Direct RF Conversion using Analog To Digital Converters

Receiver system designers are seeing a change from the widely adopted heterodyne architecture to a direct RF-sampling approach. In the traditional receiver, the designer selects the analog-to-digital converter (ADC) based on key specifications, such as signalto-noise ratio (SNR) and spurious-free dynamic range (SFDR). In a direct RF-sampling receiver, designers focus instead on how the RF ADC impacts the receiver system noise figure (NF). A key concern is its performance in a blocking environment for which the heterodyne architecture has been optimized for many years.

This paper explains the differences between a traditional heterodyne receiver and the modern RF-sampling data converter. It then compares some key design aspects, particularly for the complete signal chain line-up.