Compact Circularly-Polarized Slot Antenna with Enhanced Impedance and Axial-Ratio Bandwidths

Abstract

This paper proposes a compact circularly-polarized slot antenna with enhanced impedance and axial-ratio bandwidths. To substantially increase the axial-ratio bandwidth, the microstrip feedline is asymmetrically placed underneath the slot and several metal stubs are protruded from slot perimeter to introduce proper current distribution along two orthogonal directions. The antenna prototype achieves the measured 10-dB impedance bandwidth, the 3-dB axial-ratio bandwidth, and the peak gain of 120.8%, 95%, and 4.33 dBic, respectively. This antenna has a compact size of 0.315 lambda(0) x0.315 lambda(0) x0.02 lambda(0) at the lowest operating frequency.