Spatially Selective UHF Near Field Microstrip Coupler Device and RFID Systems Using Device

Abstract

A system having a UHF RFID transceiver is adapted to communicate exclusively with a single electro-magnetically coupled transponder located in a predetermined confined transponder operating region. The system includes a near field coupling device comprising a plurality of lines connected in parallel with an unmatched load. The near field coupling device may be formed, for example on a printed circuit board with a plurality of electrically interconnected traces and a ground plane. The system establishes, at predetermined transceiver power levels, a mutual electro-magnetic coupling which is selective exclusively for a single transponder located in a defined transponder operating region. Also included are methods for selective communication with the transponder in an apparatus such as a printer-encoder.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation-in-part of U.S. Utility Patent application No. 10 / 604,996, filed Aug. 29,2003 and hereby incorporated by reference in the entirety.BACKGROUND OF INVENTION [0002] 1. Field of the Invention [0003] The invention relates to RFID systems, operable with a variety of different dimensioned electro-magnetically coupled transponders, working at close proximity, to an RF transceiver antenna that is spatially selective for an individual transponder located in a predetermined transponder operating region to the exclusion of other adjacent transponders, and its application to printers-encoders or other systems utilizing such in UHF RFID systems. [0004] 2. Description of Related Art [0005] UHF radio frequency identification (RFID) technology allows wireless data acquisition and or transmission from and or to active (battery powered) or passive transponders using a backscatter technique. To communicate with, i.e., “re...

AI Technical Summary

Benefits of technology

[0037] In some applications, for example the modification of an existing printer configuration to add RFID read / write capability, the coupler 30 may be placed close to the web 24 due to available space and or other design considerations such as placement of the transponder operating region C proximate the printhead 18. Where the coupler 30 and the web 24 are at a close proximity to one another an impedance mismatch may occur as electrical interaction with passing transponder(s) 1 varies the effective impedance of the coupler 30. Impedance mismatch will decrease coupling range for a given output power and with significant impedance variances may cause narrow null gaps in the operational region C, for example as illustrated by d, e, f, and g in FIG. 5a, between the individual fields emitted by each line 50.

[0039] The null gaps and the ability to control their presence by manipulating the location of the coupler 30 with respect to the web 24, are evidence of the extremely local field concentrations produced by the near field effect and the precision with which the transponder operating region may be configured to have a wide area with sharply defined boundaries. These characteristics make the near field coupler 30 useful for eliminating precision transponder placement requirements for media suppliers, complex transponder location and tracking logic in media supply systems, as well as any requirements for shielding or increased transponder placement tolerance requirements. Further, the increased transponder operating region C provided by the present invention allows users increased freedom to place embedded transponder(s) 1 in media 11 at desired locations, for example to avoid the printing degradation that may occur when the printhead encounters a media surface irregularity due to the presence of a RFID transponder 1.

[0043] Obviously, at some exaggerated transceiver power level, certain transponders 1 outside the transponder operating region C may be excited. However, by this invention, at appropriate power levels in the range of normal transponder read and write power levels the mutual coupling created will be highly selective for the transponder 1 in the transponder operating region C. By mapping and then applying only the required power levels for a range of both different transponder 1 types and positions within the transponder operating region C, energy consumption and potential RF interference generation may be minimized.

[0044] The spatially-selective near field property and the lack of any other shielding requirements of the near field coupler 30 according to the invention allows the economical addition of a compact, spatially-selective transponder communication module in devices such as printer-encoders.

Problems solved by technology

When multiple passive transponders are within the range of the same RF transceiver electro-magnetic field they will each be energized and attempt to communicate with the transceiver, potentially causing errors in “reading” and or “writing” to a specific transponder in the reader field.

However, anti-collision management increases system complexity, cost and delay response.

Furthermore, anti-collision management is “blind” in that it cannot recognize where a specific transponder being processed is physically located in the RF electro-magnetic field, for example, which transponder is located proximate the print head of a printer-encoder.

This requires that the individual transponders have cumbersome shielding or a significant spatial separation.

The extra carrier substrate increases materials costs and the required volume of the transponder media bulk supply for a given number of transponders.

Having increased spacing between transponders may also slow overall printer-encoder throughput.

When transponders of different sizes and form factors are processed, the RF shielding and or anechoic chamber configuration will also require reconfiguration, adding cost, complexity and reducing overall productivity.

This may be very difficult to accomplish if the transponder also must be isolated in a shielded housing or chamber.

This creates issues for media suppliers by limiting the available space on the media 11 for transponder 1 placement and significantly increasing the necessary accuracy of the transponder 1 placement within and or under the printable media 11 and along the liner or carrier substrate 13.

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