Note: Descriptions are shown in the official language in which they were submitted.
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LOSS PREVENTION SYSTEM
TECHNICAL FIELD
The present invention relates to a system for monitoring personal possessions.
More
specifically, the present invention is a loss prevention system wherein a
monitor continuously
and automatically surveils electronically tagged personal possessions and
sounds an =alarm when
one or more tagged possessions is removed from proximity to the monitor.
BACKGROUND ART
The loss of personal possessions is a problem that has spawned numerous and
diverse
solutions. Small articles, such as a cell phone or pager, television remote
controller, briefcase,
umbrella, and other articles too numerous to count may be easily lost if
carelessly misplaced or
accidentally left behind.
One solution to the problem is illustrated by the many "finder" systems that
have been
devised, wherein an alarm tag is fastened to an article and sounds when
commanded by a signal,
such as a radio signal, from an alarm control station. When the article is
lost, a signal is
broadcast from a base station to activate the alarm tag and sound the alarm.
The article may then
be found by following the sound of the alarm tag.
U.S. Patent No. 6,297,737, issued on October 21, 2001 to D. Irvin, discloses
an object
locating system. The system includes a locating unit that comprises a wireless
communication
interface for transmitting signals to one or more locating tags. When a tagged
item is misplaced,
a signal is transmitted from the locating unit. When the tag receives the
signal, an alarm is
sounded. Additionally, the tag sends a response that is received by the
locating unit to give an
indication that the tagged item is nearby, even if the audio alarm cannot be
heard. The system is
bi-directional so that a tagged item can be used to find the locating unit
itself in the event that the
locating unit is misplaced.
U.S. Patent Publication No. 2003/0034887, published on February 20, 2003,
discloses an
article locator system that employs a tracking transceiver and a handheld
locator device. The
tracking transceiver is attached to the article to be tracked and sends a
response when
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interrogated by the handheld locator device. The handheld locator device
determines the
distance and/or direction to the tracking transceiver.
U.S. Patent Publication No. 2002/0126010, published on September 12, 2002,
discloses
an object locator system employing radio frequency (RF) signaling.
While article finder systems can be a great help in finding lost articles, or
even in keeping
track of pets and children, the above described article finder systems are
typically used in
reaction to a loss and not in a manner to prevent the loss. Typical of the
article finder systems is
the need to manually initiate an action to find the lost article.
Additionally, the article finder tags
require a power source such as a battery to continuously power a receiver and
to power an alarm
or transmitter. The article finder tags cease to function when their battery
dies, rendering them
useless.
Instead of locating an article after it is lost, it is preferable in many
circumstances to
prevent the loss of the article. Thus, a loss prevention system that signals
when an article is
removed from a given area, or that signals when an article is left behind, is
desirable to help in
preventing the article from becoming lost.
European Patent Application 1,288,878, published on March 5, 2003, discloses a
security
apparatus comprising a base station that interacts with an RFID security tag.
The base station
comprises an RF transmitter, receiver, and antenna, along with a control unit.
The control unit
sends a monitoring signal that is received by the RFID tag. The RFID tag is
inductively powered
by the monitoring signal and responds with an identity signal. Because of the
limited range of
the monitoring signal and the identity signal, removal of the RFID security
tag from proximity to
the base station causes the identity signal not to be received by the base
station. Thus, when the
base station sends a monitoring signal but no identity signal is received in
response, an alarm is
sounded. In this manner, the security apparatus functions to sound an alarm
when a tagged item
is removed from proximity to the base station. '
U.S. Patent No. 6,577,238, issued on June 10, 2003 to H. Whitesmith et al.,
discloses a
system for monitoring the position of one or more RFID tags. The system has a
detector that
incorporates circuitry for detecting changes in the range of an RFID tag from
the detector and for
triggering an alarm if the range exceeds a predetermined threshold or if the
RFID tag cannot be
detected by the detector. Range may be determined by measuring the time of a
returned radio
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signal from a tag, by measuring the strength of a returned radio signal from a
tag, or by detecting
changes in a periodic interval at which a. signal is transmitted by a tag.
U.S. Patent Publication No. 2002/0080036, published on June 27, 2002,
discloses a
system for tracking possessions. The system includes a plurality of child
units, each having a
transceiver for receiving a control signal and sending a locator signal. The
system also includes
a parent unit that has a transceiver for communicating with the child units
and a processor for
monitoring the child units. The system incorporates a GPS receiver in both the
pare,nt and child
units so that the parent unit can determine the position of, and relative
direction and distance to, a
child unit.
U.S. Patent Publication No. 2002/0145520, published on October 10, 2002,
discloses an
object tracking system for tracking the removal of objects from a location and
the replacement of
the objects at the location. The system includes an RFID tag attached to each
of the objects to be
tracked. A storage unit has a plurality of receptacles configured to receive
objects replaced at the
location. Each receptacle has an associated antenna for activating the RFID
tag of an object
placed in the receptacle.
U.S. Patent No. 5,289,163, issued on February 22, 1994 to C. Perez et al.,
discloses a
child position monitoring and locating device that monitors the position of a
child by detecting
the signal strength of a radio frequency carrier from a transmitter attached
to the child. If the
radio signal is too weak, an alarm notifies the adult that the child is too
far away.
U.S. Patent No. 5,748,087, issued on May 5, 1998 to T. Ingargiola et al.,
discloses a
remote personal security alarm system.
U.S. Patent Publication No. 2003/0063003, published on April 3, 2003,
discloses a
proximity monitoring communication system wherein an alarm is triggered in a
master
communication device in a local area network when a slave device in the local
area network has
strayed from the proximity of the local area network.
None of the above inventions and patents, taken either singly or in
combination, is seen
to describe the instant invention as claimed. Thus a loss prevention system
solving the
aforementioned problems is desired.
DISCLOSUREOF THE INVENTION
This disclosure is directed to a monitor for a loss prevention system. The
monitor includes
an RF communication circuit adapted for communication with at least one radio
frequency
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identification tag. The RF communications circuit is electrically connected to
a control circuit with
a microprocessor and a memory. An alarm is electrically connected to the
microprocessor. A
computer readable program code is stored in the memory and executes under the
control of the
microprocessor. The program code includes a means for acquiring the
identification tag by
storing a unique identifier associated with the identification tag in the
memory, and associating
the identifier with an alias. The program code also includes a means for
dropping the
identification tag by deleting the unique identifier associated with the
identification tag from the
memory, and a means for operating the RF communication circuit to interrogate
the identification
tag. The program code further includes a means for causing the alarm to
activate when the
identification tag is out of range of the RF communication circuit, and a
means for dropping the
identification tag by deleting the unique identifier associated with the
identification tag from the
memory. The means for operating the RF communications circuit systematically
polls each of the
identification tags, and the means for dropping the identification tag deletes
the unique identifier
upon subsequent polling when the identification tag is determined to be out of
range.
The disclosure is also directed to a loss prevention system. The loss
prevention system
includes a monitor with a control circuit that has a microprocessor and a
memory. A radio
frequency communication circuit with a transmitter and a receiver is.
connected to the control
circuit. A program code is stored in the control circuit memory and executes
under the control of
the microprocessor. The program code includes a means for causing an
interrogation signal to be
transmitted by the transmitter, and a means for acquiring an identification
tag number from a
response to the interrogation signal. The acquired tag number is stored and an
alias is associated
with the acquired tag number. The program code also includes a means for
repetitively transmitting
the interrogation signal, and for tracking responses to the interrogation
signal and comparing the
responses. The program further includes a means for generating an alarm when
the tracked
responses fail to include the acquired tag number, and a means for dropping
the acquired
identification tag number from memory. The tag number dropping means deletes
the acquired tag
number after repetitive tracking when the tracked responses fail to include
the acquired tag. The
loss prevention system also includes at least one radio frequency
identification tag adapted for
attachment to an article to be tracked. The article tag includes a memory with
a unique
identification number stored therein, and a transponder means for receiving
the interrogation signal
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transmitted by the monitor. The article tag transmits the unique
identification number in response to
the interrogation signal.
These and other objects of the present invention will become readily apparent
upon
further review of the following specification and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. I is a diagrammatic view of a loss prevention system according to = the
present
invention.
Fig. 2A is a block diagram of a monitor for a loss prevention system according
to the
present invention.
Fig. 2B is a perspective view of a monitor for a loss prevention system
according to the
present invention.
Fig. 2C is a block diagram of a monitor for a loss prevention system according
to the
present invention using a wireless network interface.
Fig. 3A is a block diagram of a passive RFID identification tag for a loss
prevention
system according to the present invention. ,
Fig. 3B is a block diagram of a semi-passive RFID identification tag for a
loss prevention
system according to the present invention.
Fig. 3C is a block diagram of an active RFID identification tag for a loss
prevention
system according to the present invention.
Fig. 3D is a block diagram of an identification tag for a loss prevention
system according
to the present invention using a wireless network interface.
Fig. 4 is a flowchart of a software initialization and startup process for a
monitor in a loss
prevention system according to the present invention.
Fig. 5 is a flowchart of a software process for user setup of a monitor in a
loss prevention
system according to the present invention.
Fig. 6 is a flowchart of a software process for acquiring tags by a monitor in
a loss
prevention system according to the present invention.
Fig. 7 is a flowchart of a software process for monitoring tags by a monitor
in a loss
prevention system according to the present invention.
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Fig. 8 is a flowchart of a software process for dropping tags from a monitor
in a loss
prevention system according to the present invention.
Fig. 9A is a single-slave piconet topology for a wireless network embodiment
of a loss
prevention system according to the present invention.
Fig. 9B is a multiple-slave piconet topology for a wireless network embodiment
of a loss
prevention system according to the present invention.
Fig. 9C is a scatter-net topology for a wireless network embodiment of a loss
prevention
system according to the present invention.
Similar reference characters denote corresponding features consistently
throughout the
attached drawings.
BEST MODES FOR CARRYING OUT THE INVENTION
The loss prevention system of the present invention functions to prevent
articles from
becoming lost, misplaced, or stolen. The articles are tagged with an RFID tag,
and tracked by a
monitor. The monitor periodically interrogates each RFID tag with a
transmitted RF signal, and
generates an alarm signal if an interrogated tag does not reply or is out of
range.
The monitor may be a small and portable device, carried or worn by a person.
Thus, a
person can affix a tag to commonly carried items, such as a camera, keys, a
briefcase, wallet,
laptop computer, personal digital assistant (PDA), and others. With the
monitor also carried,
worn, or clipped to the person's belt, an alarm will be sounded if any of the
tagged items are left
behind or removed from the vicinity of the person. Alternatively, the monitor
could be placed in
a fixed location, or built into a storage cabinet or shelf or the like, to
monitor valuables.
The tags are passive, semi-passive, or active RFID tags that respond, when
interrogated
by the monitor, with a unique identification code. The passive tags contain no
power source,
deriving power inductively from the RF signal transmitted by the monitor. The
range of a
passive tag varies from a few inches t6 a few meters, depending on the monitor
power output, the
sensitivity of the monitor's receiving antenna, the operating frequency, the
antenna designs of
both the monitor and the tag, and other factors. Semi-passive tags include a
battery or power
source to power a transmitter in response to the RF signal transmitted by the
monitor, allowing
the tag to send its reply over a longer distance. Active tags employ a battery
or power supply
that powers the tag's receiver, transmitter, and other circuitry, allowing a
more sensitive receiver
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and providing a transmitter with higher power to give the active tag a maximum
range. Thus,
passive, semi-passive, or active RFID tags may be employed individually or in
combination to
provide for short, medium, or long usable range with a given monitor or to
alleviate
technological limitations.
The monitor stores an identification code for each tag that is to be
monitored. Each tag
may be stored along with a name or an alias to identify the tag to the user,
so that if a tagged item
is removed from the vicinity of the monitor, the tag's name or alias can be
displayed along with
the alarm in order to help to identify the item. Each tag may also have a
specified sensitivity that
defines the distance threshold beyond which the alarm is sounded. In addition
to the maximum
physical range for each type of tag, a tag's distance from the monitor may be
determined or
approximated based on the received tag signal strength, time delay in
receiving the tag's
response to interrogation, or by other methods. Thus, a different distance
threshold may be set,
for example, for a tagged wallet versus a tagged briefcase so that the wallet
tag will trigger an
alarm if the wallet falls from the user's pocket, while the briefcase tag will
not cause an alarm
until the user has left the briefcase a significant distance behind.
The monitor employs a microcontroller to operate the monitor transceiver, to
manage the
tags, and to drive a user interface. The microcontroller allows the user to
interactively add or
remove the tag identification codes from the monitor memory, and to activate
and deactivate
stored tags.
As described above, the current invention to provides a loss prevention system
that
sounds an alarm when an electronically tagged article is removed from a
predefined area. The
loss prevention system may also be configured to monitor tagged articles and
to sound an alarm
when a tagged article is removed from the vicinity of a system monitor. The
RFID tags of the
present system may be easily added or removed from the system, as well as
activated or
deactivated. The RFID tags can also be assigned a sensitivity level so ~ that
an alarm is sounded
when the tag is at a distance from the monitor that is less than the tag's
maximum functional
distance.
As generally illustrated in Fig. 1, the loss prevention system includes a
monitor 10, which
may also be referred to as an interrogator or reader, that communicates with
Radio Frequency
IDentification (RFID) tags ("tags") 100, which may also be referred to as
transponders, that may
be affixed to, or contained within, numerous personal articles to prevent the
loss of the articles.
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The monitor 10 periodically interrogates the tags 100, sending an RF signal
that is
received by the tags 100. When interrogated, the tags 100 send a response to
the monitor 10, the
response including a unique identification code. The monitor 10 verifies that
each tag 100
responds to the interrogation. If a known tag 100 does not respond to the
interrogation, the
monitor 10 sounds an alarm. Thus, given a finite distance that the monitor 10
can transmit its
interrogation signal, as well as a (typically shorter) finite range that the
tag 100 can transmit its
response, when a tag 100 is removed a sufficient distance away from the
monitor 10; the monitor
will no longer receive the tag's response and will therefore sound an alarm
for the tag 100.
Turning to Figs. 2A and 2B, the monitor 10 includes RF circuitry 20 for
communicating
10 with the tags 100, and control circuitry 40 for controlling the RF
circuitry 20, managing tag
identification codes, monitoring the tags 100, and interacting with a user.
The RF circuitry 20
and control circuitry 40 are contained in a housing 70, along with a user
interface. The user
interface includes a display 54, such as a plurality of simple light emitting
diodes (LED), alpha-
numeric LEDs, a flat panel display such as a liquid crystal display (LCD), or
other display type,
along with an input device 56 such as a plurality of pushbuttons, a touch
screen function
incorporated in the display, a keyboard, or a device for voice control. A flat
panel LCD display
is preferred. For portable use, the housing 70 may include a belt clip 72, or
other means of
attaching the monitor 10 to a user or the user's clothing.
The monitor's RF circuitry 20 includes a modulator 24 and transmitter 22,
along with an
RF regulator 26, a modulation adjustment circuit 28, and oscillator and timing
30 circuits to
generate, encode, and transmit the interrogation signal. Additionally, the RF
circuitry 20
includes receiver, filtering, demodulating, and anti-collision circuitry 32 to
receive the responses
from the tags 100 and to resolve collisions when two or more tags' 100 reply
at the same time.
An antenna 34 is connected to transmitter 22 and receiver 32.
The monitor's control circuitry 40 includes a microprocessor 42 and memory 44,
including random access and read only memory (RAM/ROM) 48, and an electrically
erasable
programmable read only memory (EEPROM) 46. The control circuitry 40 may also
include UO
circuitry 50, and analog-to digital and digital-to-analog converters (ADC/DAC)
52. The
monitor's control circuitry 40 is best implemented with a micro-controller
device wherein the
above-described circuitry is combined within a single integrated circuit or
device.
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Microcorimputer program code is stored in the memory 44, and controls the
operation of the monitor
10.
An alarin 62, connected to the microcontroller, provides an audible, visual,
or tactile
alarann signal. The alarm 62 may be a speaker or buzzer or other sound source,
a light source, a
vibrator, or a combination of these. A battery or power supply 60 provides
power for the
monitor 10.
The microcomputer program code controls the operation of the monitor's RF
=circuitry 20,
directing the RF circuitry 20 to send an interrogation signal to the tags 100
and processing replies
from the tags 100. Additionally, the microcomputer program code performs
management of the
tag identification codes, and performs user interface functions related to
setup and operation of
the monitor 10.
Turning now to Figs. 3A-3C, a tag 100 contains a semiconductor-based Radio
Frequency
IDentification (RFID) component including an associated antenna or coil in a
configuration that
is well known to those skilled in the art. Each tag 100 is programmed with a
unique
identification code, typically set by the manufacturer to ensure that no two
tags have the same
code. Tags 100 include passive tags 100A, semi-passive tags 100B, and active
tags 100C.
A passive tag 100A, illustrated in Fig. 3A, is the simplest of the, tags 100,
comprising a
semiconductor-based Radio Frequency IDentification (RFID) component along with
an
associated antenna or coil 116. The RFID component typically includes a
receiver/demodulator
114 for receiving and demodulating the RF interrogation signal, and a
transmitter/modulator 112
for modulating and transmitting the tag's RF reply. Additional digital
circuitry 120 provides an
anti-collision protocol so that multiple tags 100 can be used, along with
memory control and
other logic functions. A memory 122 stores the tag's unique identification
code. The passive tag
100A has no battery, but is powered inductively by the RF energy emitted from
the monitor. An
inductive power supply and regulator 104, typically including a capacitor
connected to the
antenna 116, draws and stores enough energy from the received monitor signal
to power the
circuitry of the passive tag IOOA. Because no battery is used, the passive tag
100A is the
simplest, smallest and lightest of the tags 100. With no battery, however, the
passive tag 100A is
the most limited in range because of its limited ability to transmit a
response, limitations of the
receiver/demodulator 114, and the sensitivity of the monitor 10 to detect weak
responses.
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A'semi-passive tag 100B, illustrated in Fig. 3B, is similar to the passive tag
100A, except
that a battery or power source 108 is provided to power the tag 100B. The
receiver/demodulator
114 remains un-powered in the absence of a signal from the monitor 10, but a
detector/switch
106 and a battery or power supply 108 replace the inductive power supply and
regulator 104. In
response to inductive energy from the antenna 116, the detector/switch 106
applies the
battery/power supply 108 to power the tag's transponder circuits, including
the
transmitter/modulator 112, to send the tag's response. The semi-passive tag
IOOB thus remains
"dormant" until interrogated by the monitor 10, when the semi-passive tag 100B
is powered for a
short duration by the battery or power supply 108 to respond to the
interrogation. Because the
transmitter/modulator 112 is powered by the battery or power supply 108, the
semi-passive tag
100B has a greater range that the passive tag 100A. The range of the semi-
passive tag 100B
remains limited by the ability of the receiver/demodulator 114 to receive a
weak signal.
In an active tag 100C, illustrated in Fig. 3C, the battery or power supply 108
powers all
of the tag's circuits, including the receiver/demodulator 114. The
detector/switch 106 of the
semi-passive tag 100B is replaced by a simple on/off switch 110 so that the
active tag 100C may
be powered on for periods of use, and powered off for periods of non-use.
Because the battery-
powered receiver/demodulator 114 of the active tag 100C has greater
sensitivity than a
receiver/demodulator that relies on a received signal for power, the active
tag 100C has a greater
range than either the passive tag 100A or the semi-passive tag 100B.
Using either the passive tags l 00A, semi-passive tags l 00B, or active tags 1
OOC, the
monitor 10 can track various articles within a close range (using a passive
tag 100), a medium
range (using a semi-passive tag 100B), and a relatively longer range (using an
active tag 100C).
Thus, a user might, for example, tag a tagged wallet with a passive tag 100A
and a briefcase with
an active tag 100C so that the wallet's passive tag 100A triggers an alarm if
the wallet falls from
the user's pocket, while the briefcase's active tag 100C will not cause an
alarm until the user has
left the briefcase a significant distance behind. Depending on
cost/performance tradeoffs made
during design of the monitor 10, the present invention may use a low cost and
low sensitivity
version of a monitor 10 and require semi-passive tags 100B or active tags
100C, whereas a
higher cost, more sensitive monitor 10 could function exclusively with less
costly passive tags
100A.
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A- user operates the monitor 10 to learn, or "acquire" one or more tags 100
that the user
attaches to various articles that are to be monitored by the loss prevention
system. A tag 100 is
acquired when the monitor 10 interrogates the tag 100, receives an
identification code in reply
from the tag 100, and records the identification code in memory 44.
With the tags 100 acquired, the user may place the monitor 10 into a
monitoring mode.
In the monitoring mode, tags 100 are interrogated by the monitor 10, and each
tag 100 within
range of the monitor 10 sends a reply that includes the identification code.
The monitor 10
receives each reply, and compares the received identification code to the
codes stored in memory
44. If a reply is not received for each of the stored identification codes,
then an alarm is
sounded.
The user may also operate the monitor 10 to "drop" one or more tags 100 that
have been
acquired, erasing the tag's identification code from memory 44 or otherwise
flagging the tag in
memory and thus disabling any alarm when the tag's identification code is not
found in
subsequent polling.
The microcomputer code operates the display 54 and input device 56 to interact
with the
user, and controls the operation of the monitor 10 to perform monitoring of
the tags 100.
Turning now to Fig. 4, the microcomputer code performs a power-on
initialization 400 of
the monitor 10, and presents the user with a "main menu" of choices for
operation of the monitor
10 which can be revisited through the main return 402. The software tracks
whether the memory
44 is empty at step 404. The user may select from options to acquire new tags
at step 406,
monitor tags at step 416, drop tags at step 420, or perform setup functions
for the monitor 10.
The software checks whether the user wants to enter new tags at step 408, and
if so the
user is directed to the acquire tag routine at step 410, and queried as to
entering a second new tag
at steps 412 and 414. If the user does not want to acquire new tag ID numbers,
the user is
directed to the monitor tag routing at step 428. '
If the user selects monitor tags at step 416, the user may confirm the
selection at step 418,
in which case the software enters the monitor tag routine, as reflected at
step 428; otherwise, the
user is queried whether he wishes to drop ID tags from the monitor at steps
420 and 422. If the
user wants to eliminate ID tags, the software is directed to the drop tag
routine at step 424, or if
not, the software enters the user setup routine, as reflected at step 426.
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Turning to Fig. 5, the setup functions for the monitor 10 are illustrated. The
routine starts
at step 500, and queries the user whether he or she wishes to set the user
preferences at steps 502
and 504. If not, the software returns to the startup routine of Fig. 4 via the
main return 402. If
the user does wish to change preferences, the user is queried about setting a
password at steps
506 and 508. If the user does wish to set a password, the software enters a
routine to check
and/or set a password at step 510, otherwise the software queries the user
about setting the
sensitivity of the monitor at step 512. If the user wishes to set the
selectivity, the software enters
the view and/or set sensitivity routine at step 516, or if not, the software
re-enters the startup
routine of Fig. 4 via main return 402. The monitor sensitivity is set by
varying the transmitter 22
power and the receiver 32 sensitivity. The user may control both to achieve an
optimal or
preferred function of the monitor 10.
Turning now to Fig. 6, a process for acquiring tags 100 is described. The
monitor 10 will
acquire a tag 100 that is in the "near vicinity" of the monitor. In practice,
this may be
accomplished through several methods. The monitor 10 may transmit at a lower-
than-normal
power level (e.g. 25%) so that it only communicates with a tag 100 placed next
to it, so the
monitor does not interact with any other tags 100 otherwise within its normal
operating range.
Alternatively, the monitor 10 may operate at its normal power level, but
process only a tag 100
with the strongest signal. According to another method, the monitor 10 simply
"mutes", or
ignores, any tag 100 that has already been acquired. In another method, the
monitor 10 uses a
very specific directional antenna to communicate with a tag 100 that is placed
in a specific
location relative to the monitor so that the likelihood of another tag 100
responding to the
monitor 10 is relatively low.
On entry into a tag acquisition mode at step 600, the microcomputer code
enables the
acquire mode at step 602 and turns off the transmitter 22 and the receiver 32
until the user is
ready to proceed and acquire a tag 100 at step 604. The user is prompted to
acquire a tag 100 at
step 606, whereupon the user places a tag 100 to be acquired in the near
vicinity of the monitor
10, in a manner as discussed above. If the user selects to proceed and acquire
a tag 100 at step
608, the microcontroller 40 powers on the monitor's transmitter 22 and
receiver 32 to interrogate
a tag 100 that is in the near vicinity of the monitor as described above at
step 610, otherwise the
routine ends at step 628. If the monitor's receiver 32 receives a reply from a
tag 100, the
identification code is extracted from the reply at step 612, or if no tag is
read, the software re-
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enters the acquire tag routine at step 604. The microcomputer code compares
the received
identification code against those already stored in memory 44 at steps 614 and
616, and if the
identification code is not present in the memory 44, the identification code
is stored at step 618,
or if already stored in memory at 626, the user is prompted whether to acquire
another tag at step
624.
With the identification code for the acquired tag 100 stored in memory, the
user may
choose to associate an alias or a name to the identification code to identify
the article that the tag
100 will be affixed to at step 620. If the user chooses to rename the tag 100,
the user enters an
alias that is then stored in memory 44 along with the identification code at
step 622. Once a tag
100 has been acquired, the user may elect to acquire additional tags at step
624, or to return the
monitor 10 to a main menu or a main operating mode.
Once the monitor 10 has acquired one or more tags 100, the monitor 10 may be
placed in
a monitoring mode. Turning now to Fig. 7, a process for monitoring tags 100 is
described. The
monitor 10 routine begins at step 700, by enabling the monitor mode at step
702, which causes
the monitor 10 to display an appropriate message at step 704. The monitor 10
tracks all of the
tags 100 that have been acquired, or a subset of these tags 100 if some of the
acquired tags 100
have been disabled or "dropped" by the user. The microcomputer code begins an
interrogation
cycle, setting a counter for the number of tags 100 to monitor and setting a
timeout interval for
completion of the interrogation cycle, as indicated at step 706. The RF
circuitry 20 is then
powered on as indicated at 708, enabling the transmitter 22 to broadcast an
interrogation signal
to all tags 100 within range, including tags that have been disabled or
dropped, and those tags
100 that have not yet been acquired.
As tags 100 that are within range of the transmitter 22 respond to the
interrogation, the
identification codes from the various tags 100 are received, at step 710. When
an identification
code is received, the microcomputer code compares the received identification
code with
identification codes stored in memory 44 at step 712. When a received
identification code
matches a code in the memory 44, the identification code in memory is marked
as "present" at
step 714, indicating that the corresponding tag 100 answered the
interrogation, and the counter of
remaining tags is decremented at step 716.
Once the timeout interval has elapsed, the microcomputer code determines if
all of the
acquired tags 100 have responded. If one or more acquired tags 100 have not
responded, then at
13
CA 02529618 2005-12-09
step 718 -each of the non-responding tags 100 is subjected to a threshold test
to determine if an
alarm is to be set. The threshold test determines if a tag 100 has failed to
respond to a
predetermined number of consecutive interrogations, or has failed to respond
to interrogations
for a predetermined time interval. The threshold test insures that no false
alarm is issued for a
tag 100 that, although within range of the monitor 10, for some reason fails
to respond to a single
or small number of interrogations. The threshold test may also identify tags
100 that are prone to
occasionally missed replies, which may indicate a failing or incorrectly
functioning tag 100, such
as where a tag 100 consistently misses replies but below the threshold level
required for an
alarm.
If the threshold is exceeded for a tag 100, an alarm is set at step 720. In
addition to the
alarm, the monitor 10 may display a message to indicate to the user which of
the tagged articles
is associated with the alarm.
After the interrogation cycle is completed, the transmitter 22 is turned off,
step 722, and
following a short time delay, step 724, the interrogation cycle is repeated,
step 706.
Tags 100 may be dropped from the monitor 10, for example when the user no
longer
wants to monitor a particular tagged article, or when the user removes a tag
100 from an article
to dispose of the article, thus having a surplus tag 100. When a tag 100 is
dropped, its
identification code is removed from the monitor's memory 44 so that the tag
100 is no longer
known to the monitor 10. A tag 100 may be dropped by selecting its
identification code, or its
alias, from a list displayed by the monitor 10, and entering a "drop" command.
AlternativeIy, a
tag 100 may be dropped by a process similar to the acquisition process,
wherein the monitor 10
is placed into a "drop" mode and the tag 100 to be dropped is placed in the
near vicinity of the
monitor 10.
Turning now to Fig. 8, a process for dropping tags 100 is described. The drop
tag routine
begins at step 800, and proceeds to enable the drop mode, step 802. The
monitor 10 will drop a
tag 100 that is placed in the "near vicinity" of the monitor 10, as described
above. On entry into
a tag dropping mode, the microcomputer code turns off the transmitter 22 and
the receiver 32
until the user is ready to proceed to drop a tag 100, as indicated at step
804. The user is
prompted to drop a tag 100, step 806, whereupon the user places a tag 100 to
be dropped in the
near vicinity of the monitor 10, in a manner as discussed above. If the
soflware detects, at step
808, that the user selects to proceed to drop a tag 100, the microcontroller
40 powers on the
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CA 02529618 2005-12-09
monitor's transmitter 22 and receiver 32, step 810, to interrogate a tag 100
that is in the near
vicinity of the monitor as described above. If the monitor's receiver 32
receives a reply from a
tag 100, the identification code is extracted from the reply. If the tag has
been read, step 812, the
microcomputer code compares the received identification code against those
already stored in
memory 44, step 814, and if the identification code is found present in the
memory 44, step 816,
the identification code is deleted or otherwise flagged at step 818, thus
dropping the tag 100. If
the identification code is not found in the memory 44, the user is presented
with the option to
acquire the tag 100 at step 820, adding the identification code to the memory
44, step 822, as in
the acquisition process discussed above. The user is prompted at step 824 to
indicate whether
another tag 100 is to be dropped. If yes, the process is reiterated beginning
at step 804;
otherwise the drop tag routine ends at step 826 by returning to the power-up
main menu of Fig.
4.
With an understanding of an RFID embodiment of the loss prevention system, it
can be
appreciated that the system may be implemented with alternative technologies.
What is
important is that the monitor 10 has the ability to determine when a tag 100
has moved beyond a
limited range of communication with the monitor 10. An ideal alternative
technology is the
Bluetooth wireless personal area network (WPAN) based on the IEEE standard
802.15.1.
The personal area network is for devices within or moving into a "personal
operating
space" (POS) of a person; typical range of operation is from one to ten
meters. It is based on the
Bluetooth PAN technology, but is a lower power, low cost wireless technology
that can be used
in cell phones, pagers, computers, bio-monitoring devices, as well as
printers, sensors, displays,
and more.
In a WPAN implementation of the monitor 10, shown in Fig. 2C, the RF circuitry
20
includes a WPAN wireless network interface 36. Similarly, referring to Fig.
3D, a tag 100D
according to the WPAN implementation can be any device that includes a WPAN
wireless
network interface 136. Typically, such a device includes control circuitry
140, such as a
microprocessor 142 and memory 144, including random access and read only
memory
(RAM/ROM) 148, and an electrically erasable programmable read only memory
(EEPROM)
146. The control circuitry 140 may also include UO circuitry 150, and analog-
to-digital and
digital-to-analog converters (ADC/DAC) 152. The control circuitry 140 is
typically
CA 02529618 2005-12-09
implemented with a micro-controller device wherein the above-described
circuitry is combined
within a single integrated circuit or device. A power supply or battery 160
powers the tag 100D.
Turning now to Figs. 9A-9C, WPAN-enabled devices communicate with one another
in a
simple network configuration whercin, typically, one or more devices act as a
master 1010 while
one or more devices act as slaves 1100. In the simplest arrangement, shown in
Fig. 9A, a single
slave 1100 communicates with a single master 1010. Referring to Fig. 9B,
multiple slaves 1100
can communicate with a single master 1010. Configurations that include a
single master and up
to eight slaves are referred to as a"piconet" topology, while in a"scatternet"
topology, as seen in
Fig. 9C, the network may include multiple masters 1010 along with multiple
slaves 1100. The
scatternet topology allows communication between masters 1010, as well as
communication by a
slave 1100 to more than one master 1010. In either topology, WPAN devices join
a network on
an ad-hoc basis. A master 1010 may detect that a device is active within the
personal operating
space, and invite the device to connect with the master 1010 and join the
network.
It can now be appreciated that a WPAN piconet mirrors the architecture of the
RFID loss
prevention system described above, with the single master (TBD) filling the
role of the monitor
10, and at least one slave (TBD) filling the role of the tag 100. Thus,
software installed on a
monitor that incorporates a WPAN wireless network interface will perform
functions that are
similar to those described above, including acquisition, monitoring, and
dropping of WPAN
slave devices, along with user interface functions related to setup and
operation of the monitor
10.
Additionally, with a WPAN implementation of the loss prevention system,
multiple
monitors can communicate with one another in a scatternet topology, allowing
WPAN tags IOOD
to be "handed off' from one monitor 10 to another. This allows monitored
articles to be easily
passed from one individual to another, where each individual is carrying a
monitor 10 that can,
by communication and coordination with the other individual's monitor 10,
coordinate the
transfer of monitoring responsibility. Additionally, monitored articles can be
easily moved from
one monitored environment, such as an individual's home or office where the
articles are
monitored by a fixed monitor, to another environment, such as a mobile
environment, in which
the articles are monitored by a portable monitor 10.
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CA 02529618 2005-12-09
It 'is to be understood that the present invention is not limited to the
embodiments
described above, but encompasses any and all embodiments within the scope of
the following
claims.
17
