Design of 2 MHz CMOS Gm-C Complex BPF with Automatic Tuning for WSN Node

Abstract

A fourth-order complex band-pass continuous-time filter with automatic tuning for a WSN transceiver is presented. The active transconductance-capacitor (Gm-C) filter was chosen for low power consumption and designed by series of two two-order filter units. The two-order filter is achieved with the source follower structure, which could get the image rejection as large as possible under the lowest power consumption. The center frequency and bandwidth deviation due to the process corner, aging and temperature deviation are adjusted by an automatic frequency tuning circuit. The core of the filter in a 0.18 μm RF CMOS technology consumes about 0.27 mA current from a 1.8 V power supply. The simulation results show that the bandwidth is about 2.2 MHz and the center frequency is about 2 MHz with automatic frequency tuning. The voltage gain of filter is about −0.8 dB, the ripple in the pass band is lower than 0.1 dB, and the image rejection ratio is larger than 30 dB at −2 MHz.