Switched-capacitor filter.

摘要

The passive prefilter (61) is comprised only of a plurality of additional switched capacitors (62) which are added to a switched capacitor (63) common to a switched-capacitor filter (32). The switched capacitor (63) common to said switched-capacitor filter is driven by clock pulses at the sampling frequency of the filter. The prefilter samples and holds the input signal (VSin) at a rate equal to an even harmonic of the sampling frequency, combines all signals held over a sampling period, and provides the filter (32) with this summed signal (Vout). The prefilter reduces substantially any "alias signals", that is input signals (VSin) of a frequency close to the sampling frequency or to an harmonic of the sampling frequency.