A Simple Wideband Circularly Polarized Inductor-End Cross-Slot Antenna with Flat Gain

A novel compact wideband circularly polarized (CP) cross-slot antenna (CSA) with flat gain is presented in this paper. The antenna consists of a cross slot with distributed inductor endings, a pair of distributed inductors and a pair of distributed capacitors, and a simple short-ended microstrip feeding line. The two slots are placed in orthogonal positions with the same dimension to generate two orthogonal E-fields, while the 90° phase difference between the two E-fields is achieved by adjusting the distributed capacitors and inductors in the middle, resulting in a wideband CP performance. Simulation results show that the antenna has a wide impedance bandwidth (IMBW) of 2.1-4.0 GHz (63.3%) for S11 < -10 dB and axial ratio bandwidth (ARBW) of 2.3-3.6 GHz (43.3%) for AR < 3 dB. Stable radiation gain is observed across the operating band with a very flat gain at about 2.8 ± 0.2 dBi.