| 摘要 |
PROBLEM TO BE SOLVED: To flexibly cope with fluctuations of the characteristic of a radio transmission line and ensure high transmission quality, regarding an automatic frequency control device which holds a frequency of a local oscillation signal applied to heterodyne detection or synchronous detection of receiving wave to be a value adaptable to variation of frequency of the receiving wave. SOLUTION: This frequency control device is provided with a frequency variation measuring means 11 for measuring the variation of a frequency of the receiving wave, and a feedback control means 13, which decides whether the variation measured with the measuring means 11 belongs to a specified value region. When the decision results are 'true', the control means 13 performs negative feedback of the variation to a variable frequency oscillating means 12, which generates a local oscillation signal applied to the heterodyne detection or the synchronous detection of a receiving wave. When the decision results are 'false', the control means 13 holds the oscillation frequency of the oscillating means 12 to be constant or restrains update of the oscillation frequency. COPYRIGHT: (C)2003,JPO
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