The continually growing intricacy of multistandard and multimode radios in terms of desired flexibility, varied number of services, frequency bands, and complex modulation schemes is pushing the limit of common wireless transceivers. The principle aim of SDR technology is to enable such varied designs to be implemented on a single radio. A key approach to realizing this goal is by enabling further processing of the waveform, such as filtering and signal conditioning, in the digital domain, which otherwise was done in the analog domain. This can be accomplished by moving the analog/digital boundary closer to the antenna. That is not to say that the analog will be any easier, but rather that some of its complex functionality will be moved to the digital domain. The essential technology that will enable such advancement in radio design will have to come first and foremost through innovations in data conversion. The specifications of the ADC and DAC vary widely for IF sampling architecture versus, say, super-heterodyne or direct conversion.

This chapter is divided into three major sections. Section 8.1 delves into the fundamental requirements of Nyquist data converters. Topics such as quantization, oversampling, and performance are discussed in great detail. Section 8.2 addresses the various common architectures of Nyquist data converters. Popular Nyquist converters such as the FLASH converter, the pipelined and subranging converter, the folding converter, the integrating dual slope converter, and the successive approximation converter are studied. Section 8.3 contains an appendix on Gray codes.