Digital phased array beamforming using single-bit delta-sigma conversion with non-uniform oversampling

Kozak M., Karaman M.

IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL, vol.48, no.4, pp.922-931, 2001 (SCI-Expanded) identifier identifier


Digital beamforming based on oversampled delta-sigma (Delta Sigma) analog-to-digital (A/D) conversion can reduce the overall cost, size: and power consumption of phased array front-end processing. The signal resampling involved in dynamic Delta Sigma beamforming, however, disrupts synchronization between the modulators and demodulator, causing significant degradation in the signal-to-noise rat-io. As a solution to this, we have explored a new digital beamforming approach based on non-uniform oversampling Delta Sigma A/D conversion. Using this approach, the echo signals received by the transducer array are sampled at time instants determined by the beamforming timing and then digitized by single-bit Delta Sigma A/D conversion prior to the coherent; beam summation. The timing information involves a non-uniform sampling scheme employing different clocks at each array channel. The Delta Sigma coded beamsums obtained by adding the delayed 1-bit coded RF echo signals are then processed through a decimation filter to produce final beamforming outputs. The performance and validity of the proposed beamforming approach are assessed by means of emulations using experimental raw RF data.