Fast Autotuning of a Hydrogen Maser by Cavity Q Modulation
Abstract
A new fast auto-tuner for the Hydrogen Maser has been implemented. By modulating the cavity Q, a phase shift in the maser output signal is induced which is proportional to the cavity tuning error. This phase shift is detected and fed back to a varactor tuner to stabilize the cavity against long term drifts. Cavity Q modulation has similarities to two other auto-tuning methods, and significant advantages over both of them. In comparison to line Q modulation, where the frequency shift induced by a change in the atomic line Q requires a second maser for detection, the high chopping frequency allowed by cavity Q modulation gives rise to a phase shift which requires only the maser's quartz crystal "flywheel" oscillator for detection. In comparison to cavity frequency modulation, statistical noise considerations are almost identical. However, a significant advantage is the lack of phase modulation of the maser output, feedback being around the null modulation condition. Furthermore, the Q-modulator is a valuable analytical tool in maser alignment. Its advantage over signal injection schemes, which give somewhat lower statistical deviation, is a lack of systematic perturbations, Including independence to connecting cable lengths.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1985
- Accession Number
- ADA498431
Entities
People
- G. J. Dick
- T. K. Tucker
Organizations
- California Institute of Technology