FREQUENCY SYNTHESIS BASED ON THE CRYOGENIC SAPPHIRE OSCILLATOR FOR THE NIM FOUNTAIN CLOCK

In this paper a new design microwave frequency synthesis for NIM5 cesium fountain primary frequency standard was introduced. The frequency synthesizer uses a cryogenic sapphire oscillator (CSO) as an ultra-stable local oscillator. The microwave frequency synthesis includes two parts: the down converter frequency synthesis from the output frequency of CSO to 100 MHz and the up converter frequency synthesis chain from 100 MHz to cesium fountain clock transition frequency of 9.192 GHz. The short-term frequency stability of the new microwave frequency synthesis is better than 1 × 10^(-14) at 1 second.