A 1.2-V CMOS complex bandpass filter with a tunable center frequency

A 4th-order complex bandpass filter (BPF) with a tunable center frequency is designed and fabricated in a 0.13 /spl mu/m 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 /spl mu/Vrms. IIP3 and the image rejection ratio at 1.5 MHz is 25.2 dBm and 52 dB, respectively.