| 摘要 |
PROBLEM TO BE SOLVED: To provide an automatic variable attenuator which prevents a receiving signal from being distorted due to the influence of a high electric field in a receiver, without providing an attenuator circuit. SOLUTION: Upon the rise of the input signal level when a receiver goes into a high electric field area, etc., the tuning frequency of a tuning circuit is intentionally shifted from a desired frequency for reception, resulting in the attenuation of signal components at the desired frequency outputted from the tuning circuit. This absorbs the increased part of the input signal level and hence prevents a distortion from occurring in following circuits. The tuning frequency of the tuning circuit is adjustable by only changing a control signal applied to the tuning circuit, thus preventing the distortion, without needing to add a special circuit, component, etc. and without enlarging the size of the apparatus or causing the cost rise. COPYRIGHT: (C)2004,JPO
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