Analog Domain Cancellation in Hybrid Self-Interference Cancellers for In-Band Full-Duplex Radios

Abstract

In this paper, we evaluate two existing analog techniques to combat Self Interference (SI) in single antenna inband full-duplex system, namely RF-tapping technique and Inherent SI Cancellation (SIC) technique. We propose a joint implementation of the two as a potential improvement and compare the performance of these techniques in terms of hardware and computation complexity, and analog SI cancellation (ASIC) performance at 2.41GHz with 20MHz bandwidth (BW). The Two-Tap Fixed-Attenuation Technique was the chosen variant due to its low complexity without sacrificing ASIC performance compared to Adaptive-Attenuation Variants. A Wideband Impedance Mismatched Termination (IMT) circuit was designed to realize Inherent SIC with increased ASIC and BW compared to a previous design, without significantly increasing insertion loss. Finally, the joint implementation, IMT-RF-Tapped ASIC combines the best of low complexity, highly improving ASIC performance and BW at the cost of some increase in complexity and insertion loss.