Interpolating and Nyquist filters with constraints at certain frequencies (Q1180377)

Introducing the concept of constraining it is shown how the design procedures for finite impulse response interpolating or Nyquist filters can be modified to assure error-free reproduction for inputs at certain frequencies. Two generic filter design strategies are examined. For interpolation filters the technique minimizes the mean-square interpolator error for a signal with a given correlation function. For minimax stopband Nyquist filters the modifications involve factoring out a filter which implements the constraints on the transfer function. Examples are given for filters designed with and without frequency constraints.