Active biquad filter with oscillator circuit
AssigneeQUALCOMM Incorporated
InventorsRahul Karmaker, Gary Lee Brown, Jr.
Life of this patent
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Abstract
Certain aspects of the present disclosure are generally directed to a tunable active filter and a method of calibrating a tunable active filter. One example apparatus is a filter circuit that generally includes a resistor-capacitor (RC) topology tunable active filter comprising a first amplifier, a second amplifier, and a feedback path coupled between an input of the first amplifier and an output of the second amplifier. The filter circuit also includes a negative transconductance circuit coupled to a first node of the tunable active filter.
Claims29
A filter circuit comprising:
- a resistor-capacitor (RC) topology tunable active filter comprising a first amplifier, a second amplifier, and a feedback path coupled between an input of the first amplifier and an output of the second amplifier;
- and
- a negative transconductance circuit coupled to a first node of the first or second amplifier of the tunable active filter.
A method for generating one or more calibration parameters for a biquad filter, comprising:
- determining an error value of an impedance of an element of the biquad filter, the error value being associated with a quality factor (Q) of the biquad filter at a frequency, wherein the error value comprises a difference between the impedance of the element of the biquad filter at the frequency and a nominal impedance of the element;
- determining one or more other quality error factor values associated with the Q of the biquad filter at one or more other frequencies;
- and
- generating the one or more calibration parameters corresponding to the impedance of the element of the biquad filter at the one or more other frequencies based on the error value and the one or more other quality error factor values.
An apparatus for generating an oscillating signal, comprising:
- first means for amplifying an input signal;
- second means for amplifying an output signal of the first means for amplifying, the input signal being based on a feedback signal generated based on an output of the second means for amplifying, and the first and second means for amplifying being part of a tunable active filter having a resistor-capacitor (RC) topology;
- and
- means for providing negative transconductance at a first node of the first means for amplifying or the second means for amplifying to counteract losses of the tunable active filter to generate the oscillating signal.
Dependencies are inferred from the claim text.