Efficient design method of nearfield wideband beamformer for underwater radiated noise measurement

This paper proposes an efficient design method of nearfield constant mainlobe response beamformer (CMRB) for underwater radiated noise measurement, where the impinging of wideband radiated source on the acoustic array is restricted by both the angular region and the range domain conditions of the Fresnel approximation. With the Fresnel approximation, the problem of nearfield wideband beamforming can be readily transformed to a corresponding farfield issue, and the well-established farfield design method of CMRBs can be used. To reduce the design complexity of nearfield wideband beamformer under different focal distances, a set of FIR filters are designed to accurately compensate the fractional propagation delay originated from the curvature term. The representative design examples are presented to demonstrate the encouraging beamforming performance under nearfield condition.