RFID tag imager

1. A system for obtaining an image of an RFID tag comprising a transponder and a tag antenna, the system comprising:

a plurality of inductors, each inductor being associated with a capacitor to form a resonant tank circuit, wherein each resonant tank circuit has a first resonant frequency in the presence of metal and a second resonant frequency in the absence of metal;

a signal processor configured to determine a resonant frequency for each resonant tank circuit in the presence of the tag antenna; and

a processor configured to compare the resonant frequency of each resonant tank circuit to the first and second resonant frequency to determine an image of the tag antenna.

2. The system as defined in claim 1 , wherein the plurality of inductors is a linear array of inductors.

3. The system as defined in claim 1 , wherein each inductor represents a pixel of the image and wherein the processor is configured to assign a grey scale to each pixel based the comparison of the resonant frequency to the first and second resonant frequencies such that the image comprises a plurality of pixels of varying grey scales.

4. The system as defined in claim 1 , wherein the system is further configured to compare the image to a set of predetermined images so as to classify the type of tag antenna.

5. The system as defined in claim 4 , wherein the system is further configured to identify, based upon the classification of the type of tag antenna, areas of maximum current excitation in the tag antenna.

6. The system as defined in claim 5 , wherein the tag antenna is a dipole antenna having a first area of maximum current excitation in a first dipole half and a second area of maximum current excitation in a second dipole half, the system further comprising:

a capacitive encoder having a plurality of conductive elements, wherein the system is configured to select a first conductive element from plurality based upon its proximity to the first area of maximum current excitation and to select a second conductive element from the plurality based upon its proximity to the second area of maximum current excitation, the capacitive encoder being configured to drive an RF encoding signal into the first conductive element and to phase shift the RF encoding signal and drive the phase-shifted RF encoding signal into the second conductive element so as to capacitively encode the RFID tag.

7. The system as defined in claim 6 , wherein the plurality of conductive elements comprise a plurality of patches on a surface of a dielectric substrate.

8. The system as defined in claim 1 , wherein the system is further configured to analyze the image to determine locations of maximum current excitation on the tag antenna.

9. The system as defined in claim 8 , wherein the system analytically determines the locations of maximum current excitation based on a Finite Element Analysis and a Method of Moments analysis.

10. The system as defined in claim 9 , wherein the tag antenna is a dipole antenna having a first area of maximum current excitation in a first dipole half and a second area of maximum current excitation in a second dipole half, the system further comprising:

a capacitive encoder having a plurality of conductive elements, wherein the system is configured to select a first conductive element from plurality based upon its proximity to the first area of maximum current excitation and to select a second conductive element from the plurality based upon its proximity to the second area of maximum current excitation, the capacitive encoder being configured to drive an RF encoding signal into the first conductive element and to phase shift the RF encoding signal and drive the phase-shifted RF encoding signal into the second conductive element so as to capacitively encode the RFID tag.

11. The system as defined in claim 10 , wherein the plurality of conductive elements comprise a plurality of patches on a surface of a dielectric substrate.

12. A method for obtaining an image of an RFID tag comprising a transponder and a tag antenna, the method comprising:

providing a plurality of inductors, each inductor being associated with a capacitor to form a resonant tank circuit, wherein each resonant tank circuit has a first resonant frequency in the presence of metal and a second resonant frequency in the absence of metal;

placing the RFID tag in proximity of the plurality of inductors;

determining a resonant frequency for each of the resonant tank circuits as affected by the proximity of the RFID tag;

comparing each determined resonant frequency to the first and second resonant frequencies to determine an image of the RFID antenna.

13. The method as defined in claim 12 , further comprising: comparing the image of the RFID antenna to a set of predetermined images so as to classify the type of tag antenna.

14. The method as defined in claim 12 , further comprising: analyzing the image using a finite element/method of moments analysis to electromagnetically model the RFID antenna.

15. The method as defined in claim 14 , further comprising: based upon the electromagnetic model, identifying areas of maximum current excitation in the RFID antenna.