Digital beamforming using non-uniform oversampling delta-sigma conversion

A promising approach to reduce the complexity of the front-end hardware of an ultrasound imaging system is to utilize oversampling Delta-Sigma (ΔΣ) beamforming. Realization of dynamic receive focusing involves signal resampling of uniformly sampled radio frequency (RF) signals using beamforming timing. The resampling (deleting or repeating samples), however, causes a significant increase in the noise floor of the beamformer output. To overcome this problem, the authors have explored a new digital beamformer employing non-uniform oversampling. To avoid resampling during dynamic focusing, they have used a different sampling clock at each channel to sample RF echo signals non-uniformly at the time instants associated with receive focal points. The performance and validity of the new system are assessed by means of emulations using experimental 3.5 MHz RF data