High-performance frequency reference based on cryogenic sapphire oscillator

Precision measurement experiments require high-performance frequency references that have ultra-low phase noise and excellent frequency stability. In conjunction with phase noise cancellation and frequency synthesis technologies, we expect cryogenic sapphire oscillators to serve as microwave frequency references. To this end, we employed a cryogenic sapphire filter to reduce the phase noise of the cryogenic sapphire oscillator, thereby achieving the generation of a 10.798 GHz microwave signal with ultra-low phase noise of up to -165 dBc/Hz at an offset frequency of 1 MHz. Furthermore, to take full advantage of the excellent frequency stability, we designed a frequency conversion chain generating reference frequencies at 9 GHz, 100 MHz, and 10 MHz, achieving fractional frequency stability in the low 10-15 range for integration times between 100 and 1000 s. Such a signal source can become the frequency reference of choice for many scientific applications.