Design And Implementation Of High Precision Broadband Frequency Measurement System

Time and frequency measurement is one of the most basic technology in modern electronic measurement. Because of the time and frequency have the highest accuracy and stability, the high precision measurement and analysis of the time and frequency is the foundation of precision measurement of other physical quantities. In order to improve the accuracy of frequency measurement, scholars have carried out extensive research and experiment, which has made great achievements. Although the accuracy of frequency measurement can be improved to a certain extent by using appropriate method when testing in different frequency ranges and application conditions, there is lack of frequency measuring method in industrial application, which requires quickly response, high resolution, simple structure , small size and can be able to measuring both low frequency and high frequency signals with the same precision. Through the study of existing frequency measurement theory and a kind of frequency output sensor, this dissertation designed a high precision and board range real-time measurement system which is suitable for industrial promotion.This frequency measurement system is based on FPGA (Field Programmable Gate Array), DDS (Direct Digital Frequency Synthesis), PLL (Phase Locked Loop Frequency Synthesis), and STM32 microcontroller in ARM Cortex-M3. FPGA has built pulse counting module, PLL frequency division module and mixer module. STM32 is responsible for processing and display data from FPGA, and then transmiting data to the upper PC system in LabWindos CVI through the Ethernet. This system has improved the measurement accuracy through PLL doubling the difference frequency signal between the input signal and reference signal generated by DDS. Frequency measurement module translates datas to micro controller through SPI,and then the STM32 MCU processes these datas and display the current measurement frequency value by LCD and sends measurement results to software written in LabWindos CVI in PC platform through the Ethernet to real-time display and storage.The test speed is better than 1Hz and the measuring resolution is better than the 0.01 Hz.The dissertation completes the system-design measuring the frequency signal in wide range and high precision, which is suitable for small incremental frequency signal.