This Thesis presents a Voice Activity Detection (VAD) system, entirely implemented in the analog domain with a 180-nm CMOS technology. The circuit features a current consumption of 0.9 μA from a 1.8-V supply voltage. The VAD system is composed of three main blocks: a preamplifier, a signal energy computation block, and a VAD decision block. The audio signal coming from the microphone is amplified and filtered by a preamplifier that features a variable gain ranging from −12 dB to +12 dB with 6-dB steps and a bandpass transfer function with poles at 300 Hz and 6.8 kHz. The preamplifier has been implemented both with continuous-time resistors to allow large decoupling capacitors at the input, where the gain is set by the resistance ratio, and with switched resistors to reduce the chip area, where the gain is set by capacitance ratio. The second block of the circuit computes the audio signal energy in the analog domain, exploiting the transistor quadratic current-voltage relation to square the signal and integrating the resulting current with a resettable capacitance. The final block produces the VAD signal. In this block the computed signal energy is used for two different purposes: determine the background noise level and the energy average. The noise level is constantly updated and compared with the averaged energy to provide the VAD signal. The measurement results on an integrated prototype demonstrate that the analog VAD can achieve performances comparable with state-of-the-art digital implementations, but with much lower power consumption.

This Thesis presents a Voice Activity Detection (VAD) system, entirely implemented in the analog domain with a 180-nm CMOS technology. The circuit features a current consumption of 0.9 μA from a 1.8-V supply voltage. The VAD system is composed of three main blocks: a preamplifier, a signal energy computation block, and a VAD decision block. The audio signal coming from the microphone is amplified and filtered by a preamplifier that features a variable gain ranging from −12 dB to +12 dB with 6-dB steps and a bandpass transfer function with poles at 300 Hz and 6.8 kHz. The preamplifier has been implemented both with continuous-time resistors to allow large decoupling capacitors at the input, where the gain is set by the resistance ratio, and with switched resistors to reduce the chip area, where the gain is set by capacitance ratio. The second block of the circuit computes the audio signal energy in the analog domain, exploiting the transistor quadratic current-voltage relation to square the signal and integrating the resulting current with a resettable capacitance. The final block produces the VAD signal. In this block the computed signal energy is used for two different purposes: determine the background noise level and the energy average. The noise level is constantly updated and compared with the averaged energy to provide the VAD signal. The measurement results on an integrated prototype demonstrate that the analog VAD can achieve performances comparable with state-of-the-art digital implementations, but with much lower power consumption.

Analog Voice Activity Detection

CROCE, MARCO
2019-02-14

Abstract

This Thesis presents a Voice Activity Detection (VAD) system, entirely implemented in the analog domain with a 180-nm CMOS technology. The circuit features a current consumption of 0.9 μA from a 1.8-V supply voltage. The VAD system is composed of three main blocks: a preamplifier, a signal energy computation block, and a VAD decision block. The audio signal coming from the microphone is amplified and filtered by a preamplifier that features a variable gain ranging from −12 dB to +12 dB with 6-dB steps and a bandpass transfer function with poles at 300 Hz and 6.8 kHz. The preamplifier has been implemented both with continuous-time resistors to allow large decoupling capacitors at the input, where the gain is set by the resistance ratio, and with switched resistors to reduce the chip area, where the gain is set by capacitance ratio. The second block of the circuit computes the audio signal energy in the analog domain, exploiting the transistor quadratic current-voltage relation to square the signal and integrating the resulting current with a resettable capacitance. The final block produces the VAD signal. In this block the computed signal energy is used for two different purposes: determine the background noise level and the energy average. The noise level is constantly updated and compared with the averaged energy to provide the VAD signal. The measurement results on an integrated prototype demonstrate that the analog VAD can achieve performances comparable with state-of-the-art digital implementations, but with much lower power consumption.
14-feb-2019
This Thesis presents a Voice Activity Detection (VAD) system, entirely implemented in the analog domain with a 180-nm CMOS technology. The circuit features a current consumption of 0.9 μA from a 1.8-V supply voltage. The VAD system is composed of three main blocks: a preamplifier, a signal energy computation block, and a VAD decision block. The audio signal coming from the microphone is amplified and filtered by a preamplifier that features a variable gain ranging from −12 dB to +12 dB with 6-dB steps and a bandpass transfer function with poles at 300 Hz and 6.8 kHz. The preamplifier has been implemented both with continuous-time resistors to allow large decoupling capacitors at the input, where the gain is set by the resistance ratio, and with switched resistors to reduce the chip area, where the gain is set by capacitance ratio. The second block of the circuit computes the audio signal energy in the analog domain, exploiting the transistor quadratic current-voltage relation to square the signal and integrating the resulting current with a resettable capacitance. The final block produces the VAD signal. In this block the computed signal energy is used for two different purposes: determine the background noise level and the energy average. The noise level is constantly updated and compared with the averaged energy to provide the VAD signal. The measurement results on an integrated prototype demonstrate that the analog VAD can achieve performances comparable with state-of-the-art digital implementations, but with much lower power consumption.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11571/1243909
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