US 5,774,522 A · Method and apparatus for digitally based high speed x-ray spectrometer for direct coupled use with continuous discharge preamplifiers

Abstract

A high speed, digitally based, signal processing system which accepts directly coupled input data from a detector with a continuous discharge type preamplifier and produces a spectral analysis of the x-rays illuminating the detector. The system's principal elements are an analog signal conditioning section, a combinatorial logic section which implements digital triangular filtering and pileup inspection, and a microprocessor which accepts values captured by the logic section and uses them to compute x-ray energy values. Operating without pole-zero correction, the system achieves high resolution by capturing, in conjunction with each peak value from the digital filter, an associated value of the unfiltered signal, and using this latter signal to correct the former for errors which arise from its local slope terms. This correction greatly reduces both energy resolution degradation and peak centroid shifting in the output spectrum as a function of input count rate. When the noise of this correction is excessive, a modification allows two filtered averages of the signal to be captured and a corrected peak amplitude computed therefrom.

Claims35

Dependent claims

A method for applying a shaping filter, described by a set of one or more parameters, to a noisy input signal containing step-like pulses with exponential decays, described by a time constant .tau., between them to extract estimates of the step amplitudes of said pulses which are substantially independent of the slope values of the exponentially decaying components in the vicinity of the pulses, by the steps of:

applying said shaping filter to said input signal to generate a filtered signal;
generating a first weighted signal by weighting said filtered signal by a first constant that depends upon the values of the set of shaping filter parameters and upon .tau.;
generating a second weighted signal by weighting said input signal by a second constant that depends upon the values of the set of shaping filter parameters and upon .tau.;
and
forming a compensated signal by combining the first and second weighted signals, the compensated signal representing the filtered signal compensated for the exponentially decaying components' slope values in the vicinity of said step-like pulses.

2 more elements

A method for analyzing a noisy input electronic signal containing step-like pulses with exponential decays, described by a time constant .tau., between them to extract estimates of the step amplitudes of said pulses which are substantially independent of the slope values of the exponentially decaying component in the vicinity of the pulses by the steps of:

applying a filter, described by a set of one or more parameters, to said input signal to reduce its noise components;
generating a first weighted signal by weighting said filtered signal by a first constant;
and
generating a second weighted signal by weighting a time delayed version of said filtered signal by a second constant, wherein said first and second constants depend upon the values of the set of filter parameters, upon .tau., and upon the value .DELTA. of the time delay;
and
combining the first and second weighted signals to form an output signal which has a maximum for each step-like pulse, the value of said maximum being proportional to the amplitude of said pulse and substantially independent of the slope values of the exponentially decaying component in the vicinity of the pulse.

3 more elements

An apparatus for analyzing a noisy input electronic signal containing step-like-pulses with exponential decays, described by a time constant .tau., between them to extract estimates of the step amplitudes of said pulses which are substantially independent of the slope values of the exponentially decaying component in the vicinity of the pulses, comprising:

a filter, described by a set of one or more parameters, applied to said input signal to reduce its noise components and provide a filtered signal;
a circuit which generates a first weighted signal by weighting said filtered signal by a first constant;
and
a delay element which provides a time delayed version of said filtered signal;
a circuit which generates a second weighted signal by weighting said time delayed version of said filtered signal by a second constant;
where
said first and second constants depend upon the values of the set of filter parameters, upon .tau., and upon the value .DELTA. of the time delay;
and
a circuit which combines said first and second weighted signals to form an output signal which has a maximum for each step-like pulse, the value of said maximum being proportional to the amplitude of said pulse and substantially independent of the slope values of the exponentially decaying component in the vicinity of the pulse.

6 more elements

Dependencies are inferred from the claim text.

Method and apparatus for digitally based high speed x-ray spectrometer for direct coupled use with continuous discharge preamplifiers

Life of this patent

Method and apparatus for digitally based high speed x-ray spectrometer for direct coupled use with continuous discharge preamplifiers

Life of this patent

Abstract

Claims35