An ultra-miniature rubidium frequency standard

An ultra-miniature, general-purpose rubidium gas cell frequency standard with a two-cell scheme has been successfully developed, with the aim of developing one of the smallest atomic frequency standards in the world. The target volume of the new rubidium frequency standard is less than 100 cm³. It is assumed that the shape of oscillator enables to mount on a printed circuit board. In order to miniaturize the volume and height, the physics package is made small. Because the frequency of the cavity resonator is 6.834 GHz and the resonator mode is TE₁₁₁, the inside diameter of the cavity needs to be 26 mm. To reduce the inside diameter, a new cavity resonator, which contains a dielectric material, has been developed. As a result, an inside diameter of 16 mm and a capacity of 6.7 cm³ are achieved. The total size of the physics package, which contains a rubidium-lamp exciter, a preamplifier, and a single magnetic shield of mumetal, is reduced to 25 cm³. By applying the PLL method, instead of the conventional frequency multiplier for a high frequency circuit that generates resonance frequency of 6.834 GHz from a slave oscillator, the size and cost of the circuit are minimized. As for the reduction of the power consumption, a new switching regulator IC is adopted in the power circuit. In addition, with the use of DDS, it enables to set the output frequency within the range of 1 to 15 MHz. Because of these features, the new rubidium frequency standard is extremely small in volume (95 cm ³), and lightweight (180 grams)