Design And Simulation Of Digital Dual Mixer Time Difference Measurement System

High precision frequency sources are often measured by dual mixer timedifference measurement method which mixes signals at first and then detects thezero-crossing points. Zero-crossing points trigger the counter measurement. If thezero-crossing points are polluted by noise, they will cause measurement errors. Thismethod has noise sensitive properties which limit the measurement accuracy’simprovement. Currently it mainly relies on the device noise reduction for improvednoise, develops slowly, and therefore there are claims that: currently time differencemethod based on dual-mixer measurement accuracy has no risen space. This paperstudies suggest that the use of the proposed digital frequency measurement methodcan effectively solve these problems based on double balanced mixer principle.Developing a high-precision frequency measurement systems, software and hardwareplatform simulation system functions can be realized for the development of prototypepre-research.The main work of this paper includes:1.Introduce the characteristics of time-frequency signal and stability analysis.First, in the early part introduce the concepts related to time and frequency, study theeffect of phase noise model of frequency standard, random sequence expressionthrough variance inversion algorithm is derived for individual noise component,time-domain simulation and verification, and two kinds of representation of frequencystability are also introduced, the mutual transformation between time domain.2.Study the current mainstream frequency measurement technique. Focus on theclassic dual mixer time difference measurement algorithm, the advantages anddisadvantages are analyzed, designed a new type of digital measurement systemwhich combines the measurement algorithm of phase noise measurement theory andthe dual mixer time difference, retain their the advantages, break the limitation ofsimulation technology theory and improve the properties of the measurement system,and describes the key technology and module.3.System simulation. In the full study of the system architecture of the simulationin the software and hardware platform, and designs the noise source and the data werecompared to get consistent results, verify the feasibility of the system.4.The analysis of system accuracy index. Effects on deep analysis of the accuracy of the measurement system factor: the number of quantization bits andsampling rates of different groups of data, to achieve optimal allocation,satisfy thesystem requirements.