Near-field miniature coupler
A near-field coupler for a RFID system is provided. The coupler is configured to selectively communicate with a targeted transponder from among a group of multiple adjacent transponders. The coupler includes a conductive strip terminated by a load. The load is for matching an input impedance of the coupler to a source impedance of a transceiver. The conductive strip is based on a quarter wavelength of the center operating frequency. The conductive strip may have a substantially constant width and a length substantially equal to the quarter wavelength. Or the conductive strip may have a variable width defining a tapered profile and a length less than the quarter wavelength. The tapered profile may be an exponential profile or a Klopfenstein profile. Due to the overall size of the coupler to a typical transponder, the center of the coupler and the center of the transponder may be offset during coupling.
1. An RFID system for selectively communicating with a targeted transponder from among a group of multiple adjacent transponders, the RFID system comprising:
a transponder conveyance system adapted to transport at least one targeted transponder from a group of multiple adjacent transponders through a transponder encoding region;
a transceiver configured to generate a communication signal, wherein the transceiver defines a source impedance; and
a near-field coupler in electrical communication with the transceiver for receiving the communication signal, the near-field coupler defining an input impedance and including,
a grounded terminating load for substantially matching the input impedance to the source impedance, and
a conductive strip for a transmission of an electromagnetic signal within an operating frequency range into the transponder encoding region, the conductive strip defining a length that is less than or substantially equal to a quarter wavelength of a center frequency of the operating frequency range.
2. The RFID system according to claim 1 , wherein a center of the near-field coupler is offset from a center of the targeted transponder in the transponder encoding region.
3. The RFID system according to claim 1 , wherein the conductive strip defines a width that is substantially constant along the length of the conductive strip and the length is substantially equal to a quarter wavelength of the center frequency.
4. The RFID system according to claim 1 , wherein the conductive strip defines a width that varies along the length and defines a tapered profile and the length is less than a quarter wavelength of the center frequency.
5. The RFID system according to claim 4 , wherein the tapered profile is selected from the group consisting of a triangular profile, a bow-tie profile, an exponential profile, a Hecken profile, and a Klopfenstein profile.
6. An RFID printer-encoder for printing and programming a series of media units wherein at least one of the media units includes at least one transponder, the RFID printer-encoder comprising:
a printhead for printing indicia onto the series of the media units;
a media conveyance system for transporting the series of media units including the transponder along a feed path and to the printhead and a transponder encoding region;
a transceiver for generating a communication signal; and
a coupler for receiving the communication signal and creating an electromagnetic field into the transponder encoding region, wherein a center of the coupler is offset from a center line of the feed path.
7. The RFID printer-encoder according to claim 6 , wherein the coupler includes a conductive strip configured to create the electromagnetic field substantially concentrated in the near-field region of the conductive strip.
8. The RFID printer-encoder according to claim 7 , wherein the transceiver defines a source impedance and the coupler defines an input impedance and further includes a terminating load for substantially matching the input impedance and the source impedance.
9. The RFID printer-encoder according to claim 8 , wherein the conductive strip is configured to create the electromagnetic field within a range of frequencies and the conductive strip defines a width and a length, wherein the length is substantially equal to a quarter wavelength of a center frequency of the range of frequencies and the width is substantially constant along the length.
10. The RFID printer-encoder according to claim 8 , wherein the conductive strip is configured to create the electromagnetic field within a range of frequencies and the conductive strip defines a width and a length, wherein the length is less than a quarter wavelength of a center frequency of the range of frequencies and the width varies along the length and defines a tapered profile.
11. The RFID printer-encoder according to claim 10 , wherein the tapered profile is selected from a group consisting of a triangular profile, a bow-tie profile, an exponential profile, a Hecken profile, and a Klopfenstein profile.
12. A RFID system adapted to provide selective communication between a transceiver and a targeted transponder disposed among multiple adjacent transponders and in a transponder encoding region, wherein the targeted transponder includes an antenna that defines a first length, the RFID system comprising:
a near-field coupler structured to receive at least one communication signal from the transceiver and further configured to create an electromagnetic field substantially concentrated in a near-field region of the coupler and into the transponder encoding region, wherein the near-field coupler defines a second length that is substantially equal to or less than one half the first length defined by the antenna of the targeted transponder.
13. The RFID system according to claim 12 , wherein a center of the near-field coupler is offset from a center of the targeted transponder during the selective communication.
14. The RFID system according to claim 12 , wherein the near-field coupler includes a conductive strip adapted to create the electromagnetic field.
15. The RFID system according to claim 14 , wherein the transceiver defines a source impedance and the near-field coupler defines an input impedance and further includes a terminating load for substantially matching the source impedance and the input impedance.
16. The RFID system according to claim 14 , wherein the conductive strip is configured to create the electromagnetic field within a range of frequencies and the conductive strip defines a width and a length, wherein the length is substantially equal to a quarter wavelength of a center frequency of the range of frequencies and the width is substantially constant along the length.
17. The RFID system according to claim 14 , wherein the conductive strip is adapted to create the electromagnetic field within a range of frequencies and the conductive strip defines a width and a length, wherein the length is less than a quarter wavelength of a center frequency of the range of frequencies and the width varies along the length and defines a tapered profile.
18. The RFID system according to claim 17 , wherein the tapered profile is selected from a group consisting of a triangular profile, a bow-tie profile, an exponential profile, a Hecken profile, and a Klopfenstein profile.