Interpolation of filter coefficients

摘要

The frequency response of a digital filter, such as a pre-emphasis filter in a signal transmitter having a phase-locked loop, is adjusted using interpolation of the filter coefficients, enabling sets of filter coefficients to be pre-computed or generated as needed in the transmitter. The phase error behavior of the digital filter can be significantly improved.

主权项

1. A method in a digital processor circuit of generating a set of interpolated coefficients of a digital filter configured with at least one net, wherein a net includes a group of filter coefficients of a respective feedback or feed-forward loop in the digital filter, the method comprising:
finding, by the digital processor circuit for a net, a smallest slope in sets of estimation coefficients for filter coefficients of the net, wherein a respective set of estimation coefficients for each filter coefficient includes a base coefficient value and a slope; generating a respective interpolated filter coefficient of the smallest slope based on a frequency difference value according to an interpolation function and the slope; computing an adjusted frequency difference value based on the frequency difference value; and generating remaining interpolated filter coefficients of the net based on the respective estimation coefficients and the adjusted frequency difference value according to the interpolation function.