Analysis of Self-Interference Cancellation and Experimental Results of 2×2 MIMO In-Band Full-Duplex Radio Front-End

This paper presents experimental results of self-interference cancellation of a 2×2 MIMO in-band full-duplex radio front-end. The proposed RF front-end consists of two rat race coupler and four antennas network, where passive suppression is done, and four self-interference reference generator, where active cancellation is done by making identical signal with residual self-interference signal, then subtracting it from received signal. As every antenna, followed by two rat race couplers, is used for transmitting and receiving simultaneously, MIMO antenna network can be constructed maintaining its own passive suppression. Also, a new type of time delay circuit, having high dynamic range of variable time and wideband performance, is used to be fit to arbitrary residual self-interference, after the passive suppression, and achieve wideband self-interference cancellation. Experimental results show 50-dB self-interference cancellation over 90-MHz, centered at 2.53 GHz.