A third order active RC complex band pass filter for wireless sensor network application

A third order active RC complex band pass filter design for wireless sensor network (WSN) application is presented. The filter is based on leapfrog structure and uses an automatic tuning system to make the RC time constant stable. It is designed in TSMC 0.18 μm CMOS technology. The simulation results show that the filter is centered at 2 MHz with 3 MHz of bandwidth after tuning, the pass band gain of the filter is about -2 dB and the ripple in the pass band is about 0.5 dB. The image rejection ratio (IRR) is about 30 dB around -2 MHz and the adjacent channel rejection (ACR) around 6 MHz is about 30 dB. The precision of the automatic tuning system is within 3%. The filter consumes 3.6 mA under 1.8 V power supply.