An implementation of a quadrature charge sampler and a complex bandpass switched-capacitor (SC) filter in 0.8 /spl mu/m BiCMOS applicable to narrowband low-IF receivers is presented. The circuit quadrature downconverts a 49.85-MHz IF input signal to a low IF of 15 kHz by charge-mode subsampling and performs further complex narrowband filtering on the signal. The measured image rejection is more than 44 dB on the 26.3 kHz -3 dB bandwidth.