A Dual-Band and Dual-Circularly-Polarized Array Antenna with a Single Element

A dual-band and dual-circularly-polarized (CP) array antenna is presented to achieve the wide axial ratio (AR) bandwidths. The TM
₁₀
and TM
₀₁
modes of a dual-fed linearly polarized element are used to obtain the dual-frequency simultaneously. Sequential rotation technique with proper phase arrangement is used to achieve the dual-CP radiations. This antenna can radiate with left hand circular polarization (LHCP) in the lower band and right hand circular polarization (RHCP) in the higher band at the same time. Due to the single element on a single-layer substrate, the array antenna can be fabricated easily with less cost. This antenna has been investigated numerically and experimentally. Simulated results show that the -10-dB return loss bandwidths are 21.0% (8.6-10.6 GHz) and 12.5% (11.2-12.7 GHz) in the lower band centered at 9.5 GHz and higher band centered at 12 GHz, respectively. The 3-dB AR bandwidths in the low- and high-band are 8.4% (8.8-9.6 GHz) and 7.5% (11.8-12.7 GHz) respectively.