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Abstract

Method and apparatus for cancelling in-band interference in real time. A cancellation circuit is provided where one demodulator circuit provides a demodulated output having interference voltage owing to interference between carrier signals, between a carrier signal and noise, or a combination of both. Cancellation of interference is particularly directed to narrowband applications. Because the interference is within the band of the desired signal, it cannot be filtered without materially harming the quality of the message. A separation circuit is provided for removing the interference voltage component from the message signal. Outputs are provided to a second demodulator for creating a phase-shifted near replica signal of the dominant carrier signal without an interference voltage component. The separation circuit includes an isolation circuit. Further described are applications of the cancellation circuit, including demultiplexing a power-multiplexed signal, demodulation of two or more carrier signals, and removal of interference from modulated and unmodulated carrier signals.

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First Claim