Heterodyning technique to improve performance of delta-sigma-basedbeamformers

摘要

Delta-sigma (ΔΣ) modulators can implement a simplerndigital ultrasound beamformer than can traditional architectures basednon multi-bit analog-to-digital converters (A/D). The signal-to-noisenratio (SNR) of the ΔΣ modulators, however, suffers fromnlimited oversampling ratios. To improve the SNR of each channel, anmixing signal heterodynes narrowband signals to lower frequencies wherenthe baseband ΔΣ modulator performs better. Noise figurenanalyses are presented that illustrate the effectiveness of thisntechnique in improving noise performance. Also, spectral Doppler andncolor flow simulations are presented that realistically emulate a 32nchannel oversampled beamformer and compare these results withntraditional and ideal systems