TDFD-based measurement of analog-to-digital converter nonlinearity

Analog-to-digital converters (ADCs) are central to modern audio, video, and RF systems, with some modern converters providing 23 plus "significant" bits. With such systems, performance is usually limited by audible distortion. Consequently linearity tests, analogous to distortion measurements, are adapted to test performance. The total difference-frequency distortion (TDFD) test is a modern standard for distortion measurement in the audio field, and its uniquely powerful advantages may be transferred to the realm of ADC testing. Building on existing work, a straightforward TDFD test for ADC systems is described and demonstrated. Measurements of example ADC systems are presented. A simple relationship between distortion and effective bits is derived, as a measure of performance, and testing guidelines are given.