10-15 Frequency Stability Microwave Synthesizer for Atomic Fountain Frequency Standard

This paper presents the design and phase noise measurement of microwave frequency synthesizer for atomic fountain frequency standard. In this synthesizer, a voltage-controlled DRO is locked to 100MHz hydrogen maser signal through a divider chain. The required interrogation frequency 9192631770 Hz is generated by mixed with 7368230 Hz and 400 MHz signals. The experimental results show that the phase noise of interrogation signal at 9.192 GHz is -88dBc/Hz@ offset 1Hz. With such performances, the expected Dick effect contribution to atom fountain frequency standard is reported at a level of 1.0×10-15 at 1 s integrating time, that is a factor 10 higher than quantum noise limit of atom frequency standard. The carrier spectral spur of microwave synthesizer signal impacted on atomic fountain frequency standard is also discussed.