Miniaturized Circularly Polarized Square Slot Antenna With Enhanced Axial-Ratio Bandwidth Using an Antipodal Y-strip

A novel single-fed, wideband, circularly polarized slot antenna is proposed and fabricated. Wideband circular polarization is obtained by introducing an antipodal Y-strip to a square slot antenna. The feedline is a U-shaped microstrip line that provides a wide impedance bandwidth. The overall size of the antenna is only 28 × 28 mm
²
(0.3 λ
_o
× 0.3 λ
_o
). A prototype of the antenna is fabricated and tested. The measured bandwidths for the axial ratio (AR <; 3 dB) and relative impedance (|S
₁₁
| <; -10 dB) are 41.3% (from 4.4 to 6.67 GHz) and 84% (from 3.25 to 8 GHz), respectively, and the antenna has a stable radiation pattern and a gain of greater than 3 dBi over the entire circular polarization frequency band.