A Simple Structure Dual-Band Dual-Circularly Polarized Antenna With Controlled Frequency Ratio

This paper proposes a dual-band dual-circularly polarized (CP) aperture-coupled patch antenna with controlled frequency ratio. By simply etching a modified S-shaped slot at the central of a circular patch, dual-band dual-CP operation is realized. In addition, the frequency ratio of the two CP bands can be controlled by optimizing the length parameters of the S-shaped slot arms. As a result, the frequency ratio can be tuned from 1.12 to 1.46 according to different requirements. For demonstration, the circularly polarized patch antenna operating at 3.42 and 3.85 GHz is manufactured and tested. The measured 3-dB axial-ratio (AR) bandwidth is 1.1% and 2.3% for the right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP), respectively. The measured gains at the lower and upper bands are 9.4 and 9.8 dBic, respectively.