Design of a wideband high gain antenna using FSS for circularly polarized applications

This paper presents a high gain, wideband circularly polarized (CP) antenna. High gain of the antenna is achieved by employing an FSS as a reflector. The antenna is a coplanar waveguide (CPW) fed structure with a modified L-shaped radiating patch. The unit element of the FSS is formed by connecting two modified dipoles at an angle 90°. The FSS array is made from unit elements of varying size such that the bigger size elements are at the center while smaller are at the edges. After application of the reflector, the antenna and FSS dimensions are further optimized to get maximum impedance bandwidth and axial ratio bandwidth (ARBW) simultaneously. Also the FSS array is made defected by etching out two elements of the array to maintain the ARBW. The antenna with reflector has a measured impedance bandwidth of 74.3% (2.2-4.8 GHz) and a 3-dB ARBW of 62% (2.2-4.18 GHz). The measured boresight gain of the proposed antenna is increased by around 3-4 dB after applying FSS in the CP operation band. The radiation patterns of the antenna with the FSS are also measured and compared with simulated patterns. The various aspects of effect of FSS on CP antenna performance are also discussed.