A reduced sample rate bandpass sigma delta modulator

Sigma delta modulators have been in widespread use for some time now. The relaxed analog component requirements of a sigma delta modulator (achieved through low bit counts and oversampling) make it a simple and elegant solution to the problem of analog to digital conversion. The disadvantage of conventional sigma delta modulators is that the sample rate must be many times higher than the highest frequency to be sampled (to achieve a sufficiently high oversampling ratio). This is not a major problem when the signal to be sampled is at baseband, but narrowband, high frequency signals (e.g. radio frequencies), would require extremely high sample rates.