A Novel Dual-Functionality Beamforming Technique for Next-Generation Integrated Systems

Abstract

This dissertation proposes transmit and receive beamformer design approaches for radar and communication integrated systems. The works are categorized into two topics: (1) Beam Synthesis under Feasible Scenarios for Radar and Communication Combined Systems, and (2) Transmit and Receive Beamforming Based Interference Robust MIMO-OFDM Radar Integrated with Multi-User Communication. In the first topic, I consider a feasible scenario under which all the multiple antennas at the base station are used for joint transmission of radar beams and communications signals. As the global unmanned aerial vehicle (UAV) payload market has become widely popular, the value of UAV is attracting significant interest in its application for radar and communication. However, since the radio spectrum is crowded recently, bandwidth division and utilization problems arise between radar and communication, of which performance depends on the bandwidth. To deal with the radio spectrum shortage problem, radar and communication integrated systems have been proposed in several recent literature. With careful consideration of the 3GPP-based direction channel models, a conventional beam synthesis algorithm is reviewed in joint multiple-user multiple-input-multiple-output (MU-MIMO) communication and MIMO radar sensing. The second topic introduces orthogonal frequency division multiplexing (OFDM)-based radar concept to MIMO radar and MU-MIMO communication integrated systems. Conventional OFDM-based radar systems are sensitive to the Doppler shift, which causes serious degradation in target detection performance. By utilizing beamforming techniques for a UAV’s transmitter and receiver modules, this paper proposes a novel MU-MIMO OFDM radar system to reject intercarrier-interference caused by the Doppler shift and to mitigate the reflected signals from clutter. For transmitter and receiver modules, communication performance is maximized subject to the constraint that the radar’s actual beampatterns match to the radar’s desired beampatterns by the transmit beamforming, and received signals from the direction of departure are processed to remove the impact of Doppler shift while canceling the signal from clutters by the receive beamforming. My proposed scheme significantly enhances the dynamic range and yields improved trade-off between radar and communication performance.