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 delayed and frequency offset version of a transmitted signal from the location of the received signal, the method comprising converting the received signal and a sample of the transmitted signal to digital form;
- tracking variations in delay, frequency offset and frequency dependent gain and phase variation between the interfering signal and the sample of the transmitted signal to produce a compensating signal;
combining the compensating signal and the received signal to cancel the interfering signal and produce the signal of interest;
generating an error signal from the signal of interest representing any uncanceled components of the interfering signal in the signal of interest; and
controlling said tracking with the error signal to minimize offsets between the compensating signal and the interfering signal.
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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.
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Citations
31 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 delayed and frequency offset version of a transmitted signal from the location of the received signal, the method comprising converting the received signal and a sample of the transmitted signal to digital form;
- tracking variations in delay, frequency offset and frequency dependent gain and phase variation between the interfering signal and the sample of the transmitted signal to produce a compensating signal;
combining the compensating signal and the received signal to cancel the interfering signal and produce the signal of interest;
generating an error signal from the signal of interest representing any uncanceled components of the interfering signal in the signal of interest; and
controlling said tracking with the error signal to minimize offsets between the compensating signal and the interfering signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
- tracking variations in delay, frequency offset and frequency dependent gain and phase variation between the interfering signal and the sample of the transmitted signal to produce a compensating signal;
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14. A method of canceling at a receiving site an interfering signal in a received signal that contains the interfering signal and a signal of interest, the interfering signal corresponding to a delayed and frequency offset version of a transmitted signal transmitted from the site, the method comprising converting the received signal and a replica of the transmitted signal from intermediate frequency form to baseband digital form;
- estimating first offsets corresponding to coarse delay and frequency differences between the transmitted signal and the interfering signal;
applying first delay and frequency compensations corresponding to the estimated offsets to the replica of the transmitted signal to produce a first compensated replica of the transmitted signal;
tracking variations in delay, frequency, amplitude and phase offset between the first compensated replica and the interfering signal to produce a second compensated signal;
combining the second compensated signal 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 minimize offsets between the second compensated signal and the interfering signal. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
- estimating first offsets corresponding to coarse delay and frequency differences between the transmitted signal and the interfering signal;
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24. An interference canceler for canceling an interfering signal corresponding to a delayed and frequency shifted version of a transmitted signal from a received signal containing the interfering signal and a signal of interest, comprising a variable delay for applying a first delay compensation to a replica of the transmitted signal;
- a variable frequency element for tracking changes in frequency and for applying a first frequency compensation to the replica of the transmitted signal;
an adaptive filter for tracking delay, amplitude and phase variations in said replica following said first compensations for delay and frequency to produce 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 (25, 26, 27, 28, 29, 30, 31)
- a variable frequency element for tracking changes in frequency and for applying a first frequency compensation to the replica of the transmitted signal;
Specification