| 摘要 |
PURPOSE:To perform communication at arbitrary communication speed with one carrier, by providing a synthesizer capable of setting an arbitrary transmission/reception channel and a modem capable of performing modulation/demodulation at arbitrary signal speed with one device, selecting the transmission/reception channel in which a desired frequency band area can be obtained corresponding to transmission speed, and setting it on the synthesizer. CONSTITUTION:A transmission data inputted from a terminal 15, after being modulated at the modem 16, is frequency-converted at a frequency converter 17, and is transmitted from an antenna 10 through a transmission/reception shared apparatus 18. Adversely, a reception wave obtained at the antenna 19 passes through the transmission/reception shared apparatus 18, and is frequency-converted at the frequency converter 17, and is converted to a reception data at the modem 16, and is outputted to a terminal 14. At this time, the available state of a channel is always stored in a vacant channel memory device 21, and when the transmission speed fb is changed, a bit of channel information in which the frequency band area corresponding to the fb is found by searching the vacant channel memory device 21 is searched, and based on the above information, the synthesizer 23 is set at the frequency by controlling a channel allocation control device 22.
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