Digitally tuned analog notch filter circuit
AssigneeThe Boeing Company
InventorDonald R. Cargille
Life of this patent
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Abstract
A notch filter circuit is provided including a first stage circuit and a second stage circuit. The first stage circuit sums a filter input signal with a filter output signal to form a summation signal. The second stage circuit includes a first tee network and a second tee network. The first tee network low-pass filters the filter input signal to form a first tee output signal. The second tee network high-pass filters the summation signal to form a second tee output signal. A first multiplying digital-to-analog converter is electrically coupled to the first tee network and the second tee network. The first converter modifies the gain of the second tee network in response to a gain signal to form a corrected second tee network signal, thereby adjusting a notch filter frequency.
Claims20
A notch filter circuit comprising:
- a first stage circuit comprising a first stage input and a first stage output terminal, said first stage circuit summing a filter input signal with a filter output signal to form a summation signal;
- and
- a second stage circuit having a second stage output terminal and comprising;
- a first tee network electrically coupled to said first stage input and low-pass filtering said filter input signal to form a first tee output signal;
- a second tee network electrically coupled to said first stage output terminal and high-pass filtering said summation signal to form a second tee output signal;
- and
- a first multiplying digital-to-analog converter electrically coupled to said first tee network and said second tee network, said first multiplying digital-to-analog converter modifying gain of said second tee network in response to a gain signal to form a corrected second tee network signal;
- said second stage circuit summing said first tee output signal with said corrected second tee output signal to form said filter output signal.
A system comprising:
- a controller generating a gain signal;
- and
- a notch filter circuit comprising:
- a first stage circuit comprising a first stage input and a first stage output terminal, said first stage circuit summing a filter input signal with a filter output signal to form a summation signal;
- and
- a second stage circuit having a second stage output terminal comprising;
- a first tee network electrically coupled to said first stage input and low-pass filtering said filter input signal to form a first tee output signal;
- a second tee network electrically coupled to said first stage output terminal and high-pass filtering said summation signal to form a second tee output signal;
- and
- a first multiplying digital-to-analog converter electrically coupled to said controller, said first tee network, and said second tee network, said first multiplying digital-to-analog converter modifying gain of said second tee network in response to said gain signal to form a corrected second tee network signal;
- said second stage circuit summing said first tee output signal with said corrected second tee output signal to form said filter output signal.
A method of adjusting notch filter frequency of a notch filter circuit comprising:
- summing a filter input signal with a filter output signal to form a summation signal;
- low-pass filtering said filter input signal via a first tee network to form a first tee output signal;
- high-pass filtering said summation signal via a second tee network to form a second tee output signal;
- modifying gain of said second tee network in response to a gain signal to form a corrected second tee output signal;
- and
- summing said first tee output signal with said corrected second tee output signal to form said filter output signal.
Dependencies are inferred from the claim text.