Traditional continuous-time receivers face issues of high area and power requirements and low selectivity, as outlined in the following Section 23.1, when used in integrated software defined radios. Low selectivity puts increased demands on the analog-to-digital converters used in software defined radio receivers.

Organized into six sections, this chapter is devoted to programmable, sampling-based radio receivers. Early sampling combined with discrete-time filters can reduce the power required for analog-to-digital conversion by increasing selectivity while maintaining easy programmability and reduced power consumption. The required theory to understand such sampling filters is outlined in Section 23.2. In each of Sections 23.3 and 23.4, we look at the advantages and disadvantages, associated challenges, and the state of the art of programmable zero intermediate frequency and low intermediate frequency discrete-time receivers, respectively. As an exercise, we review a case study of an integrated AM/FM super-heterodyne receiver in Section 23.5. Finally, in Section 23.6, we present a summary and conclusions.