Fast frequency switching in a resonant high-Q analog filter
AssigneeAnlotek Limited
InventorJorgen Staal Nielsen
Life of this patent
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Abstract
A variable filter and method of switching a resonant frequency of the variable filter from an initial frequency to a desired frequency, where the variable filter has a tunable frequency and a variable Q. With the variable filter operating at the initial frequency and an initial Q, the variable filter is Q-spoiled toward a low-Q state. The variable filter is tuned toward the desired frequency and the tunable resonator is Q-enhanced from the low-Q state to achieve a desired filter response.
Claims17
A method of switching a resonant frequency of a variable filter from an initial frequency to a desired frequency, the variable filter comprising an active feedback bandpass filter having a tunable frequency and a variable Q, the method comprising the steps of:
- with the variable filter operating at the initial frequency and an initial Q, Q spoiling the variable filter toward a low-Q state;
- and
- tuning the variable filter toward the desired frequency and Q-enhancing the variable filter from the low-Q state to achieve a desired filter response.
A method of switching a resonant frequency of a variable filter from an initial frequency to a desired frequency, the variable filter comprising an active feedback bandpass filter having a tunable frequency and a variable Q, wherein in operation, the variable filter is described by one or more poles in an s-plane plot having a real axis and an imaginary axis, the method comprising the steps of:
- with the variable filter operating at an initial pole location in the s-plane plot, Q-spoiling the variable filter to cause one or more poles to move away from the imaginary axis and toward a low-Q state;
- and
- tuning the tunable frequency and controlling the variable Q to achieve a desired pole location corresponding to the desired frequency and a desired Q.
A variable filter, comprising:
- an active feedback bandpass filter (AFF) comprising a signal loop connected between a signal input and a signal output, the signal loop comprising at least a tunable resonator and a variable gain block, the signal loop generating a filter response;
- a controller connected to tune a frequency of the tunable resonator and vary a gain factor of the variable gain block, the controller being programmed to tune the filter response of the signal loop from an initial frequency to a desired frequency by:
- Q-spoiling the AFF toward a low-Q state;
- tuning the tunable resonator toward the desired frequency;
- and
- Q-enhancing the AFF from the low-Q state to achieve a desired filter response.
Dependencies are inferred from the claim text.