Algorithms for accurate spectrum measurement of high-resolution analog-to-digital converter with non-coherent sampling.

In Analog-to-Digital Converter (ADC) spectrum measurement, the realization of coherent sampling is difficult to implement, which has always been one of the bottlenecks. When coherent sampling is not available, researchers have been looking for some precise methods to test high-resolution ADCs under non-coherent sampling conditions. This study introduces two algorithms to, respectively, resolve harmonic distortion and ADC amplitude clipping problems with non-coherent sampling based on the idea of replacement. In algorithm 1, in order to accurately depict a signal spectrogram with harmonics under non-coherent sampling, signal fundamental and harmonics are basically estimated twice, a rough estimate and a fine estimate to get accurate values, and then they are replaced by a coherent sampling spectrum. In algorithm 2, we first determine the sampling period, then propose a three-parameter approach to calculate parameters of clipped signal, analyze and correct the parameter error, and finally apply the corresponding idea signal to replace the clipped signal. This paper proves the two algorithms' superiority through a lot of simulation results, such as 12-bit, 14-bit, and 16-bit ADC tests. Finally, we process the experiment on the ADC chip automatic test system to obtain 16-bit AD9268 spectrum data and verify the effectiveness of the two algorithms. The two algorithms correct the spectrum error caused by non-coherent sampling and clipping, ideally suitable for high-resolution ADCs.