Dissertation Defense

High Resolution ADCs for Acoustic Processing and Other Applications

Seungjong Lee

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Acoustic applications usually require high-resolution ADCs to deal with the wide dynamic range of acoustic signals. Furthermore, beamforming is essential for a high accuracy automatic speech recognition system since the acoustic signal is vulnerable to interference. Beamforming offers spatial filtering, effectively enhancing the target signal and suppressing noise, leading to a robust system.

A continuous-time sigma-delta modulator offers high resolution with a good power efficiency. For that reason, this type of ADCs is widely used in acoustic and other applications. Recently, the modulators with noise shaping quantizers take advantage of high quantizer resolution and higher power efficiency.

In this dissertation, we propose two acoustic beamforming feature extraction systems and the continuous-time sigma-delta modulators used in these systems. The ADCs exploit the fast bitstream output to realize a fine resolution delay-and-sum beamformer. Moreover, the second ADC can change its conversion methods, and supports 3 different operating modes. Next, to satisfy a variety of high-resolution and bandwidth demands, a high-performance continuous-time sigma-delta modulator will be proposed. The modulator takes advantage of the high efficiency of a noise-shaping quantizer, and true-time interleaving enables calibration-free high-efficiency architecture.

Chair: Professor Michael P. Flynn