Methods and apparatus for electromagnetic signal polarimetry sensing

• US 9,037,414 B1
• Filed: 01/13/2012
• Issued: 05/19/2015
• Est. Priority Date: 01/14/2011
• Status: Active Grant

• Current Assignee: University of Notre DAME Du Lac
• Original Assignee: University of Notre DAME Du Lac
• Inventors: Pratt, Thomas G.
• Primary Examiner(s): Tsai, Carol S
• Application Number:
  US13/349,968
• Time in Patent Office: 1,222 Days
• Field of Search: 702/2, 342/22, 356/73.1, 455/73, 455/118, 455/190.1
• US Class Current: 702/2
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 13/95 for meteorological use
• CPC Class Codes: G01S 7/024 using polarisation effects in waveguides H01P1/165; for aerials H01Q, e.g. H01Q15/22, H01Q15/24, H01Q19/195
• CPC Class Codes: G01S 7/282 Transmitters
• CPC Class Codes: G01S 7/38 Jamming means, e.g. producing false echoes
• CPC Class Codes: G01S 7/41 using analysis of echo signal for target characterisation; Target signature; Target cross-section
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

A system and method of identifying changes utilizing radio frequency polarization includes receiving a reflected and/or transmitted polarized radio frequency signal at a receiver, filtering, amplifying and conditioning the received signal, converting the received signal from an analog format to a digital format, processing the digital signal to elicit a polarization mode dispersion feature of the received signal, and comparing the polarization mode dispersion features to a known calibration to detect a change in a characteristic of the target object.

Claims

1. A method of identifying changes utilizing radio frequency polarization comprising:

receiving dual-polarized components of at least a partially polarized radio frequency signal at a receiver, the radio frequency signal being at least one of reflected or transmitted through a target object;

filtering the received signal;

amplifying the received signal;

conditioning the received signal;

converting the received signal from an analog format to a digital format;

processing the digital signal to elicit a polarization mode dispersion feature of the received signal; and

detecting a change in a polarization response of the target object.

2. A method as defined in claim 1, wherein detecting a change in the polarization response of the target further comprises comparing the polarization mode dispersion features to a known calibration.

3. A method as defined in claim 2, wherein the known calibration is determined by measuring the polarization mode dispersion signature and comparing the measured polarization mode dispersion signature to a known standard measurement.

4. A method as defined in claim 1, wherein detecting a change in the polarization response of the target further comprises comparing the polarization mode dispersion features to a previously elicited polarization mode dispersion feature of the received signal.

5. A method as defined in claim 1, wherein detection of a change in the target object comprises detection of a change in moisture content.

6. A method as defined in claim 5, further comprising outputting the detected change in the target object moisture content.

7. A method as defined in claim 6, further comprising utilizing the outputted change in the target object moisture content to control irrigation of the target object.

8. A method as defined in claim 1, wherein detection of a change in a characteristic of the target object comprises detection of at least one of vibration, position change, attitude change, mechanical fault, electrical fault, electromagnetism, reflectivity, liquid phase, solid phase, structural change, or foreign object contamination of the target object.

9. A method as defined in claim 1, wherein elicitation of the polarization mode dispersion feature of the received signal comprises computing a Stokes Parameter versus a frequency index.

10. A method as defined in claim 1, further comprising visually mapping the polarization mode dispersion curves over time.

11. A method as defined in claim 2, wherein the known calibration is a predictive model and wherein comparing the polarization mode dispersion features to the known calibration allows for prediction of an impending change in the target object.

12. A method as defined in claim 1, wherein the received polarized radio frequency signal is a bistatic signal.

13. A method as defined in claim 1, further comprising receiving a second signal polarized radio frequency signal of a different frequency at the receiver, the second polarized radio frequency signal being at least one of reflected or transmitted through a target object;

filtering the received second signal;

amplifying the received second signal;

conditioning the received second signal;

converting the received second signal from an analog format to a digital format;

processing the second digital signal to elicit a polarization mode dispersion feature of the received second signal; and

comparing the polarization mode dispersion features of the received second signal to the polarization mode dispersion features of the signal to detect a change in a characteristic in the polarization response of the target object.

14. A method as defined in claim 1, further comprising receiving a second signal polarized radio frequency signal of a different frequency at the receiver, the second polarized radio frequency signal being at least one of reflected or transmitted through a target object;

filtering the received second signal;

amplifying the received second signal;

conditioning the received second signal;

converting the received second signal from an analog format to a digital format;

processing the second digital signal to elicit a polarization mode dispersion feature of the received second signal; and

comparing the polarization mode dispersion features of the received second signal to detect a change in a characteristic in the polarization response of the target object at a depth different than the first signal.

15. A method as defined in claim 1, further comprising:

measuring an external factor; and

compensating the processing of the digital signal based upon the measured external factor.

16. A method as defined in claim 15, wherein the external factor is temperature.

17. A system for identifying changes utilizing radio frequency polarization comprising:

a dual-polarized receiver for receiving a polarized radio frequency signal, the polarized radio frequency signal being at least one of reflected or transmitted through a target object;

a signal filter for filtering the received signal;

a signal amplifier for amplifying the received signal;

a signal conditioner for conditioning the received signal;

an analog to digital converter for converting the signal from an analog format to a digital format;

a processor for processing the digital signal to elicit a polarization mode dispersion feature of the received signal; and

wherein the processor detects a change in a characteristic of the target object.

18. A system as defined in claim 17, wherein the processor detects the change in a characteristic of the target response by comparing the polarization mode dispersion features to a known calibration stored in a memory.

19. A system as defined in claim 18, wherein the known calibration is determined by measuring the polarization mode dispersion signature and comparing the measured polarization mode dispersion signature to a known standard measurement.

20. A system as defined in claim 17, wherein the detected changes in the target object comprises detection of a change in moisture content.

21. A system as defined in claim 17, further comprising utilizing the outputted change in the target object moisture content to control irrigation of the target object.

22. A system as defined in claim 17, wherein detection of a change in a characteristic of the target object comprises detection of at least one of vibration, position change, attitude change, mechanical fault, electrical fault, electromagnetism, reflectivity, liquid phase, solid phase, structural change, or foreign object contamination of the target object.

23. A system as defined in claim 17, wherein elicitation of the polarization mode dispersion feature of the received signal comprises computing a Stokes Parameter versus a frequency index.

24. A system as defined in claim 18, wherein the known calibration is a predictive model and wherein comparing the polarization mode dispersion features to the known calibration allows for prediction of an impending change in the target object.

25. A system as defined in claim 17, wherein the received polarized radio frequency signal is a bistatic signal.

26. A method of identifying changes utilizing electromagnetic signal polarization comprising:

receiving dual-polarized components of at least a partially polarized electromagnetic signal at a receiver, the signal being at least one of reflected or transmitted through a target object;

converting the received signal from an analog format to a digital format;

processing the digital signal to elicit a polarization mode dispersion feature of the received signal; and

detecting a change in a polarization response of the target object.