Experimental Results on a Frequency Standard Based on a Rubidium 87 Maser

This paper gives some experimental results related to the study and the development of an atomic frequency standard using a rubidium 87 maser as the reference oscillator. The main features of the maser design are a sealed quartz coated bulb, a mixture of N2-CH4 buffer gas, an atmospheric pressure proof enclosure, a threefold oven and a four-layer magnetic shield. The characteristics of these features are presented. The design of a modular low noise coherent receiver needed to phaselock the quartz oscillator is also discussed and its phase noise contribution, measured. The transfer of frequency stability between the maser and the quartz oscillator is tudied experimentally for short averaging times. A preliminary measurement of the mid term frequency stability is also obtained and an estimated overall performance of the frequency standard is given.