Sampling rate conversion using fractional-sample delay

In this paper we demonstrate application of the fractional sample delayor (FSD) to constructing sampling rate converters for incommensurate sampling rates. We use Lagrange polynomials for interpolating the values of the signal between sampling instants. It is shown that to deploy this technique effectively one has to use polynomials of high degree. Otherwise the interpolation error for high frequencies (above half Nyquist) is very big. Increasing the polynomial´s degree leads inevitably to numerical problems. The interpolation process may be improved when additional samples of the signal are generated before interpolation. It is shown that FSD can be used for achieving this task. The final version of the sampling rate converter comprises two FSDs and a very simple four-point interpolator based on a Lagrange polynomial