Theoretical assessment of a synthetic aperture beamformer for real-time 3-D imaging

Real-time 3-D imaging requires a beamformer that can generate many beams simultaneously. In this paper we evaluate a suitable synthetic aperture beamformer based on a pipelined network of high speed digital signal processors. Using linear interpolation-based beamforming, only a few calculations per pixel are required for each channel and an entire 2-D synthetic aperture image can be formed in the time of one transmit event. Computer simulations of the beamformer were used to assess how sampling rate and amplitude quantization affect the relative levels of secondary lobes in the radiation patterns. The results show that the proposed beamformer and a conventional beamformer using baseband demodulation are equivalent, provided the sampling rate is approximately ten times the center frequency of the transducer.