Abstract：The digital attenuator controlled by Complex Programmable Logic Device (CPLD) outputs two coherent pulsed microwave signals.They interact with hydrogen atoms and induce Ramsey interference.So the line width of hydrogen maser is reduced and the performance of frequency stability could be improved.Single Chip Micyoco(SCM) controls Direct Digital Synthesizer(DDS) to implement frequency sweep.So the Ramsey fringe is obtained.It’s all based on conventional passive hydrogen maser.So far,The Ramsey fringe was observed and its line width is about 1.2 Hz,which is only 40% of that of conventional passive hydrogen maser in the same condition.
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2012, Vol. 33 
