RF/Analog self-interference canceller for 2×2 MIMO full-duplex transceiver

Abstract

This paper presents a compact, highly-linear RF/Analog self-interference canceller (SIC) for a 2×2 MIMO full-duplex (FD) transceiver to suppress the existing strong selfinterference (SI) at the receiver input in order to prevent the receiver from saturation. Linearity requirements of RF/Analog SIC, as well as corresponding variable attenuator and delay/phase module, are derived and a RF/Analog SIC with good linearity for high power transmission is proposed. A prototype with compact size is fabricated on a multilayer PCB for a 2×2 MIMO inband FD transceiver, and is implemented with highly-linear, custom-made tunable attenuator and delay/phase-shift module to suppress nonlinear distortion. The measurement results in anechoic-chamber reveal that this RF/Analog SIC prototype integrated with a dual-polarized antenna can provide over 80dB cancellation for +30dBm and 20MHz OFDM signal centered at 2.27GHz. Typical 34dBm OIP3 of the prototype is measured. The simulation with following digital canceller reveals a negligible SNR degradation of 0.3dB due to the nonlinear distortion of this prototype.