Importance

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Abstract

An interference cancellation system automatically couples and decouples intself from a radio receiver system when no interfering signals are present. The interference cancellation system, which is adapted to be connected to the radio receiver system having a receiver antenna, a receiver and a receiver transmission line interconnecting the receiver antenna and the receiver, includes an auxiliary antenna, a first directional coupler connected to the auxiliary antenna, a second directional coupler connected to the receiver transmission line, a third directional coupler connected to the first directional coupler, a synchronous detector connected to the third and second directional couplers, a signal controller connected to the synchronous detector and a subtractor connected to the receiver transmission line and to the signal controller. A detector is connected to the third directional coupler, and a comparator is connected to the detector and is provided with a predetermined threshold voltage level. The comparator compares the detected output signal from the detector with the predetermined threshold voltage level, and provides an output signal to a switch circuit interposed between the signal controller and the subtractor. When an interfering signal is detected, the switch circuit provides an electrical path from the signal controller to the subtractor so that a cancellation signal may be injected into the receiver transmission line. If no interfering signal is detected, the switch circuit opens the connection between the signal controller and the subtractor so that no noise from the interference cancellation system is injected into the radio receiver system.

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First Claim