Evaluating analog-to-digital converters

Dynamic performance of an A/D converter cannot be assessed by conventional tests since they employ slowly varying inputs. In this paper, a digital computer procedure is developed to determine the presence and extent of errors due to time jitter, nonlinearity, gain, quantization, and locked bits. The procedure is based on discrete power-spectrum analysis of recorded outputs of the A/D converter using a weighted or nonweighted sine wave input. In the latter case, a discrete weighting of the recorded output must be performed before power-spectrum analysis. Outside of the narrow band containing the signal spectrum, the power spectrum corresponds to the errors in the A/D converter. Error models are suggested and implemented in a simulation program which is executed to show the power spectra for various combinations of errors. On this basis an A/D converter evaluation procedure is proposed and illustrated by an example.