Joint Equalization and Fractional Delay Filter Design for Wideband Digital Beamforming

In wideband digital array radars (DARs), channel equalization and fractional delay (FD) are needed for digital beamforming (DBF) since they can compensate the amplitude and phase imbalance between each channel as well as the aperture effect. Traditionally, the compensations were usually implemented separately via different finite impulse response (FIR) filters based on different design criterions. In this paper, equalization and FD are realized jointly in one FIR filter based on the Farrow structure that provides a general polynomial approximation. The presented filter provides satisfactory compensation performance for both the channel mismatch and the aperture effect with low complexity. Simulation results have confirmed the correctness and effectiveness of the joint filter design, showing that it's suitable for wideband DBF applications.