak gain is increased from 9.42 dBic to 14.44 dBic. In addition, the AR bandwidth has been increased from 27.73% to 44.42%. In order to further increase the AR bandwidth of the CP antenna, some simple metal strips have been added to the FPC substrate. The AR bandwidth has been enhanced from 44.42% to 53.46% (4.07 - 7.04 GHz). Compared with other CP antennas with FPC, our proposed antenna shows advantages in terms of substantially broadened impedance and AR bandwidth, high gain, and low fabrication cost.