United States Patent (19)
`Tuttle
`
`USOO6097301A
`Patent Number:
`11
`(45) Date of Patent:
`
`6,097,301
`Aug. 1, 2000
`
`54) RFIDENTIFICATION SYSTEM WITH
`RESTRICTED RANGE
`
`75 Inventor: John R. Tuttle, Boise, Id.
`73 Assignee: Micron Communications, Inc., Boise,
`Id.
`
`21 Appl. No.: 08/628,125
`22 Filed:
`Apr. 4, 1996
`(51) Int. Cl." ....................................................... H04Q 1700
`52 U.S. Cl. ..................................... 340/693.9; 340/572.7;
`340/10.1; 342/42
`58 Field of Search ............................... 340/825.54, 572,
`340/505, 432, 572.7,572.8, 693.9, 10.1;
`342/.51, 42
`
`56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,354,189 10/1982 Lemelson ........................... 340/825.31
`4,684.933 8/1987 Dill ..........
`... 340/572
`5,214,410 5/1993 Verster .................
`... 340/572
`5,340.968 8/1994 Watanabe et al. ...
`... 235/380
`5,500,651 3/1996 Schuermann .............................. 342/42
`5,534,847 7/1996 McGregor ............................... 340/432
`
`5,627,517 5/1997 Theimer et al. ........................ 340/572
`
`Primary Examiner Brian Zimmerman
`Attorney, Agent, or Firm-Robert J. Stern
`57
`ABSTRACT
`A method of adjusting the 2-way communication range of an
`RFID system to assist a human operator to individually
`handle and interrogate a plurality of tagged objects, Such as
`Suitcases, that each include an RFID tag transceiver. An
`RFID interrogator transceiver is mounted on the human
`operator. The 2-way communication range between the
`interrogator transceiver and the tag transceiverS is adjusted
`to only slightly exceed the closest distance between the
`interrogator and the tag while the operator is handling the
`tagged object. Preferably, the 2-way communication range is
`Short enough that other tagged objects will remain outside
`the communication range and will not respond to messages
`from the interrogator. Another aspect of the invention is a
`method of verifying whether an object to be transported has
`reached its intended destination. In this aspect, an interro
`gator transceiver at a first destination interrogates an RFID
`tag transceiver on the object, and in response the tag
`transmits its intended destination.
`
`5 Claims, 3 Drawing Sheets
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`50
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`56
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`CONTROL
`LOGIC
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`U.S. Patent
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`Aug. 1, 2000
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`Sheet 1 of 3
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`6,097,301
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`U.S. Patent
`30
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`Aug. 1, 2000
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`Sheet 2 of 3
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`6,097,301
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`36
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`CONTROL
`LOGIC
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`CONTROL
`LOGIC
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`FIG. 3
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`U.S. Patent
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`Aug. 1, 2000
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`Sheet 3 of 3
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`6,097,301
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`1
`RF IDENTIFICATION SYSTEM WITH
`RESTRICTED RANGE
`
`FIELD OF THE INVENTION
`The invention relates generally to RF identification tags
`and interrogators, that is, to Systems for identifying objects
`by communication between a radio frequency transceiver
`mounted on each object (RF identification “tag”) and a radio
`frequency transceiver “interrogator'. More specifically, the
`invention relates to Such a System in which one or more
`human operators each has his own interrogator, and in which
`the 2-way communication range between each operator's
`interrogator transceiver and the tags is adjusted So as to
`prevent communications between the interrogator and more
`distant tags.
`
`BACKGROUND OF THE INVENTION
`Radio frequency identification (RFID) systems have been
`proposed for identifying tagged objects for Such purposes as
`taking inventory or tracking movements of objects being
`transported. Examples are described in commonly assigned
`U.S. Pat. Nos. 5,300,875; 5,365,551; and 5,448,110.
`RFID systems generally employ a passive or active RF
`transceiver, called a “tag”, mounted on each object to be
`identified or tracked. An interrogator transceiver periodi
`cally transmits RF interrogation Signals. Upon receiving an
`interrogation Signal, a tag responds by transmitting a
`response Signal containing data which identifies the object
`and contains any other information which may have been
`Stored or programmed in the tag.
`Conventional RFID systems provide little or no interac
`tive feedback in response to actions performed by handling
`perSonnel. Specifically, conventional RFID Systems lack any
`means for discriminating in favor of an individual tagged
`object a human operator is working with at any given
`moment; instead, conventional RFID Systems generally
`would confuse the operator by providing information
`regarding all the tagged objects in the vicinity. Furthermore,
`if a number of perSonnel are working close to each other,
`conventional RFID systems cannot direct information about
`a tag to the Specific individual who is handling the tagged
`object.
`For example, Suppose a number of airport baggage han
`dler perSonnel are Sorting or routing tagged Suitcases accord
`ing to the airline flight destination encoded in a tag attached
`to each Suitcase. Conventional RFID Systems lack any
`means for detecting which individual Suitcase a human
`operator or baggage handler is about to pick up So as to
`provide to the operator only the destination or routing
`information for the Suitcase that person currently is
`handling, to the exclusion of information about other nearby
`Suitcases. Presumably because of this and other shortcom
`ings of conventional RFID systems, RFID tags never
`entered commercial use for tagging airline baggage.
`
`SUMMARY OF THE INVENTION
`The present invention is a method of adjusting the 2-way
`communication range of an RFID System to assist a human
`operator to individually handle and interrogate a plurality of
`tagged objects, Such as Suitcases, which each include an
`RFID tag transceiver. An RFID interrogator transceiver,
`preferably mounted on the operator, periodically broadcasts
`interrogation messages. Any tag transceiver which is within
`2-way communication range of the interrogator receives the
`broadcasted message and responds by transmitting an iden
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`tifying message containing data identifying the tagged
`object. The interrogator transceiver receives the response
`message from the tag and presents to the operator the
`identifying data contained in the response message, typically
`via an aural transducer or visual display.
`In a first embodiment of the present invention, the 2-way
`communication range between the interrogator transceiver
`and the tag transceiverS is adjusted to only Slightly exceed
`the closest distance between the interrogator and the tag
`while the operator is handling the tagged object.
`Consequently, other tagged objects will remain outside the
`communication range and will not respond to interrogation
`messages. Therefore, the operator can be confident that the
`identifying information he receives from the interrogator
`pertains to the individual tagged object which the operator
`currently is handling, rather than pertaining to other tagged
`objects nearby.
`The interrogator transceiver can be mounted anywhere on
`the operator's perSon So as to leave both of the operator's
`hands free for handling the tagged objects. For example, the
`interrogator can be mounted on the person's belt.
`Furthermore, the interrogator can have an antenna mounted
`Separately, preferably on the operator's wrist band or simi
`larly near the perSons hand, So that the operator can extend
`his hand toward a tagged object to bring the antenna within
`close communication range of the RFID tag on the object.
`This allows reducing the communication range So as to
`minimize the possibility of responses from RFID tags other
`than the one associated with the individual tagged object
`which the operator currently is handling.
`A Second embodiment of the invention does not neces
`Sarily limit the interrogator to communicating with a single
`tag as in the first embodiment. Instead, an objective of the
`Second embodiment is to prevent one operators interrogator
`from communicating with tagged objects being handled by
`other operators working nearby in the Same facility. In this
`embodiment, the 2-way communication range between one
`operator's interrogator and the tags is adjusted So that all
`tagged objects being handled by other operator perSonnel are
`outside the range. Unlike the first embodiment, the 2-way
`communication range between the interrogator and the tags
`need not be So short that only one tagged object at a time can
`be within the range.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a Schematic depiction of an airport baggage
`Sorting facility employing the present invention.
`FIG. 2 is a block diagram of an RFID tag transceiver used
`in the present invention.
`FIG. 3 is a block diagram of an RFID interrogator
`transceiver used in the present invention.
`FIG. 4 is a schematic depiction of the reliable, unreliable,
`and Zero two-way communications Zones Surrounding an
`interrogator transceiver.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`1. Overview
`The invention will be described in the context of an
`exemplary implementation, depicted in FIG. 1, in which the
`human operatorS 10 are baggage handler perSonnel working
`in an airport baggage Sorting facility, and the tagged objects
`12 are airline baggage. However, the invention is equally
`applicable to any other objects to which RFID tags may be
`attached.
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`In the airport example, a number of baggage handler
`personnel 10, hereinafter called “operators', are responsible
`for loading a large number of Suitcases 12 and other baggage
`pieces into various freight containers 14, where each freight
`container has been designated to be loaded on a specific
`aircraft flight. An operator's job is to read the designated
`flight number and/or destination from a tag 16 attached to
`each Suitcase and then to load the Suitcase in the correct
`freight container.
`Personnel at the airport passenger check-in counter attach
`an RFID tag 16 to each Suitcase 12. Preferably, the RFID tag
`is mounted near a handle 18 of the Suitcase So that an
`operator's hand will be as close as possible to the tag when
`the operator grasps the handle to pick up the Suitcase. For
`example, the tag may be attached to the handle by a Strap 19,
`as shown in FIG. 4.
`A Semiconductor memory 38 within the tag is pro
`grammed to Store information on the itinerary of the
`Suitcase, Such as flight number, time, and destination.
`Optionally, the tag's memory may be programmed with
`additional information Such as the name of the owner and
`Special handling instructions.
`The tag's memory can be programmed by any conven
`tional means for Storing data in a memory device connected
`to an RF transceiver. For example, the RF communications
`protocol used by the tag transceiver can include commands
`for Storing data, So that Such commands could be transmitted
`to the tag's transceiver by a transmitter used by airport
`check-in perSonnel. Alternatively, the tag may include physi
`cal connectors for connecting the tag to a conventional
`memory programming apparatus used by airport check-in
`perSonnel.
`After mounting an RFID tag on the Suitcase, the check-in
`counter perSonnel place the Suitcase on a conveyor belt 24
`which carries the Suitcase to a large baggage Sorting facility
`such as the sorting facility shown in FIG. 1. The sorting
`facility includes a plurality of freight containers 14, each
`container being labelled with the flight number of an aircraft
`whose baggage is to be loaded into that container by the
`baggage handler personnel (i.e., the operators). After the
`operators load the appropriate baggage into a container, the
`container is wheeled from the baggage Sorting facility to the
`aircraft, where other baggage handler perSonnel transfer the
`baggage from the container to the aircraft. The process is
`performed in reverse when the aircraft reaches its destina
`tion.
`Each baggage handling operator 10 in the Sorting facility
`carries a battery-powered RFID interrogator transceiver 20,
`the interrogator preferably being attached to the operator's
`body or clothing So as to leave the operators hands free and
`not obstruct the operator's movements. For example, the
`interrogator may be attached to a belt 22 worn around the
`operator's waist. (Alternatively, the interrogator may be
`attached to a Strap or belt worn around the operator's leg,
`arm, or wrist.) As the operator moves within a certain
`proximity of an individual Suitcase 12, the tag 16 on the
`Suitcase receives an interrogation Signal transmitted periodi
`cally from the operators interrogator 20. The tag 16
`responds by transmitting a message containing the itinerary
`information Stored in the tag's memory. The interrogator 20
`receives the message and conveys the itinerary information
`to the operator, preferably either visually or aurally. The
`operator uses the itinerary information to decide which
`freight container 14 the Suitcase should be loaded into.
`When the aircraft reaches its destination, each of the
`perSonnel who unload baggage from the airplane preferably
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`also carries an RFID interrogator 20 attached as described
`above. Each interrogator carried by the unloading perSonnel
`would include memory in which a code representing the city
`(or airport) in which the interrogator is actually located. The
`interrogator periodically broadcasts interrogation messages
`and receives a response from each tagged object picked up
`by the person carrying the interrogator. The control logic 56
`in the interrogator is programmed to compare the intended
`destination city transmitted by each tag with the interroga
`tor's actual location city stored in memory 58. If the
`intended and actual destinations do not match, the interro
`gator presents a warning Signal to the unloading person to
`alert him that the piece of baggage he currently is unloading
`does not belong in that city.
`For baggage unloading, an alternative to each unloading
`perSon carrying an interrogator is to mount a single RFID
`interrogator 20 at each aircraft door through which baggage
`is unloaded. AS described in the preceding paragraph, the
`interrogator should announce a warning if a piece of bag
`gage exiting the door has an intended destination different
`from the actual destination Stored in the interrogator. The
`interrogator can be battery-powered for portability, and can
`be mounted near the aircraft cargo door by any means. Since
`the interrogator only needs to be mounted during the short
`time baggage is being unloaded, the mounting means can be
`temporary. A presently preferred mounting means is a Suc
`tion cup affixed to the interrogator, allowing it to be tem
`porarily attached to the aircraft skin or door panel.
`Mounting an interrogator transceiver adjacent to a cargo
`door, as described in the preceding paragraph, also is useful
`when first loading baggage on an aircraft to Verify that no
`baggage is loaded which was intended for a different flight.
`For purposes of loading rather than unloading, the airplane
`flight number or similar identification should be stored in the
`interrogator's memory 58. The control logic 56 in the
`interrogator Should be programmed to compare the intended
`flight number transmitted by each tag to the flight number
`Stored in the interrogator memory, and then Signal human
`perSonnel in the event of a discrepancy.
`Any of the interrogator transceivers described above can
`re-transmit data received from tags to a central computer 80.
`The central computer should include an RF receiver for
`receiving the data and a memory for Storing it. The data
`Stored in the central computer is useful for tracking the
`progreSS of baggage in case of an inquiry or a lost object.
`The RFID tag transceivers 16 and RFID interrogator
`transceiver 20 used in the present invention can be any
`conventional RFID (radio frequency identification)
`transceivers, examples of which are described in U.S. Pat.
`No. 4,075,632 to Baldwin et al., U.S. Pat. No. 4,857,893 to
`Carroll; U.S. Pat. No. 4,862,160 to Ekchian et al.; U.S. Pat.
`No. 5,055,659 to Hendricket al; U.S. Pat. No. 5,144,314 to
`Malmberg et al.; and U.S. Pat. No. 5,245,346 to Nishimura
`et al. The entire contents of each of these patents is hereby
`incorporated into this patent application.
`A preferred physical implementation of an RFID tag
`transceiver 16 is described in U.S. Pat. Nos. 5,406,263;
`5,448,110; and 5,497,140. A preferred protocol for commu
`nications between the interrogator 20 and the tags 16 is
`described in U.S. Pat. No. 5,500,650. The entire contents of
`each of these patents is hereby incorporated into this patent
`application.
`FIG. 2 shows an RFID tag transceiver 16 suitable for use
`with the present invention. An antenna 30 connects to the
`output of a transmitter 32 and to the input of a receiver 34.
`A control logic circuit 36, Such as a programmable
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`microcomputer, receives data which has been received and
`demodulated by the receiver 34, provides data to the trans
`mitter 32 with which the transmitter is to modulate the
`transmitted RF signal, and provides control Signals to both
`the receiver and the transmitter. The control logic circuit 36
`also exchanges data with a memory 38. All the components
`just described are conventionally included in an RFID tag
`transceiver. AS described below, the tag transceiver option
`ally includes an RF signal amplitude detector 40. Such
`amplitude detectors are well known, but are not convention
`ally included in RFID transceivers.
`FIG. 3 shows an RHID interrogator transceiver 20 Suit
`able for use with the present invention. The interrogator has
`the same components as the tag, namely, an antenna 50,
`transmitter 52, receiver 54, control logic circuit 56, memory
`58, and optional RF signal amplitude detector 60.
`2. Excluding Nearby Tags from Communication Range
`When the operator 10 receives itinerary information for a
`Suitcase 12, it is important for the operator to know which
`Suitcase the information pertains to. In the present invention,
`this is accomplished by limiting the transmitter power and/or
`the receiver Sensitivity of the operators interrogator, of the
`tags, or of both So that 2-way communication between the
`interrogator and the tags is possible only over a very short
`range. Specifically, the maximum range or distance acroSS
`which the interrogator 20 and tags 16 can reliably commu
`25
`nicate should be adjusted So that it is only Slightly greater
`than the distance between the antenna of the operator's
`interrogator and the tag attached to the Single Suitcase the
`operator is handling. All other Suitcases 12" in the baggage
`handling facility should be outside this range.
`More specifically (see FIG. 4), depending on the trans
`mitter power, receiver Sensitivity, and antenna radiation
`pattern of the RFID tags 16 and the interrogator 20, there
`will be a “reliable 2-way communication' inner Zone 70
`Surrounding the antenna 50 of the operator's interrogator
`within which an RFID tag 16 will be close enough to reliably
`communicate with the interrogator, and a Zero 2-way com
`munication” outer Zone 72, defined by a boundary 73
`surrounding the inner Zone, beyond which boundary 73 an
`RFID tag cannot Successfully communicate with the opera
`tor's interrogator. Between the respective boundaries 71 and
`73 of the inner and outer Zones 70 and 72 is an “unreliable
`2-way communication' intermediate Zone 74 within which
`a tag can communicate with the interrogator with uncertain
`reliability.
`The distance between the antenna 50 of the operator's
`interrogator and the tag 16 on a Suitcase will be minimum
`when the operator 10 grasps the Suitcase 12 to move it to the
`container 14 for the appropriate aircraft. The reliable 2-way
`communication range 70 between an operators interrogator
`and the nearby tags should be adjusted to only slightly
`exceed this minimum distance. Specifically, the reliable
`2-way communication range should be adjusted So that (i) a
`Suitcase being grasped or otherwise handled by the baggage
`handling operator is within the “reliable 2-way communi
`cation inner Zone' Surrounding the interrogators antenna,
`and (ii) all other nearby Suitcases 12' are outside this inner
`Zone, and preferably are outside the boundary of the “Zero
`2-way communication' Outer Zone. If the 2-way communi
`cations range is adjusted according to these criteria, only the
`tag on the Single Suitcase currently being handled will be
`close enough for 2-way communication with the operator's
`interrogator. Therefore, the operator can be confident that
`the identifying information he receives from the interrogator
`pertains to the individual Suitcase 12 the operator currently
`is handling, rather than pertaining to other Suitcases 12
`nearby.
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`An interrogator and tag are considered to be within
`reliable 2-way communication range of each other only if
`the tag can reliably receive RF signals from the interrogator
`and the interrogator can reliably receive RF signals from the
`tag. If RF signals can be reliably received by the interrogator
`from the tag, but not by the tag from the interrogator-or
`Vice versa-then only one-way reliable communication is
`possible, and the interrogator and tag are not considered
`within reliable 2-way communication range. In other words,
`the reliable 2-way communication range is the lesser of (a)
`the maximum distance over which the interrogator can
`reliably receive RF signals from the tag, and (b) the maxi
`mum distance over which the tag can reliably receive RF
`Signals from the interrogator.
`Consequently, the reliable 2-way communication range
`can be reduced by reducing the reliable one-way commu
`nication range in either direction, that is, by reducing either
`the tag-to-interrogator one-way range “a” or the
`interrogator-to-tag one-way range "b' defined in the preced
`ing paragraph.
`The one-way communication range from the tags to the
`operator's interrogator (range “a” defined above) can be
`reduced either by reducing the transmitter power of all the
`tags which otherwise could be within communication range
`of the interrogator or by reducing the receiver Sensitivity of
`the interrogator. Conversely, the one-way communication
`range from the operator's interrogator to the tags (range “b'
`defined above) can be reduced either by reducing the trans
`mitter power of the interrogator or by reducing the receiver
`sensitivity of all the tags which otherwise could be within
`communication range of the interrogator.
`There are various conventional circuit designs for adjust
`ing transmitter output power or receiver Sensitivity. For
`example, to permit adjusting the Sensitivity of the receiver
`Section of each tag and/or the interrogator, the receiver
`Section can include a conventional circuit 40, 60 for detect
`ing the amplitude of the received signal (i.e., the signal
`Strength), and a comparator which rejects any received
`Signal whose Strength is below a certain threshold. The
`threshold can be adjusted to adjust the communications
`range. Preferably, the comparator and threshold are imple
`mented by Suitable programming of the control logic circuit
`36, 56.
`The adjustments to the transmitter power and/or receiver
`Sensitivity of the tags and interrogators can be made at the
`time of their manufacture. The adjustments to an interroga
`tor also can be performed when the interrogator is placed in
`Service in a given facility, thereby permitting customization
`of the communication range based on the actual distances
`between the interrogator and the tagged objects in that
`facility. Alternatively, the interrogator can include circuitry
`for automatically adjusting its transmitter output power
`and/or receiver Sensitivity to achieve 2-way communication
`with only the Single tagged object being handled at a given
`time.
`A particularly preferred embodiment of the interrogator
`transceiver automatically adjusts the 2-way communication
`range by reducing its transmitter RF output power, thereby
`attaining the additional advantage of reducing its battery
`consumption. In this embodiment, the interrogator trans
`ceiver initially broadcasts an interrogation Signal at a very
`low transmitter RF output power level. If no tag responds,
`the interrogator broadcasts the interrogation signal again at
`a higher power level. If again no tag responds, the interro
`gator broadcasts the interrogation Signal at progressively
`higher power levels until either a tag responds or the
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`interrogator reaches its maximum transmitter output power.
`In the latter case, the interrogator waits a certain period of
`time (for example, 0.2 second), then repeats the process
`Starting with the lowest power level.
`When a tag does respond to an interrogation signal which
`the interrogator transmitted at a given power level, the
`interrogator maintains that power level for all Subsequent
`transmissions to that tag. Thus, the interrogator employs the
`lowest transmitter power needed to communicate with the
`tag, thereby minimizing power drain from the interrogator's
`battery. Furthermore, when the interrogator or its antenna is
`close to a tag (as when the operator is grasping or handling
`a tagged object), this embodiment of the interrogator inher
`ently adjusts its transmitter output power to a level just high
`enough to reliably communicate with the closest tag, but not
`high enough to communicate with other, more distant tags.
`Therefore, this embodiment of the interrogator performs
`automatically the adjustment of 2-way communication
`range described earlier. The adjustment Steps preferably are
`implemented by programming the control logic circuit 56.
`In a preferred embodiment of the RFID tags, which
`advantageously limits the 2-way communication range
`between the tags and the interrogator, each tag is a passive
`RF transceiver, also called a modulated backscatter RF
`transceiver. Such a transceiver responds to an interrogator
`Signal by modulating the RF carrier of the interrogator Signal
`with the itinerary information and reflecting or re-radiating
`the modulated Signal back toward the interrogator. Examples
`of modulated backscatter transceivers are described in U.S.
`Pat. No. 3,832,530 issued Aug. 27, 1974 to Reitboecket al.;
`U.S. Pat. No. 4,075,632 issued Feb. 21, 1978 to Baldwin et
`al.; U.S. Pat. No. 4,857,893 issued Aug. 15, 1989 to Carroll;
`and U.S. Pat. No. 5,313,211 issued May 17, 1994 to Tokuda
`et al., the entire contents of each of which are hereby
`incorporated into this patent specification. The amplitude of
`the RF signal received by the interrogator from a modulated
`backScatter tag will decline approximately in proportion to
`the fourth power of the distance between the respective
`antennas of the tag and the interrogator, assuming both
`antennas are fairly omnidirectional. In contrast, if the tags
`had active transmitters with fixed output power, the ampli
`tude would decline only in proportion to the Square of the
`distance.
`Using the just described RFID tags with modulated back
`scatter RF transceivers in combination with the previously
`described preferred interrogator with automatically adjust
`ing transmitter power, I have found that the interrogator
`reliably communicates with a tagged Suitcase 12 when it is
`grasped by a human operator, while reliably ignoring the
`tags on other Suitcases 12 nearby.
`3. Antenna Location
`The mounting location of the antenna 50 of the interro
`gator also affects the ability of the interrogator to discrimi
`nate against Suitcases other than the one currently being
`handled by the operator. The most convenient and unobtru
`Sive location of the antenna typically is in the same housing
`as the interrogator transceiver 20, which, as described above,
`may be attached to the operator's clothing Such as a belt 22
`worn around the operator's waist. With the interrogator and
`its antenna mounted on the operators torSo, the required
`2-way communication range between the interrogator and
`the tag depends on how close the operators torso
`approaches the Suitcase during normal handling.
`To prevent tags on adjacent Suitcases from responding to
`the interrogator, the distance from the operators torSo to the
`Suitcase being handled should be much Smaller than the
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`distance from the operators torSo to any nearby Suitcases. If
`the Suitcases are too close together to Satisfy this condition,
`then it is preferable to mount the antenna of the interrogator
`transceiver on the operators hand, wrist, or forearm So that
`the operator can extend his arm toward the tag mounted on
`the individual Suitcase the operator currently is handling,
`thereby reducing the distance between interrogator antenna
`and the tag.
`For example, the antenna 50 of the interrogator trans
`ceiver can be mounted in a wrist Strap worn on the operator's
`wrist (see FIG. 4). If the tag is attached to the handle of a
`Suitcase, then the interrogator antenna will be closest to the
`tag (a distance of only two or three inches) when the
`operator grasps the Suitcase handle. The 2-way communi
`cation range between the interrogator and tags should be
`adjusted, as described above, so that the “reliable 2-way
`communications inner Zone' is only slightly greater than this
`closest distance (i.e., a few inches). Preferably, a conse
`quence of this adjustment is that the “Zero 2-way commu
`nication outer Zone' boundary is on the order of one foot
`from the interrogator antenna, whereby the Suitcase being
`handled will be within the inner Zone and all other Suitcases
`will be outside the boundary of the outer Zone.
`The antenna and interrogator can be fabricated as an
`integral unit which is mounted on the operator's hand, wrist,
`or forearm, if the interrogator is Small enough to be worn
`comfortably in this manner.
`4. Interrogator Presentation of Information to Operator
`AS described above, when a human operator approaches
`close enough to a tagged Suitcase for the operator's inter
`rogator and the tag to be within 2-way communication
`range, the tag will receive an interrogation Signal from the
`interrogator and will respond with a message identifying
`itself to the interrogator. The interrogator then should
`present to the operator relevant portions of the identifying
`information, Such as airline flight number or destination. The
`information can be presented aurally or visually.
`Specifically, the identifying information can be presented
`aurally through a loudspeaker mounted in the same enclo
`Sure as the interrogator. More preferably, to prevent opera
`tors in the Same vicinity from disturbing each other, the
`information can be presented through headphones or similar
`Sound transducers worn or in or adjacent to the operator's
`ears. Alternatively, the information can be presented visually
`by a Small video display panel mounted on the same
`enclosure as the interrogator or, more preferably, by a
`conventional heads-up display incorporated in eye goggles
`or eyeglasses worn by the operator.
`In the previously described example of an aircraft bag
`gage Sorting facility for loading baggage onto departing
`aircraft, the information the interrogator presents to the
`baggage handling operator when he picks up a Suitcase
`typically would be the flight number of the aircraft on which
`the Suitcase belongs and the destination city of the Suitcase.
`Using this information, the operator then loads the Suitcase
`into the container or truck designated for that flight number.
`The invention also is useful for baggage handling opera
`tors who unload Suitcases from an arriving aircraft. Because
`a given flight typically stops in Several destination cities, the
`baggage unloading operators in a given destination city must
`ensure they only unloadbaggage whose intended destination
`is that city. For this application, the name or identification
`code for the current city should be Stored in a Semiconductor
`memory in each operator's interrogator. The interrogator
`should be programmed to compare the Stored city code with
`the destination city information transmitted by each tagged
`
`APPL-1032/ I