Improved Method of Resolving the Frequency Difference Between Two Very Accurate and Stable Frequency Signals

摘要

With the advance in accuracy and stability of modern atomic clocks, the need for a very precise method of detecting instabilities in their signals has arisen. For example, with two hydrogen masers with a 1 in 10(15) frequency difference, the drift rate of phase due to the frequency difference will be 1fs per second or 3.6ps per hour. No ordinary universal counter would be capable of resolving the difference between the two signals.