| 摘要 |
PURPOSE:To improve the reliability of a telecasting equipment and also to prevent the break of a program signal owing to switching actions of video modulator, by using a rubidium atom oscillator to operate plural different video modulator in parallel with each other and therefore omitting a switch for those modulators. CONSTITUTION:The output of a rubidium atom frequency standard unit 93 is supplied to a reference frequency oscillator 93 for generation of a signal of the standard frequency. The video modulators 111 and 121 apply the frequencies of the output signals of crystal oscillators 13 and 14 as well as the reference frequency to comparators 91 and 92. When the outputs of both oscillators 13 and 14 have variance, the comparators 91 and 92 produce the error signals between the output frequencies of oscillators 13 and 14 and the reference frequency for control of the output voltages of oscillators 13 and 14 of modulators 111 and 121. Thus it is possible to obtain a constant output that is stable and synchronous with the reference frequency. The control is carried out for the output level or modulators even with different modulators 11 and 12 as long as the reference frequency is constant. Then the synthesizing is possible after setting the output levels at the same value.
|
