A 10.7-MHz N-Path Fourth-Order Bandpass Sigma-Delta Modulator

High-order high-frequency bandpass sigma-delta modulators are becoming the standard front-end for radio-frequency systems. They allow direct digital demodulation of intermediate frequency signals, thus avoiding tuning of analog demodulators. This paper presents a suitable solution for the design of a fourth-order bandpass sigma-delta modulator. The designed modulator has been implemented in a 1.2-¿m BiCMOS technology and gives 9 bits of resolution for a 42.8 MHz sampling rate over a signal band of 200 kHz.