HK1167733B - Rfid portal system with rfid tags having various read ranges - Google Patents

Description

RFID gate system configured with RFID tags having various read ranges

Technical Field

The present invention relates generally to a radio frequency identification ("RFID") system, and more particularly, to a method and system for distinguishing between short-range RFID tags and long-range RFID tags and identifying only tags that pass through an RFID portal.

Background

One key application of RFID is inventory (inventory) control. The ability to track RFID tags as they are tagged on items and moved through the supply chain will facilitate operation of the supply chain. However, due to cost and complexity of the solution, RFID readers are not installed to cover the entire supply chain. Rather, the RFID reader is deployed at an inspection/transfer point along the supply chain, such as at a loading dock entrance between a warehouse and a car, an entrance between a back office and a retail store, and so forth. RFID readers at these locations are sometimes referred to as gate readers. The RFID tag on an item should only be read when the item passes through the gate. However, some "long range" RFID tags are typically designed to maximize the gain and efficiency of their antennas. This mixed tag environment causes long range RFID tags near the gate but far from the doorway to be inadvertently read, resulting in erroneous tracking of the tagged item. This problem is commonly referred to as an over-range problem.

In order to limit the range of the RFID reader to the doorway, it is sometimes desirable to reduce the reader transmission power. This scheme requires that all RFID tags have similar read ranges. As other RFID applications have been developed, some projects now require the use of small "short range" tags with lower read ranges. Small tags cannot be read at reduced transmission power. Therefore, configuring the transmission power of the RFID reader to accommodate all tags in the hybrid environment will result in over-range or failed reads.

In addition to reducing the level of transmission power as described above, attempts have also been made to improve the performance of small tags. This attempt has resulted in inefficiently physically larger tags than what is actually required for the application due to the physical phenomenon behind the electromagnetic radiation and the interaction of the antenna structure of the RFID tag.

RFID readers with more complex antenna systems have been designed to focus the RF field and limit the read range to a limited area or volume. However, the configuration of a complex antenna naturally causes higher costs.

Accordingly, there is a need for a method and system for distinguishing between short range RFID tags and long range RFID tags and identifying only tags that pass through an RFID interrogation zone (e.g., an RFID portal).

Disclosure of Invention

The present invention advantageously provides a system and method for selectively reading radio frequency identification ("RFID") tags located within an RFID interrogation zone. Generally, each RFID tag is programmed with an identifier that is related to the operating range of the RFID tag. Only the RFID tag programmed with the predetermined identifier is selected for reading according to the transmission power level of the RFID reader.

According to one embodiment of the present invention, a method of selectively reading RFID tags within a radio frequency identification RFID interrogation zone is provided. A portion of the RFID tags have a first operating range and a portion of the RFID tags have a second operating range different from the first operating range. Each RFID tag is programmed with an identifier associated with its operating range. A first interrogation signal is transmitted having sufficient power to activate RFID tags having a first operating range that are within an RFID interrogation zone. A response signal is received from each RFID tag capable of receiving the first interrogation signal. Each response signal indicates an identifier of the associated RFID tag. Each RFID tag having an identifier associated with the first operating range is selected.

In accordance with another aspect of the invention, a reader for selectively reading RFID tags within an RFID interrogation zone includes a transceiver and a processor. A portion of the RFID tags have a first operating range and a portion of the RFID tags have a second operating range different from the first operating range. Each RFID tag is programmed with an identifier associated with its operating range. The transceiver is operable to transmit a first interrogation signal having sufficient power to activate an RFID tag having a first operating range that is within an RFID interrogation zone; and receiving a response signal from each RFID tag capable of receiving the first interrogation signal. Each response signal indicates an identifier of the associated RFID tag. A processor electrically coupled to the transceiver, the processor operable to select each RFID tag having an identifier associated with a first operating range.

In accordance with yet another aspect of the present invention, an RFID system includes a plurality of RFID tags and an RFID reader. A portion of the RFID tags have a first operating range and a portion of the RFID tags have a second operating range. The first operating range is less than the second operating range. Each RFID tag is programmed with an identifier associated with its operating range. The RFID reader is operable to transmit a first interrogation signal having sufficient power to activate RFID tags having a first operating range that are within an RFID interrogation zone; and receiving a response signal from each RFID tag capable of receiving the first interrogation signal. Each response signal indicates an identifier of the associated RFID tag. The RFID reader is further operable to select each RFID tag having an identifier associated with the first operating range; and reading each selected RFID tag.

Drawings

The full scope of the invention, together with the attendant advantages and features thereof, will be best understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a block diagram of an exemplary radio frequency identification ("RFID") system constructed in accordance with the principles of the present invention;

FIG. 2 is a block diagram of an exemplary RFID reader constructed in accordance with the principles of the present invention;

FIG. 3 is a flow chart of an exemplary RFID tag discrimination process according to the principles of the present invention;

FIG. 4 is a diagram of an exemplary RFID system for identifying short-range tags, in accordance with the principles of the present invention; and

fig. 5 is a diagram of an exemplary RFID system for identifying long range tags in accordance with the principles of the present invention.

Detailed Description

Before describing in detail exemplary embodiments that are in accordance with the present invention, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to a system and method for discriminating between short range radio frequency identification ("RFID") tags and long range RFID tags such that only the RFID tags passing through an RFID portal are read. Thus, the system and method components have been represented where appropriate by conventional numbers in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

As used herein, relational terms, such as "first" and "second," "top" and "bottom," and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. Further, as used herein, the terms "RFID tag" and "RFID label" are used interchangeably.

One embodiment of the present invention advantageously provides a method and system for discriminating between short range RFID tags and long range RFID tags. In general, one embodiment of the present invention provides an RFID reader with the ability to switch to different transmission levels and read stored information within the read range of the tag, thereby overcoming over-range or improper reading problems due to different ranges of tags of different designs. The RFID tag is identified as either a short range tag or a long range tag by setting at least one identification bit in the RFID tag. When the reader is at a high transmission level, the reads associated with the short range tags are all valid, while at a low transmission level, both short range tag reads and long range tag reads are valid. Thus, in order for the reading to be valid, the reader requires a message relating to the read range of the tag, which can be stored in and read out from the memory of the RFID tag.

Referring now to the drawings in which like reference designators refer to like elements, there is shown in FIG. 1 the structure of an exemplary RFID system 10 constructed in accordance with the principles of the present invention and disposed at, for example, a facility entrance. RFID system 10 includes a pair of pedestals 12a, 12b (collectively pedestals 12) on opposite sides of the portal. One or more antennas for the EAS detection system 10 may be included in pedestals 12a, 12 b. An antenna disposed in the pedestals 12 is electrically coupled to the RFID reader 14, and the reader 14 transmits radio frequency signals between the pedestals 12a, 12b, thereby forming an interrogation zone 16. The reader 14 is capable of distinguishing between long-range RFID tags 18a, 18b, 18c (collectively "long-range tags 18") and short-range RFID tags 20a, 20b, 20c, 20d, 20e, 20f (collectively "short-range tags 20").

In one embodiment, each tag 18 and 20 includes an RFID chip having a memory (not shown) designed for information related to the manufacture of the RFID chip. For example, the TID memory location of the RFID chip may be used to distinguish between two tag designs during inventory-one with a small embedded design ("short range") and the other with a large embedded design ("long range"). The transponder ID ("TID") memory location may be programmed at the time of manufacture with a specific 12-bit tag model number, e.g., bits 14h through 1Fh are currently allocated for use as tag model numbers. One model number may specify a short range label and another model number may specify a long range label. A standard product electronic code ("EPC") over-the-air protocol may be used to perform and inventory tours tailored to each tag design, for example, by utilizing the EPC SELECT command.

Referring now to FIG. 2, an exemplary RFID reader 14 may include: a controller 22 (e.g., a processor or microprocessor), a power supply 24, a transceiver 26, a memory 28 (which may include non-volatile memory, or a combination thereof), and a communication interface 30. The controller 22 controls radio frequency communications, storage of data in the memory 28, and transfer of stored data to other devices. A power source 24 (e.g., a battery or AC power source) supplies power to the RFID reader 14.

The transceiver 26 may include a transmitter 32 electrically coupled to one or more transmitting antennas 34 and a receiver 36 electrically coupled to one or more receiving antennas 38. Alternatively, a single antenna or a pair of antennas may be used as the transmission antenna 34 and the reception antenna 38. The transmitter 32 transmits a radio frequency signal using the transmitting antenna 34 to "energize" passive RFID tags and/or communicate with active RFID tags in the interrogation zone 16 of the RFID system 10. Receiver 36 detects the output power level of the RFID tag using receiving antenna 38. The gain controller 40 controls the output power level of the transmitter 32 and/or the sensitivity of the receiver 36 to switch the transceiver 26 between the short-range tag detection mode and the long-range tag detection mode.

The memory 28 may include an RFID tag discriminator 42 for determining the type of RFID tag response within the interrogation zone. The operation of the RFID tag discriminator 42 will be described in more detail below.

Referring now to FIG. 3, a flowchart is provided that describes exemplary steps performed by RFID reader 14 to identify only RFID tags that are within interrogation zone 16. In this embodiment, the RFID system 10 uses the EPC TID memory of the RFID tag during inventory to specifically prevent reading and reporting of RFID tags (e.g., EPC numbers) outside of the expected range of the RFID gate. It should be noted that the RFID system 10 may include multiple RFID readers 14 and antennas 12 that perform inventory functions for different access areas. The RFID reader 14 prepares to inventory the short range tags 20 ("short range tag inventory") by setting the transmission power to a setting that is optimal for these short range tags 20. Fig. 4 illustrates the scenario for short range tag inventory. The short-range tag power setting may be determined in practice by determining the maximum transmission power required to read the short-range tag 20 within the desired gatekeeper range 16 with reasonable reliability. It is desirable that short range tags 20 outside the portal range 16 (e.g., in area 44 of fig. 4) be unread due to insufficient power. Reader 14 sends a SELECT command to specify only the short range tag model number in the tag TID (step S104). Due to the SELECT command, the long range tag 18 will not respond to a subsequent inventory round. Without the present invention, it is expected that long range tags 18 outside the portal range 16 (e.g., in region 46 of FIG. 4) will typically respond during inventory at this reader transmit power level. The SELECT command advantageously blocks these long range tags 18 from responses. Subsequently, the RFID reader 14 reads the short-range tags 20 within the desired portal range 16 to complete the short-range tag inventory (step S106).

Once the "short range tag inventory" is completed, the RFID reader 14 prepares to inventory the long range tags 18 ("long range tag inventory") by setting the transmission power to a setting value that is optimal for these long range tags 18 (step S108). Fig. 5 illustrates a long range tag inventory scenario. The long range power setting may be determined in practice by determining the maximum transmission power required to read the long range tag 18 within the desired gate range 16 with reasonable reliability. The long range power should be a transmission power smaller than the set value used in the "short range tag inventory". Thus, it is desirable that the long range tags 18 and short range tags 20 outside the portal range 16 (e.g., in areas 48 and 50 of FIG. 5) be out of range and not respond. The RFID14 reader sends a SELECT command to specify only the long range tag model number in the tag TID (step S110). Due to the SELECT command, it is expected that the short range tags 20 within the portal range 16 will not respond to the subsequent inventory round, and only the long range tags 18 within the portal range 16 are expected to be read (step S112). Alternatively, at this lower power setting, the SELECT command may be omitted and all tag models read in a subsequent inventory round. Note that the process shown in fig. 3 may be periodically repeated by the reader 14 at predetermined intervals to update the inventory in the interrogation zone 16.

An alternative embodiment of the present invention employs an EAS bit. The EPC global hardware action group is currently proposing and re-discussing the existence of EAS bits; however, the function of the EAS bit is not explicitly used. This alternative is particularly suited for combined EAS and RFID item level intelligence applications (itemlevel intelligence application) where over-range/improper reading problems are first discovered. In this project-level intelligence application, hard tags with small footprints are required. The small footprint limits the read range of the tag. With an EAS bit (which should always be active in an EAS hard tag), the reader can determine that it is a short read range tag. Another advantage of using EAS bits in RFID is that the EAS bits can be accessed directly before the ID of the tag is accessed, thereby enabling fast determination of short range tags without the need to read the model code.

The present invention can be realized in hardware, software, or a combination of hardware and software. Any kind of computing system, or device adapted for carrying out the methods described herein, may be adapted to perform the functions described herein.

A typical combination of hardware and software could be a specialized or general purpose computer system having one or more processing elements and a computer program stored on a storage medium that, when loaded and executed, controls the computer system such that it carries out the methods described herein. The present invention can also be embedded in a computer program product, which comprises all the features enabling the implementation of the methods described herein, and which, when loaded in a computer system is able to carry out these methods. Storage medium refers to any volatile or non-volatile storage device.

A computer program or application in the present context means any expression, in any language, code or notation, of a set of instructions intended to cause a computer system having an information processing capability to perform a particular function either directly or after either or both of a) conversion to another language, code or notation, and b) reproduction in another material form.

Moreover, unless indicated to the contrary in the foregoing, it should be noted that all of the accompanying drawings are not to scale. It will be apparent that the invention can be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.

Claims (12)

1. A method of selectively reading RFID tags within a radio frequency identification, RFID, interrogation zone, a first portion of the RFID tags having a first operating range and a second portion of the RFID tags having a second operating range, wherein the first operating range is less than the second operating range, each RFID tag including an identifier associated with the operating range of the RFID tag, the method comprising:

transmitting a first interrogation signal having sufficient power to activate both RFID tags within an RFID interrogation zone having the first operating range and RFID tags within an RFID interrogation zone having the second operating range;

receiving a response signal from each RFID tag capable of receiving the first interrogation signal, each response signal indicating an identifier of the associated RFID tag;

selecting each RFID tag having an identifier associated with the first operating range;

reading each selected RFID tag; and

transmitting a second interrogation signal having a lower signal power than the first interrogation signal sufficient to activate RFID tags within the RFID interrogation zone having the second operating range, but not sufficient power to activate RFID tags outside the RFID interrogation zone.

2. The method of claim 1, further comprising:

selecting each RFID tag having an identifier associated with the second operating range; and

reading each selected RFID tag having an identifier associated with the second operating range.

3. The method of claim 2, further comprising: each RFID tag that responds to the second interrogation signal is read.

4. A radio frequency identification, RFID, reader for selectively reading RFID tags within an RFID interrogation zone, a first portion of the RFID tags having a first operating range and a second portion of the RFID tags having a second operating range, wherein the first operating range is less than the second operating range, each RFID tag including an identifier associated with the operating range of the RFID tag, the RFID reader comprising:

a transceiver operable to:

transmitting a first interrogation signal having sufficient power to activate both RFID tags within an RFID interrogation zone having the first operating range and RFID tags within an RFID interrogation zone having the second operating range; and

receiving a response signal from each RFID tag capable of receiving the first interrogation signal, each response signal indicating an identifier of the associated RFID tag; and

a processor electrically coupled to the transceiver, the processor operable to select each RFID tag having an identifier associated with a first operating range,

wherein the transceiver is further operable to read each selected RFID tag; and is

The transceiver is further operable to transmit a second interrogation signal having a lower signal power than the first interrogation signal sufficient to activate RFID tags within the RFID interrogation zone having the second operating range, but not sufficient power to activate RFID tags outside the RFID interrogation zone.

5. The RFID reader of claim 4, wherein the identifier is a tag model code.

6. The RFID reader of claim 4, wherein the identifier is at least one Electronic Article Surveillance (EAS) bit.

7. The RFID reader of claim 6, wherein:

the processor is further operable to select each RFID tag having an identifier associated with a second operating range; and

the transceiver is further operable to read each selected RFID tag having an identifier associated with the second operating range.

8. The RFID reader of claim 6, wherein the processor is further operable to read each RFID tag that responds to the second interrogation signal.

9. A radio frequency identification, RFID, system comprising:

a plurality of RFID tags, a portion of the RFID tags having a first operating range and a portion of the RFID tags having a second operating range, the first operating range being less than the second operating range, the RFID tags being programmed with an identifier associated with the operating range of each RFID tag; and

the RFID reader according to any one of claims 4-8.

10. The RFID system of claim 9, wherein the identifier is a tag model code.

11. The RFID system of claim 10, wherein each RFID tag includes an RFID chip having a memory, the identifier programmed at a transponder id (tid) memory location of the RFID chip.

12. The RFID system of claim 9, wherein the identifier is at least one Electronic Article Surveillance (EAS) bit.