The Acquisition And Processing System Of Cavity Ring-down Signal Based On ZYNQ

Cavity ring down technology is a high-precision optical loss detection technology based on time attenuation method.The relaxation effect of laser in optical passive cavity is used to increase the optical path of laser in resonant cavity.By measuring the ring down time of resonant output light of optical passive cavity,important information such as cavity loss and gas concentration can be retrieved.It has become a standard method for ultra-low loss measurement at home and abroad.In the practical application of cavity ring down technology,it is an important problem for how to process the CRD signal accurately at high speed.Especially,how to accurately extract the ring down time from the cavity ring down signal is the key to the successful application of cavity ring down technology.Therefore,the accurate acquisition and real-time processing of cavity ring down signal has always been a research hotspot in the field of science and engineering technology at home and abroad.To solve those proble,based on the special architecture and embedded system of Xilinx ZYNQ Series Chip GA+ARM,a cavity decay signal acquisition and processing system based on ZYNQ is proposed and designed in this paper.The system makes use of the powerful hardware logic control ability and rich IP core resources of the FPGA to design and implement part of the hardware logic function of the FPGA.Then,the high speed data transfer bus inside ZYNQ chip is used for data interaction.Finally,the ARM part is developed and designed as the upper computer to complete the functions of data fitting and result display.Based on the requirements,device selection and modular function design are carried out,and system schematic diagram and 12-layer PCB design are completed with Altium Designer.The system achieves a sampling rate of 500 Msps and a quantization number of 16 bits finally;In the 500 MHz frequency range,the effective number of bits are greater than 10.3 bits and the spurious free dynamic range is greater than 69 d B.The repetitive measurement accuracy is less than 0.5% by actual measurement,which verifies the reliability of the system.It can basically achieve or even surpass the performance of the original cavity-decay signal acquisition and processing system,and greatly improve the volume and cost.The work done in this paper lays a solid foundation for the following typical applications of cavity ring-down technology,such as optical cavity loss measurement,weak gas concentration measurement based on cavity ring-down method and the popularization of precision spectral measurement.At the same time,the ZYNQ-based signal acquisition and processing system developed in this paper can also be widely used in other important occasions that require high-speed signal sampling and analysis.