A continuous-time delta-sigma modulator for biomedical ultrasound beamformer using digital ELD compensation and FIR feedback

Yi Zhang, Chia-Hung Chen, Tao He, Gabor C. Temes

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

This paper presents the design of a continuous-time ΔΣ modulator (CTDSM) to be used in an ultrasound beamformer for biomedical imaging. To achieve better resolution, the prototype modulator operates at 1.2 GHz. It incorporates a digital excess loop delay (ELD) compensation to replace the active adder in front of the internal quantizer. A digitally controlled reference-switching matrix, combined with the data-weighted averaging (DWA) technique, results in a delay-free feedback path. A multi-bit FIR feedback DAC, along with its compensation path, is used to achieve lower clock jitter sensitivity and better loop filter linearity. The modulator achieves 79.4 dB dynamic range, 77.3 dB SNR, and 74.3 dB SNDR over a 15 MHz signal bandwidth. Fabricated in a 65 nm CMOS process, the core modulator occupies an area of only 0.16 mm2 and dissipates 6.96 mW from a 1 V supply. A 58.6 fJ/conversion-step figure of merit is achieved.

Original languageEnglish
Article number7116629
Pages (from-to)1689-1698
Number of pages10
JournalIEEE Transactions on Circuits and Systems I: Regular Papers
Volume62
Issue number7
DOIs
StatePublished - 1 Jul 2015

Keywords

  • Continuous-time ΔΣ modulator
  • digital excess loop delay compensation
  • FIR feedback DAC
  • ultrasound beamformer

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