| 摘要 |
PROBLEM TO BE SOLVED: To receive an orthogonal frequency division multiplex signal stably. SOLUTION: A demodulator 15 specifies setting of an attenuation for improving the receiving conditions by measuring the variation in receiving level when attenuation is switched in any one of variable attenuators 9-12 in an interval corresponding to the guard interval section of a receiving signal. The demodulator 15 resets the attenuation switched for the purpose of receiving level measurement at the ending timing of an interval corresponding to the guard interval section. When a decision is made that the receiving level is raised by switching attenuation, the demodulator 15 varies attenuation of a receiving signal stepwise every time when an interval corresponding to the guard interval section arrives.
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