Effor-Free Pulse Compression Method for Ultrasound Beamforming using Sigma-Delta Modulation

In this paper, we present a hardware efficient SDM beamformer architecture which introduces no compression errors. In the proposed architecture, the over-sampled I-bit SDM data is correlated with the over-sampled multi-bit transmit waveform. If the over-sampling ratio is OSR and the length of transmit waveform at the Nyquist rate is N, the correlator length would be OSR.N. Since the 1-bit SDM data contains the original transmit waveform and quantization noise pushed out of signal band, the correlator outputs the compressed waveform and the quantization noise correlated with the over-sampled transmit waveform. To filter out, the out-of-band quantization noise in the compression process, the transmit waveform is designed to have a BPF response. Preliminary experimental results show that the proposed architecture provides almost the same SNR compared to when pulse compression is done on each channel in a conventional beamforming system, with greatly reduced hardware complexity.