Progress on prototype synthesizer electronics for /sup 199/Hg/sup +/ at 40.5 GHz

Description

This item was taken from the IEEE Periodical ' Progress on prototype synthesizer electronics for /sup 199/Hg/sup +/ at 40.5 GHz ' The design and specifications of a synthesizer for the /sup 199/Hg/sup +/ ion standard are presented. A fractional frequency stability of 5*10/sup -15/ at 100 s will be required in order to reach the fundamental linewidth imposed by the shot noise of the atomic signal. This might be achieved by first locking a low-noise 5-MHz oscillator to an active hydrogen maser. A 100-MHz oscillator can then be locked up to the 5-MHz oscillator to reduce close-in phase noise. A commercial digital synthesizer can be used to offset-lock a 100.018-MHz oscillator to the 100-MHz signal. Frequency resolution and modulation capabilities will be provided by the digital synthesizer. The 100.018 MHz will be multiplied by five, filtered, amplified, and routed through a step recovery diode. The 81st harmonic will be extracted to probe the hyperfine resonance of /sup 199/Hg/sup +/ ions. A long-term stability of 6*10/sup -17/ is expected from the first prototype.<>