Subsampling architecture for low power receivers

Subsampling receivers have several advantages over the direct conversion or low-intermediate-frequency architectures when implementing a low power and flexible receiver. The subsampling receiver requires a lower frequency synthesizer. This paper describes the fundamentals to consider when designing a subsampiing receiver. An optimum frequency plan for the subsampling receiver is outlined in a general equation. The specifications for bandpass anti-aliasing filtering are defined by deriving the fundamental relationship between subsampling ratio and filter Q. The noise figure and jitter of the subsampling receiver are also derived in general terms. Finally, a brief description of a 900-MHz example receiver is shown.