Using Sampling Aliases For Sharp Programmable Filtering: Some Radio Applications
Sharp, programmable, linear, integrated filters are enabling components for software defined and cognitive radio applications. However, they are difficult to realize: SAW and MEMS based filters are sharp and linear but not very programmable; active filters can be sharp and programmable but are not very linear; sampled charge domain filtering is sharp and programmable but the burden of the linearity is on the front end voltage-current converter. This talk descirbes an alternative approach that uses time-varying (as opposed to time-invariant) circuits to realize sharp, programmable, linear, integrated filters. The technique exploits sampling aliases to effectively realize very sharp, linear filtering prior to sampling. This talk will describe the basics of this time-varying circuit design approach and illustrates its application to radio front-ends and spectrum scanners. Measurement results from recent prototype integrated circuits will also be presented.