Design Of FPGA-based Sinusoidal Signal Phase Difference Measurement Method

Phase difference refers to the difference between the phases of the two-way sinusoidal signal with the frequency,also known as phase difference.For two sinusoidal signals of the same frequency,the phase difference is equal to the difference of their initial phase and is a constant that does not change with time.In recent years,the measurement of the phase difference between the two sinusoidal signals is widely used in signal analysis,industrial automation,intelligent control,electronic and communication technology,biomedicine,radar,sonar,water quality monitoring and and other fields.Therefore,to accurately measure the phase difference between the two sinusoidal signals received by the sensor has important theoretical significance and application value.After analyzing the commonly used method of measuring the phase difference of sinusoidal signals,this paper designs three kinds of phase difference measurement methods based on FPGA(Field Programmable Gate Array)and hardware circuits for the existing defects,and the three designed phase difference measurement methods were verified,and the phase difference measurement method based on FPGA and FFT technology is applied to the measurement of dissolved oxygen content in water.The results show the validity of the phase difference measurement method based on FPGA and FFT technology designed in this paper.The main contents and achievements of the paper are summarized as follows:(1)Three phase-difference measurement methods and circuits based on FPGA are respectively designed,and three measurement circuits are designed on the same hardware circuit board,including subtraction measurement circuit,multiplication measurement circuit and FFT method measurement circuit,and the AGC(Automatic Gain Control)circuit,the second-order active band-pass filter circuit,the second-order active low-pass filter circuit,the DAC(Digital to Analog Converter)module and the ADC(Analog to Digital Converter)module,the DDR2(Double Data Rate 2)interface circuit and other module circuits are also designed.(2)After studying the basic principle of DDS(Direct Digital Synthesizer),two standard sinusoidal signals with a certain phase difference are generated by using DDS IP(Intellectual Property)core in FPGA and hardware circuit module,and they are used to verify the feasibility of the phase difference measurement method designed in this pape.The phase difference measurement method based on FPGA and FFT technology designed in this paper is realized by using FFT IP core in FPGA.(3)The three phase difference measurement methods designed in this paper are respectively verified,the measurement accuracy and measurement error of the three measurement methods are analyzed based on the experimental data.Then the three measurement methods were comprehensive comparative analysis.Finally,the phase difference measurement method based on FPGA and FFT technology were used in the measurement of dissolved oxygen content in water.The results show the validity of the phase difference measurement method based on FPGA and FFT technology designed in this paper,it can achieve ppb(parts per billion)measurement accuracy when measuring dissolved oxygen content in water.