Spurious frequency attenuation servo
First Claim
1. A spurious frequency attenuation servo, comprising:
- a first function generator that generates a first signal at a first frequency, the first signal including at least one spur at at least one respective spurious frequency;
a second function generator that generates a second signal in-phase with the first signal and at a spurious frequency;
a third function generator that generates a third signal ninety degrees out-of-phase with the first signal and at the spurious frequency;
an in-phase mixer configured to input the second signal and a feedback signal;
a quadrature-phase mixer configured to input the third signal and the feedback signal;
an in-phase error accumulator configured to input the signal from the in-phase mixer;
a quadrature-phase error accumulator configured to input the signal from the quadrature-phase mixer;
an in-phase multiplier to multiply an output from the in-phase error accumulator with the second signal;
a quadrature-phase multiplier to multiply an output from the quadrature-phase error accumulator with the third signal; and
at least one summing node to sum the first signal, an output from the in-phase multiplier, and an output from the quadrature-phase multiplier to form an output signal that is fed back to the in-phase mixer and the quadrature-phase mixer, wherein the at least one spurious frequency of the first signal is canceled from the first signal output from the summer.
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Abstract
A spurious frequency attenuation servo is provided. The spurious frequency attenuation servo includes a first function generator that generates a first signal at a first frequency and at a spurious frequency; a second function generator that generates a second signal in-phase with the first signal and at the spurious frequency; a third function generator that generates a third signal ninety degrees out-of-phase with the first signal and at the spurious frequency; in-phase and quadrature-phase mixers to input a feedback signal and the second and third signals, respectively; in-phase and quadrature-phase error accumulators; an in-phase and quadrature-phase multiplier to multiply an output from the in-phase and quadrature-phase error accumulators with the second and third signals, respectively; and a summing node to sum the first signal with output from the in-phase and quadrature-phase multipliers to form an output signal that is fed back to the in-phase mixer and the quadrature-phase mixer.
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Citations
20 Claims
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1. A spurious frequency attenuation servo, comprising:
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a first function generator that generates a first signal at a first frequency, the first signal including at least one spur at at least one respective spurious frequency; a second function generator that generates a second signal in-phase with the first signal and at a spurious frequency; a third function generator that generates a third signal ninety degrees out-of-phase with the first signal and at the spurious frequency; an in-phase mixer configured to input the second signal and a feedback signal; a quadrature-phase mixer configured to input the third signal and the feedback signal; an in-phase error accumulator configured to input the signal from the in-phase mixer; a quadrature-phase error accumulator configured to input the signal from the quadrature-phase mixer; an in-phase multiplier to multiply an output from the in-phase error accumulator with the second signal; a quadrature-phase multiplier to multiply an output from the quadrature-phase error accumulator with the third signal; and at least one summing node to sum the first signal, an output from the in-phase multiplier, and an output from the quadrature-phase multiplier to form an output signal that is fed back to the in-phase mixer and the quadrature-phase mixer, wherein the at least one spurious frequency of the first signal is canceled from the first signal output from the summer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of cancelling one or more spurs in a spurious frequency attenuation servo, the method comprising:
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generating a first signal at a first frequency, the first signal including at least one spur at at least one respective spurious frequency; generating a second signal in-phase with the first signal and at a spurious frequency; generating a third signal ninety degrees out-of-phase with the first signal and at the spurious frequency; inputting the second signal and a feedback signal to an in-phase mixer; inputting the third signal and the feedback signal to a quadrature-phase mixer; inputting the in-phase mixer output to an in-phase error accumulator; inputting the quadrature-phase mixer output to a quadrature-phase error accumulator; multiplying an output from the in-phase error accumulator with the second signal at an in-phase multiplier; multiplying an output from the quadrature-phase error accumulator with the third signal at a quadrature-phase multiplier; summing the first signal, an output from the in-phase multiplier, and an output from the quadrature-phase multiplier to form an output signal; and feeding back the output signal to the in-phase mixer and the quadrature-phase mixer, to cancel the at least one spurious frequency from the first signal. - View Dependent Claims (12, 13, 14)
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15. A spurious frequency attenuation servo, comprising:
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a dual direct digital synthesizer that generates a digitized signal and a square wave signal at a first frequency; a low pass filter to input the digitized signal and to output a reconstructed signal at the first frequency, the reconstructed signal including at least one spur at at least one respective spurious frequency; a frequency multiplier to multiply the square wave signal by a factor, wherein the frequency-multiplied-square wave signal is in-phase with the digitized signal and at a spurious frequency; an in-phase mixer configured to input the multiplied-digitized signal and the reconstructed signal; a ninety-degree phase shifter to phase-shift the multiplied-digitized signal; a quadrature-phase mixer configured to input the phase-shifted-frequency-multiplied signal and the reconstructed signal; an in-phase error accumulator configured to input the signal from the in-phase mixer; a quadrature-phase error accumulator configured to input the signal from the quadrature-phase mixer, wherein processed output from the in-phase error accumulator and the quadrature-phase error accumulator is fed back to the dual direct digital synthesizer to cancel the at least one spur at the spurious frequency. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification