Research And Implementation Of Digital Circuit-Based Frequency Identification Algorithm

Frequency measurement technology,as an important means of detecting weak signals in phasemeters,is widely used in important equipment and devices in industry,electric power,agriculture,transportation,aerospace,national defense construction and other sectors,and is of great significance in national security,aerospace and social economy.In the field of frequency measurement,it is particularly important to improve the accuracy and sensitivity of frequency measurement,and it has become a major research trend in this field to achieve higher accuracy frequency measurement based on digital circuits.Based on the study of frequency measurement techniques for frequency domain curve fitting and the basic principles of phase-locked loops,the thesis designs a real-time and high-precision frequency measurement method and device,which mainly consists of a front frequency measurement module and a post frequency measurement module.The core structure of the front frequency measurement module is the local spectrum fitting measurement structure,which mainly includes the LIF function integration module,curve fitting module and iterative frequency measurement module.The front frequency measurement module can measure the input signal frequency with high accuracy within a certain error range,providing a stable and highly accurate centre frequency for the post frequency measurement module.The core structure of the post frequency measurement module is a phase-locked loop structure,which mainly contains modules such as phase discriminator,loop filter and CNC oscillator.To address the problem that the accuracy and bandwidth of the post measurement module cannot be balanced,the higher accuracy frequency provided by the front measurement module is used as the center frequency of the post measurement module to ensure the bandwidth,and at the same time,the post measurement module can work in the high accuracy mode normally.Based on the basic principle of curve-fitting frequency measurement algorithm and the influence of each parameter on the measurement accuracy,the article firstly digitally designed the pre-frequency measurement circuit,and the design index is the measurement frequency range of 2 MHz-10 MHz,and the measurement frequency error is one ten thousandth of the measured frequency..Then,the thesis addresses the digital design of the post-measurement algorithm of the phase-locked loop algorithm with a design index of no less than 100 ppb measurement accuracy at 10 MHz,and simulates the effect of different structural parameters in the simulation domain..Finally,based on the digital design of the front and post measurement modules,the two modules are integrated and the on-board verification is done for different input signals,thus achieving a high accuracy measurement result of 50 ppb at 10 MHz.Besides,the thesis also explains the hardware structure,communication module,and upper computer module of the whole frequency measurement device.The hardware structure uses the XC7K325T(kintex-7)FPGA chip from Xilinx as the computing carrier,and designs the FPGA board including various modules such as AD9268,AD9767,PHY,etc.Other functions such as heat dissipation of the board case are also designed to make the whole system a complete device.