1-V CMOS similarity measurement chip for binary pattern identification

The design of a new low-voltage similarity measurement circuit is proposed in this paper. The similarity measurement between two binary patterns is represented by Hamming metric, that is, average absolute differential function. Using clock bootstrapped and level shift techniques, the supply voltage of the circuit is reduced to 1 V, which can efficiently operate within a battery supply. Some simple elements such as capacitor array, switch, and exclusive NOR gates are adopted to achieve Hamming metric function. An experimental chip is implemented by using a 0.25 μm CMOS technology. The simulation results show the circuit responds a 21-mV difference for each one-pixel difference between two binary patterns. The patterns have dimension 6 × 4 pixels.