Dual-Polarized Microstrip Patch Planar Array Antennas With Improved Port-to-Port Isolation

A method of preventing the degradation in the isolation between the orthogonal polarization ports caused by beamforming network routing in combined edge/aperture fed dual-polarized microstrip-patch planar array antennas is described. The simulated and measured performance of such planar arrays is demonstrated. Measured port isolations of 50 dB at center frequency, and more than 40 dB over a 4% bandwidth, are achieved. In addition, insight into the physical reasons for the improved port-to-port isolation levels, of the proposed element geometry and beamforming network layout, is obtained through prudent use of the electromagnetic modelling.

I. Introduction

Single-frequency band full-duplex systems sometimes use orthogonal polarizations to isolate transmit (TX) and receive (RX) channels. The isolation between the orthogonally-polarized ports of antennas used in such applications needs to be maximized. Sophisticated transceiver designs are possible whereby knowledge of the transmitted signal can be used to improve this isolation through signal processing performed on the transmitted and received signal. The burden for such circuitry can be made lighter if the port-to-port isolation of the antenna, which is not directly dependent on the far-zone radiation pattern cross-polarization levels, can be made at least 40 dB. Physically separate arrays could be used, but this duplication of hardware is often undesirable for reasons of space and cost.