RADIO FREQUENCY TRANSPONDER SYSTEM

• US 20120161931A1
• Filed: 05/19/2011
• Published: 06/28/2012
• Est. Priority Date: 11/20/2008
• Status: Active Grant

• Current Assignee: RFID Technologies Pty., Ltd.
• Original Assignee: Monash University
• Inventors: Karmakar, Nemai Chandra, Balbin, Isaac
• Granted Patent: US 9,164,169 B2
• Time in Patent Office: Days
• US Class Current: 340/10.1
• CPC Class Codes: G01S 13/753 using frequency selective elements, e.g. resonator
• CPC Class Codes: G01S 13/825 with exchange of information between interrogator and responder
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• CPC Class Codes: H01Q 9/0442 with particular tuning means

Abstract

A radio frequency transponder is disclosed. In one embodiment, the transponder includes: a substrate and at least one planar antenna on the substrate, the antenna having a shape determining a corresponding resonant frequency of the antenna, wherein the antenna is configured to cause a phase difference between backscattered signals generated in response to excitation of the antenna by orthogonally polarized interrogation signals at the resonant frequency, and the phase difference represents a code of the antenna.

Claims

1. A radio frequency transponder, comprising:

a substrate; and

a plurality of planar antennas on the substrate, wherein each antenna has a shape configured to determine a corresponding resonant frequency of the antenna, wherein the antenna is configured to cause a phase difference between backscattered signals generated in response to excitation of the antenna by orthogonally polarized interrogation signals at the resonant frequency, and wherein the phase difference represents a code of the antenna and

wherein the antennas have respective different resonant frequencies, and wherein the codes determined from the phase differences between the backscattered signals at each of the resonant frequencies are configured to generate a unique code for the transponder.

2. A radio frequency transponder as claimed in claim 1, wherein the shape of the antenna determines the phase difference.

3. A radio frequency transponder as claimed in claim 2, wherein the antenna includes a load element to control a value represented by the code.

4. A radio frequency transponder as claimed in claim 3, wherein the shape is a polygon with equal sides.

5. A radio frequency transponder as claimed in claim 4, wherein the shape is square.

6. A radio frequency transponder as claimed in claim 5, wherein the load element is a stub of the antenna, and wherein the stub has a length which determines the value of the code.

7. A radio frequency transponder as claimed in claim 6, further comprising a conductive ground plane, wherein the substrate is on the ground plane.

8. A radio frequency transponder as claimed in claim 1, wherein the antenna is printed using electrically conductive ink on the substrate which is dielectric.

9. A radio frequency transponder as claimed in claim 1, further comprising arrays of antennas with the same resonant frequency and having a symmetrical layout.

10. A radio frequency transponder as claimed in claim 9, wherein each array represents a frequency signature with one of a number of phase signatures determined from the phase difference of the backscattered signals at the resonant frequency for the array, and wherein the phase signature represents a value of the code.

11. A radio frequency transponder as claimed in claim 10, wherein the layout of the arrays is symmetrical to cancel mutual coupling effects of the non-radiating antennas and provide a symmetrical response at each resonant frequency.

12. A radio frequency transponder as claimed in claim 11, further comprising a first layer of the layout with arrays of higher resonant frequencies than arrays of a second layer of the layout surrounding the first layer.

13. A radio frequency transponder as claimed in claim 1, wherein the transponder is passive and chipless.

14. A radio-frequency identification transponder, comprising:

a dielectric substrate; and

a plurality of antennas formed on the substrate and configured to generate backscattered radiation at different resonant frequencies for different polarizations, wherein the antennas comprise a plurality of load elements each of which is configured to determine a phase difference of the different polarizations of the backscattered radiation, and wherein the phase difference represents a value of a code of the transponder.

15. A radio frequency transponder as claimed in claim 14, wherein the transponder is passive and chipless.

16. A radio frequency transponder system, comprising:

a radio-frequency identification transponder, comprising;

i) a dielectric substrate, ii) a plurality of antennas formed on the substrate and configured to generate backscattered radiation at different resonant frequencies for different polarizations and iii) load elements of the antennas each of which is configured to determine a phase difference of the different polarizations of the backscattered radiation, wherein the phase difference represents a value of a code of the transponder; and

a reader for generating the interrogation signals and reading the backscattered signals to extract the code.

17. A radio frequency reader for interrogating a radio frequency transponder, comprising:

a frequency interface unit configured to transmit a plurality of polarized interrogation signals and receive a plurality of backscattered signals from the transponder in response; and

a signal processing unit configured to determine a code of the transponder from the phase difference of the backscattered signals.

18. A radio frequency reader as claimed in claim 17, wherein:

the frequency interface unit includes a phased array antenna configured to transmit and receive frequency modulated continuous wave signals with frequency and polarization diversity to read multiple transponders; and

the signal processing unit is configured to process the received signals using a direction of arrival and phase difference detection process.

19. A radio frequency transponder as claimed in claim 17, wherein the interrogation signals are orthogonally polarized and wherein the phase difference is the phase difference of the orthogonal components of the backscattered signals.

20. A radio frequency process, comprising:

transmitting polarized interrogation signals;

receiving backscattered signals including orthogonal components from a transponder in response; and

determining a code of the transponder from the phase difference between the orthogonal components of the backscattered signals.

21. A radio frequency transponder, comprising:

means for transmitting polarized interrogation signals;

means for receiving backscattered signals including orthogonal components from a transponder in response; and

means for determining a code of the transponder from phase difference between the orthogonal components of the backscattered signals.