Method and apparatus for analog signal conditioner for high speed, digital x-ray spectrometer
AssigneeWilliam K. Warburton
InventorsWilliam K. Warburton, Bradley Hubbard
Life of this patent
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Abstract
A signal processing system which accepts input from an x-ray detector-preamplifier and produces a signal of reduced dynamic range for subsequent analog-to-digital conversion. The system conditions the input signal to reduce the number of bits required in the analog-to-digital converter by removing that part of the input signal which varies only slowly in time and retaining the amplitude of the pulses which carry information about the x-rays absorbed by the detector. The parameters controlling the signal conditioner's operation can be readily supplied in digital form, allowing it to be integrated into a feedback loop as part of a larger digital x-ray spectroscopy system.
Claims39
A method for reducing the number of analog-to-digital converter bits required to extract a digital representation of a signal of interest (SOI) from an original analog input signal (OAIS) which can be decomposed into the sum of a parametrically describable (PD) fraction having a high dynamic range and a remainder signal fraction having a significantly smaller dynamic range, which remainder fraction contains the SOI, the method comprising the steps of:
- providing a signal generator, controlled by a set of at least one control parameter, said set being referred to as the control parameter set, capable of generating a class of at least one signal which includes the PD signal fraction as a member;
- adjusting said control parameter set so that said signal generator produces a generated signal which is an approximate replica of the PD signal fraction;
- generating a difference signal representative of the difference between said OAIS and said generated signal;
- and
- digitizing said difference signal to produce a digital representation of said SOI.
A method for producing a digital representation of an original analog input signal (OAIS) composed of a parametrically describable (PD) fraction having a high dynamic range and a signal-of-interest (SOI) fraction having a significantly smaller dynamic range, the method comprising the steps of:
- generating a replica of the PD fraction using a set of at least one control parameter, said set being referred to as the control parameter set;
- generating a difference signal representative of the difference between said OAIS and said replica of the PD fraction;
- digitizing said difference signal;
- determining whether said difference signal is within a permissible range;
- and
- if not, adjusting said control parameter set by adjusting at least one control parameter value to adjust said replica so as to bring said difference signal into the permissible range.
A method in x-ray or gamma-ray spectroscopy for extracting photon energy information contained in an original preamplifier input signal (PAIS) that is characterized by a series of accumulating steps that is intermittently reset, the steps having step heights representative of photon energies, the PAIS thus being composed of (i) a parametrically describable (PD) fraction comprising a resetting ramp, the PD fraction having a high dynamic range, and (ii) a "signal of interest" (SOI) fraction comprising a train of pulses having pulse heights corresponding to the step heights, the SOI fraction being superimposed on the PD fraction and having a significantly smaller dynamic range, the method comprising the steps of:
- generating a resetting ramp signal that is an approximate replica of the PD fraction using a set of at least one control parameter;
- generating a difference signal representative of the difference between said PAIS and said resetting ramp signal, the difference signal thus being characterized by a dynamic range significantly less than the dynamic range of the PD fraction;
- and
- digitizing said difference signal to obtain a digital signal that includes information on the heights of the pulses.
An apparatus for reducing the number of analog-to-digital converter bits required to extract a digital representation of a signal of interest (SOI) from an original analog input signal (OAIS) which can be decomposed into the sum of a parametrically describable (PD) fraction having a high dynamic range and a remainder signal fraction having a significantly smaller dynamic range, which remainder fraction contains the SOI, the apparatus comprising:
- a signal generator controlled by a set of at least one control parameter, said signal generator, in response to an adjusted control parameter, producing a generated signal which is an approximate replica of the PD signal fraction;
- a subtracting stage which generates a difference signal representative of the difference between said OAIS and said generated signal;
- and
- an analog-to-digital converter (ADC) which digitizes said difference signal to produce a digital representation of said SOI.
An apparatus for producing a digital representation of an original analog input signal (OAIS) composed of a parametrically describable (PD) fraction having a high dynamic range and a signal-of-interest (SOI) fraction having a significantly smaller dynamic range, the apparatus comprising:
- a LFF generator which generates a replica of the PD fraction, wherein the operation of the LFF generator is controlled by a set of at least one control parameter, said set being referred to as the control parameter set;
- a subtracting stage which generates a difference signal representative of the difference between said OAIS and said replica of the PD fraction signal;
- an analog-to-digital converter (ADC) which digitizes said difference signal;
- a comparator which determines whether said difference signal is within a permissible range;
- and
- means, responsive to a determination that said difference signal is outside the permissible range, for adjusting said control parameter set by adjusting at least one control parameter value so as to bring said amplified difference signal into the permissible range.
An apparatus in x-ray or gamma-ray spectroscopy for extracting photon energy information contained in an original preamplifier input signal (PAIS) that is characterized by a series of accumulating steps that is intermittently reset, the steps having step heights representative of photon energies, the PAIS thus being composed of (i) a parametrically describable (PD) fraction comprising a resetting ramp, the PD fraction having a high dynamic range, and (ii) a "signal of interest" (SOI) fraction comprising a train of pulses having pulse heights corresponding to the step heights, the SOI fraction being superimposed on the PD fraction and having a significantly smaller dynamic range, the apparatus comprising:
- a signal generator which generates a resetting ramp signal that is an approximate replica of the PD fraction using a set of at least one control parameter;
- a subtracting stage which generates a difference signal representative of the difference between said PAIS and said resetting ramp signal, the difference signal thus being characterized by a dynamic range significantly less than the dynamic range of the PD fraction signal;
- and
- an analog-to-digital converter (ADC) which digitizes said difference signal to obtain a digital signal that includes information on the heights of the pulses.
Dependencies are inferred from the claim text.