Interference cancellation and improved signal-to-noise ratio circuits, systems, and methods
First Claim
1. A demodulation circuit, comprising:
- an interference estimation circuit adapted to;
receive an input signal having a desired signal component and an interfering signal component;
sample the input signal to produce a plurality of digital values;
perform a first complex multiplication on the plurality of digital values;
filter values produced by the complex multiplication to generate an interference estimation signal from the input signal;
re-modulate the interference estimation signal to produce a representation of the input signal;
perform a second complex multiplication on the interference estimation signal; and
filter product values from the second complex multiplication to isolate an in-band portion of the interfering signal component;
an adaptive filtering circuit coupled to the interference estimation circuit and operable to perform spectral and amplitude inversion on the in-band portion of the interfering signal component to obtain a spectrally inverted in-band interference signal, the adaptive filtering circuit further operable to re-modulate the spectrally inverted in-band interference signal to obtain an inverted signal; and
a summing circuit coupled to the adaptive filtering circuit and operable to sum the inverted signal and the input signal to substantially cancel interference contained in the input signal.
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Abstract
Interference cancellation for wideband and narrowband communications systems is provided without apriori knowledge of statistical information about an interfering signal. In one embodiment a demodulator circuit can operate in an environment where a “no lock” situation would normally occur to remove the interference and acquire signals in low signal-to-noise ratio conditions and high signal-to-interference ration conditions. In other embodiments, performance is improved by introducing statistics of the interfering signal, and these statistics regarding the communications channel and interference properties (i.e., characteristics of the interfering signal) can be adaptive or “learned” in other embodiments.
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Citations
20 Claims
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1. A demodulation circuit, comprising:
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an interference estimation circuit adapted to; receive an input signal having a desired signal component and an interfering signal component; sample the input signal to produce a plurality of digital values; perform a first complex multiplication on the plurality of digital values; filter values produced by the complex multiplication to generate an interference estimation signal from the input signal; re-modulate the interference estimation signal to produce a representation of the input signal; perform a second complex multiplication on the interference estimation signal; and filter product values from the second complex multiplication to isolate an in-band portion of the interfering signal component; an adaptive filtering circuit coupled to the interference estimation circuit and operable to perform spectral and amplitude inversion on the in-band portion of the interfering signal component to obtain a spectrally inverted in-band interference signal, the adaptive filtering circuit further operable to re-modulate the spectrally inverted in-band interference signal to obtain an inverted signal; and a summing circuit coupled to the adaptive filtering circuit and operable to sum the inverted signal and the input signal to substantially cancel interference contained in the input signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of demodulation, comprising:
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receiving an input signal at an input of an interference estimation circuit, the input signal having a desired signal component and an interfering signal component; generating from the input signal, with the interference estimation circuit, an interference estimation signal, said generating including; sampling the input signal to produce a plurality of digital values; performing a first complex multiplication on the plurality of digital values; and filtering values produced by the complex multiplication to isolate the interference estimation signal; isolating an in-band portion of the interfering signal component, said isolating including; re-modulating the interference estimation signal to produce a representation of the input signal; performing a second complex multiplication on the interference estimation signal; and filtering values produced by the second complex multiplication to isolate the in-band portion of the interfering signal component; performing, with an adaptive filtering circuit, a spectral and amplitude inversion on the interference estimation signal to obtain a spectrally inverted in-band interference signal; re-modulating the spectrally inverted in-band interference signal to produce an inverted signal; and applying the inverted signal to the input signal to substantially cancel interference contained in the input signal. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A method to detect and remove an interfering portion of a signal having the interfering portion and a desired portion, the method comprising:
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receiving an input signal at an input of an analog-to-digital converter, the input signal having a desired signal component and an interfering signal component; sampling the input signal with the analog-to-digital converter to produce a plurality of digital values; performing a first complex multiplication on the plurality of digital values; filtering values produced by the complex multiplication to isolate an estimate of the interfering signal component; re-modulating the estimate of the interfering signal component to produce a representation of the input signal; performing a second complex multiplication on the estimate of the interfering signal component; filtering product values from the second complex multiplication to isolate an in-band portion of the interfering signal component; performing spectral and amplitude inversion of the in-band portion of the interfering signal component to produce a spectrally inverted in-band interference signal; re-modulating the spectrally inverted in-band interference signal to produce a representation of an interference signal to be removed; and summing the representation of the input signal with the representation of the interference signal to be removed to produce an interference-corrected signal. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification