Isolation Improvement and Beam Manipulation of Dual-Polarized RIS-Halved Lens Antennas for Compact Transceiver Systems

Abstract

A pair of mirror-symmetrical half-lens antennas separated by two finite back-to-back reactive impedance surfaces (RISs) is proposed to improve the isolation between the transmitting and receiving high-gain dual-polarized antennas for a compact monostatic transceiver system. By introducing the desired surface wave and reducing the interference between the source and its image, the RIS is able to manipulate the deflected boresight beam and suppress the increased sidelobes for TM-polarized waves, while TE-polarized performance is maintained as in the case where a perfect electrical conductor (PEC) is used. The effects of RIS properties and feeder orientation on antenna isolation and far-field performance are discussed and compared with the PEC cases. To validate this method, two identical ${X}$ -band half plano-convex dielectric lenses with a diameter of 237 mm and a thickness of 154 mm integrated with two 32°-rotated feeders and RISs of $479\times258.3$ mm2 with a characteristic impedance of $\text{j}189~\Omega $ are designed as an example. The measured results show that the isolation of >51 and >36 dB over a 10dB return loss bandwidth of 2 GHz is achieved for TE and TM polarization, respectively. Compared to the PEC case, the boresight beam correction reaches 7.5° and the first sidelobe close to the adjacent antenna even vanishes in TM polarization when using the RIS. A boresight gain of 20 dBi/21 dBi at 10 GHz is realized for TE/TM polarization, respectively. Hence, the proposed method is a good option for radar systems requiring compact high-performance transceivers.