| 摘要 |
A radio receiver having a narrow effective beamwidth includes a receiver antenna, a receiver and a receiver transmission line interconnecting the two, and an interference cancellation system having an auxiliary antenna, a first directional coupler connected to the auxiliary antenna, a second directional coupler connected to the receiver transmission line, a synchronous detector connected to the first and second directional couplers, a signal controller and a subtractor connected to the signal controller and to the receiver transmission line. The receiver antenna is selected to exhibit an omni-directional antenna pattern, while the auxiliary antenna is selected to exhibit a null in its antenna pattern. The null is directed toward the desired signal such that any signals outside of a predetermined angle from the center of the null will be cancelled by the interference cancellation system, and the desired signal which is received within a predetermined angle from the center of the null will be substantially unaffected by the interference cancellation system.
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