T.K. Horiuchi and R. Etienne-Cummings
Sonar, change detection, low-power
A time-series processor chip, intended for sonar mapping and novelty detection applications, has been designed, fabricated, and tested. The chip, when coupled with an external sonar bearing estimation unit, receives an image of the sonar environment as a voltage waveform. The bearing of an object is given to the chip by the magnitude of the voltage, and its range is given by the time following the transmission of the sonar “ping". The chip stores this voltage waveform in a bank of sample-and-hold (S/H) elements and compares it to a previously stored trace. Objects (echo returns) that move in either azimuth or range are immediately detected and reported. The chip contains 54 S/H and detector elements that are sequentially triggered by an on-board clock. Operating in the CMOS subthreshold region of operation, the novelty detection chip is designed for ultra-low power and miniature smart surveillance systems. Implemented in a CMOS 0.5 µm process, it consumes less than 20 µW@ 8 Hz repetition rate (and less than 6 µW in a fully quiescent mode) with a 3 V supply, and occupies less than 0.3 sq. mm.
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