Controlling Q-factor of filters
First Claim
1. A method of controlling a Q-factor for a filter including an oscillatory circuit having a tunable central frequency and bandwidth, the method comprising:
- isolating said filter using a first isolation amplifier at an input terminal to the filter and a second isolation amplifier at an output terminal of the filter;
stabilizing an active feedback to provide a variable feedback in said filter, the variable feedback being provided via a feedback path formed within the first and second isolation amplifiers, the feedback path being coupled to the oscillatory circuit;
varying the active feedback based on an input signal to said filter; and
in response to the variable feedback, producing a desired Q-factor for said filter at a first frequency band.
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Abstract
The present invention provides a method and an apparatus for controlling a Q-factor for a filter. The method comprises stabilizing an active feedback to provide a variable feedback in a filter, varying the active feedback based on an input signal to the filter, and producing a desired Q-factor for the filter at a first frequency band, in response to the variable feedback. The method further comprises reconfiguring a center frequency and a bandwidth of the filter based on a channel bandwidth of the input signal to the filter to adjust the Q-factor for the filter in response to a second frequency band different than the first frequency band. By reconfiguring a center frequency and a bandwidth of a filter, the Q-factor for the filter, such as a flexible or reconfigurable filter, may be controlled across a multiplicity of frequency band signals. Using software, for example, a common signal path may be provided for the multiplicity of frequency band signals within a frequency agile radio of a base station by tuning the radio based on a variable feedback through realization of a negative parallel resistance. Thus, tuneability of the Q-factor may provide frequency agile radios that include flexible or reconfigurable filters in a base station to serve different frequency bands without changing hardware. In this way, significant savings associated with frequency agility may be obtained.
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Citations
35 Claims
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1. A method of controlling a Q-factor for a filter including an oscillatory circuit having a tunable central frequency and bandwidth, the method comprising:
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isolating said filter using a first isolation amplifier at an input terminal to the filter and a second isolation amplifier at an output terminal of the filter; stabilizing an active feedback to provide a variable feedback in said filter, the variable feedback being provided via a feedback path formed within the first and second isolation amplifiers, the feedback path being coupled to the oscillatory circuit; varying the active feedback based on an input signal to said filter; and in response to the variable feedback, producing a desired Q-factor for said filter at a first frequency band. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of controlling a Q-factor for a filter, the method comprising:
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stabilizing an active feedback to provide a variable feedback in said filter by developing a negative parallel resistance to provide the variable feedback; varying the active feedback based on an input signal to said filter; and
in response to the variable feedback, producing a desired Q-factor for said filter at a first frequency band by;disposing said filter in a transceiver associated with a communication node in a wireless network; providing a feedback path and a resonant circuit having an input terminal and an output terminal in said filter; coupling the feedback path to said resonant circuit to realize the desired Q-factor for said filter of said transceiver; and placing a first isolation amplifier at said input terminal and a second isolation amplifier at said output terminal of said resonant circuit to control the desired Q-factor in a stable manner that substantially avoids oscillation. - View Dependent Claims (19)
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20. A method of controlling a Q-factor for a filter, the method comprising:
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combining an electrical shield of a resonant structure with an isolation amplifier to encapsulate a resonant circuit from its surroundings; stabilizing an active feedback to provide a variable feedback in said filter; varying the active feedback based on an input signal to said filter; and in response to the variable feedback, producing a desired Q-factor for said filter at a first frequency band; burying the resonant structure of said resonant circuit into at least one inner layer to electrically shield said resonant circuit of said filter to control the desired Q-factor in a stable manner that substantially avoids oscillation; and mapping a coupling variation into a gain variation of said feedback path to avoid a mechanical variation in a distance between a pair of coils coupling into each other for enabling the resonant structure.
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21. A filter comprising:
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a resonant circuit having an input terminal and an output terminal; a first isolation amplifier coupled to an input terminal of said resonant circuit; a second isolation amplifier coupled to an output terminal of said resonant circuit, wherein said first and second isolation amplifiers encapsulate said resonant circuit from its surroundings; and a feedback path coupled to said resonant circuit, stabilization of feedback in said feedback path to provide a variable feedback, wherein said resonant circuit to stabilize an active feedback in said filter, vary the active feedback based on an input signal to said filter and produce a desired Q-factor for said filter at a first frequency band in response to the variable feedback. - View Dependent Claims (22, 23, 24)
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25. A filter comprising:
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a resonant circuit having an input terminal and an output terminal; a feedback path coupled to said resonant circuit, stabilization of feedback in said feedback path to provide a variable feedback, wherein said resonant circuit to stabilize an active feedback in said filter, vary the active feedback based on an input signal to said filter and produce a desired Q-factor for said filter at a first frequency band in response to the variable feedback; a first isolation amplifier coupled to said input terminal of said resonant circuit; and a second isolation amplifier coupled to said output terminal of said resonant circuit, wherein said first and second isolation amplifiers to encapsulate said resonant circuit from its surroundings and said feedback path to develop a negative parallel resistance in said filter.
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26. A filter comprising:
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a resonant circuit having an input terminal and an output terminal; a feedback path coupled to said resonant circuit, stabilization of feedback in said feedback path to provide a variable feedback, wherein said resonant circuit to stabilize an active feedback in said filter, vary the active feedback based on an input signal to said filter and produce a desired Q-factor for said filter at a first frequency band in response to the variable feedback; a resonant structure buried into at least one inner layer to electrically shield said resonant circuit of said filter to control the desired Q-factor in a stable manner that substantially avoids oscillation; and analog circuitry including a buffer amplifier coupled to a programmable gain amplifier; and a logic and driver module coupled to said first and second isolation amplifiers, said programmable gain amplifier and said resonant circuit to overcome a tolerance of the active feedback for the variable feedback to provide the desired Q-factor and hide a variation in at least one of an external source and a load impedance of said filter from said resonant circuit to stabilize an amount of enhancement of the Q-factor. - View Dependent Claims (27, 28, 29)
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30. A filter, comprising:
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a resonant circuit having an input terminal and an output terminal; a feedback path coupled to said resonant circuit, stabilization of feedback in said feedback path to provide a variable feedback, wherein said resonant circuit to stabilize an active feedback in said filter, vary the active feedback based on an input signal to said filter and produce a desired Q-factor for said filter at a first frequency band in response to the variable feedback; and analog circuitry including one or more signal processing stages coupled to a storage storing instructions to tune a center frequency and a bandwidth over a wide range based on one or more characteristics of said filter during operation thereof and support a distributed filtering across said one or more signal processing stages, wherein said analog circuitry further comprising; an oscillatory circuit having a capacitor and an inductor, wherein said instructions to cause the variable feedback to tune said capacitor, and based on the tuning of said capacitor, obtain the center frequency and the bandwidth of said filter that realizes the desired Q-factor for said filter in a stable manner that substantially avoids oscillation across a multiplicity of frequency bands in a frequency agile radio, wherein said filter is disposed in a transceiver associated with a communication node in a wireless network.
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31. An article comprising a computer readable storage medium storing instructions that, when executed cause a system to:
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isolate a filter using a first isolation amplifier at an input terminal to the filter and a second isolation amplifier at an output terminal of the filter; stabilize an active feedback to provide a variable feedback in said filter, the variable feedback being provided via a feedback path formed within the first and second isolation amplifiers, the feedback path being coupled to an oscillatory circuit in the filter, the oscillatory circuit having a tunable central frequency and bandwidth; vary the active feedback based on an input signal to said filter; and produce a desired Q-factor for said filter at a first frequency band in response to the variable feedback. - View Dependent Claims (32, 33, 34)
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35. An article comprising a computer readable storage medium storing instructions that, when executed cause a system to:
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stabilize an active feedback to provide a variable feedback in said filter; vary the active feedback based on an input signal to said filter; produce a desired Q-factor for said filter at a first frequency band in response to the variable feedback; combine an electrical shield of a resonant structure with an isolation amplifier to encapsulate a resonant circuit from its surroundings; develop a negative parallel resistance to provide the variable feedback; map a coupling variation into a gain variation of a feedback path coupled to said resonant circuit; store calibration data in a non-volatile semiconductor memory for fine-tuning a feedback amount for the variable feedback based on the calibration data; enable a digital access to a capacitor to tune the center frequency; and based on the tuning of said capacitor, obtain a center frequency and a bandwidth of said filter that realizes the desired Q-factor for said filter in a stable manner that substantially avoids oscillation.
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Specification