| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an automatic frequency control apparatus, capable of being applied to either of an analog signal and a digital signal, and capable of being achieved by a simple circuit. <P>SOLUTION: The variation of the output signal (frequency detecting signal Sd) of a frequency detecting circuit 3 is detected, the difficulty of stable frequency control is decided when the value of the variation exceeds a predetermined threshold, and the frequency control is stopped. Specifically, the variation component Sp1 of the frequency detecting signal Sd is detected. The absolute-value signal Sp2 of the detected variation component Sp1 is generated, and a signal Sp3 obtained smoothing the signal Sp2 is compared with the threshold St. A stop signal Ss is output when the signal Sp3 exceeds the threshold St, and the frequency control of a partial oscillation signal So by a control circuit 5 is stopped. <P>COPYRIGHT: (C)2011,JPO&INPIT</p> |
