Development of 4.596 GHz RF source for chip-scale atomic clock

作者：Ji Lei; Tang Liang^*; Zhang Zhongshan

来源：High Power Laser and Particle Beams, 2015, 27(2): 24130.

DOI：10.11884/HPLPB201527.024130

• Chip-scale atomic clocks
• Digital phase locked loops
• Fractional-N frequency synthesizers
• Loop filter
• Microwave signal source
• Peripheral control
• RF sources
• Short term stability

Chip-scale atomic clock (CSAC) mainly includes an RF source, a physics package and other peripheral control circuits. The RF source which is related to the short-term stability of the CSAC plays an important role in CSACs. The technology of digital phase-locked loop is used to realize the 4.596 GHz RF source in this paper. The RF source is made up of three parts, including the fractional-N frequency synthesizer chip, the voltage-controlled oscillator (VCO) and the loop filter. Advantages of digital phase-locked loop used in the microwave signal source are low phase noise and pure spectrum. Furthermore, as the fractional-N frequency synthesizer chip is programmable, the output frequency can be swept by configuring the values of R divider and N divider, making the frequency control of CSACs easy. With the related formula, parameters of the loop filter are calculated approximately, and a loop filter with 300 kHz loop bandwidth and 55°phase margin is designed. Finally, The whole RF source based on the digital phase-locked loop is simulated, fabricated and tested. The result shows that the phase noise of the RF source is -74.02 dBc/Hz at 300 Hz offset, which meets the requirement of the RF source for CSACs.

• 出版日期2015