A MICROPOWER ANALOG CIRCUIT IMPLEMENTATION OF HIDDEN MARKOV MODEL STATE DECODING

We describe the implementation of a hidden Markov model state decoding system, a component for a wordspotting speech recognition system. The key specification for this state decoder design is microwatt power di ssipation: this requirement led to a continuous-time, analog circuit i mplementation. We describe the tradeoffs inherent in the choice of an analog design and explain the mapping of the discrete-time state decod ing algorithm into the continuous domain. We characterize the operatio n of a ten-word (81-state) state decoder test chip.