A High-Isolation Two-Port Planar Antenna System for Communication and Radar Applications

This paper presents a novel approach to achieve a very high level of isolation between the two ports of a compact antenna system for communication and radar applications. Orthogonal polarization and a special symmetric arrangement of two-element arrays of transmitter and receiver antennas are used to achieve high isolation levels. Identical rectangular patch antennas are designed for operation at 6 GHz, and are arranged in a square grid configuration with 90° rotational symmetry in this design. A pair of transmitters and a pair of receivers are fed perfectly out of phase with 180° couplers. The entire system is simulated and fabricated. We measure the prototype antenna's isolation, and use the absolute gain measurement technique and standard far field antenna pattern measurement technique to characterize it's realized gain and radiation pattern. It is found that exploiting symmetry in this manner leads to isolation of 63.7 dB. This indicates that carefully designed and constructed systems could reasonably exhibit isolation on the order of 70 dB or more using this method.