Adaptive feedforward noise cancellation circuit
First Claim
1. A method of performing noise cancellation comprising the steps of:
- receiving a signal having a frequency band;
generating a cancellation signal responsive to the signal for at least one predetermined frequency sub-band of the frequency band;
in which the signal is a transmit signal for a transceiver and the predetermined frequency sub-band corresponds to a receive frequency of the transceiver, andcombining the cancellation signal with a time-delayed copy of the signal whereby to provide an output signal having a reduced amplitude region corresponding to the predetermined frequency sub-band.
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Accused Products
Abstract
A method and apparatus for noise cancellation in communications systems. The method is applicable in situations where an interfering signal or noise must be cancelled within a specified bandwidth. A sample of the interfering signal is used to synthesize a cancellation signal which is of equal amplitude but opposite phase to the original interference signal. Introduction of the cancellation signal into the interference signal path results in substantially complete suppression of the interference signal through vector subtraction of the superposed signal fields. Adaptive cancellation is also provided in that the frequency and bandwidth of the cancellation signal can be controlled. The adaptive nature of the cancellation loop also tracks out imbalances between the interference and cancellation signals caused by temperature variation and component tolerances. The adaptive nature of the cancellation system also allows the system to lock onto and track an interfering signal.
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Citations
23 Claims
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1. A method of performing noise cancellation comprising the steps of:
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receiving a signal having a frequency band; generating a cancellation signal responsive to the signal for at least one predetermined frequency sub-band of the frequency band; in which the signal is a transmit signal for a transceiver and the predetermined frequency sub-band corresponds to a receive frequency of the transceiver, and combining the cancellation signal with a time-delayed copy of the signal whereby to provide an output signal having a reduced amplitude region corresponding to the predetermined frequency sub-band. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A noise cancellation circuit comprising:
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a first circuit arranged for receiving a signal having a frequency band; a second circuit, coupled to the first, and arranged for generating a cancellation signal responsive to the signal for at least one predetermined frequency sub-band of the frequency band; in which the signal is a transmit signal for a transceiver and the predetermined frequency sub-band corresponds to a receive frequency of the transceiver, and a third circuit, coupled to the second, and arranged for combining the cancellation signal with a time-delayed copy of the signal whereby to provide an output signal having a reduced amplitude region corresponding to the predetermined frequency sub-band. - View Dependent Claims (19, 20, 21)
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22. A program for a computer on a machine readable medium comprising code portions arranged to:
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control receipt of a signal having a frequency band; control generation of a cancellation signal responsive to the signal for at least one predetermined frequency sub-band of the frequency band; in which the signal is a transmit signal for a transceiver and the predetermined frequency sub-band corresponds to a receive frequency of the transceiver, and control combination of the cancellation signal with a time-delayed copy of the signal whereby to provide an output signal having a reduced amplitude region corresponding to the predetermined frequency sub-band.
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23. A method of performing noise cancellation at a transceiver having a transmit path and a receive path comprising the steps of:
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sampling a signal in the transmit path of the transceiver, the signal having a frequency band; generating a cancellation signal responsive to the signal for at least one predetermined frequency sub-band of the frequency band, the predetermined frequency sub-band corresponding to a receive frequency used in the transmit path of the transceiver at which it is desired to minimize noise; combining the cancellation signal with a time-delayed copy of the signal whereby to provide an output signal for transmission having a reduced amplitude region corresponding to the predetermined frequency sub-band.
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Specification