Switched-capacitor bandpass decimator for high-frequency narrowband channel filtering and downconversion

A subsampled two-stage switched-capacitor (SC) narrowband bandpass decimator is proposed to simultaneously implement the functions of frequency downconversion and narrowband filtering. In order to downconvert a 25 kHz bandwidth signal from 21.4 MHz down to 455 KHz, as required in many radio receivers, the proposed structure comprises a multinotch FIR decimator section followed by a 6th order bandpass IIR decimator section. Since no external components are required, the proposed structure is adequate for co-integration with baseband digitization and signal processing circuitry in CMOS technology.