| Summary: | With the development of VLSI and wireless communication
technology, portable devices such as personal digital assistants
(PDAs), pocket PCs, and mobile phones have gained a lot of
popularity. Many such devices incorporate a speech recognition
engine, enabling users to interact with the devices using
voice-driven commands and text-to-speech synthesis.
The power consumption of DSP microprocessors has been
consistently decreasing by half about every 18 months, following
Gene's law. The capacity of signal processing, however, is still
significantly constrained by the limited power budget of these
portable devices. In addition, analog-to-digital (A/D) converters
can also limit the signal processing of portable devices. Many
systems require very high-resolution and high-performance A/D
converters, which often consume a large fraction of the limited
power budget of portable devices.
The proposed research develops a low-power audio signal
enhancement system that combines programmable analog signal
processing and traditional digital signal processing. By
utilizing analog signal processing based on floating-gate
transistor technology, the power consumption of the overall
system as well as the complexity of the A/D converters can be
reduced significantly. The system can be used as a front end of
portable devices in which enhancement of audio signal quality
plays a critical role in automatic speech recognition systems on
portable devices. The proposed system performs background audio
noise suppression in a continuous-time domain using analog
computing elements and acoustic echo cancellation in a
discrete-time domain using an FPGA.
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