Application of pole-zero cancellation circuit in nuclear signal filtering and shaping algorithm

In radiation measurement and digital nuclear spectrum systems, traditional nuclear signal processing circuits in nuclear electronics have been gradually replaced by digital algorithm modules with the application of high-performance programmable hardware logic devices (such as FPGA or DSP). Referring to the digital realization method of inverse RC integral circuit systems, the function of the pole-zero cancellation (PZC) circuit was analyzed, a new modified cascade equivalent model of PZC was established, and the time-domain digital PZC (DPZC) recursive algorithm was derived in detail in this study. Two parameters k I and k D are included in the new algorithm, where k I should match the exponential decay time constant of the input signal to realize the pole-zero compensation, while the decay time constant of the output signal can be changed with the adjustable parameter k D (which is larger than the decay time constant of the input signal). Based on the new DPZC algorithm module, two trapezoidal (triangular) shaping filters were designed and implemented. The amplitude–frequency characteristics of the output signal of the proposed trapezoidal shaping algorithm and the convolution trapezoidal shaping algorithm were compared, with fixed peaking time. The results show that the trapezoidal shaping algorithm based on DPZC can better suppress high-frequency noise. Finally, based on the NaI (Tl) scintillator ( φ 75 mm × 75 mm) detector and 137 Cs source, the effect of the k D value on the energy resolution of the DPZC trapezoidal (triangular) shaping algorithm was studied. The experimental results show that, with an increase in k D , the energy resolution of the system improved and reached the maximum when k D was greater than 10, and the optimal energy resolution of the system was 7.72%.