Subthreshold FIR filter architecture for ultra low power applications

Subthreshold design has been proposed as an effective technique for designing signal processing circuits needed in wireless sensor nodes powered by sources with limited energy. In this paper we propose a subthreshold FIR architecture which brings the benefits of reduced leakage energy, reduced minimum energy point, reduced operating voltage and increased operating frequency when compared with recently reported subthreshold designs. We shall demonstrate this through the design of a 9-tap FIR filter operating at 220 mV with operational frequency of 126 kHz/sample consuming 168.3 nW or 1,33 pJoules/sample. Furthermore, the area overhead of the proposed method is less than that of the transverse structure often employed in subthreshold filter designs. For example, a 9-tap filter based on transverse structure has 5* higher area than the filter designed using our proposed method