High Self-Interference Cancellation Antenna for In-Band Full Duplex Communication System

This paper demonstrates a dual-polarized microstrip patch antenna with high interport isolation for in-band full duplex transceiver. The proposed antenna consists of four port linearly polarized signal radiating elements with differential feedings at input/output ports. The defected ground structure (DGS) under patch has been adopted for enhancement of antenna return loss bandwidth. To achieve high isolation, two identical differential feeding networks using wideband branch-line Balun have been utilized as a self-interference circuit. The analytical design equations have been derived for achieving high isolation in the proposed antenna. For experimental verification, the prototype has been fabricated at the center frequency of 2.5 GHz. The fabricated antenna provides more than 47 dB RF isolation between TX-to-RX port for 100 MHz bandwidth.