| 摘要 |
PURPOSE:To obtain a group and a supergroup pilot frequency generating system without need of frequency maintenance, by comparing a frequency of a main oscillator and a pilot frequency and driving a voltage controlled oscillator with the comparison output via an up-down counter. CONSTITUTION:In a generating system of group/supergroup pilot frequency of an FDM carrier device, a fundamental frequency fFUND from a main oscillator 1 is 1/N-frequency-divided at a frequency-divider 2 to be a reference frequency fs and inputted to a frequency converter 3. An output of a voltage controlled oscillator VCO5 is 1/M-frequency-divided at a frequency divider 4 to be a frequency fm and inputted and compared with the fs at the comparator 3. The output of the comparator 3 controls an up-down counter 6 to +1, -1 or as it is depending if the fm is higher, lower than or equal to the fs. The output of the counter 6 is inputted to a D/A converter 7 to control the frequency of the VCO5 with a voltage proportional to the count value and this operation is continued until the fs is equal to the fm. The frequency of the VCO5 is 1/L- frequency-divided at a frequency divider 8 and outputted from a filter 9 as a specified frequency. |
