Adaptive spatial filtering for interference cancellation between co-site phased arrays

Co-site interference is a well-known problem for scenarios where the antennas of different radio systems are adjacent to each other. Although extensive research has been done for interference cancellation between single-antenna systems, little has been reported for that of phased arrays. We identify that a major challenge of cancelling co-channel interference between phased arrays is that the interference coupling channel is frequency dispersive. The channel dispersion is caused by spatial propagation, radiation near-field coupling, and beamforming at the transmitters and the receivers. To tackle this problem, we propose to apply adaptive filtering in spatial domain, which is enabled by using an antenna array to acquire reference signals from space. The reference array provides multiple degrees of freedom for spatial processing, similar to the delay taps of FIR filters in time-domain processing. The proposed method is evaluated with extensive simulations. The results show that the cancellation ratio can be as high as 75dB with a small reference array size, which highlights the potential of the proposed method.