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US 6,643,675 B2Granted
Filtering method and filter
AssigneeNokia Corporation
InventorOlli Piirainen
Life of this patent
Estimating the term…
Abstract
The invention relates to a filtering method and a filter implementing the filtering method. In the solution, a signal is filtered by at least one real FIR filter having at least one stop frequency pair whose different frequencies are symmetrically on different sides of at least one alias frequency.
Claims24
A filtering method, the method comprising:
- processing a signal digitally including filtering said signal using at least one real infinite impulse response (IIR) filter;
- then
- changing a sampling frequency of said signal by a coefficient M which is a positive integer and which defines alias frequencies on the frequency band of a filter;
- then
- filtering the signal by at least one real finite impulse response (FIR) filter having at least one stop frequency pair whose frequencies are located symmetrically on different sides of at least one of said alias frequencies.
2 more elements
A filter arranged to process a signal digitally having a sampler for changing a sampling frequency of said signal by a coefficient M which is a positive integer and which defines alias frequencies on a frequency band, the filter comprising:
- at least one real FIR filter having at least one complex stop frequency pair whose frequencies are located symmetrically on different sides of at least one alias frequency;
- and
- at least one real IIR filter,
- wherein the sampler is operational between the at least one IIR filter and the at least one FIR filter.
1 more element
Dependencies are inferred from the claim text.