A fourth order CMOS band pass filter for PIR sensors

This paper describes a fourth order continuous time band pass filter used to filter analog signals coming from passive infrared sensors (PIR). Specifications for this filter are characterized by an extremely large time constant which strongly condition the topology of the filter used. Moreover, very low power consumption is also required, since these filters are implemented together with the sensor in wireless sensor motes for ambient intelligence applications where power dissipation is a key factor. In this paper a low power and low frequency fourth order CMOS band pass filtering for PIR signal conditioning is presented. Results obtained from simulations of this circuit show the initial validity of the proposed approach.