A figure of merit for digital filters
Larry John Fruit · 2005
The combined effects of amplitude quantization are brought together in such a way that the designer can readily choose cost effective word lengths for his A-D converter and digital filter. A degradation factor is suggested which relates the performance of the digital circuit to its analog counterpart in terms of the filter's frequency transfer characteristic, sampling rate, input noise, dynamic range and word length. Only low-pass filters using fixed-point arithmetic and rounding are considered. A practical design illustration is presented using the degradation factor and a Fortran IV computer program to define word lengths and to choose the best realization from among the parallel or cascade digital filter realizations with first and second-order sections.