Signal Pulse Arrival Time Determination Using Rising Edge Shape Analysis
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Solution Overview
Problem
Existing digital methods for determining the arrival time of signal pulses in radiation detectors face challenges such as high processing resource requirements, time walk errors, and increased power consumption, particularly in multi-channel systems like gas detectors and scintillators, due to limitations in pulse shape analysis and sampling phase errors.
Innovation Solution
A method that calculates the arrival time of signal pulses by determining the shape of the rising edge as either linear, non-linear without a turning point, or S-like, using specific equations to adjust for different pulse shapes, allowing for optimal time resolution with reduced processing resources and low power consumption, implemented in an evaluation unit like an FPGA or ASIC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex digital methods (dCFD with nonlinear interpolation, momentary analysis, fitting) are used to reduce sampling phase error, then time resolution is improved, but processing resource requirements and power consumption increase significantly
Solution Approach 1:
The patent changes the parameter of interest from pulse peak value to pulse rise time. By measuring the time interval between two fixed threshold crossings on the rising edge of the pulse, the method achieves time resolution independent of pulse amplitude variations and sampling phase, thereby improving measurement precision without requiring complex processing resources for peak detection or waveform fitting
Solution Approach 2:
The patent extracts only the essential timing information from the pulse waveform by measuring the rise time between two threshold levels. This extraction approach eliminates the need to process the entire pulse waveform or perform complex operations like nonlinear interpolation and waveform fitting, significantly reducing processing resource requirements while maintaining accurate time measurement
2Measurement precision
If high sampling rate is used to reduce quantization error in digital methods, then time resolution is improved, but power consumption and cost increase significantly
Solution Approach 1:
The patent changes the measurement parameter from absolute arrival time to rise time interval. This parameter transformation allows accurate time measurement at lower sampling rates because the rise time is determined by the pulse shape itself rather than by the sampling clock, eliminating the need for high sampling rates and reducing power consumption
Solution Approach 2:
The patent uses simple threshold comparison operations instead of expensive high-speed sampling and complex processing. By using fixed thresholds and measuring the time interval between threshold crossings, the method achieves accurate timing with low-cost, low-power digital circuitry that does not require high sampling rate ADCs or complex processing resources
3Ease of operation
If leading-edge discrimination method is used, then simplicity is maintained, but time walk error occurs due to dependence on pulse amplitude
Solution Approach 1:
The patent changes the measurement parameter from absolute threshold crossing time to rise time interval between two thresholds. This transformation eliminates the time walk error because the interval between two fixed threshold crossings on the rising edge is independent of the pulse amplitude, maintaining measurement precision while preserving the simplicity of the method
Solution Approach 2:
The patent applies preliminary action by establishing fixed threshold levels before measurement. By defining two fixed thresholds on the pulse rising edge and measuring the time interval between their crossings, the method pre-compensates for amplitude variations, eliminating time walk error while maintaining operational simplicity
Data Source
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AI summary
The invention relates to a method for determining an arrival time (tm) of a digitised signal pulse (P) representing a physical measured variable, in which the shape of the rising edge (F) of the signal pulse (P) is determined, the shape being selected from the group comprising - an at least substantially linear gradient, - a non-linear gradient without an inflection point (pi) and - an S-shaped non-linear gradient having at least one inflection point (pi). In all three cases, a difference between the time (t1) of the first sampling point (s1) of the signal pulse (P) and the arrival time (tm) of the signal pulse (P) is calculated by means of the equation (I), the arrival time (tm) of the signal pulse (P) being calculated taking the value obtained for Δt into consideration. The invention also relates to an evaluation unit and a device for determining an arrival time of signal pulses representing a physical measured variable, an evaluation system and a beam detection system.