A 650-μW 4-Channel 83-dBA-SNDR Speech Recognition Front-End With Adaptive Beamforming and Feature Extraction

A speech recognition front-end combines a four-channel adaptive beamformer and a 40-feature Mel frequency extractor. The prototype processes the bitstream outputs of third-order delta-sigma modulators with a robust generalized sidelobe canceller (RGSC) for accurate steering. For a given steering vector, the beamformer adaptively places a null in the direction of the noise. Hardware sharing and DSP clock optimization reduce area and power consumption. The prototype is fabricated in 40-nm CMOS and occupies an active area of 0.89 mm
²
. The prototype beamformer improves speech recognition accuracy in noisy conditions from 64% to 90%.