Ratio-reference measurement of the arrival time and/or amplitude of a digitized electronic pulse

Inventors

Warburton, William K. • Hennig, Wolfgang G.

Assignees

XIA LLC

Abstract

A digital processing technique for measuring a characteristic of a digitized electronic signal pulse, particularly including its time of arrival and/or maximum. The technique is particularly suited for in-line implementation in a field programmable gate array or digital signal processor. For each detected pulse, one or more ratios are created from values of the pulse above baseline, obtained from regions of the pulse where the values change as its arrival time offset changes, and the ratio or ratios are used as variables in a reference table or equation to generate the value of the desired characteristic. The table or equation is created beforehand by using a secondary technique to study pulses of the type being measured, to establish the relationship between the ratio value or values and the desired characteristic, and to codify that relationship in the reference table or equation. Time resolutions of 2-3% of the sampling interval are demonstrated.

Core Innovation

The disclosed invention relates to ratio-reference digital processing for estimating a desired characteristic of a photon or particle from digitized electronic signal pulses generated by a detector assembly. A photon or particle striking the detector generates a signal pulse, which is digitized by an analog-to-digital convertor (ADC), and then processed by a digital computing device to estimate the desired characteristic from the digitized signal pulse. The processing includes baseline subtraction when the pulse has a baseline and extracting amplitude values above baseline from regions where amplitude changes as a function of time.

For the digitized pulse, the computing device computes one or more ratios of obtained amplitude values and, in some protocols, time-related values. The ratio or ratios are then used as variables in a reference calibration table or reference equation to generate an estimated value of the desired characteristic. The reference table or equation is created beforehand by analyzing pulses of the type being measured to establish a calibration relationship between the desired characteristic and the ratio value or ratio values, and to codify that relationship in the table or equation.

Specific examples of the desired characteristic include pulse arrival time and pulse maximum (M). For arrival time, a ratio B/A of amplitude values A and B for a pair of samples is used to compute a pulse arrival offset φ defined relative to digitization time. For pulse maximum (M), a ratio B/A is used to compute an amplitude correction factor dM in relation to the amplitude of the pulse at a selected reference point from the reference calibration table or equation.

Claims Coverage

The document includes six independent claim sets directed to methods and apparatus. Across these claims, the coverage centers on computing amplitude-change-based ratios from baseline-subtracted, digitized pulses and applying the ratios as variables in a pre-established reference calibration table or reference equation to estimate a desired characteristic, with specific mapping for arrival time and pulse maximum M.

Across the independent claims, the core claim coverage ties together digitizing detector-generated signal pulses with an ADC, extracting amplitude above baseline from regions where amplitude changes as a function of time, computing one or more ratios from obtained values, and then using those ratios as variables in a pre-created reference calibration table or reference equation to generate the estimated desired characteristic.

Stated Advantages

Documented Applications