Interference canceller for the protection of direct-sequence spread-spectrum communications from high-power narrowband interference
AssigneeBae Systems Canada Inc.
InventorsShane Michael Joseph Young, David Charles Bongfeldt
Life of this patent
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Abstract
A system for canceling contaminating narrowband interference for a wideband DSSS receiver by weighting a channelized copy of the signal of interest in accordance with the result of a correlation between a narrowband copy of the channelized signal of interest centered around the center frequency of the contaminating narrowband interference and a narrowband copy of a wideband feedback signal centered around the center frequency of the contaminating narrowband interference.
Claims16
An interference cancellation system that mitigates deleterious effects of one or more narrowband interference (NBI) signals against a wideband signal of interest in a received signal in a received signal path, the system comprising:
- auxiliary sample means for extracting a copy of said received signal to obtain a wideband auxiliary signal;
- feedback sample means for extracting from said received signal path a wideband error feedback signal downstream from the auxiliary sample means, and for processing said error feedback signal to isolate a narrowband feedback signal in response to a variable frequency control signal determining a central frequency of said narrowband feedback signal;
- means for generating a narrowband reference signal from said auxiliary signal in response to a variable frequency control signal determining a central frequency of said narrowband reference signal, said narrowband reference signal containing one of said one or more NBI signals and having a strong correlation with respect to said narrowband feedback signal as a result of said NBI and not as a result of said signal of interest;
- controller means for sweeping through at least a portion of a frequency range of the wideband signal of interest by setting said variable frequency control signal, for determining whether the wideband signal of interest is contaminated by NBI by examining said narrowband reference signal, and for generating in response to detection of NBI an NBI cancellation control signal;
- means for correlating said narrowband reference signal and said narrowband feedback signal and for generating a complex correlation signal;
- means providing an injection signal containing said one of said NBI signals;
- complex weighting means for adjusting an amplitude and a phase of the injection signal in response to the correlation signal, and for generating, subject to said NBI cancellation control signal, an NBI cancellation signal;
- and
- means for injecting said NBI cancellation signal into said received signal path downstream of said auxiliary sample means and upstream of said feedback sample means, whereby the contaminating NBI is cancelled from the wideband signal of interest in the received signal path.
A method of canceling NBI in a wideband signal comprising:
- extracting a reference signal and a feedback signal in a receiver signal path;
- scanning said reference signal for contaminating NBI to determine the central frequency of said contaminating NBI;
- isolating narrowband copies about said central frequency from said reference signal and said feedback signal, wherein said narrowband copy of said reference signal is strongly correlated with said narrowband copy of said feedback signal as a result of said NBI and not as a result of a signal of interest;
- correlating said narrowband copies;
- complex weighting an injection copy of the wideband reference signal using a result of the correlation;
- and
- injecting the weighted injection copy into said receiver signal path at a point between a point of extraction of said reference signal and of said feedback signal,
- whereby an equivalent of a notch filter is applied to the wideband signal of interest at the frequency of said contaminating NBI.
Dependencies are inferred from the claim text.