ADC Testing Using a Resonator-Based Observer: Processing Very Long Time Records and/or Testing Systems With Limited Stability

A common method to test analog-to-digital converters (ADCs) is sine fitting. If a very large set of samples needs to be processed (long records), the iterative four-parameter sine fit algorithm is very sensitive to the initial estimate of the fundamental frequency. Even a slight error in the initial guess can spoil the fit because of the several local minima in the error surface. We propose a robust algorithm to fit the sine wave to the samples by using a resonator-based state observer and an adaptive Fourier analyzer. The method has the advantage that the amplitude and frequency drift of the signal generator can be detected and compensated. Moreover, its recursivity allows the processing of many data points without requiring large amounts of memory. This method is also advantageous if the internal ADC of a microcontroller or a digital signal processor needs to be tested in an embedded system, where the clock frequency cannot be arbitrarily tuned and the absolute precision of the sampling frequency is also limited.