Methods and apparatus for electromagnetic signal polarimetry sensing
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.
1. A method of identifying changes utilizing polarization comprising:
receiving polarized and coherent components of an at least partially polarized multipath signal at a receiver, wherein at least one signal path of the multipath signal is at least one of reflected off of a surface of a target object or transmitted through the target object;
computing the Stokes parameter versus the frequency index of the subcarrier present within the received signal;
calculating polarization as a function of frequency to determine the polarization mode dispersion of the received multipath signal;
detecting a change in a polarization mode dispersion in response to a change in the target object; and
displaying on a user interface the detected change in the polarization mode dispersion as a digital representation of the change in the target object.
2. A method as defined in claim 1 , wherein detecting a change in the polarization mode dispersion in response to a change in the target object further comprises comparing the polarization features of the processed signal to a known calibration.
3. A method as defined in claim 2 , wherein the known calibration is a predictive model and wherein comparing the polarization features of the processed signal to the known calibration allows for prediction of an impending change in the target object.
4. A method as defined in claim 2 , wherein the known calibration is determined by measuring a polarization signature of the processed signal and comparing the measured polarization signature to a known standard measurement.
5. A method as defined in claim 1 , wherein detecting a change in the polarization mode dispersion in response to a change in the target object further comprises comparing a polarization mode dispersion feature of the processed signal to a previously elicited polarization mode dispersion feature of the received signal.
6. A method as defined in claim 1 , wherein detecting a change in the polarization response of the target object is indicative of a change in a characteristic of the target object comprising at least one of vibration, attitude change, mechanical fault, structural change, or foreign object contamination of the target object.
7. A method as defined in claim 1 , wherein an elicited polarization feature in a first subband of the received signal is compared against an elicited polarization feature of the received signal in a second subband.
8. A method as defined in claim 1 , wherein the elicited polarization feature is a polarimetric mode dispersion of at least one subband of the received signal.
9. A method as defined in claim 1 , wherein detecting a change in the polarization response of the target object is indicative of a change in a characteristic of the target object comprising at least one of electrical fault, electromagnetism, reflectivity, liquid phase, or solid phase.
10. A system for identifying changes utilizing polarization comprising:
a polarized receiver for receiving polarized and coherent components of a polarized multipath signal at a receiver, wherein at least one signal path of the multipath signal is at least one of reflected off of a surface of a target object or transmitted through the 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 computing the Stokes parameter versus the frequency index of the subcarrier present within the received signal and calculating a polarization mode dispersion feature of the received signal,
wherein the processor detects a change in the polarization mode dispersion signature of the target object; and
a display for displaying on a user interface the detected change in the polarization mode dispersion signature of the target object.
11. A system as defined in claim 10 , wherein the processor detects a change in a characteristic of the polarization mode dispersion signature of the target object by comparing the detected polarization mode dispersion signature of the dispersion signature to a known calibration stored in a memory.
12. A system as defined in claim 11 , wherein the known calibration is determined by measuring the polarization mode dispersion signature of the target object and comparing the measured polarization mode dispersion signature to a known standard measurement.
13. A system as defined in claim 10 , wherein detection of the change in the polarization mode dispersion signature of the target object is indicative of a change in a characteristic of the target object comprising at least one of vibration, attitude change, mechanical fault, structural change, or foreign object contamination of the target object.