Patent ID: 6581080
Filing Date: 2003-06-17
Classification: H03H

Abstract:
A method of generating coefficients in a digital filter, comprising the steps of:(a) providing a gain control signal setting a value of reference gain, (b) providing a frequency control signal setting a value of reference frequency (c) calculating, according to a model of the frequency/gain characteristic of a prototype analogue filter, a plurality of gain and/or frequency points at frequencies equal to and less than Nyquist frequency (where Nyquist frequency is half the sampling frequency of the digital filter) and which match corresponding gain and/or frequency points in the corresponding digital filter characteristic, (d) calculating from the said calculated points, pre-warped parameters of a model of the analogue filter, (e) applying a transform to the resulting pre-warped analogue model to convert the pre-warped analogue model to the digital domain and (f) generating filter coefficients from the transformed model and applying them to the filter.