A Multimode 157 μW 4-Channel 80 dBA-SNDR Speech Recognition Frontend With Direction-of-Arrival Correction Adaptive Beamformer

• Published in: IEEE journal of solid-state circuits Vol. 59; no. 6; pp. 1794 - 1808
• Main Authors: Kang, Taewook, Lee, Seungjong, Song, Seungheun, Haghighat, Mohammad Reza, Flynn, Michael P.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-06-2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adaptive beamforming (ABF); Analog to digital converters; Array signal processing; Beamforming; continuous-time sigma-delta modulator (SDM) analog-to-digital converter (ADC); Delays; Digital signal processing; Direction of arrival; direction-of-arrival (DOA); Direction-of-arrival estimation; Error compensation; Finite impulse response filters; greedy blocking matrix (GBM); Noise reduction; Power consumption; Power demand; Signal to noise ratio; Speech recognition
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2023.3327967

This work introduces a speech recognition frontend system that solves the problems of conventional adaptive beamforming (ABF) with: 1) low digital signal processing (DSP) power consumption (3<inline-formula> <tex-math notation="LaTeX">\times </tex-math></inline-formula> lower than state-of-the-art ABF) thanks to an innovative greedy blocking matrix (GBM) employing simple calculations; 2) automatic direction-of-arrival (DOA) error compensation with direction tracking delay-and-sum beamformer aided by the GBM; 3) a multimode hybrid analog-to-digital converter (ADC) adapts to signal conditions; and 4) multimode beamforming takes advantage of high-signal signal-to-noise ratio (SNR) to reduce total power by 54%. A prototype fabricated in a 40 nm process occupies 0.94 mm2 while consuming 157 and 72 <inline-formula> <tex-math notation="LaTeX">\mu \text{W} </tex-math></inline-formula> in high-power and low-power modes, respectively. The proposed system improves speech recognition accuracy from 54% to 83% under noisy conditions.