Frequency multiplexed radio frequency identification

• US 10,025,960 B1
• Filed: 06/28/2017
• Issued: 07/17/2018
• Est. Priority Date: 06/29/2016
• Status: Active Grant

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Fink, Patrick W., Lin, Gregory Y., Kennedy, Timothy F., Ngo, Phong H.
• Primary Examiner(s): ALUNKAL, THOMAS D
• Application Number:
  US15/635,923
• Time in Patent Office: 384 Days
• CPC Class Codes: G06K 19/0724 the arrangement being a circuit for communicating at a plurality of frequencies, e.g. for managing time multiplexed communication over at least two antennas of different types
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• CPC Class Codes: G06K 19/07767 the first and second communication means being two different antennas types, e.g. dipole and coil type, or two antennas of the same kind but operating at different frequencies
• CPC Class Codes: G06K 7/10069 the collision being resolved in the frequency domain, e.g. by hopping from one frequency to the other frequency hopping or spread spectrum techniques H04B7/00
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas
• CPC Class Codes: H01Q 1/2208 associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems methods or arrangements for sensing record carriers, e.g. for reading patterns G06K7/00; record carrier for use with machines and with at least a part designed to carry digital markings G06K19/00
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 15/0013 said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
• CPC Class Codes: H01Q 15/242 Polarisation converters
• CPC Class Codes: H01Q 21/0075 Stripline fed arrays H01Q21/065 takes precedence
• CPC Class Codes: H01Q 21/08 the units being spaced along or adjacent to a rectilinear path waveguide fed H01Q21/0037
• CPC Class Codes: H01Q 21/205 providing an omnidirectional coverage turnstile aerials H01Q21/26
• CPC Class Codes: H01Q 3/22 varying the orientation in accordance with variation of frequency of radiated wave
• CPC Class Codes: H01Q 3/40 with phasing matrix
• CPC Class Codes: H01Q 9/0428 radiating a circular polarised wave
• CPC Class Codes: H01Q 9/045 with particular feeding means for circular polarisation H01Q9/0428
• CPC Class Codes: H04B 1/713 using frequency hopping
• CPC Class Codes: H04L 5/08 each combination of signals in different channels being represented by a fixed frequency
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex

Abstract

A radio frequency identification (RFID) system for frequency multiplexing includes, in an exemplary embodiment, an RFID interrogator configured for generating an RFID signal, wherein a channel frequency of the RFID signal changes over time within an operating bandwidth; and one or more electromagnetic transmissive elements each extending between a first end thereof and a second end thereof, each of the electromagnetic transmissive elements electrically coupled with the RFID interrogator at the first end thereof, each of the electromagnetic transmissive elements comprising a frequency dependent load at the second end thereof and configured for transmitting the RFID signal from the RFID interrogator to the frequency dependent load, wherein the frequency dependent load presents different electromagnetic characteristics to the RFID signal transmitted to the frequency dependent load depending on the channel frequency of the RFID signal. Other embodiments include a method for frequency multiplexing including similar components.

Claims

1. A system comprising:

an RFID interrogator configured for generating an RFID signal, wherein a channel frequency of the RFID signal changes over time according to a frequency hopping spread spectrum protocol within an operating bandwidth, the operating bandwidth comprising a first portion thereof and a second portion thereof, the first portion of the operating bandwidth not overlapping with the second portion of the operating bandwidth; and

one or more electromagnetic transmissive elements each extending between a first end thereof and a second end thereof, each of the electromagnetic transmissive elements electrically coupled with the RFID interrogator at the first end thereof, each electromagnetic transmissive element comprising a passive frequency dependent load at the second end thereof and configured for transmitting the RFID signal from the RFID interrogator to the frequency dependent load, wherein each passive frequency dependent load presents different electromagnetic characteristics to the RFID signal transmitted thereto depending on the channel frequency of the RFID signal,

each passive frequency dependent load designed for appearing substantially as an open circuit or as a short circuit at the second end for at least one channel frequency in at least one of the first portion and the second portion of the operating bandwidth such that, in operation, the system frequency multiplexes the RFID signal according to the channel frequencies arising from the frequency hopping spread spectrum protocol.

2. The system according to claim 1, wherein at least one of the passive frequency dependent loads comprises a lumped element resonator.

3. The system of claim 1, wherein at least one of the passive frequency dependent loads comprises a narrow band antenna.

4. The system according to claim 1, wherein each of the electromagnetic transmissive elements is an at least partly open transmission line having a length equal to an odd or even integer multiple of a quarter of a wavelength, the wavelength being a wavelength at a center of the operating bandwidth.

5. The system according to claim 1, further comprising a distributed diplexer through which all of the electromagnetic transmissive elements are jointly electrically coupled with the RFID interrogator via a single port of the RFID interrogator.

6. The system according to claim 1, wherein at least one of the electromagnetic transmissive elements is mounted on an open surface.

7. The system according to claim 1, wherein at least one of the electromagnetic transmissive elements is mounted on a surface of a wall of a cavity or waveguide, the cavity or waveguide coupling the RFID interrogator and the at least one electromagnetic transmissive element.

19. The system of claim 1, wherein the RFID interrogator is compatible with an EPCGlobal RFID protocol and the frequency hopping spread spectrum protocol is defined by the EPCglobal protocol.

8. A method, comprising:

generating an RFID signal, wherein a channel frequency of the RFID signal generated changes over time according to a frequency hopping spread spectrum protocol;

frequency multiplexing the RFID signal to one or more electromagnetic transmissive elements at different times, respectively, depending on the channel frequency of the RFID signal generated;

transmitting a first electromagnetic signal having a first channel frequency in response to a first distributed RFID signal having the first channel frequency; and

transmitting a second electromagnetic signal having a second channel frequency in response to a second distributed RFID signal having the second channel frequency,

wherein the one or more electromagnetic transmissive elements comprises a passive frequency dependent load.

9. The method according to claim 8, wherein the RFID interrogator is compatible with an EPCGlobal RFID protocol and the frequency hopping spread spectrum protocol is defined the EPCglobal protocol.

10. The method according to claim 8, wherein the frequency multiplexing of the RFID signal to each of the one or more electromagnetic transmissive elements, respectively, depending on the channel frequency of the RFID signal generated, is performed using a bandpass filter or a surface acoustic wave filter.

11. The method according to claim 8,

wherein the frequency multiplexing of the RFID signal to each of the one or more electromagnetic transmissive elements is performed by using a first narrow band antenna and a second narrow band antenna, the first narrow band antenna filtering out frequencies falling outside of a first range of frequencies and the second narrow band antenna filtering out frequencies falling outside of a second range of frequencies, the first range of frequencies being different from the second range of frequencies.

12. The method according to claim 8,

wherein the first electromagnetic signal having the first channel frequency has a first polarization, and the second electromagnetic signal having the second channel frequency has a second polarization, the first polarization and the second polarization being characterized by different orientations.

13. The method according to claim 12, further comprising:

determining an orientation of an RFID tag based on a channel frequency of a third electromagnetic signal sent by the RFID tag in response to the first or second electromagnetic signal,

wherein if the third electromagnetic signal is predominantly within the first channel frequency the tag is determined to have an orientation corresponding to the first polarization, and if the third electromagnetic signal is predominantly within the second channel frequency the tag is determined to have an orientation corresponding to the second polarization.

14. The method according to claim 8, further comprising:

providing a frequency selective surface within a range of the transmitted first electromagnetic signal having the first channel frequency and/or a range of the transmitted second electromagnetic signal having the second channel frequency; and

scattering, in a particular pattern, and/or altering a polarization, in a particular manner, of the transmitted first electromagnetic signal, the transmitted second electromagnetic signal, and/or a third electromagnetic signal sent by an RFID tag in response to the transmitted first or second electromagnetic signal, the particular pattern and/or particular manner depending on a channel frequency of the transmitted first electromagnetic signal, the transmitted second electromagnetic signal, or the third electromagnetic signal, respectively.

15. The method according to claim 8, further comprising receiving a third electromagnetic signal transmitted by an RFID tag in response to the transmitted first or second electromagnetic signal.

16. The method according to claim 8, further comprising determining information pertaining to a location and/or orientation of an RFID tag based on a third electromagnetic signal received from the RFID tag in response to the transmitted first or second electromagnetic signal.

17. The method according to claim 16, further comprising refining the determination of the information pertaining to a location and/or orientation of an RFID tag based on another instance of receipt of a third electromagnetic signal from the RFID tag in response to the transmitted first or second electromagnetic signal.

18. The method according to claim 8, further comprising transmitting electromagnetic energy to an RFID tag by near-field coupling or radiation from the first and second electromagnetic signals, wherein the plurality of electromagnetic transmissive elements comprise the plurality of at least partially open transmission lines.