Enhanced In-Band Self-Interference Suppression by Combining Bandpass Filter-Based RF Cancellers and Dual-Polarized Antennas

A compact self-interference suppression solution for in-band full duplex (IBFD) is proposed using a tandem of a dual-polarized microstrip patch antenna and a single-branch bandpass filter (BPF)-based RF canceller. Size compactness is achieved through a multilayer vertically-integrated RF hardware solution where the BPF-based RF canceller is placed conveniently underneath the antenna. For proof-of-concept validation purposes, the antenna front-end module was designed, manufactured, and tested between 2–3 GHz. Whereas the dual-polarized antenna element exhibited an average isolation of 35 dB within a 10 dB return-loss bandwidth (BW) between 2.21-2.57GHz (15%), the BPF-based RF canceller improves the antenna isolation by 15–40 dB. As such, the overall antenna-front-end interface module has a 50–75 dB dB isolation within a 20 MHz of BW. The isolation BW can be augmented to 200 MHz (from 2.32-2.52 GHz) by tuning the frequency of the BPF.