Wideband circularly-polarized patch antenna

A novel wideband circularly-polarized patch antenna is presented. First, a new broadband 90 degrees hybrid feed network is proposed to have a bandwidth of 75% for the 10-dB return loss, good two output ports amplitude balance and a consistent 90 degrees (+/- 3 degrees) phase difference between two output ports. Then, a circular patch antenna fed by four sequential-rotation proximity-coupled L-probes orientated to have phase of 0 degrees, 90 degrees, 180 degrees and 270 degrees is presented. The four L-probes are connected to the respective ports of a feed network comprising a pair of the proposed broadband 90 degrees hybrid. It is found that the antenna can deliver a measured impedance bandwidth of 79.4% from 1.04 to 2.41 GHz for SWR < 2, measured 2-dB and 3-dB axial-ratio bandwidths of 57% from 1.3 to 2.35 GHz and 82% from 1 to 2.4 GHz, respectively, and a measured gain bandwidth of 56.1% from 1.26 to 2.32 GHz for gain > 3 dBi. The simulated impedance bandwidth is 94% from 0.9 to 2.5 GHz for SWR < 2. The simulated 3-dB axial-ratio bandwidth is 63.8% from 1.25 to 2.42 GHz. The simulated gain bandwidth is 59.3% from 1.33 to 2.45 GHz for the gain > 3 dBi. Good agreement is observed between simulation and measurement.