Time-domain nearfield wideband beamforming based on fractional delay filters

In order to reduce the design burden of the wideband beamforming systems, a method of time-domain nearfield wideband beamforming is proposed in this paper. The proposed method which combines the nearfield compensation method together with fractional delay filters first performs nearfield compensation to the received signals using FIR fractional delay filters, before a time-domain farfield wideband beamformer which could remain unchanged with the source distance, as shown in Fig.1. A design example of a 30-element uniform linear array was given, and the design results show that, the nearfield broadband beampatterns obtained by this method can meet the expected design requirements of low sidelobe level and constant beamwidth, thus ensuring the performance of the time-domain nearfield wideband beamformer. The design example has proved that, this time-domain nearfield wideband beamforming method is a practical and feasible scheme, which can greatly reduce the design complexity of time-domain nearfield wideband beamforming systems.