Research Of DDS Signal Source In Optical Frequency Standards

Time is one of the seven basic physical quantities in physics.Time and frequency standards with high precision play an important role in the field of fundamental physics research and navigation communication.Aluminum ion optical frequency standard is one of the optical frequency standards whose uncertainty have reached the level of 10^-18 at present.Since it has the smallest blackbody radiation shift,it is a promising ion optical frequency.During the operation of the aluminum ion optical frequency standard,it is necessary to control the frequency of each laser with high precision.Generally,the laser frequency control in the experiments is realized by controlling the RF signal on the acousto-optic modulator in the optical path.In the optical frequency standards,we need to perform complex and fast operation on these RF signals,so it requires that the RF signal source not only has high frequency resolution and stability,but also can achieve fast frequency jumping.But commercial standard RF source instruments or the voltage controlled oscillators can't meet the requirements.So we need to develop home-made signal source that has fast frequency jumping function.Direct Digital Synthesizer?DDS?has many advantages,such as fast frequency conversion,high frequency resolution,frequency switching with continuous phase,easy realization of multiple modulation functions,easy for microprocessor control,and low phase noise.Furthermore,the signal source based on DDS chip is fully digital,and has superior performance and small size.Therefore,this thesis carried out the research on the signal source based on DDS chip.This thesis systematically introduces the research work on the low frequency DDS signal source based on AD9854 and the high frequency DDS signal source based on AD9914,including the hardware circuit's design,fabrication and the program control.The program control is realized by NI company's integrated Field-Programmable-Gate-Array?FPGA?board NI7856R.After debugging,the low DDS circuits are constructed successfully.Finally,we measure the performance of the circuits.The test results show that the maximum output frequency of the signal source based on AD9854 is 120MHz,its frequency stability of 10MHz signal is 3.8×10^-11@1s,and its frequency jumping time is about 200ns.The frequency stability of the 450MHz signal output for the high-speed signal source based on AD9914 is 8.5×10^-14@1s,the phase noise is-135dBc/Hz?offset frequency is 100kHz at 450MHz?,the frequency jumping time is about 150ns.The performance meets the experimental requirements of aluminum ion frequency standard.