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US 6,778,023 B2Granted
Tunable filter and method of tuning a filter
AssigneeNokia Corporation
InventorKaare Tais Christensen
Life of this patent
Estimating the term…
Abstract
A bandpass filter is tuned by converting the filter into an oscillator using a negative resistance circuit, tuning the oscillator by using conventional tuning techniques such as tuning a varactor via a phase locked loop, sampling and holding the tuning signal and switching off the negative resistance circuit to convert the oscillator back into a bandpass filter.
Claims8
A method of tuning a filter, the filter being associated with a center frequency, comprising:
- configuring said filter as an oscillator;
- tuning said oscillator to a desired frequency according to a tuning signal;
- reconfiguring said oscillator to operate as said filter with said desired frequency as said center frequency;
- and
- recording the tuning signal which causes said oscillator to operate at the desired frequency.
2 more elements
A programmable filter comprising:
- a filter circuit;
- a compensation circuit;
- and
- a memory for storing at least one digital word;
- wherein the compensation circuit is operable to configure said filter circuit as an oscillator, whereby to permit said oscillator to be tuned to at least one desired frequency in accordance with a tuning signal, said tuning signal being derived from said at least one digital word, said compensation circuit further being operable to reconfigure said oscillator to operate as said filter after tuning.
2 more elements
Dependencies are inferred from the claim text.