Wideband Loop Antenna With Electronically Switchable Circular Polarization

This letter presents a novel printed antenna with wide bandwidth, high gain, and reconfigurable circular polarizations. A loop antenna is printed on both sides of a dielectric substrate: A dual-p-i-n-diode loaded loop is printed on one side, while a dual-gap loaded smaller loop is printed on the other side. By controlling the on-off states of the p-i-n diodes, the polarization of the proposed antenna can be switched electronically to right-hand circular polarization (RHCP) or left-hand circular polarization (LHCP) over a wideband frequency range. A prototype is fabricated and measured to verify the performance of the antenna. The measured results indicate that the antenna achieves an impedance bandwidth of over 30%, and a 3-dB axial-ratio (AR) bandwidth of 12.7% and 14.9% for RHCP and LHCP, respectively. The measured gain is around 8 dBic for the LHCP state and 7 dBic for the RHCP state. Due to the advantages of wide overlapped bandwidth, simple feeding structure, and high gain, this antenna is promising for applications in dual-CP wireless communication systems.