Abstract: Physics package is the key assembly of rubidium frequency standards (RFS). By analyzing the factors affecting frequency stability, the interior structure of physics package is modified. This physics package is designed according to the three cells scheme, in which an optical filter and a magnetron microwave cavity are used. A preliminary test shows that the temperature coefficient (TC) is 9.7×10^-14/℃ and the frequency stability of the RFS is nearly 1×10^-12τ^-1/2(1s≤τ≤10 000s).

Key words: Rubidium frequency standards, Physics package, Optical filter, Magnetron microwave cavity, Temperature coefficient