| 摘要 |
PROBLEM TO BE SOLVED: To enable automatic, accurate and secure switchover of reception between a high-speed communication mode and a low-speed communication mode. SOLUTION: In case of reception in the high-speed communication mode, receiving signals Ra, Rb are demodulated in demodulator circuits 24a, 24b, respectively, while in case of reception in the low-speed communication mode, the receiving signals Ra, Rb are respectively demodulated in demodulator circuits 25a, 25b, and supplied to a control circuit 26, one of which is then selected and output from an output terminal 27a. A third receiver receives by successively switching a plurality of channels in the high-speed communication mode, and the receiving signal Rc thereof is demodulated in demodulator circuit 24c and supplied to the control circuit 26. The control circuit 26 calculates a mean quality value on a channel-by-channel basis of a demodulation signal Ds from the demodulator circuit 24c. When the mean quality values of the entire channels are a set reference value or less, the receiving mode is set to the low-speed communication mode, whereas when at least one mean quality value exceeds the set reference value, the receiving mode is set to the high-speed communication mode. COPYRIGHT: (C)2008,JPO&INPIT
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