基于FPGA的多通道动态光散射自相关器的研制

为提高多角度动态光散射(MDLS)实验的测试效率与测量精度，开发了一种基于现场可编程门阵列(FPGA)的多通道动态光散射自相关器。该自相关器利用FPGA同时采集4个散射角度的光子脉冲信号，实现高频脉冲计数和自相关计算；设计双计数器模块保证高频无丢失计数，结合片内环形寄存区与片外DDR3芯片实现动态存储数据；提出multi-tau相关器结构设计自相关器的相关计算模块，通过USB通信模块传输自相关计算结果。该自相关器利用有限的FPGA内部硬件资源，实现了多通道自相关运算，解决了大量计数数据的存储问题，提高了MDLS实验的测试效率。利用自相关器对50～200 nm的聚苯乙烯颗粒进行MDLS实验，实验结果与样品的标称粒径表现出良好的一致性，表明该设计能有效地表征颗粒粒径信息。

Development of Multi-channel Dynamic Light Scattering Autocorrelator Based on FPGA

In order to improve the measurement efficiency and accuracy of multi-angle dynamic light scattering (MDLS) experiment, a multi-channel dynamic light scattering autocorrelator based on field programmable gate array (FPGA) is developed. The autocorrelator uses FPGA to sample photon pulse signals from four scattering angles at the same time, which realizes high-frequency pulse counting and autocorrelation calculation. A double counters module is designed to ensure high-frequency lossless counting. Dynamic data storage is realized by in-chip ring register combining with out-of-chip DDR3 chips. The correlation calculation module is designed by multi-tau correlator structure. The autocorrelation calculation results are transmitted through the USB communication module. Using the limited hardware resources of FPGA, the autocorrelator realizes multi-channel autocorrelation calculation, solves the storage problem of a large number of counting data, and improves the test efficiency of MDLS experiment. Polystyrene particles sized from 50nm to 200nm are used in MDLS experiment by the autocorrelator. The results are in good consistency with the nominal particle size of the sample, which shows that the system can effectively characterize the particle size.