Sine output DDSs. A survey of the state of the art

Abstract

This paper presents a survey of the latest techniques and hardware advances in sine output direct digital synthesizers (DDSs). First, a brief description of the theory of sine output DDSs is presented. A sine output DDS has the advantage of being able to synthesize high spectral purity sine wave signals over a wide range of frequencies utilizing compact digital integrated circuits containing an accumulator, a sine look-up table, and a digital-to-analog converter (DAC). (The DDS is completed with an output filter.) The DDS can produce an output frequency from zero to a maximum frequency that is on the order of 1/3 of the clock frequency of the digital components. The principal advances in DDSs have been in increasing the maximum frequency (clock speed) and in increasing the spectral purity (spur reduction). Second, sine output DDS designs are examined that fall into two broad categories: designs for high speed and spectrally clean performance and designs for applications that require special features. Results are presented showing how the spectral purity of the DDS is related to the complexity and performance parameters of the digital components. Recent advances in architectural techniques are described that are designed to optimize spectral performance while minimizing architectural complexity. Finally, a survey of the latest DDSs and components developed by several manufacturers are described presenting key performance parameters such as clock speed, spectral purity, frequency resolution, DC power consumption, and special features. A plot of reported spurious performance on DDSs (or DACs for DDSs) is presented revealing a performance barrier that designers are striving to break. The advances necessary to break this barrier will be discussed.