| 摘要 |
PURPOSE:To select a reception system with a large instantaneous CNR at all times by shifting a level detection characteristic excellent in sensitivity toward the lower reception level by the difference of sensitivity so as to decide the quantity of the instantaneous CNR. CONSTITUTION:Signals Sa, Sb received by reception antennas 1a, 1b are sent to detection sections 4a, 4b via RF IF sections 2a, 2b. A comparator 5 compares outputs of level detectors 3a, 3b to throw a changeover switch 6 to the reception system larger in level. The level detection characteristic of the better reception sensitivity is shifted to a lower reception input level depending on the reception sensitivity difference of the reception system in the level detection characteristic of the level detectors 3a, 3b. As a result, the comparator 5 selects the reception system having a large instantaneous CNR to change over the switch 6.
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