Decimation for bandpass sigma-delta analog-to-digital conversion

The authors explain their view of ΣΔ modulation and use this understanding to develop bandpass ΣΔ from lowpass ΣΔ. The problem of narrow bandpass filtering and decimation of a bit stream is examined. It is shown that with the proposed scheme the digital filter is only marginally more complex than in the low-pass case. The scheme does filtering and translation to baseband, thus simultaneously accomplishing channel-selection, demodulation, and analog-to-digital conversion of AM signals