A Very Low Voltage 9th Order Linear Phase Baseband Switched Capacitor Filter (RESEARCH NOTE)

Abstract

A very low voltage 9th order linear phase baseband switched capacitor (SC) filter has been designed to be used as part of a cellular GSM (Global System Mobile) receiver. A Gaussian-to-6dB filter of the order of seven is chosen and a second order function is added to reduce the group delay variations around. The filter uses a fully differential topology to increase the dynamic range and reduce the clock feed-through noise and the distortion due to low voltage amplifier. Using a chopper stabilization technique in opamp design reduces the flicker noise. In order to reduce the charge injection two methods of delayed clock phases and dummy switches are used. The filter is realized by cascading the biquad sections. The filter has been designed in a 0.35μm CMOS technology and simulated with Hspice using BSIM 3V3 model. The filter operates at 2MHz sampling frequency and 1MHz chopping frequency with a corner frequency of 100KHz and 7mW power consumption.