ADC Testing with Verification

An important method of analog-to-digital converter (ADC) testing is sine wave fitting. By this, the device is excited with a sine wave, and another sine wave is fitted to the samples at the output of the ADC. The acquisition device can be analyzed by looking at the differences between the fitted signal and the samples. The fit happens with the least squares (LS) method. If the samples of the error (the difference of the fitted signal and the samples) were random and independent of each other and of the signal, the LS fit would have very good properties. However, when the error is dominated by the quantization error, especially when low bit number is used, these conditions are not fulfilled. The estimation will be biased, the estimation must be corrected. The independence of the error samples is more or less true if the sine wave is noisy, or dither is used. In these cases the correction is not necessary. Therefore, it is reasonable to analyze the effect of the maybe unnecessary correction to noisy data, and it is desirable to know the magnitude of the noise. In this paper, these two questions are investigated. A new noise estimation method is developed and analyzed.