【作者】 邓晓；

【导师】 邵贝贝；

【作者基本信息】 清华大学 ， 核科学与技术， 2008， 博士

【摘要】 近年来,基于数字信号处理的辐射探测技术在高能物理、辐射成像等领域中应用的越来越广泛。相对于模拟电路,数字滤波电路具有灵活、稳定、自适应等优点,但其性能受到模数转换器采样参数的影响。对于辐射探测中随机脉冲测量,由于采样引起的误差分析,目前还没有系统的理论分析。因此,有必要研究ADC采样参数对随机脉冲测量中数字滤波性能的影响,为用于辐射探测的数字滤波器设计提供指导。比如,随着探测通道数目的增加,功耗成为信号处理电路的关键问题,需要定量研究数字滤波性能与采样参数的关系,尽可能降低ADC的功耗。本文针对目前比较通用的辐射探测数字信号处理电路结构,分析了随机脉冲幅度测量的数字滤波性能与ADC采样频率的关系,主要包括以下几个内容:1)推导了采样后的信号频谱和噪声功率谱,在此基础上分析了数字滤波幅度测量性能与采样频率的定量关系,给出了在一定采样频率下数字滤波所能获得的最佳信噪比和几种常用的数字滤波器噪声指数。2)研究了随机到达时刻造成数字滤波测量误差与采样频率的关系,包括幅度均值偏移和涨落。这两种误差都会随着采样频率的增加迅速下降,而当采样周期降低到脉冲上升时间的1/3到1/5时,这种误差基本可以忽略。此外,还提出采用定时估计算法来校正幅度测量,并进行了初步的分析。本文还通过数值仿真和基于数字示波器采样的幅度测量系统,对幅度测量误差与采样频率的关系进行了验证。实验测得的ORTEC 142AH电荷灵敏前放的噪声和CdTe探测器的241Am能谱分辨率,随采样频率的变化规律与理论分析基本一致,较好的验证了理论分析。更多还原

【Abstract】 Recently, radiation detection based on the digital signal processing has been widely applied in the fields as high energy physics, radiation imaging and so on. Compared with analog circuits, the digital filters have the advantages as flexibility stability and adaptivity, although its performance is limited by the Analog-to-Digital Converter （ADC）. In random pulse measurement of radiation detection, there has been no systemic study in theory on the ADC sampling induced error analysis. The study on effect of ADC parameters to digital filtering performance is necessary for digital filter design. For example the power consumption becomes critical issue for signal processing circuit when the number of readout channels increases significantly. In such case, the quantitative study of the dependence of the filter performance on ADC parameters is necessary for reducing ADC power consumption.This thesis analyzes the dependence of digital filtering performance on ADC sampling frequency in random pulse measurement based on commonly applied digital signal processing circuit. The thesis includes the following parts. 1) Derive the signal spectrum and the noise power spectral density after sampling, analyze quantitatively the amplitude measurement performance on the sampling frequency, and then obtain the optimum signal-to-noise ratio under certain sampling frequency as well as noise index for several commonly applied digital filters. 2) Analyze the random arriving time induced measurement errors on sampling frequency, including the expected amplitude shift and fluctuation, which decrease significantly with increasing sampling frequency. When the sampling interval is less than 1/3 to 1/5 of the signal rising time, the measurement errors can be ignored. The timing estimation algorithm is proposed to amplitude measurement correction and analyzed preliminary.The dependence of amplitude measurement fluctuation on the sampling frequency is demonstrated by the numerical simulation and measurements with digital oscilloscope sampling. The dependence of experimental results on the sampling frequency is consistent with the theoretical results, which include the noise of ORTEC 142AH charge sensitive preamplifier and the ²⁴¹Am energy spectrum of CdTe detector. The theoretical analysis is demonstrated.更多还原