OSCILLATION SYSTEM FOR HIGHLY STABLE REFERENCE FREQUENCY

摘要

PURPOSE:To transmit a signal of highly stable and highly accurate frequency by providing a variable loop filter of the output of a phase comparing circuit, obtaining phase synchronism by a phase comparing circuit, and then adding band limitation to the variable loop filter and controlling a highly stable voltage- controlled oscillator. CONSTITUTION:The phase of a signal obtained through the 1/176 frequency dividion of a highly stable 10 MHz oscillator 9 is compared by a phase compar ing circuit 7 with the phase of a signal obtained by divding the frequency of the 3.58 MHz voltagecontrolled oscillator 5 by 63 and the loop filter 8 synchronizes the 3.58 MHz voltage-controlled oscillator 5 with the highly stable 10 MHz oscillator 10. The 3.58 MHz oscillator 5 is held highly stably. A phase comparing circuit 2 compares the phase of the output of the highly stabilized 3.58 MHz oscillator 5 with a color burst signal outputted by an extracting circuit 1. A lock detecting circuit 3 monitors the phase comparing circuit 2 and lowers the cutoff frequency of the variable loop filter 4 on detecting the acquisition of synchronism, thereby controlling the highly stable 10 MHz voltage- controlled oscillator 10 slowly.