Interpolation of Filter Coefficients
AssigneeST-Ericsson SA
InventorsJens Rosendahl, Ville Ruuska, Mika Salmi
Life of this patent
Estimating the term…
Abstract
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.
Claims11
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.
A digital filter configured with at least one net, each net including a group of filter coefficients of a respective feedback or feed-forward loop in the digital filter, the filter comprising:
- a digital processor circuit configured to generate a set of interpolated coefficients of the digital filter by at least:
- finding, 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.
Dependencies are inferred from the claim text.