Accurate Spectral Testing With Arbitrary Noncoherency in Sampling and Simultaneous Drifts in Amplitude and Frequency

Accurate spectral testing plays a crucial role in modern high-precision analog-to-digital converters' (ADCs') evaluation process. One of the challenges is to be able to cost-effectively test the continually higher resolution ADCs accurately. Due to its stringent test requirement, the standard test method for ADCs can be difficult to implement with low cost. This paper proposes an algorithm that relaxes the requirements of precise control over source amplitude and frequency, and of the need to achieve coherent sampling. The algorithm divides the output data into segments, and estimates drift fundamental via Newton iteration. By removing the estimated drift fundamental and replacing with a coherent, nondrift fundamental in time domain, accurate spectral results can be achieved. Various simulation results have validated the accuracy of the proposed algorithm. The proposed algorithm is capable of tolerating various test condition variations such as any-level of noncoherency, various input frequency range and different numbers of segmentations. In addition, several measurement results from different ADCs have verified the accuracy of the proposed algorithm, which is able to accurately obtain spectral performance of an 18 b high-resolution ADC. Such algorithm relaxes the standard test requirement such as precise control over source frequency and amplitude, which dramatically reduces the test setup complexity and cost.