Posteriori Frequency Spectrum Correction for Test Signal Imperfections in ADC Testing at 1MHz – Practical Experience

Abstrac t- In the last several years, many high-resolution and high-speed ADCs have appeared on the market. Since the signal purity of commercial generators particularly at MHz frequencies has not essentially increased in the same period, the problem of how to test ADCs has rose. This fact initiated the research of alternative methods based on either the application of special signals or posteriori correction of the measured sine-wave signal [1]. The latter method concerning a simple correction in the frequency domain was analyzed in [2], extended and practically applied in [3]. The application and the results of this extended method at the frequency of 1 MHz are presented in this paper. I. Proposed approach The method of frequency spectrum correction introduced in [2] is based on two different measurements by the tested ADC (see Fig. 1) and posteriori computation of generator and ADC harmonic distortion. The signal produced by a common harmonic generator, G(jω), is filtered by one of two filters with different frequency characteristics, F(jω), H(jω), and the signal on filter output, X(jω), is measured by the tested ADC. When both filters are linear and have the same amplitude frequency characteristics (attenuation) at the fundamental frequency, the same ADC harmonic distortion1, D(jω), is added to generator harmonic distortion modified by filters in both measurements. ADC harmonic distortion ca