Radio Frequency Certificates of Authenticity and Related Scanners

• US 20070159400A1
• Filed: 11/30/2006
• Published: 07/12/2007
• Est. Priority Date: 01/11/2006
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Kirovski, Darko, DeJean, Gerald
• Granted Patent: US 7,659,851 B2
• Time in Patent Office: Days
• US Class Current: 343/700.MS
• CPC Class Codes: H01Q 1/243 with built-in antennas
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 19/005 Patch antenna using one or more coplanar parasitic elements
• CPC Class Codes: H01Q 9/0421 with a shorting wall or a shorting pin at one end of the element H01Q9/0414 takes precedence

Abstract

Radio frequency certificates of authenticity (RFCOAs) and associated scanners are presented. In one implementation, an array of miniaturized antenna elements in an RFCOA scanner occupies an area smaller than a credit card yet obtains a unique electromagnetic fingerprint from an RFCOA associated with an item, such as the credit card. The antenna elements are miniaturized by a combination of both folding and meandering the antenna patch components. The electromagnetic fingerprint of an exemplary RFCOA embeddable in a credit card or other item is computationally infeasible to fake, and the RFCOA cannot be physically copied or counterfeited based only on possession of the electromagnetic fingerprint.

Claims

1. An apparatus for reading an electromagnetic fingerprint associated with a radio frequency certificate of authenticity (RFCOA), wherein the apparatus transmits RF energy at the RFCOA to create the electromagnetic fingerprint and receives electromagnetic effects back from the RFCOA, the electromagnetic effects representing the electromagnetic fingerprint of the RFCOA, comprising:

an array of antenna elements capable of being positioned in a near-field of the RFCOA;

each antenna element comprising multiple electrically conductive surfaces;

wherein a folded and meandered geometry of the conductive surfaces enables each antenna element to be miniaturized to one-eighth or less of the wavelength of the radio frequency (RF) energy used to obtain the electromagnetic fingerprint of the RFCOA.

2. The apparatus as recited in claim 1, wherein each antenna element possesses a fractional resonant length comprising a fraction of the wavelength of the RF energy, the fractional resonant length determined in part by the geometries of the conductive surfaces.

3. The apparatus as recited in claim 2, wherein the multiple electrically conductive surfaces comprise a ground plane, and multiple microstrip antenna patches disposed in layers above the ground plane.

4. The apparatus as recited in claim 3, wherein each antenna element comprises a miniaturized antenna element that includes:

folded microstrip antenna patches and a folded ground plane;

meandered microstrip antenna patches; and

wherein the folded microstrip antenna patches, the folded ground plane, and the meandered microstrip antenna patches possess the fractional resonant length.

5. The apparatus as recited in claim 3, wherein each antenna element has an operating frequency of approximately 5 GHz.

6. The apparatus as recited in claim 3, further comprising electrically conducting vias to achieve the folding by shorting each microstrip antenna patch to the ground plane such that the folded microstrip antenna patches and the folded ground plane shorten the physical length of the antenna element without changing the resonance frequency of the antenna element.

7. The apparatus as recited in claim 6, wherein the electrically conducting vias are connected to short the microstrip antenna patches of adjacent layers on opposite sides of each other to create alternating radiating edges in the antenna element.

8. The apparatus as recited in claim 7, further comprising multiple folded and shorted microstrip antenna patches in each antenna element of the antenna array, wherein the multiple folded and shorted microstrip antenna patches comprise a fractional resonant length of one-fourth of the wavelength of the RF energy and comprise a physical length of one-eighth of the wavelength of the RF energy.

9. The apparatus as recited in claim 8, wherein one or more of the microstrip antenna patches have strip cutouts to create the meandering in order to:

increase the path of electrical conduction in the microstrip antenna patch;

decrease a resonance frequency of the microstrip antenna patch;

miniaturize the microstrip antenna patch;

or

tune the microstrip antenna patch to a resonance frequency of a different microstrip antenna patch in the same antenna element.

10. The apparatus as recited in claim 3, further comprising a first microstrip antenna patch in a first layer above the ground plane, and a second microstrip antenna patch in a second layer above the first layer, wherein the resonant length of the first microstrip antenna patch is smaller than the resonant length of the second microstrip antenna patch.

11. The apparatus as recited in claim 10, further comprising a first substrate layer between the ground plane and the first microstrip antenna patch and a second substrate layer between the first and second microstrip antenna patches, wherein the first and second substrate layers have a high dielectric constant for further reducing the physical size of the antenna element for a given resonance frequency of the antenna element.

12. The apparatus as recited in claim 11, wherein the substrate layers are between approximately 30 mils and approximately 40 mils thick.

13. The apparatus as recited in claim 1, wherein:

each antenna element has a length of approximately 130 mils and a width of approximately 110 mils, wherein a mil comprises approximately one-fortieth of a millimeter;

wherein the array of antenna elements has rows and columns of the antenna elements;

wherein the distance between two antenna elements is between approximately 130 mils and approximately 160 mils; and

wherein the array of antenna elements is smaller in area than the area of one side of a typical credit card.

14. The apparatus as recited in claim 13, wherein the array has either three columns and three rows of the antenna elements or has five columns and ten rows of the antenna elements.

15. The apparatus as recited in claim 1, further comprising a field analyzer communicatively coupled with each of the antenna elements in the array of antenna elements, wherein the field analyzer evaluates the electromagnetic effects received independently at each antenna element of the array to obtain the electromagnetic fingerprint of the RFCOA.

16. The apparatus as recited in claim 15, wherein only a first subset of the antenna elements of the array transmit the RF energy at the RFCOA and the field analyzer evaluates the electromagnetic effects only at a second subset of the antenna elements of the array.

17. A system, comprising:

a reader for obtaining an electromagnetic fingerprint from a radio frequency certificate of authenticity (RFCOA);

an antenna array associated with the reader capable of being placed within a millimeter of a surface of the RFCOA;

antenna elements in the antenna array, each antenna element comprising a folded ground plane and one or more folded and meandered microstrip antenna patches;

wherein the folded ground plane and the one or more folded and meandered microstrip antenna patches are capable of transmitting and receiving radio frequency (RF) energy to and from the RFCOA; and

wherein the longest dimension of each antenna element is equal to or less than one-eighth the wavelength of RF energy.

18. The system as recited in claim 17, further comprising:

an RF source communicatively coupled with at least some of the antenna elements of the antenna array;

a network analyzer communicatively coupled with each antenna element in the antenna array to obtain the electromagnetic fingerprint.

19. The system as recited in claim 17, wherein:

the reader comprises a credit card reader;

the antenna array covers an area less than the area of one side of a credit card; and

the antenna array includes a number of the antenna elements, wherein the number is in a range from nine to one hundred.

20. A credit card, comprising:

an embedded radio frequency certificate of authenticity (RFCOA);

the RFCOA comprising an agent to interact with radio frequency (RF) energy such that an array of RF antennae in a credit card scanner obtains a unique electromagnetic fingerprint of the RFCOA in the credit card;

stored information representing the electromagnetic fingerprint obtained from a scan of the RFCOA for comparison with subsequent scans of the RFCOA;

wherein the electromagnetic fingerprint is computationally infeasible to fake;

wherein the RFCOA is infeasible to physically copy based only on possession of the electromagnetic fingerprint; and

wherein the stored information resides in a barcode, a magnetic strip, or a chip.