Low phase noise microwave frequency synthesizer for cold atom clock

Abstract

We present a low phase noise microwave frequency synthesizer for the integrating sphere cold atom clock. The synthesizer is based on an ultralow-phase-noise oven-controlled crystal oscillator and employs a phase-locking technique. The absolute phase noise performance of the 6834 MHz signal was measured to be −60 and −120 dBc/Hz at offset frequencies of 1 Hz and 10 kHz, respectively. For the new scheme, the direct digital synthesizer is used to tune the clock output. The frequency tuning resolution was improved to 3.4 × 10−15. This scheme for the microwave frequency synthesizer can also be used in other precision measurements.

A low phase noise microwave source for high‐performance CPT Rb atomic clock

“…We have also measured the residual frequency stability of the 3.417 GHz microwave chain with the similar method in Ref. [19]. The 100 MHz OCXO splits into three arms, the first arm drives the 3.417 GHz signal chains as shown in Fig.…”

“…With the absolute phase noise of the 3.417 GHz microwave obtained with our method and estimated from the formula (1), the microwave's contribution to the atomic clock frequency stability through intermodulation effect is 4.7 × 10 −14 at 1 s averaging time, which is about half order of magnitude smaller than the state-of-the-art frequency stability of the CPT clock. We have also measured the residual frequency stability of the 3.417 GHz microwave chain with a similar method in [18]. The 100 MHz OCXO splits into three arms, the first arm drives the 3.417 GHz signal chains as shown in Figure 1, the second arm drives the 3.427 GHz signal with the same architecture.…”