Adaptive canceller for frequency reuse systems
DCFirst Claim
1. A method of canceling an interfering signal contained in a received signal which includes a signal of interest, the interfering signal being a relayed version of a transmitted signal from the location of the received signal, the method comprisingconverting the received signal and a replica of the transmitted signal to digital signals;
- tracking variations in predetermined signal parameters resulting from relaying the transmitted signal between the interfering signal and the replica of the transmitted signal to produce a compensation signal;
combining the compensation signal and the received signal to cancel first variations between the interfering signal and the sample of the transmitted signal to produce the signal of interest;
generating an error signal representing uncanceled second variations between the interfering signal in the signal of interest; and
controlling said tracking with the error signal to reduce differences between the compensation signal and the interfering signal to produce the signal of interest.
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Abstract
An adaptive interference canceller for canceling an interfering signal corresponding to a delayed, frequency translated, amplitude and phase offset version of a transmitted signal contained in a composite received signal relayed through a relay system such as a satellite transponder. The canceller digitally downconverts the received signal and a local replica of the transmitted signal from IF to baseband, applies a variable delay and frequency compensation to the replica as a coarse delay and frequency correction, and tracks fine delay, amplitude and phase differences using an adaptive finite impulse response filter to generate a cancellation signal corresponding to the delayed and frequency shifted version. A minimum output power process produces an error signal that drives the variable delay and adaptive filter to minimize the power in the signal of interest to maximize cancellation of the interfering signal.
96 Citations
21 Claims
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1. A method of canceling an interfering signal contained in a received signal which includes a signal of interest, the interfering signal being a relayed version of a transmitted signal from the location of the received signal, the method comprising
converting the received signal and a replica of the transmitted signal to digital signals; -
tracking variations in predetermined signal parameters resulting from relaying the transmitted signal between the interfering signal and the replica of the transmitted signal to produce a compensation signal; combining the compensation signal and the received signal to cancel first variations between the interfering signal and the sample of the transmitted signal to produce the signal of interest; generating an error signal representing uncanceled second variations between the interfering signal in the signal of interest; and controlling said tracking with the error signal to reduce differences between the compensation signal and the interfering signal to produce the signal of interest. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of operating at baseband on digital signals to cancel an interfering signal in a received signal that contains the interfering signal and a signal of interest, the interfering signal corresponding to a relayed version of a transmitted signal, the method comprising:
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estimating first differences in predetermined signal parameters between the transmitted signal and the interfering signal, said signal parameter differences resulting from relaying said transmitted signal; applying first compensations corresponding to the estimated first differences to produce a first compensated version of the transmitted signal; tracking variations in second differences between the first compensated version and the interfering signal to produce a second compensated version of the transmitted signal; combining the second compensated version and the received signal to cancel at least in part the interfering signal and produce the signal of interest; generating an error signal from the signal of interest; and controlling said tracking with said error signal to reduce said second differences between the second compensated version and the interfering signal. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. An interference canceller for canceling an interfering signal corresponding to a relayed version of a transmitted signal from a received signal containing the interfering signal and a signal of interest, comprising
a first variable signal parameter compensator for applying a first signal parameter compensation to a replica of the transmitted signal; -
a second variable signal parameter compensator for applying a second signal parameter compensation to the of the transmitted signal; an adaptive filter for tracking variations in said first and second signal parameters in said following said first and second compensations and for producing a cancellation signal; and a combiner for combining the received signal and the cancellation signal to cancel the interfering signal and produce the signal of interest. - View Dependent Claims (19, 20, 21)
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Specification