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Analysis of the Distortion Mechanism in Delta-Sigma Beamforming. | LitMetric

Analysis of the Distortion Mechanism in Delta-Sigma Beamforming.

IEEE Trans Ultrason Ferroelectr Freq Control

Published: September 2016

AI Article Synopsis

  • Dynamic receive beamforming using a Delta-Sigma modulator's low-resolution output faces an increased noise floor, which makes it ineffective.
  • The paper investigates the reasons for this noise increase, identifying that it's due to aliasing of quantization noise linked to specific frequency ranges.
  • The authors propose a new architecture that combines a cascaded integrator-comb filter with an insert zero compensation technique, demonstrating through simulations that it effectively reduces noise and is cost-efficient compared to other methods.

Article Abstract

Dynamic receive beamforming on a Delta-Sigma modulator's low-resolution output bit-stream suffers from a severely increased noise floor, rendering the promising method infeasible. This paper addresses the mechanism behind the increased noise floor. By using multirate theory and bifrequency analysis, we show that the increased noise floor is caused by aliasing/imaging of the powerful quantization noise from specific frequency regions according to the focus depth. We analyze both the conventional delay-and-sum method and the previously proposed insert zero compensation method. For the latter technique, we show that the alias/image bands have the first-order suppression because of a zero at the origin. This finding leads to the proposal of an architecture combining a cascaded integrator-comb filter with the insert zero compensation method. Backed by simulations of beamformed Delta-Sigma modulated sequences and point spread functions, we compare this architecture to different compensation methods and the ideal Delta-Sigma beamformer. The proposed technique is shown to have low implementation cost and achieve levels of dynamic range comparable to those of the ideal Delta-Sigma beamformer.

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Source
http://dx.doi.org/10.1109/TUFFC.2016.2582779DOI Listing

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