Abstract: Frequency stability is the most important parameter of a rubidium atomic frequency standard, which depends mainly on the signal-to-noise ratio (SNR) of the rubidium atomic discrimination signal (RADS). In this paper, we analyzed the effects of several factors on the SNR of the RADS, including the configuration of the microwave cavity, the spectrum purity of the rubidium spectrum lamp and the isotope filtering scheme. It was shown that the SNR of the RADS could be improved by using a microwave cavity with proper microwave field mode and high microwave filling factor, a rubidium spectrum lamp with high spectrum purity and a separated isotope filtering scheme in the physics package design. The performance of the rubidium atomic frequency standard could be improved by taking all these factors into consideration.

Key words: rubidium frequency standard, signal-to-noise ratio, microwave cavity, rubidium spectrum lamp, isotope filtering