Han Ho-San, Kim Jung-Jun, Song Tai-Kyong
Department of Electronic Engineering, Sogang University, Seoul, Korea.
Ultrason Imaging. 2009 Apr;31(2):101-19. doi: 10.1177/016173460903100102.
An efficient ultrasound beamforming algorithm based on sigma-delta modulation (SDM) is proposed, which performs dynamic focusing at the Nyquist rate as in conventional delay-sum beamformers. Specifically, a block of consecutive SDM samples for each focal point is selected on each channel according to the focusing delay. The data blocks for all channels are then added up on a bit-to-bit basis and the resulting block of multibit samples is fed to the demodulation filter to produce the focused signal. Since the SDM samples in each data block are not altered at all, the proposed method does not cause any signal distortion. Two hardware structures are also proposed for minimum hardware implementation of the proposed error-free SDM beamforming method. It is verified that compared to the delay-sum beamformer using 10-bit ADCs, the proposed algorithm provides almost the same image quality with a greatly reduced hardware complexity. In addition, it can be implemented with a lower hardware complexity than that of the conventional SDM beamformer when the number of channels is 64 or less.
提出了一种基于sigma-delta调制（SDM）的高效超声波束形成算法，该算法与传统延迟求和波束形成器一样，以奈奎斯特速率进行动态聚焦。具体而言，根据聚焦延迟在每个通道上为每个焦点选择一组连续的SDM样本。然后将所有通道的数据块逐位相加，并将得到的多位样本块馈送到解调滤波器以产生聚焦信号。由于每个数据块中的SDM样本完全不变，因此该方法不会引起任何信号失真。还提出了两种硬件结构，以最小化所提出的无误差SDM波束形成方法的硬件实现。验证结果表明，与使用10位ADC的延迟求和波束形成器相比，该算法在大大降低硬件复杂度的情况下提供了几乎相同的图像质量。此外，当通道数为64或更少时，它可以以比传统SDM波束形成器更低的硬件复杂度来实现。
