Design And Implementation Of The Characteristic Test System For The Physical Resonator Of Cesium Atomic Clock

Accurate time and frequency parameters are indispensable in scenarios such as national defense construction,satellite navigation,digital communications,and scientific experiments.Since the 1967 International Metrological Conference changed the definition of seconds from astronomical timing to atomic seconds,the timing standard officially entered the atomic age.As a device that can reproduce the definition of seconds,the cesium atomic clock is of great significance to the establishment of the national time-frequency system.As the core component of the cesium atomic clock physical system,the resonator's characteristic test result is an important parameter to measure the performance of a cesium atomic clock.This article first briefly introduces the development of the cesium atomic clock and frequency synthesis technology,analyzes the working principle and structure of the cesium atomic clock,and designs a test system solution to solve the problem that the existing test system has complex modulation and close connection between devices,which cannot complete the test independently..The system can be divided into four parts: microwave frequency synthesizer hardware,intermediate frequency signal modulation module,spectrum line acquisition module,and host computer software.The host computer software realizes the adjustment of hardware modulation parameters and transition spectrum line drawing,to achieve the purpose of simplifying the test.The microwave frequency synthesizer combines the three technologies of direct frequency synthesis,phase-locked frequency synthesis,and direct digital frequency synthesis,and can output a highly stable microwave signal to excite the resonator.Secondly,the frequency synthesis principle and output signal parameters of the direct digital frequency synthesis technology are studied.Based on the AD9854 chip,the intermediate frequency modulation module is implemented.The STM32 controls the output of intermediate frequency signals that meet the linear sweep,frequency hopping,and point frequency modes required for resonator testing.The output signal parameters can be dynamically configured via USB,and work in conjunction with ADC acquisition and DMA transmission to achieve the matching of the transition signal acquisition data with the current output frequency and improve the accuracy of the test results.The host computer software is realized based on the WinForm graphics program development platform.The software is divided into three modules: spectral line drawing,hardware parameter adjustment,and data communication according to the requirements of the test system.The spectral line drawing module draws based on GDI+ technology,improves drawing efficiency,solves the problems of flickering and freezing of the native control when data points are refreshed fast,and provides functions such as line width calculation,range adjustment,and panel screenshots.The data communication module realizes the data communication between the upper and lower computers based on the USB protocol.After the lower computer is connected,it can automatically complete the identification and connection work,and notify the user to simplify the design of the main program by adding custom events.Finally,the software control function of the host computer and the setting accuracy of the IF modulation module and the quality of the output signal of the microwave frequency synthesizer are tested separately,and then the system is connected to the cesium atomic clock physical system for resonator testing to verify the feasibility of the system design.