Transmit Beamforming for MIMO Dual Functional Radar-Communication With IQI

Multiple-input-multiple-output (MIMO) dual-func- tional radar communication (DFRC) provides a solution to the severe spectrum scarcity challenge. MIMO systems may be prone to the hardware impairments (HWI). Considering I/Q-imbalance (IQI), the most common type of HWI, we study the optimal transmit beamforming design for MIMO DFRC. Both radar-centric and communication-centric scenarios are investigated. For the radar-centric design, the radar beampattern and communciations user signal-to-interference-plus-noise ratio (SINR) with IQI are derived. Then, the radar beampattern is optimized by using the semidefinite relaxation (SDR) method. For the communication-centric design, the achievable rate with IQI is derived. Then, the transmit beamforming is optimized with the constraint on the MIMO radar receive signal-to-noise ratio (SNR). Moreover, the computational complexity is analyzed. Numerical results verify that IQI amplitude mismatch, IQI phase mismatch and the IQI mitigation error can significantly degrade the system ' s overall performance. Also, for the communication-centric scenario, IQI phase mismatch at the CUs is much more important than that at the BS.