A cryogenic sapphire oscillator (CSO) has been implemented at 11.2 GHz using a low-vibration design pulsetube cryocooler. Compared with a state-of-the-art liquid helium cooled CSO in the same laboratory, the square root Allan variance of their combined fractional frequency instability is σy = 1.4 × 10-15τ-1/2 for integration times 1 < τ < 10 s, dominated by white frequency noise. The minimum σy = 5.3 × 10-16 for the two oscillators was reached at τ = 20 s. Assuming equal contributions from both CSOs, the single oscillator phase noise Sφ -96 dB.rad 2/Hz at 1 Hz set from the carrier.
|Number of pages||5|
|Journal||IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control|
|Publication status||Published - May 2010|