A 5th-order switched-capacitor complex filter for low-IF narrowband wireless receivers

A 5th-order switched-capacitor (SC) complex filter is implemented in 0.2-µm CMOS technology. In order to reduce the die size and current consumption of the complex filter, a novel SC integrator is developed. The filter is centered at 24.8 kHz with bandwidth of 20.2 kHz. The Image channel is attenuated by more than 40 dB. The in-band 3rd order harmonic input intercept point (IIP3) is 15 dBm and the in-band output noise is 70 µVrms. The complex filter consumes 350 µA with a 2.0-V power supply. The die size of the fabricated filter is 0.578 mm2. Owing to the proposed SC integrator, the fabricated filter achieved 27% reduction in die size without any characteristic degradation, including noise performance, compared to the conventional equivalent.