Planar antenna system for full-duplex applications

Abstract

The effectiveness of using symmetry to cancel radiated fields and improve isolation between the transmitter and receiver of a single-frequency full-duplex patch antenna system is investigated. Orthogonal polarization is used to achieve isolation, and taking advantage of symmetric geometries serves to further reduce field coupling. A U-slotted rectangular patch antenna is designed for wideband operation over the 1.7 GHz–2.2 GHz band, and another patch antenna without a slot is designed at 1.95 GHz for comparison. Using the U-slotted patch as a transmitting element, and both patches as receivers, several configurations are simulated to determine the best isolation between transmit and receive ports. Performance of orthogonally polarized and adjacently placed transmitter and receiver pairs are compared to that of a configuration with two transmitting elements placed symmetrically on either side of a single receiver. It is found that exploiting symmetry in this manner leads to isolation improvement of 6.2 dB using a U-slotted receiver, and 12.0 dB using a receiver without the slot. lnitial investigations indicate that isolation on the order of 60–70 dB may be possible using more complex symmetric geometries.