Equivalent-Time Sampling and Real-Time Digital Oscillography Interpolation

Two methods for increasing the sampling rate in digital oscilloscopes are analyzed. The equivalent-time sampling is carried out via measuring and accumulating a series of oscillograms with a random phase and leads to nonuniform sampling. As a result, for few accumulations, the output noise level increases and the effective number of bits decreases. Interpolation in digital oscilloscopes is performed by sinx xfunctions and its errors are determined by the length of the interpolating FIR filter. A table for choosing the filter length, depending on the interpolation coefficient and the normalized band of the reconstruction filter is presented. Obtaining a high interpolation coefficient requires considerable computational power.