| 摘要 |
PURPOSE:To unnecessitate setting of preamble and to improve the transmission efficiency by measuring a frequency of a modulation wave while a clock recovery preamble is sent and converting the frequency into a frequency of a reference signal. CONSTITUTION:A timer 26 of a gate signal generating circuit 25 and a timer clock 27 are used to generate a gate signal in response to a time equivalent to an integral number of multiple of the period of the symbol in the frequency measurement of a modulation wave and a counter 23 counts edges of the modulation wave by a gate time represented by a gate signal. Thus, the average frequency of the modulation wave measured in this way is converted into a data representing the frequency of the reference signal by a reference signal conversion circuit 29. Thus, the frequency of the reference signal is obtained from the clock recovery preamble. The preamble signal provided separately is not required to measure the frequency of the reference signal. |
