Wideband Circularly Polarized Filtering Hybrid Antenna

Abstract

In this paper, a wideband circularly polarized (CP) filtering hybrid antenna is presented. The liquid dielectric resonator (DR) is excited by a microstrip-coupled cross-slot to generate CP radiation. Four inverted L-shaped strips are loaded on the ground plane to introduce an additional CP resonant point, then two adjacent axial ratio (AR) minima are combined to improve the bandwidth of the single-feed CP antenna. By etching a U-shaped slot and loading a C-shaped microstrip stub on the microstrip line, two tunable radiation nulls near the edges of the working band can be obtained without any extra filtering circuits. To verify the design, a filtering CP antenna is designed, fabricated, and tested. Measured results show that the antenna provides wider 3-dB AR and an impedance bandwidth of 38.8% from 1.36 to 2.02 GHz and 39.4% from 1.37 to 2.04 GHz, respectively. The realized gain of the proposed antenna is stable at about 7.8 dBi within the whole working band. A reasonable agreement between measured and simulated results is observed.