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US 7,680,607 B1Granted
System and method for gas recognition by analysis of bispectrum functions
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsJanusz Smulko, Laszlo B. Kish, Gabor Schmera
Life of this patent
Estimating the term…
Abstract
A System and Method for Gas Recognition by Analysis of Bispectrum Functions is based on the Higher-Order Spectral analysis of time series measurements of resistance fluctuations in Metal Oxide Semiconductor (MOS) gas sensors, such as Taguchi-type sensors. A two-dimensional contour plot module of the bispectrum function is treated as a pattern. These patterns include information about the analyte(s) whereby characteristics of the gas can be identified.
Claims6
A method of analyzing a chemical analyte, said method consisting of the steps of:
- generating a fluctuation output signal in response to a plurality of resistance fluctuations of a Metal Oxide Semiconductor (MOS) gas sensor;
- adjusting current flow through said sensor using a biasing circuit to achieve current differentials sufficient to detect different analytes, and sufficient for obtaining a measurement of said fluctuation output signal;
- normalizing said measurement of said fluctuation output signal for current differentials by dividing by the standard deviation of a time series of sampled current;
- and
- transforming said fluctuation output signal into a bispectrum signal represented by the bispectrum function
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- using positive and negative values for frequencies f1 and f2 of said bispectrum function;
- establishing a contour graph that is representative of the results of said transforming step, said contour graph created using said positive and negative values for said frequencies f1 and f2;
- comparing said contour graph to a database of reference contour graphs, said reference contour graphs created using said positive and negative values for said frequencies f1 and f2 corresponding to known analytes;
- generating an analyte output signal that identifies a characteristic of said analyte;
- and
- determining if said contour graph utilizing said positive and negative values for said frequencies f1 and f2 corresponds to one of said reference contour graphs from said database.
77 more elements
A chemical sensor system consisting of:
- a metal oxide semiconductor (MOS) gas sensor;
- measurement means for generating a fluctuation output signal responsive to a plurality of resistance fluctuations of said MOS gas sensor represented as a time series of sampled current;
- a biasing circuit for adjusting current flow through said sensor as is sufficient to detect different analytes;
- a means for transforming said time series of sampled current into a bispectrum signal represented by the equation
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- said bispectrum equation using positive and negative values for frequencies f1 and f2;
- a graphing means for establishing a contour graph that is representative of said bispectrum signal, said contour graph using said positive and negative values for said frequencies f1 and f2;
- a means for normalizing said time series of sampled current by dividing said time series of sampled current by the standard deviation;
- a database of reference contour graphs created using said positive and negative values for said frequencies f1 and f2 corresponding to known said bispectrum signals, which further correspond to known said analytes;
- and,
- a decision means, coupled to said bispectrum means, for generating an analyte output signal that identifies a characteristic of said chemical analyte if said contour graph corresponds to one of said reference contour graphs from said database created using said positive and negative values for said frequencies f1 and f2.
77 more elements
A computer apparatus configured with software for use with a chemical sensor system including a metal oxide semiconductor (MOS) gas sensor comprising:
- a machine-readable recording medium;
- a first instruction means, recorded on said recording medium, for directing said chemical sensor system to generate a fluctuation output signal in response to a plurality of resistance fluctuations of said MOS gas sensor;
- a second instruction means capable of calculating the standard deviations of said fluctuation output signal;
- a third instruction means for normalizing said fluctuation output signal by dividing said fluctuation output signal by said standard deviation of said fluctuation output signal;
- a fourth instruction means, recorded on said recording medium, for directing said chemical sensor system to transform said fluctuation output signal into a bispectrum signal represented by the equation
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- using positive and negative values for frequencies f1 and f2;
- a fifth instruction means further establishing a contour graph using said positive and negative values for said frequencies f1 and f2 that is representative of the results of said bispectrum signal;
- a database of reference contour graphs corresponding to said bispectrum signals using said positive and negative values for said frequencies f1 and f2 of known said analytes;
- and
- a sixth instruction means, recorded on said recording medium, for directing said chemical sensor system to generate an analyte output signal that identifies a characteristic of said chemical analyte if said contour graph established by said fourth instruction means corresponds to a characteristic of one of said reference contour graphs from said database.
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Dependencies are inferred from the claim text.