Digitally compensated direct conversion receiver
First Claim
1. In a direct-conversion receiver for recovering an information signal from a carrier signal modulated by the information signal, in which the modulated carrier signal is separated into a base-band in-phase signal and a base-band quadrature signal, an apparatus for digitally compensating for an interfering signal comprising:
- first means for generating digital samples of the base-band in-phase signal and the base-band quadrature signal;
means for detecting a presence of a second-order product signal having a time-varying spectral content produced by the interfering signal; and
means, in communication with the first means and the detecting means, for digitally compensating the digital samples by removing the second-order product signal, thereby producing compensated digital samples, wherein the compensating means applies to the digital samples a non-linear, time-varying compensation corresponding to the spectral content of the second-order product signal.
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Abstract
A digitally compensated direct-conversion receiver includes devices for generating digital samples of a base-band in-phase signal and a base-band quadrature signal and for detecting the presence of a second-order product signal produced by an amplitude-modulated interfering signal. Also, the apparatus comprises a device for digitally compensating the digital samples by removing the second-order product signal, thereby producing compensated digital samples. In one method of digitally compensating samples of an information signal quadrature-modulating a carrier signal, estimated samples of a second-order product from a switched carrier signal are formed by averaging the digital samples during two time periods and by determining a time of ramps in the in-phase and quadrature signals that occur between the time periods due to the interfering signal. The digital samples may be differentiated and the results smoothed in determining the time of the ramps. In another apparatus, the estimated samples of the second-order product signal are produced by a device for averaging a square of a difference between respective digital samples of the in-phase signal and the quadrature signal, thereby determining an amplitude of the amplitude-modulated carrier signal, and a device for combining the amplitude and the digital samples, thereby generating the estimated samples.
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Citations
16 Claims
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1. In a direct-conversion receiver for recovering an information signal from a carrier signal modulated by the information signal, in which the modulated carrier signal is separated into a base-band in-phase signal and a base-band quadrature signal, an apparatus for digitally compensating for an interfering signal comprising:
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first means for generating digital samples of the base-band in-phase signal and the base-band quadrature signal; means for detecting a presence of a second-order product signal having a time-varying spectral content produced by the interfering signal; and means, in communication with the first means and the detecting means, for digitally compensating the digital samples by removing the second-order product signal, thereby producing compensated digital samples, wherein the compensating means applies to the digital samples a non-linear, time-varying compensation corresponding to the spectral content of the second-order product signal. - View Dependent Claims (2, 3, 4, 5)
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6. In a method of recovering an information signal from a carrier signal modulated by the information signal that includes separating the modulated carrier signal into a base-band in-phase signal and a base-band quadrature signal, a method of digitally compensating for an interfering signal comprising the steps of:
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generating digital samples of the base-band in-phase signal and the base-band quadrature signal; detecting a presence of a second-order product signal having a time-varying spectral content produced by the interfering signal; and digitally compensating the digital samples by removing the second-order product signal, thereby producing compensated digital samples, wherein a non-linear, time-varying compensation corresponding to the spectral content of the second-order product signal is applied to the digital samples. - View Dependent Claims (7, 8, 9, 10)
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11. In a direct-conversion receiver for recovering an information signal from a carrier signal modulated by the information signal, in which the modulated carrier signal is separated into a base-band in-phase signal and a base-band quadrature signal, an apparatus for digitally compensating for an amplitude-modulated interfering signal comprising:
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first means for generating digital samples of the base-band in-phase signal and the base-band quadrature signal; second means for generating estimated samples of a second-order product signal produced by the amplitude-modulated interfering signal, wherein the second means comprises; first means for averaging a square of a difference between respective digital samples of the in-phase signal and the quadrature signal, thereby determining an amplitude of the modulated carrier signal; and means for combining the amplitude and the digital samples, thereby generating the estimated samples; and means for removing the estimated samples from the digital samples, thereby generating compensated digital samples. - View Dependent Claims (12, 13)
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14. In a direct-conversion receiver for recovering an information signal from a carrier signal modulated by the information signal, in which the modulated carrier signal is separated into a base-band in-phase signal and a base-band quadrature signal, a method of digitally compensating for an amplitude-modulated interfering signal comprising the steps of:
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generating digital samples of the base-band in-phase signal and the base-band quadrature signal; generating estimated samples of a second-order product signal produced by the amplitude-modulated interfering signal by the steps of; averaging a square of a difference between respective digital samples of the in-phase signal and the quadrature signal, thereby determining an amplitude of the modulated carrier signal; and combining the amplitude and the digital samples, thereby generating the estimated samples; and removing the estimated samples from the digital samples, thereby generating compensated digital samples. - View Dependent Claims (15, 16)
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Specification