Synchronization of Sampling-Based Measuring Systesm

The amplitude and the phase of a measured single-tone signal can accurately be calculated from the discrete Fourier transform (DFT) components in case of coherent sampling. When the synchronization is not perfect, spectral leakage appears and errors are introduced in the determination of the signal parameters. In this paper, a new method to synchronize the sampling frequency with the frequency of the measured signal is presented. The method is based on the information contained in the fundamental and the sideband components of the DFT of the measured signal. A single measurement gives the synchronization error and permits the correction of the sampling frequency required to become coherent. Moreover, the error on the amplitude measurement relative to a quasi-coherent sampling is also discussed and quantitatively modeled. The results of the model as well as the synchronization process are experimentally verified and compared with the interpolated DFT algorithm.