A 4th-order complex bandpass filter (BPF) with a tunable center frequency is designed and fabricated in a 0.13 μm CMOS technology. The transfer function is changeable dynamically. The passband center frequency can be set to 0 Hz, 1 MHz, 1.5 MHz and 2 MHz so that the filter can work as a complex BPF in the receiver path and as a LPF in the transmit path. An OpAmp-RC filter is used to obtain a wide dynamic range. The filter operates with the supply voltage as low as 1.2 V. The input referred noise for 1.4 MHz band width is 53 μVrms. IIP3 and the image rejection ratio at 1.5 MHz is 25.2 dBm and 52 dB, respectively.