Sigma-Delta Receive Beamformer Based on Cascaded Reconstruction for Ultrasound Imaging Application

A pre-delay reconstruction sigma-delta beamformer (SDBF) was recently proposed to achieve higher level of integration in ultrasound imaging system. Nevertheless, the high order reconstruction filter used in each channel of SDBF makes the beamformer highly complex. The beamformer can be simplified by reconstructing the signal after the delay-and-sum process with only one filter. However, this post-delay reconstruction-based design degrades image quality when dynamic focusing is performed. This paper shows that employing simple pre-delay filter is sufficient to achieve similar performance as conventional pre-delay reconstruction SDBF, as long as the pre-delay filter provides the required pre-delay signal-to-quantization noise ratio (SQNR). Based on this finding, we proposed a cascaded reconstruction beamformer which utilizes a boxcar filter as the pre-delay filter in each channel. Simulations using real phantom data demonstrate that the proposed beamforming method can achieve a contrast resolution comparable to that of the pre-delay reconstruction beamforming method. Besides, the hardware can also be greatly simplified compared to the pre-delay reconstruction beamformers.