Nuclear pulse signal trapezoidal forming method suitable for FPGA
By performing digitized sampling, differential, delay and integral operations on the detector signal, a ladder-forming pulse signal suitable for FPGA is formed, which solves the problems of complex systems and low counting in the prior art, and achieves stable and efficient ladder-forming operation and rapid parameter adjustment.
Patent Information
- Application Number
- CN202510688793.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-27
- Publication Date
- 2025-08-19
AI Technical Summary
When the prior art uses infinite impulse response digital filtering method to form a ladder in FPGA, there are problems such as complex system, low counting pass rate, slow computing speed and difficult to quickly adjust the trapezoid parameters.
High-speed digital sampling of the detector output signal is used to form a ladder-forming pulse signal through differential, delay and integral operations. The specific steps include digital sampling, differential, delay synthesis and integral operations, and the use of digital delay lines to adjust the trapezoid parameters.
It realizes stable ladder forming operation, avoids overflow, improves count pass rate, is simple in logic, is suitable for FPGA implementation, and can quickly adjust trapezoidal parameters.
Smart Images
Figure CN120507784A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to nuclear energy spectrum measurement in radioactivity measurement, and in particular to a nuclear pulse signal trapezoidal shaping method suitable for FPGA in the process of nuclear energy spectrum measurement. Background Art
[0002] In nuclear energy spectrum measurements, to reduce the effects of noise and ballistic loss on energy spectrum measurements, nuclear pulses must be shaped in a multi-channel pulse amplitude analyzer before analysis. Digital multi-channel pulse amplitude analyzers have rapidly developed in energy spectrum measurements. Trapezoidal shaping is a commonly used pulse shaping method, which improves differential nonlinearity and avoids the effects of ballistic loss when the trapezoidal flat-top time is greater than the detector charge collection time. In digital multi-channel pulse amplitude analyzers, fast and slow channels are implemented separately. The fast channel uses narrower trapezoidal shaped pulses to extract pulse time information, while the slow channel uses wider trapezoidal shaped pulses to extract pulse amplitude information.
[0003] Currently, existing methods for calculating trapezoidal shaping use infinite impulse response (IIR) digital filtering within an FPGA. IIR digital filters have feedback units. To avoid the accumulation of quantization and rounding errors, they are implemented in a cascaded structure. Swapping the order of the cascaded subsystems does not affect the final output. While swapping the order of the subsystems can prevent feedback error accumulation, the presence of continuously accumulating feedback subsystems can eventually lead to output overflow. Historical data stored in the relevant subsystems must be cleared during periods of no signal, complicating the system, reducing the system's throughput, and impacting computational speed and accuracy. Furthermore, the fixed structure of IIR filters makes it difficult to quickly and easily adjust trapezoidal parameters in practical applications. Summary of the Invention
[0004] The present invention provides a core pulse signal trapezoidal shaping method suitable for FPGA, aiming to solve the deficiencies of the above-mentioned technology.
[0005] The specific technical solutions adopted to solve the above problems are: Step 1: Perform high-speed digital sampling on the original exponential decay signal output by the detector to obtain a discrete digitized detector signal v n ; Step 2: Use the differentiation algorithm to calculate the discrete digitized detector signal v n Perform the operation to obtain the differential pulse signal p n ; Step 3: Use a digital delay line to delay the pulse signal p n Delay to form 3 delayed pulse signals, and then the pulse signal p nPerform synthesis operation with 3 delayed pulse signals to obtain the synthetic pulse signal sequence s n ; Step 4: For the synthesized pulse signal sequence s n Perform integration operation to obtain the trapezoidal shaped pulse y n .
[0006] Further: In step 2, the discrete digitized detector signal v n Perform differential operation, the specific calculation formula is: p n =v n –kv n-1 Where n represents the data number of the digitized pulse sequence, k= e -T / τ , T is the sampling interval of the detector signal, and τ is the decay time constant of the detector pulse signal.
[0007] Further: In step 3, the pulse signal p n The calculation process of delaying and obtaining the synthetic pulse signal is: s n =(p n -p n-a -p n-b +p n-c )·(M / a) / M Wherein, a is the number of sampling points of the rising edge of the trapezoidal pulse, b is the sum of the number of sampling points of the rising edge and the flat top of the trapezoidal pulse, c=a+b, and the value of M is a positive integer power of 2.
[0008] Furthermore: in step 4, the specific operation process is: y n = 2y n-1 -y n-2 + s n An isosceles trapezoidal pulse signal with the same amplitude as the original exponentially decayed signal output by the detector is obtained.
[0009] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects: The trapezoidal forming method proposed by the present invention has no continuous accumulation operation link, will not overflow, and has stable operation. At the same time, the logic for implementing the trapezoidal forming is simple, suitable for pipeline operation, and has a high counting pass rate.
[0010] The trapezoidal shaping method proposed by the present invention only requires changing the number of delay sampling points of the digital delay line. The sampling point parameters of the rising edge and flat top of the trapezoidal pulse can be changed. The logic is simple and suitable for FPGA implementation.
[0011] The trapezoidal shaping method proposed in the present invention can share the calculation process that is independent of the parameters of the trapezoidal rising edge and flat top sampling points when realizing fast channel and slow channel trapezoidal shaping pulses, thereby reducing the usage of FPGA logic resources. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 Flowchart of an embodiment; Figure 2 Digital sampling waveform of detector pulse signal; Figure 3 Pulse signal waveform after differentiation; Figure 4 Differentiated signal waveform diagram after digital delay processing; Figure 5 Synthesized pulse signal sequence waveform; Figure 6 Trapezoidal pulse waveform diagram. DETAILED DESCRIPTION
[0013] The technical solution of the present invention will be further described below in conjunction with a specific embodiment and the accompanying drawings, but the present invention is not limited to this embodiment.
[0014] like Figure 1 The flowchart of this embodiment is a core pulse signal trapezoidal shaping method applicable to FPGA. The specific implementation steps include: Step S101: Use a high-speed ADC with a sampling frequency of 80 MHz to perform high-speed digital sampling on the detector output single exponential decay original pulse signal to obtain a discrete digitized detector signal v n (1); Figure 2 is the waveform of the discrete detector signal after sampling, the discrete digitized detector signal v n (1) The function expression is v n =u m e -nT / τ , where u m is the amplitude of the single exponential decay signal, T is the signal sampling period, τ is the time constant of the single exponential decay signal, and n is the serial number of the digitized sampling signal data point.
[0015] Step S102: using a differential algorithm to calculate the discrete digital detector signal v n (1) Perform calculation to obtain the differential pulse signal p n (2); Differentiation pulse signal p n =v n –kv n-1 = u m e -nT / τ-ku m e -(n-1)T / τ Where k = e -T / τ .
[0016] Step S103: Differentiate the pulse signal p n (2) Delay and obtain the differential delay signal p n-a (3) Differential delay signal p n-b (4) Differential delay signal p n-c (5); Figure 4 is the differentiated pulse signal p n (2) and 3 delayed pulse signal sequence waveforms; After differentiation, the pulse signal p n (2) Perform synthesis operation with the three delayed pulse signal sequences to obtain the synthetic pulse signal s n (6), the calculation method is as follows: s n =(p n -p n-a -p n-b +p n-c )·(4096 / a) / 4096 Where a is the number of sampling points on the rising edge of the trapezoidal pulse, b is the sum of the number of sampling points on the rising edge and flat top of the trapezoidal pulse, and c = a + b.
[0017] Step S104: synthesized pulse sequence signal s n (6) Perform integral operations; First, the trapezoidal shaping signal y n (7) Delay 1 and 2 sampling points respectively to obtain the delayed signal y n-1 and y n-2 , trapezoidal shaping signal y n The initial value of (7) is 0; Then calculate according to the following formula: y n = 2y n-1 -y n-2 +s n The trapezoidal shaped signal y is obtained with the same amplitude as the single exponential decay signal output by the detector. n (7).
[0018] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.
Claims
1. A core pulse signal trapezoidal shaping method suitable for FPGA, characterized in that: The method comprises the following steps: Step 1: Perform high-speed digital sampling on the original exponential decay signal output by the detector to obtain a discrete digitized detector signal v n ; Step 2: Use the differentiation algorithm to calculate the discrete digitized detector signal v n Perform the operation to obtain the differential pulse signal p n ; Step 3: Use a digital delay line to delay the pulse signal p n Delay to form 3 delayed pulse signals, and then the pulse signal p n Perform synthesis operation with 3 delayed pulse signals to obtain the synthetic pulse signal sequence s n ; Step 4: For the synthesized pulse signal sequence s n Perform integration operation to obtain the trapezoidal shaped pulse y n .
2. The method for trapezoidal shaping of a nuclear pulse signal suitable for FPGA according to claim 1, wherein: In step 2, the discrete digitized detector signal v n Perform differential operation, the specific calculation formula is: p n =v n –kv n-1 Where n represents the sampling data number of the digitized pulse sequence, k= e -T / τ , T is the sampling interval of the detector signal, and τ is the decay time constant of the detector exponential decay pulse signal.
3. The nuclear pulse signal trapezoidal shaping method suitable for FPGA according to claim 1, characterized in that: In step 3, the pulse signal p n The calculation process of delaying and obtaining the synthetic pulse signal is: s n =(p n -p n-a -p n-b +p n-c )·(M / a) / M Wherein, n represents the sampling data sequence number of the digitized pulse sequence, a is the number of sampling points of the rising edge of the trapezoidal pulse, b is the sum of the number of sampling points of the rising edge and the flat top of the trapezoidal pulse, c=a+b, and the value of M satisfies the positive integer power of 2.
4. The nuclear pulse signal trapezoidal shaping method suitable for FPGA according to claim 1, wherein: In step 4, the specific integration operation process is: y n = 2y n-1 -y n-2 + s n Wherein, n represents the sampling data number of the digitized pulse sequence; After the integration operation, an isosceles trapezoidal pulse signal with the same amplitude as the original exponential decay signal output by the detector is obtained.