A discrete-time charge-domain filter with bandwidth calibration for LTE application

A discrete-time charge-domain filter (CDF) with bandwidth calibration was proposed for LTE application. The CDF, based on feedback gain and delay, could suppress sinc distortion to achieve a like brick-wall filtering. Moreover, CDF with non-decimation and multi-stage topology could overcome the noise-folding issue and save chip area. The measurement showed that CDF performed a >;59dB adjacent channel rejection (ACR), >;85dB stop-band attenuation, and 5-to-26 MHz reconfigurable bandwidth. The chip also possessed 41dB conversion gain under 7mA current from a 1.2V power supply. The chip, including whole CDF and clock circuits, occupies 0.52mm² in 65nm CMOS process.