Robust Transmit Beamforming for Self-Interference Cancellation in STAR Phased Array Systems

In simultaneous transmit and receive (STAR) phased array systems, suffering from the multi-dimensional cross-coupling strong self-interference (SI), the radio frequency (RF) front-end of receive array is severely saturated. Against this issue, we present a transmit beamforming (TxBF) SI cancellation (SIC) design to construct the TxBF vector, where a robust TxBF SIC optimization problem with maximum receive power constraints and a worst-case uncertainty channel error model is formulated, the approximation solution of which is solved by the semidefinite relaxation and S-procedure. Simulation results show that our design effectively avoids the RF front-end saturation at the cost of near-minimum beamforming gain loss within a given uncertainty channel error bound.