| 摘要 |
PURPOSE:To realize the highly-exact measurement of a distance based on a reference signal which is correct constantly even when the relative distance between transmission and reception sides is changed, by providing high-stability signal sources on the transmission and reception sides respectively, and further providing a reference signal source on the third side. CONSTITUTION:The carrier wave of a VLF signal received by an antenna 31 and a signal obtained by converting the output signal of a rubidium oscillator 33 with a frequency control terminal by a frequency synthesizer 36 are supplied to a phase comparator 34. The comparator 34 discriminates whether the output signal of the synthesizer 36 lags or leads in relation to the VLF signal, and delivers a signal proportional to the amount of the phase shift. This signal is integrated by an integrator 35 having a long time constant so as to obtain a control output proportional to a value obtained by integrating a phase difference for a long time. This control output is made to be a control signal of the oscillator 33 and thereby the phase difference is compensated. Accordingly, the output of the oscillator 33 is made synchronous in phase with the VLF signal with high exactitude, and the frequencies of rubidium oscillators 12 and 21 on the transmission and reception sides which are synchronized in phase with each other by the VLF signal are in accord with high exactitude. |
