Improvement On Correlation Parameters Of CPT Atomic Frequency Standard

The thesis is devoted to optimize passive CPT atomic frequency standard, we have done the following jobs from three aspects in view of the frequency stability, frequency accuracy and the resource consumption reduction of laser loop.Firstly, we propose a digital quadrature demodulation method based on CORDIC algorithm. The method uses pipeline structure, only shift and addition unit, occupying less resources, higher efficiency, easy to FPGA implementation. We apply the method to laser frequency locking loop, avoiding phase matching adjustment step and reducing DC scanning process, and directly accessing to the best demodulation results and simplifying the atomic frequency standard debugging.Secondly, we propose a method to improve the light shift performance of CPT atomic frequency standard. The frequency stability of CPT atomic frequency standard largely depends on the performance of the physics system, so we change the microwave modulation index and the total light intensity by actively adjusting the temperature of VCSEL, change the laser detuning by adjusting the current of VCSEL, the experiment results show that when the temperature of used VCSEL is32℃and the current of VCSEL at949μA, the light shift performance of atomic frequency standard is optimized. The results reveal that the method is feasible for improvement of light shift performance of CPT atomic clock frequency standard and further upgrading the frequency stability of atomic frequency standard.Thirdly, we introduce a method that satellites1PPS signal discipline CPT atomic frequency standard. We make the output frequency of CPT atomic frequency standard doubled to200MHz, measuring the time interval between the satellite1PPS signal and CPT atomic frequency standard output in the gate time, achieve the measurement of frequency deviation, we use the frequency deviation to adjust the negative feedback which use the method of the rough adjustment of the register of phase-locked loop chip and the fine adjustment of the current of C field, locking frequency accuracy within1×10-10is achieved. Because the current satellite receiver’s output signal is not ideal, we achieve the performance significantly improved1PPS signal by the method of Kalman filter and hardware window.