Transmit–Receive Duplexing Using Digital Beamforming System to Cancel Self-Interference

A near-field cancellation duplexing system is demonstrated using multiple coordinated transceivers with symmetrically arranged antenna elements and a digital backend for baseband waveform phase and amplitude weighting controls. By adapting weights of multiple transmit elements, coupled interference at receiver elements deconstructively interferes, providing up to 50 dB of additional isolation over the coupling of a single transmitter to a receiving element. Bandwidth considerations of the array are presented. It is shown that uncorrelated transmit noise from multiple transmitters can be removed through tunable filtering or through adaptive beamforming of multiple receiving elements, both providing an additional 30-40 dB of interference reduction that is tunable over the frequency range of the system.