| 摘要 |
For the transmission of information via short wave, for example telex signals or data, the modulation rate must not be selected to be too high, because of short-term atmospheric interference. Modulation rates of 200 bauds are normal. In the transmission of a bit rate of an information data flow rate which substantially exceeds a normal modulation rate, it is therefore necessary to distribute the data signal over a substantial number of closely adjacent channel carrier frequencies, to which the information is added in the form of frequency-differential phase modulation. The modem (MCD) used for this purpose represents a functional unit which interacts with the actual radio transceiver device (S/E). The fact that the adjustment of the radio receiver (EM) is relatively slow-acting in this context proves disadvantageous in terms of optimum transmission. It is proposed to provide, in the demodulation part (D) of the modem on the input side, a high-speed level-monitoring circuit which uses a periodically reset integrator (I) to recover the control signal. In this case, the integration time of the integrator is defined for a period of the fundamental frequency common to the orthogonal channel carrier frequency group, and the integration time is expediently positioned mid-way between two phase shifts which occur in time with the modulation rate within the composite channel signal (Ue). <IMAGE>
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