| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a frequency control device for a reference clock signal in which a free run frequency is controlled into a specified frequency value with a change of the free run frequency caused by a change in a circuit component with the passage of time, repair, a circuit change and the like. <P>SOLUTION: An IF input of a satellite radio wave is received by a receiving circuit 6, and a PCR signal contained in its subcode area is extracted by a demodulation circuit 7 on the next stage and inputted to a CPU 12 as a reference clock. A loop control part composed of a PWM generator 9, an integration circuit 10 and a quartz resonator 11 is provided. Circuit constant data for determining the free run frequency are stored in a nonvolatile memory 13 connected to the CPU 12 and when the received signal is not proper such as when the extracted signal is not obtained from the received signal or when an antenna is not connected, the loop control is performed by using the circuit constant data stored in the nonvolatile memory 13 to obtain the accurate frequency. <P>COPYRIGHT: (C)2004,JPO |
