Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
N~'l`U~,h' Uh','l'~,h'_l,N,V~N'l',l~N
'~'his invention relates to a passive
electromagnetically activated electronic transponder
identilication ta~ and to an identification method and
apparatus using such a tag.
B,A~K~tQ,UND OE''l'HE_INVhNT,fON,
Many systems are known ~or automatically
determining whether an ob~iect or person is passing a
predetermined location and whether such ob,~ect or person
1~ is authorized to pass such location. 1~' such passage is
alathorized, the ob,ject or person may continue unhindered.
lf such passage is not authorized. action may be taken ~'or
its prevention.
~ uch systems are o~'ten u.sed in the~'t security
systems. A special security tag is placed upon an object.
such as an article ~or sale in a .store. If a thiet'
attempts to remove the article ~'rom the store. detectors
located at the store exits will determine the presence o~'
the tag. A1arms indicate to security personnel that a
theJ`t is being committed and the thie~' may be apprehended.
l~ the article is paid for by a legitimate customer. the
tag is removed. deactivated or changed at a check-out
station~ so tha-t no tag i5 de-tected by the detector.s at
the store exits.
Other applications of such systems may occux in
mail or 1uggage handling systems and personnel and
livestock detection or countin~ systems.
~ xamples of such applications. systems and
associated devices are disclosed in United States ~atents
Nc)s. 3.~18.0S9. 3.'7~0.940. 3,7$4.~26. 4.~21.'7~S.
.4~. ~,U~ l'7~ 4,~4~ 4.~:3,
~l.;3:3~.~31 and 4~342~.9U4.
~ ome detection sy.stems make use o~ ta~s having
permanent magnets or radioactive mclterial. 'l'ags wit~
permanent ma~nets are bulky and heavy. 'l'a~s using
radioactive material pose health risks. ~ther systems
ie.g . United ~tates Patent No, 4~242~'71~ m~y require a
pieæoelectric tag which re-transmits a delaYed signal. Yet
other systems (e.g., ~nited States ~atents Nos. 3~7~0~940
1~ ancl ~021,705) may use a tag having a resonant electronic
circuit for retransmitting a generated signal. Some
~aterlts (3.764.22~, 4.~'74.~4~ and 4.2~2.~17) disclose the
use o~ electroma~netically activated passive .signal
~--nerator ta~s. All of the, ahove devices Kenerall~ can
only be used to determine the presence or non-presence ot
a tag. '1'hey cannot determine the speci~ic identitY of the
ta~ed ob,~ect.
It is desirable to have a system rlo-t only ~or
detectin~ ob~iects or persons~ but a1so for automatically
2U identi~yin~ same. ~uch an automatic identification system
makes possible a more flexible. less labour-intensive~
less expensive mail, baggage or material handling system
and more reliable livestock and personnel identification.
~ther applications ~or identification systems may be
possible.
~xamples of such identification systems are
disclosed in United States Letters Patent Nos. 3~ll5~6
:3~l8,0~, 3.832.530. 4~134~3~ and 4.~ .0~3.
Some identification sys-tems (e.~.. United ~tates
Patents Nos, 3.11~22, 3~618.~5~ and 4.2'74.~83~ disclose
~ --2-
~.c~ Q9~
-t.he use 0~ an active, battery-operated radio -transmitter
'ju~h device~ identi~Y a tagged oh~iect by detection o~` a
ll~li~Ue radio siFnal emanatin~ ~rom the transmit-ter on the
~ owever, radio transmitter devices may be exPensiVe.
'I'hev may also be inconvenient and unreliable because of
the limited uset'ul battery life.
'l'he s~stem disclo.sed in United ~tates ~atent No.
3.~ 3U depends upon the existence of Gurrent pulses in
and the absorption of energy within an electronic circuit
lU at~ixed to a ta~. Such current pulses induce voltage
pulses in a detector circuit. 'l'he current pulses o~' the
tag can be uniquely coded to identi~'y the tagged obiect.
~uch a system re~uires a high degree of sensitivitY so as
to be able to distinguish small incremerlts of energy
absorption in thè circuit corre~ponding to different
identi~'ication codes.
'1'he system disclosed in United ~tates Patent No.
4.13'~.S38 makes use of electromagnetically activated.
passive signal generator tags. Such tags require the
selection and dimensioning of magnetic material to provide
unique generated signals ~or each tag to. thus. uniquely
identify the ta~ged ob~iect. A disadvantage of such system
is that it is dif~'icult to select arld size the necessary
magnetic material so -that the ta~ will generate a signal
capable of being uniquely and reliably distinguishable
~rom the signals of other tags. ~uch a tag may also be
somewhat bulky and cumbersome if the system must have the
capacity to handle a large number of ob,iects to be
identi~`.ied .
3~ It is there~ore desirable to provide an
~ 2~9~
iclerlti~icatic)n system WhiCll i5 inexpensive. reliable.
conYenient to use. uses a tag ot` convenient siæe. has long
li~e. and has the capacity to handle various numbers ot`
ob.iects that are likely to ~e required -to be handled.
~TA'1'~,~3~N,1,1 0~,'',,,'l',~h_,1,Ny,hN,'~'l,(~
With a view to overcoming the above-noted
problems and to providing the advantages discussed. the
invention comprises a method, a sys-tem and a device for
the automatic identification of` any member o~ a set of
lU objects or persons to be identi~`ied. The device is an
identification tag to be used on an object or person to be
identi~'ied~ in as,sociation with an identification system
which system establishes an oscillating electromagnetic
field within a predetermined interrogation zone~ said tag
comprisin~ a core strip of rnagnetically resPonsiVe
material o~` a type which abruptly reaches saturation at a
predetermined level ot` ma~netic ~ield . an electroma~netic
masking coil wrapped around said strip~ switch means in
circuit with said coil~ electronic circuitry means for
controlling opening and closin~ o~' said switch means
according to a predetermined sequence in timed relation to
the oscillations of the electromagnetic field~ which
se~uence defines an identification code ~`or the tag~ and
first antenna means connected to said circuitry wherebY
said circuitry may be operated by power derived ~'rom the
electromagnetic ~`ield.
The system comprises an oscillator~ ~`ield coils
connec-ted to the oscillator whereby at least one
oscillating electromagnetic ~ield is established in an
3~ interrogation zone~ an identi~'ication tag as described
r ~
-~ ~ ~ 4
9'7
above associated with each member o~ the set of ob~iects or
persons, ~'ield detection means for detecting and measurin~
the electromagnetic ~ield. and decoder means to determine
the iclentity o~' a tag according to the measurements.
The method comprises -the operation of the system
described above to identi~`y tags~ and thus ob~iects or
persons and distinguish them from each other.
Accordingly, it is an obiect of the invention to
provide an identification system which is inexpensive,
1~ reliable and convenient to use.
lt is a further obiect of the invention to
provide an identificatiorl system which utilizes a durable
identi~'ication tag of convenient size which has long life.
~ t i5 a further ob,ject of the invention to
provide an identification system which has the capacity to
handle various numbers of objects or persons that are
likely to be required to be handled.
In accordance with the invention, the
magIIetically responsive material in the tag is a material
which i5 saturable, magnetically in a magnetic field of a
predetermined streng-th. When sub~iected to a magrletic
~'ield o~' this strength. the material undergoes a sudden
transition to saturation, and thus a sudden c~lange in its
response. 'l'his abrupt or sudden change or response can be
detected by measuring the overall magnetic field in the
interrogation zone. l'he abrupt changeover produced by
saturation o~'-the material will produce a "blip", which is
detectable in the presence o~' the primary field.
ln accordance with the invention, the response
of the saturable member may be maskedl by the ef~ect of
b-
o~
the electromagnetic masking coil~ when the switch in its
circuit is closed.
When the switch is open. and there is there~ore
rlo circuit. the masking coil is not in circuit. and thus
no masking ot the core strip takes place.
The masking coil is switched in and out o~
circuit in a predetermined sequence. thereby producing a
predetermined number of "blips". interspersed with an
absence of such "blips".
1~ It is thus possible to provide a unique code of
"blips", and absences of "blips". which code can be
identitied with a particular objec-t or individual unique
to the wearer of the tag.
'The various ~eatures oY the novelty which
characterize the invention are pointed out with
particularity in the claims annexed to and formin~ a part
of this disclosure. E`or a better understanding of the
invention, its operating advantages and speci~ic objects
attained by its use, reference should be had to the
accompanying drawings and descriptive matter in which
there are illustrated and described pre~erred embodiments
ot` the invention.
lN_THE ~
Figure 1 is a schematic drawin~ o~ an
identification system according to the invention;
Figure 2 is a schematic diagram of one
embodiment of an identification tag according to -the
invention;
Figure 3 is a schematic diagram ot` the
3~ electronic circuitxy of the tag of ~'igure ~;
Q9~7
~ `igure ~l is a graphical representation ot the
electromagnetic ~ield prior to passage o~` a tag according
t,o the invention;
E'igure b is a graphical representation o~ the
electromagnetic field durin~ passage o~ a piece o~ a
response member as userl in a tag according to the
invention;
E`igure ~ is a ~raphical representation ot the
electroma~netic ~ield durin~ passage ot a tag according to
1U the invention; and.
~ 'igure I is a schematic represe~ltation ot a
portion of an a.lternate embodiment.
,rl'IO,,N O~,l'.,A _P,~.'1E~ .M~ "IJ~,UT
~ eferrin~ to ~'igure 1, an identi~:ication sys-tem
according to the invention is indicated generally as 10.
An ob.,iect or a package 1~ passes through system 1~.
Identi~ication tag 14 is attached to an ob.ject or a
package 1~ and passes through system 10 with packagè 1~.
'I'ag 14 and. thus. package 1~. are detected and identified
by system 10. The system 1~ uses such identity
in~`ormation as required. Eor instance, such intormation
may be used to operate conveyor belts (not shown) ~o tha-t
package 12 is directed to the appropriate des-ti.nation.
Sys-tem lV may mere:Ly record the in~ormation that a
particular package 12 has pa.ssed a speci~ic locat.ion. Sl~ch
in~orination rnay be important to trace the path of an
ob~iect through a proce.ssing system and to determine
whether certain operations have been carried out orl the
ob~iect.
Such a system wou.ld be suitable ~or handling
., .
'7
bag~Jage. 'l'he ob~iect may o~ course be an animal. vr a
person. 'l'he tag would then Iunction to identi~`y the
:indivi~ual. lt could be used to trace individuals in a
buildirlg. or the pas.sage ot individuals through a
il.it,Y.
'I'he identitication system 10 includes an
interrogation gate l~. comprising two pedestals 18 between
Wtlich package 1~ must pass. ~ate 16 de~`ines an
interrogation zone within which packa~e 12 may be
1~ identi~`ied. Gate 16 includes at .least one pair of
electromagnetic field coils 20. ~ne each of coils 2~ is
located in each pedestal 18. Such coils and pedestals are
well-known in the art. More detailed descriptions of such
coils as used in identi~ication systems may be ~ourld in
United ~-tates Pa-tents Nos. 3,'7b4.22~. 3,832.S30 and
4.~'l4,~49. In order to improve the detection capabilities
of system 1~ to the passage of a tag at dif~erent
orient~tions relative to the coils. gate 1~ may include
two or three mutually orthogonal pairs of electromagnetic
tield coils 20.
Field coils ~0 are electrically connected to
~ield oscillatvr 22. Oscilla-tor 2~ takes power ~rom a
~ower source (not .shown) and establishes an oscillating
electromagnetic field between pairs of coils 20.
~enerally. such an oscillator 22 will establish an
electromagnetic field which oscillates at a predetermined
~requency. ~uch oscillators ~2 are conventional devices
well~known in the electrical ar-ts. hligure 4 presents a
graphical representation of the electromagnetic ~ieJ.d, as
3U i-t may be established br osciLla-tor ~2.
o~
~ ate 1~ ~`urther includes an antenna coil 24 ~`or
rec:ei~ing signals ~rom ~ield coils 2~ and responses which
may be emitted by tag 14 as it passes through the
electromagnetic tie.ld. Antenna ~4 is elec-trically
connected to a signal amplifier ~. which in turn is
connected to decoder ~8. Antenna ~4. amplifier ~ and
decoder ~8 may all be standard components~ well understood
in the art~
The output of decoder 28 is an electrical
1U signal~ corresponding to the identity o~ package 1~. ~uch
a signal~ and other signals (such as~ ~'or example~ a time
signal)~ may be inputted to computer 3CJ. C,omputer ~u may
simply store such information or computer 3() may.
accordi.ng to its programming, issue instructions to other
devi,ces (not showrl) to control ~`urther movement of package
1~. C')~ course~ the output o~ decoder ~ may be fed to a
suitable indicator (not shownJ for visually displaying the
identity of package 12. Appropriate manual action could
then be taken. either in con,junction with or to over-ride
an~ action taken by computer 3C).
.All of the above components~ except ta~ 14~ o~`
identi~ication system lC) are essen-tially standard and are
well. known in the.art. Such components are described only
in order that the invention may be better understood~ and
not in order to limit the scope o~ the invention in any
way. Kather. it is the intention that the scope o~' the
invention covers any detection or identi~'ication system
using an identifica~ion tag according to the invention.
~eferring to ~igure ~ tag 14 comprises a base
3C) .3~ to which is affixed or in which is embedded a strip 34
~;
1 _g_
~ .~p,,~ Q9~7
oi ma~netically responsive material. ~uch material may
cc>nveniently be a t`erromagnetic alloy ot nickel.
molvbderlum, iron and manganese (commonly referred to as
supermalloy~. ~ther lerromagnetic materials having a
coercivity ranging betwesn 0.1 Oersteds and U~Ol Oersteds
may be equally suitable.
This type o~` ma-terial has the property of high
permeability in a magnetic field.lt further has the
property o~` reaching an abrupt level o~` magnetic
saturation at a predetermined level of magnetic ~ield
within the material.
When it reaches saturation there is an abrupt
chan~e in permeability. ~ermeability rises suddenly to a
peak and then ~all~ of sharply. Li'or the purposes of this
explanation, the precise level or intensitY of magnetic
~ield is not relevant, and is refered to herein as ~
~auss. 'l'his is the level oi ma~netic field at which a
given sample o~ the material abruptly becomes saturated.
'l'he level will vary ~rom one material to
another~ and also depending upon the size and shape of the
strip 'i4. as is well understood in the art.
The abrupt transition to saturation. at the
saturation point of the material results in ~ measurable
electromagnetic response. which will produce a measurable
signal in the presence of the primary oscillating field. A
response signal would normally be ~letectable on each hal~
cycle of the field.
Wrapped around strip 34 is electromagnetic
masking coil 36. Coil 36 is electrically connected by
~i~ line 3'1 to solid state maskin~ relay switch. indicated
-lIJ-
o~
~enerally as 3~.
When switch 38 is open. no cuxrent can flow in
mlasking coil 36. ~witch 38 is operated by electronic
circuitry, indicated ~enerally as .3~. which in turn is
electrically connected to a tag antenna 40. The
oscillating electromagnetic field through which tag 14
passes induces corresponding alternating current in the
tag antenna 40. ~uch current is used to power circuitry
:~9 .
~uch current is induced solely as a reponse to
the oscillating field. and will o~' course cease as soon as
the tag is removed ~rom the field. or if the field should
be switched off Yor some reason.
Normally the oscillating electromagnetic
is on continuously.
Xeferring to Figure 3, circuitry 3~ includes a
rectifier and voltage stabilizer circuit 42 which is
connected to antenna 40. Circuit 42 establishes a
substantially constant voltage output across two output
terminals. The circuitry 3g of tag 14 cannot conveniently
be grounded. ~owever, circuitry 3~ may define a common
point. which, insofar as the operation o~ circuitry 39 is
concerned. acts in a fashion similar to a ground. E'or
convenience. one of the two output terminals o~' recti~'ier
and stabilizer 42 is defined -to 'be such a common point and
is named voltage source terminal 44. l'~e other of the two
output terminals of circuit 4~ is de~ined to be a voltage
drain terminal 46.
Recti~ier and stabilizer 42 also defines a clock
3~ signal. A voltage pulse is ~enerated for each half-cycle
Y '
!--`` -11-
j
~2~9~
oscillation of the current in antenna 40. ~uch voltage is
le~irled across volta~e source terminal 44 and a third
output terminal o~ rectifier and stabilizer 4~. namely
clock termin~l ~8.
Voltage drain terminal 46 and clock terminal 48
are electricall~ connected to integrated circuitry decade
counter chip ~ hip 50 is also connected to voltage
source terminal 44. ~hip 50 functions similarlY to a
series of ten electronic switches (not shown). Each such
1~ switch connects volta~e drain terminal 46 to one o~ ten
counter chip output terminals 52a to 52j. A single
voltage pulse of the clock sigr~ rom clock termlnal 48
cause,s one o~ such switche.s to close and~ m~re or less
simultaneous1y, a previouslY closed switch to open.
allowing the volta&~e drain si~nal to pass to th~
particular output terminal ~ associated with such swi-tch.
A subsecluent voltage pulse from clock terminal 48 will
cause the same switch to open and a subsequen-t switch to
close. A further clock si~nal will cause a next switch to
operate in identical fashion. A series o~ ten voltage
pulses will cause each o~ the switches to close and open
once. A subse~uent pulse will cause the switch last
closed to open and the first switch to close a second
time. The entire sequence will subseguentlY be repeated.
Each of counter chip output terminals 5~a to 5~i
is connected to a column line 54 o~ identification code
matrix 56~ Matrix 56 also includes a series o~ row lines
58, the ends of which define matrix output terminals 6U.
~olumn lines 54 and row lines ~8 may be electrically
3~ connected bY one or more diodes 6~. but otherwise are not
,~, .
~.2r~3L0~37
conn~ct~d. l'he speci~`ic posi-tionin~ o~ such diodes ~ to
.ioin certain column lines h~1 and row lines 58 define a
particular identi~ication code. as explained below. Each
o1 ~latrix row lines ~ is connec-ted through resistors ~3
to volta~e source terminal 44 in order to provide a path
to source terminal 44 for stray currents when no voltage
drain signal is present in row lines ~8. --
The remaining counter chip output terminal 52.ii5 connected to index terminal 64 to integrated circuitry
data .selector chip ~. Matrix output terminals 60 are
conrlected to a serie.s of selector chip input terminals 68.
Selector chip ~6 is also connected to voltage source
terminal 44. Selector chip ~ ~unctiorls in simi.lar
~ashion to counter chip bO. ~'hip 66 ~unctions similarly
to a series o~ electronic switches (not shown7 each
connectin~ a selector chip input terminal 68 to selector
chip output terminal 7~. A signal from counter chip
output terminal 5~j causes one o~ such switches to close
and. more or less simultaneously. a previously closed
switch to open. A subsequent signal ~rom terminal ~
causes such first switch to open and a subse~uen-t switch
to close. l'hus. signals arriving from terminal b~j will
cause the switches of selector chip ~ to consecutively
close and open. After the last switch is opened. the
cycle will commence again at -the ~irst switch.
~elector chip output terminal 70 is conrlected to
solid state relay switch 38 in line 3'1. ~ach time a
si~nal (which will correspond to the signal in voltage
drai.n terminal 46) appears at output terminal 70 switch 38
3~ will c1ose. thus allowing alternating current induced in
-1.3-
)97
coil :~fi by the passage v-~ tag 14 through -ttle
eleclromagnetic ~`ield to ~ w. Line 37 is also connected
to voltage source termiIlal 44.
ALl o~ the above cornponents. namely the
recti~`ier and s-tabiliæer 4~ the decade counter chip b~.
the identi~'ication code matrix ~6~ the selector chip 66
and switch 38 are well-known and understood in the art.
ln operation. the tag 14 will be passed through
the oscillating electromagnetic field generated at gate 16
1~ between pedestals 18. l'he peaks o~ each half' cycle of the
magnetic field in this zone are greater than the intensitY
required to produce abrupt saturation o~ strip 34. When
switch 38 is open, current cannot be induced in coil 3~
and response strip .34 i5 ~'re~ to respond unhirldered to the
iniluence o~ the electromagnetic field. Each hal~' cycle
o~' the slectromagnetic Y'ield thus causes both a rever.sal
o~ the magnetic polarization o~' response strip ~4 and also
causes an abrupt saturation of the stxip 34. Each such
reversal and saturation af~'ects the elec-tromagnetic field
itself in a gradual and then abrupt manner. As the ~'ield
intensity rises from zero the strip causes a gradual
distortion ot` the ~ield. When the abrupt saturation takes
place there is an abrupt distortion which has the ei~'ect
o~' adding an impul.se signal or "blip" to the field (see
E'igures 4 and ~). Such "blips" are detectable by the
~'ield detection system. namely antenna 24. ampli~'ier 26
and decoder 28. It will be appreciated such impulse
.si~nals or "blips" will occur only during the existence of
the primary oscillating electroma~netic f'ield.
3~ Accordingly~ it is o~ partlcular signii'icance to the
~ -14-
0~'7
invention that such signals are detectable by the ~`ield
detection system during the presence ~` the primary field.
'l'he signals detected by the detection coil will
be processed so as to as ~ar as possible cancel ou-t the
primary ~ield response and enhance the coded pulses or
blips" ~rom the response member 34.
It will of course be appreciated that the
generation ot such signals or "blips" in accordance with
the invention is dependant upon the continued oscillation
o~ the primary ~ield, which in turn is responsible ~or the
generation both of the alternating current in the tag
antena 4~ and a1so ~`or the gerleration o~ a response in the
strip 34 itsel~.
1'hus assurning the SWitCtl remain.s open, therl each
hall cycle o~ the primary field will produce a
complimentary response signal or "blip" caused by the
strip 34
However, when switch 38 is c10sed, alternating
current is induced in coil 36, by the primarY
electromagnetic field. 'I'he alternating current in turn
induces its own electromagnetic Yield which ef~ective1Y
cancels or at least reduces the primary ~ield. in the
region of the strip 34, below that necessary to reach
saturation. 'l'hus. if switch .38 is closed. coil 36 acts as
a shield or mask between response strip ~4 and the primary
electromagnetic field. ~trip 34 is isolated from the
influence of the electromagnetic field. There will be no
signal or "blip" caused by abrupt saturation o~ the strip
34. ~onsequently, the primaxy electromagnetic field is
3~ no-t a~ected. No impulse signal i~ added to the
-16-
~'2.~ac~37
oscillating primary i`ie,ld signal. as would be the case if
t,he switch ~ and circuit to coil 36 were open.
onsequently, a graphical represen-tati~n o~ the ti.eld in
t,llis c:ondition woulcl look similar to tha-t when J10 tag was
present (see ~igure 4).
'l'he tag 14 according to the invention thus
al.lows certain impulse signals to be added to particular
half cycles oJ the ~ield. Thus~ the presence ot` a
specific tag 14 in the field results in a specific train
o~ tag impulses being superimposed on the field
oscillations, 'l'his ~unction is accomplished by opening and
closin~ oY switch 38 and the circuit to coil 36 in a
predetermined sequence. which se~uence de~ines the
identi~ication cocle oY tag lA. As explained below. the
sequence for the opening and elosing o~ switch 38 is
controlled by the positioning of diocles in matrix 5~.
I'he operation of matrix ~6 in con~iunc-tion with
counter chip 50 and selector chip ~6 is explained with
reference to the embodiment illustrated in E'igure 3. It
will be appreciated that such embodiment represents only
one identification code pa-ttern out of a multiplicity of
po.ssible patterns~ It will also be appreciated that the
numbsr o~ possible code patterns is dependent on the
number oJ column lines and courlter chip output terminals
and the number o~ row lines and selector chip input
terminals. Although in the illustrated embodiment there
are nine column lines and eight row lines, the principle
oJ: the invention may be applied with varyin~ numbers of
co.Lumn lines and row :lines. It will also be appreciated
that although chip 5~ counts by tens ancl chip ~ counts by
-16-
97
ei~hts, other chips counting by other numbers may also be
us~
~ th~r circuits might be used in place of the
rna~rix. E'or example a ring counter. or a series of ring
counters (not shown), could be used in place of the
matrix. 'l'he circuitry might be more complex to achieve a
Large number of unique codes. but in some circumstances
this might be acceptable.
For the purposes of this description. it is
lu assumed that the first switch of counter chip 5~ to be
closed is the switch connecting voltage drain terminal 46
to counter chip output terminal 52a. lt is also assumed
t~la-t the t'irst swi.-tch ot' selector chip 6~ to be closed is
the switch connecting selector chip input terminal ~8a to
c:elector chip output terminal 7~.
As the switch to terminal 5~a is closed, the
voltage drain signal is passed to column line 54a and
through diode 62aa to row line 58a and terminal ~8a.
Because column line 54a and row line 58a are not connected
to any other column lines 5~ or row lines 58. the volta~e
drain signal does not reach any other terminal 68. As the
switch between terminal 68a and -terminal '70 is closed, the
voltage drain signal passes to switch 38 and the circuit
to coil 3~ is closed. Thus .strip ~4 is masked and does
not at'fect the t'ield during such halt cycle. As a second
ha.Lf cycle of the field commences, -the clock signal opens
the terminal 52a switch and closes the terminal 52b
switch, energizin~ column line 54b.
~'olumn line 54a is no lon~er connected to
voltage drain terminal 4~. Consequently, row line 5~a is
.,
-17-
~2~19~
nc longer ener~ized via diode 6~aa. ~eGaUSe there is no
diode connection between column lirle 54b and row line ~8a,
row line ~8a is no longer energized at aLl. ~owever.
~lere is a cliode ~ cb connec-ting column line ~4b and r~w
line ~c. 'l'hus, row line ~8c and terminaL ~8c are
ener~i~ed by the voltage d.rain si~nal. ~owever. because
only the switch between terminals 68a and '7~ is open~ the
signal at terminal 68c is not passed to switch 38. Thus
the circuit to coil 36 is open and strip 34 reacts to add
1~ an impulse signal to the second hal~' cycle o~' the field.
Similarly, the third hal~ cycle adds an impulse
to the field sigrlal.
On the ~ourth half cycle, row line 58a is again
energized, but through diode 62ad. A voltage drain signal
is pas.sed to termina.l 70 and switch 38 is closed. No
impulse is added to the Yield signal.
On thc ~i~th to ninth hal~' cycles impulses are
added to the ~ield signal.
On the tenth half cycle, the switch between
~0 terminal b2~i and volta~e drain terminal 46 closes. thus
sending a signal to index terminal 64. ~uch signal causes
the terminal 68a switch to open and the terminal ~8b
switch to close. No other action occurs, thus on every
tenth hal~ cycle no signal passes to switch 38 and an
impulse signal is added to the ~ield signal.
On the eleventh hal~ cycle, the terminal ~a
switch closed ~'or a second time, thus energizin~ column
line 54a a second time. Again, the voltage drain si~nal
is passed thxough diode 6~aa to row line 58a. ~owever,
now the terminal 68a switch is open. -thus no si~na.l can
-l8-
q
r~ach switch ~8 and an impulse is added~
~ n the twel~th to fourteenth hal~ cycles. no
sigllals reach switch 38.
~ n the ~i~'teenth half cycle~ column line ~4e is
energized as is row line 58b via diode ~be. ~ecause the
terminal ~8b switch is closed. the voltage drain signal is
passed to switch 38 and coil 36 is closed. ~hus. the
~ `teenth hal~ cycle o~ the 1`ield possesses no added
impulse~
1~ ~imilarly, on the sixteenth half cycle. column
line ~4r is energized. as is row line 58b via diode 6~br.
'I'hus~ the sixteenth half cycle of the tield possesses no
added impulses.
With each ~'urther halY cycle, the electronic
switches of counter chip b~ and selector chip ~ con-tinue
to open and close. A train of impulses passes to switch
3~ in the fa,shion described above. A corresponding train
of irnpulses or "blips" is superimposed on the primarY
field. The initial half cycles of such primary field are
illustrated in figure 6. After the final hal~ cycle.
corresponding to the closed position of the column line
b3i switch and o~ the input terminal 68h switch. the
entire irnpulse train of "blips" will be repeated. l'hus.
tag 14 will continue to generate its particular irnpulse
train and af~'ect the electromagnetic field for as long as
tag 14 is within the ~ield. that is, passing through or
near Kate 1~.
~y positioning diodes ~ in dirt`erent positions
in rnatrix 5~ dif~'erent impulse trains may be generated.
3~ E'or any given number of counter chip output terminals and
--lg-
6)9~7
ol selector chip input terminals~ the number of possible
identi~'ication codes which may be utilized are determined
bl,Y the ~'ollowing relatinship:
N = ~mn
where N = number o~' possible codes
n = number of matrix column lines
m = number of matrix row lines
Di~des ~2 may be installed within matrix 56 to
d~fine a particular code at the time tag 14 is
1~ manufactured. It may also be possible to allow the
operator to choose his own codes. in this case. the
manufacturer will manufacture a tag 14 in which diodes 6~
are installed to connect each column line b4 with each row
line ~ (.see E'igure 7). lrl such an embodiment, each line
'/4 from a column line 54 to a diode ~ and a row line 58
is provided with a removable electrical connection 'l~.
~uch a connection 7~ may be easily removed or broken by
the the oper~tor, thus preventing an electrical connection
between a particular column line and a particular row
line. The removal or breaking o~' connections '7~ thereby
defines an identification code. ln such an embodiment it
may be n~cessary to increase the physical size o~ tag 14
in order to allow sufficient space for the operator to
conveniently remove or break particular COïlneCtiOnS.
In a further embodiment it may be possible for
ta~ 14 to .include a con-trol strip (not shown) o~'
ferromagnetic material in proximity to strip 34. Such a
con-trol strip may be used to deactivate the identification
capabilities of tag 14. ~uch control strips are well
known in the art (for example see United States ~a-ten-t No.
097
2~5l'i). `I'he ferromagne-tic material ol the control
s~rip ~las a coercivity signi~icantlY greater -than tha-t o~`
strip :j~. 'l'he material o~' the control strip may
cooveniently be a terromagrletic alloy o~ iron. cobalt. and
vanadium (co~monly referred to as vical:Loy~. At'ter the
control strip is magnetized in a deactivation unit.. the
control strip prevents the reversal of the magnetic
polarization of strip 34 under the influellce of the
electromagnetic fie1d. In such a condition. tag 14 cannot
1~ emit a unique identification code.
It wil:l be appreciated that an identi~'ication
tag according to the invention may be used not only in
material handling applications. but a1so in any other
application wher.e identiYicati.Qrl of objects or per.40rlne1
i.s required. E'or instance, without limiting the
gellerality o~ the foregoirlg, an identification tag may be
conveniently used for livestock identification. A tag may
be a~'~'ixed to an animal at birth. Breeding, ~'eedin~,
health treatment and other information may be more
converliently recorded with the automatic idsntification of
the animal concerned. A tag may even remain with an
animal carcass after the animal has been slaughtered.
'rhus, meat bu~ers may be provided w1th a reliable means of
i.dentifying and obtaining the history of an animal.
Identification tags according to the invention
may be used in personnel identi~ication and security
systems. A computer connected to a series of
interrogation gates placed within a high securj.ty area may
record the pa-th of an individual through such area.
3~ ~ertain doors may be locked or unlocked by the computer
09~7
according to whether an individual is authorized to pass
through such door.
'rhe tag may also be used to identi~'y library
books, or ~'iLes in an automated ~'ilin~J system. 'l'he ga-tes
1~ may be fabricated on a reduced scale and used as a "tag
reader". In this way security o~ filing systems couLd be
increased. Handlin~ o~` ~'iles in a computerised word
processing or accounting facility could be automated to a
much higher degree.
1~ lt will be appreciated that although an
identification tag according to the invention has been
described using solid state or electronic circuity. other
electrical parts or components may be used without
departing ~rom the principle of the invention. Slach an
embodiment may have application where small tag size is
not a requirement.
Having described what is believed to be the best
mode by which the invention may be per~'ormed, it will be
seen that the invention may be particularly defined as
Yollows:
An identification system ~or use in association
with a set of ob~iects ! such as persons, animals, packages
or the like, whereby any member o~ said set may be
identified while said member is located within a
predetermined interrogation zone, wherein said system
comprises;
interrogation ~'ield means whereby at least one
oscillating electromagnetic interrogation field may be
established in said interrogation zone;
~U response si~nal detection means operable to
i
~l~4109~
morlitor said interroga-tion zone;
an identit`ication tag associated with each
merll~er o~' said set. each tag comprising;
a response member formed of a magnetical:ly
permeable material adapted to reach saturation abruptly at
a predetermined level of magnetic flux and responsive to
halY cycles of said interrogation field when present in
said interrogation zone. upon abrupt magnetic saturation
thereo~, to abruptly distort said field thereby generating
1~ a series of Yield distortion pulses correspondin~ to
successive hal~ cycles of said interrogation Yield and
detectable during said half cycles;
an electromagrletic maskirlg coil around the said
response member selectively operabl,e to magnetica1ly mask
the same and thereby prevent saturation of said response
member and adapted to be rendered inoperable whereby no
such masking takes place;
switch means in circuit with said masking coil
selectively operable during a half cycle to control said
masking coi.l;
circuitry means connected with sai~ switch means
and operable to control opening and closing of said switch
means according to a predetermined sequence in timed
reLation to said half cycles o~ said interrogation Yield
thereby establishing during the presence ot' said
interro~ation field a series of interrogation field
distortion pulses caused by abrupt saturation o~' said
res~ponse member, said series of interrogation :~ield
distortion pulses being interrupted by a unique series o~
3~ discontinuities in said series of distortion pulses which
r
A ~ _
3~! t'~
deiines a~l identi~ication code ~or said ta~;
power means ~or said circuitry means whereby the
sarne may be operatecl. and,
signal pro-essing mean.s connected to said
detection means ~or processing and decoding said series of
distortion pulses.
Additionally. the invention provides an
identi~'ication tag which may particularly de~ined as
~`ollows:
1~ An identi~`ication tag to be used in association
wi1;h an ob,ject such as a person, animal, package or the
like to be icientit'ied~ and an identi~ication system which
system establishes an oscillating electromagne-tic
interrogation t'ield within a prsdeterMirled interrogation
ZO~le, said tag coMprising, a response signal member
responsive to said continuou~ interrogation t'ield to
abruptly reach ma~netic saturation thereby generatin~ a
series ot' response signal pulses correspon~ing to
successive hal~ cYcles o~ said interrogatiorl l'ield and
detectable during said half cycles, electromagne-tic
masking coil means around said response si~nal member
selectively operable to magnetically mask the same and
adapted to be rendered inoperable whereby no such masking
takes place. switch means in circuit with said masking
coil meansl and selectively operable during a .saicl hal~'
cycle to control said masking coil means. electronic
circuitry means connected with said switch rneans ancl
operable -to control the opening and clos:in~ ot' said switch
~eans according to a predetermined sequence in timecl
relation to the oscillations ot' said interrogation t'ield
~ 24-
14~ 3~7
t~l~reby establishing during tlle presence ol said
int~rrogation tield a series o.t re~ponse signal pulses
~enera-te(i by said response signal rnember~ said series
beirlLt i~lterrupted by selective op~ration o~ said maskin~
coil means to produce a unique sequence oi' discontinuities
in said series o~ respon.se si~nal pulses, which sequerlce
de~'ines an identi~'ication co~e for said tag. and! power
means to power said circuitry means.
Additionally, the inven-tion also embraces a
1~l method ~`or identi~'ying each member o~` a set and which
method is broadly defined as folLows:
A method for identit'ying each member o~ a set of
obiects such a,s persons, animals, packages or the like
said method comprising:
establishing a contirluous oscillating
interrogation field, at an interrogation zone;
providing each said member ot` said set with an
identifieation -tag. said tag comprising a response signal
member responsive to continuous oscillations o-t said
~U in~errogation ~`ield to abruptly reach magnetie saturàtion
on each half cycle thereby ~enerating a series o~ response
signal pulses eorresponding to successive hal~' cycles of
said interrogation ~ield and detectable during said half
cycles. and further comprising masking coil means around
said re.sponse signal member. switch means in circuit with
said masking coil means. whereby said maskirlg coil means
is selectively operable by said switch means to mask said
response signal member durin~ the presence of a said half
c~cle o~' said inte:rrogation -~`ield. elec1,ronic circuitry
3~ means connected with said switch means and operable to
J~ 2~-
Q9~
contlol opening and closin~ of said switch means according
to a predetermined sequence in timed relation to the
os-illations of said continuous interrogation field
thereby establishing during the presence o~` said
continuous interrogation signal a response si~nal
cc>nsistin~ of a series of response signal pulses ~enerated
by said response signal member. said series of response
signal pulses being interrupted by a unique series o~
discontinuities in said series o~' response signal pulses,
1~ which sequence defines an iden-ti~'ication code for said
tag, and said tag having pick up means responsive to said
continuous interrogation field to power from said
continuous interrogation ~`ield, for powering said
circuitry means;
placing a member of said .set, with a tag. in
said continuous interrogation field established in said
interrogation zone;
detecting the electroma~netic field in said
intcrrogation zone whereby to detect said sequence of
response signals in the presence of said continuous
interrogation field; and.
processing and decoding said sequence of
response signals to determine the identity of said tag and
said member o~` said set.
The ~oregoing is a description of a preferred
embodiment of the invention which is given here by way of
example onl,-~. The invention is not to be taken as limited
to any of the specific features as described, but
comprehends all such variations thereof as come within the
3V scope o~ the appended claims.
