The Novel W Parasitic Strip for the Circularly Polarized Microstrip Antennas Design and the Mutual Coupling Reduction Between Them

Abstract

This paper presents a novel W-shaped parasitic strip to design the circularly polarized (CP) simultaneous transmit and receive antennas and reduce the mutual coupling (MC) between them. By disturbing the current fields and inducing the current distribution on the antenna patches, the CP radiation and MC reduction are achieved. The designed CP antennas have 30 MHz 10 dB impedance bandwidth, 16 MHz 3 dB axial ratio bandwidth, and approximate 5.08 dBic peak CP gain. This technique also reduces the MC from -7 to -50 dB when the antennas are placed with a 0.18λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> center-to-center distance and a 0.033λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> edge-to-edge distance, where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength. When achieving the MC reduction, the antenna radiation pattern restores to that of the isolated antenna. Furthermore, the antenna CP gain and efficiency are improved comparing those of the antenna without the parasitic strip or the classic corner cut CP antenna.