Study And Design Of Heterodyne Frequency Meter With Virtual Instrument

A scheme adopting VI(Virtual Instrument) technology to realize heterodyne frequency measurement is presented in this paper by studying the application of the virtual instrument in high-precision frequency measurement field. A set of prototype of heterodyne frequency measurement system based on technology of VI is designed, and accomplished.With the development and popularization of computer technology, the advantage of VI to replace traditional device has shown gradually; along with the rapid development of high-stabilization source of frequency and the application of accurate frequency measurement, the requirement for frequency measurement is more rigorous. The disadvantage of the conventional instruments and methods of frequency measurement has been emerged, especially lacking of the accuracy of measurement and the ability of process and analysis of data. Improving the ability of conventional instruments is necessary.Advancing the accuracy of heterodyne frequency measurement and decreasing the cost of instruments are the main objective of our study in this paper. The approach of combining the VI technology with the technology of heterodyne frequency is put forward in detail in this paper. The sinusoidal signal from phase detector that includes the information of frequency under test is transformed into digital signal and then fed into computer, correlative arithmetic is operated to analyze the digital signal and then the results of high-precision frequency measurement are gained. The strict research about all units of the frequency measurement system is made in the paper. According to the work flow, the entire system can be divided into several modules: heterodyne device module, data acquisition module, software interface module, data processing units. These units have been subdivided into single function parts, which are designed and tested, respectively.In this paper, the testing contrast between heterodyne frequency measurement of VI and heterodyne frequency measurement of traditional instrument is practised. The results of experiment that the new method has higher precision than the traditional method are proved. The accuracy reaches 1×10-15/2s at 10MHz frequency. The accuracy has achieved the advanced level in the world. The system of heterodyne frequency measurement with VI can reduce the cost, increase flexibility when it is compared with the traditional measurement. Finally, the main factors which influence the precision of frequency measurement are analyzed in detail in this paper.The experiment results show that, the high-precision frequency measured can be realized by this system; also it can provide the function of data analysis, data processing, data saving, frequency plots and rich interface output.