核脉冲信号滤波成形电路的数字化研究

Digitalization of filter shaping circuit for nuclear pulse signal

核脉冲信号的滤波成形电路用于改变脉冲形状、提高核谱仪器系统的信噪比,从而获取更佳的性能指标。从极零相消电路与Sallen-Key电路的工作原理出发,推导了基于数字极零相消、数字Sallen-Key在时域中的成形递推函数,分别获取其在Z域中的传输函数,在频域中对其滤波性能、幅频响应特性进行了分析。对仿真核信号,采用数字极零相消、数字高斯成形递推函数模型,实现不同参数下的极零相消与高斯成形处理。对Si-PIN探测器测量55Fe和NaI探测器测量137Cs的核脉冲信号,实现了数字极零相消、不同参数下的数字高斯成形处理,从时域与频域两个方面对结果进行了分析,研究成果可应用于核脉冲信号极零相消、滤波成形参数的最优化选取。

[Background] Filter shaping of pulsed signals is used to change the pulse shape and increase the system signal-to-noise ratio for better performance in a nuclear spectrometer system.[Purpose] This study aims at digitalization of filter shaping circuit for nuclear pulse signal.[Methods] Based on the principle of digital pole-zero cancellation and digital Sallen-Key in the time domain, the shape recursive function was derived, and the transfer function of them in the Z domain was obtained respectively. The filtering performance and amplitude-frequency response characteristics in the frequency domain were analyzed. Then the digital pole-zero cancellation and digital Gaussian shaping recursive function model are used to realize the simulated nuclear pulse signal processing with different parameters. Furthermore, 55Fe and 137Cs radioactive sources were measured with the Si-PIN detector and NaI detector respectively, obtained nuclear pulse signals were processed by the digital pole-zero cancellation and digital Gaussian shaping processing with different parameters.[Results and Conclusion] The results in both the time domain and the frequency domain show the efficiency of proposed digitalization approaches of filter shaping circuit for nuclear pulse signal. These approaches can be applied to the optimization of the pole-zero cancellation and filter shaping parameters of nuclear pulse signals.