NON-DESTRUCTIVE DETERMINATION OF ELECTROMAGNETIC PROPERTIES

• US 20100277184A1
• Filed: 04/29/2009
• Published: 11/04/2010
• Est. Priority Date: 04/29/2009
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Geren, William Preston
• Granted Patent: US 8,400,166 B2
• Time in Patent Office: Days
• US Class Current: 324/638
• CPC Class Codes: G01R 27/00 Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
• CPC Class Codes: G01R 27/2658 Cavities, resonators, free space arrangements, reflexion or interference arrangements G01R27/2647 takes precedence; optical methods G01R27/2682

Abstract

Systems and methods to determine electromagnetic properties are provided. A particular method includes directing electromagnetic energy toward an article under test. The method also includes taking measurements of electromagnetic energy scattered by the article under test. The method further includes determining expected baseline values of at least one electromagnetic property of the article under test. The expected baseline values are based on electromagnetic energy scattered by a control article. The method also includes determining output data based on a difference between the expected baseline values and characteristic values of the article under test determined based on the measurements of electromagnetic energy scattered by the article under test. The output data includes values indicative of inhomogeneous distribution of an electromagnetic property of the article under test.

Claims

1. A method, comprising:

directing electromagnetic energy toward an article under test;

taking measurements of electromagnetic energy scattered by the article under test;

determining expected baseline values of at least one electromagnetic property of the article under test, wherein the expected baseline values are based on electromagnetic energy scattered by a control article;

determining output data based on a difference between the expected baseline values and characteristic values of the article under test determined based on the measurements of electromagnetic energy scattered by the article under test, wherein the output data includes values indicative of inhomogeneous distribution of an electromagnetic property of the article under test.

2. The method of claim 1, further comprising determining a number of measurements to be taken to limit measurement error due to noise before determining the output data.

3. The method of claim 2, wherein the number of measurements to be taken is determined based on baseline measurements of the control article, and wherein the control article is substantially homogeneous.

4. The method of claim 1, further comprising:

taking measurements of electromagnetic energy scattered by the control article; and

determining the expected baseline values based on the measurements taken of the electromagnetic energy scattered by the control article.

5. The method of claim 1, wherein the electromagnetic property is homogeneous in the control article.

6. The method of claim 1, wherein the electromagnetic energy is directed toward the article under test from a plurality of incident angles.

7. The method of claim 1, wherein the electromagnetic energy comprises an electromagnetic plane wave.

8. The method of claim 1, wherein the inhomogeneous distribution of the electromagnetic property is determined to about one sixteenth of a wavelength of the electromagnetic energy in the dielectric material.

9. The method of claim 8, wherein the inhomogeneous distribution of the electromagnetic property is determined with about thirty-five percent or less error.

10. The method of claim 1, wherein the output data is determined using a distorted wave Born approximation and singular value decomposition to estimate values of an electromagnetic field internal to the article under test based on the measurements of electromagnetic energy scattered by the article under test.

11. A computer-readable storage medium, comprising:

instructions executable by a processor to access expected baseline values of an article under test based on electromagnetic energy scattered by a control article;

instructions executable by the processor to determine difference values between the expected baseline values and characteristic values of the article under test, wherein the characteristic values of the article under test are determined based on electromagnetic energy scattered by the article under test when an electromagnetic plane wave is directed toward the article under test; and

instructions executable by the processor to determine output data based on the difference values, wherein the output data includes values indicative of inhomogeneous distribution of an electromagnetic property of the article under test.

12. The computer-readable storage medium of claim 11, wherein the inhomogeneous distribution of the electromagnetic property includes values of a dielectric constant of the article under test at a plurality of physical locations.

13. The computer-readable storage medium of claim 11, further comprising instructions executable by the processor to provide control input to a manufacturing process when the inhomogeneous distribution of the electromagnetic property satisfies an inhomogeneity threshold.

14. The computer-readable storage medium of claim 11, further comprising instructions executable by the processor to generate an alert when the inhomogeneous distribution of the electromagnetic property satisfies an inhomogeneity threshold.

15. The computer-readable storage medium of claim 11, further comprising instructions executable by the processor to generate an alert when a difference between the inhomogeneous distribution of the electromagnetic property and the expected baseline values satisfies a skew threshold.

16. A system, comprising:

an antenna to direct an electromagnetic plane wave toward an article under test;

at least one probe to take measurements of electromagnetic energy scattered by the article under test;

a memory storing expected baseline values of at least one electromagnetic property of the article under test, wherein the expected baseline values are based on electromagnetic energy scattered by a control article; and

a processor to determine output data including difference values between the expected baseline values and a plurality of measured characteristic values of the article under test determined based on the measurements of electromagnetic energy scattered by the article under test, wherein the output data includes values indicative of inhomogeneous distribution of an electromagnetic property of the article under test.

17. The system of claim 16, wherein the expected baseline values include predicted average values of the article under test determined by testing a substantially homogenous test article.

18. The system of claim 16, wherein the electromagnetic plane wave has a frequency in a microwave range.

19. The system of claim 16, wherein the measurements include measurements at multiple frequencies to determine frequency dependent electromagnetic characteristics of the article under test.

20. The system of claim 16, wherein the article under test comprises an aircraft component.