Design considerations for direct delta-sigma receivers

Modern CMOS technology development is driven by the needs of digital circuitry. Higher density, speed, and energy efficiency are obtained as minimum transistor sizes scale down with each new technology node. This trend also drives RF designs toward digital-type circuits that benefit from the scaling. All-digital phase-locked loops have been widely used in cellular synthesizers, and even more aggressive direct digital synthesis methods have been studied in academia. Likewise, transmitter demonstrations of power digital-to-analog converters (DACs) have pushed the boundary of digital signal processing to the power amplifier output node.