CA2006749A1 - Antenna structure for an electronic article surveillance system - Google Patents
Antenna structure for an electronic article surveillance systemInfo
- Publication number
- CA2006749A1 CA2006749A1 CA002006749A CA2006749A CA2006749A1 CA 2006749 A1 CA2006749 A1 CA 2006749A1 CA 002006749 A CA002006749 A CA 002006749A CA 2006749 A CA2006749 A CA 2006749A CA 2006749 A1 CA2006749 A1 CA 2006749A1
- Authority
- CA
- Canada
- Prior art keywords
- antenna
- lead
- receiver
- load
- electronic article
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
- H01Q7/04—Screened antennas
Abstract
ABSTRACT OF THE DISCLOSURE
The transmitting and/or receiving antenna of an electronic article surveillance system utilizes a paired-lead loop configuration. One lead forms the active loop.
The other lead forms a passive loop, which parallels and is mutually coupled to the active loop, but not conductively connected to it. This other lead is resistively loaded.
The passive loop of the receiving antenna can also be used to conduct signals between the receiver circuitry and the alarm reporting devices associated with the receiver.
The transmitting and/or receiving antenna of an electronic article surveillance system utilizes a paired-lead loop configuration. One lead forms the active loop.
The other lead forms a passive loop, which parallels and is mutually coupled to the active loop, but not conductively connected to it. This other lead is resistively loaded.
The passive loop of the receiving antenna can also be used to conduct signals between the receiver circuitry and the alarm reporting devices associated with the receiver.
Description
~20~
ANTENNA sTRucruRE FOR AN
~;Ç~IÇ~I~S~I;~a~YSTEM
B~a~ound o~ the In~
Th2 pre~ent lnvantion primarily r~late3 to ~lec~ronlc ~acurity ~y~ta~, and in particular, to an improvQd antenna structure ~or an electronlc artit:le survaillanc~ ~y~tem.
A varle~y Or el~c~ronic ~r~icl~ ~urv~llancs ~ystems h~vo b~en propo~ed and i~pl~m~nt~d ~o r~r~ct ~hla unauthoriz~d removal o~ artlcl~ roDI a partIcular promi~2~. On~ conmon ~orla of this 1~ electronic articl~ ~urvelll~nca ~y~ whlch 2~a~
coms to ba placed near the exit~ o~ rotail ~$ltabli~ nta, librar~ e~ and th~ lik~. Howover, electronio article ~ur~reill~nce ~y~t~m~ ar~ o u~d ~or purpo0~1- o~ proc~ and lnv~ntory controls, to tr~ck articl~a ~ thoy pas~ through a particular sy~tem, a~ong oth~r application~.
Irr~spectiY~ Or ~he application involved, ~uch ~31Qctronic a~tlcl~ ou~ nc~ oyst~ g~n~r~lly op4rate lpon a coDul~on principlQ. Artlcle~ to b~ ~onitor~d ~ provld~od wlth tags (o~ v~xlou~ r~nt ty~of~) whlch con~alrl a circuit ( r~onant c:l~cult) ~or r~ctlng Wl~h an appli~d rad1s-rr~aque~ncy rl~ld. A txan~itto~ ~nd a ~an~itting ant~ aro proYlded to dQV0l0p th~ appliQd ~i~ld, and a r~cei~-,r amd a rec:~iving ant~ ar~ pro~rid~d to d~t~ct disturbanc~ in th~ appli~d ~iold.
I~ th~ ~ctlva clrcult oP a tag 1~ p ~ed bst~n th~ tr~n~itting and receivlrlg antanr~ which ara generally plac~d ne~r tha polnt of exlt ~ro~ a glven prami~a~, tha applled ~iald 1~ a~ectsd ln such ~ashion ~h~t ~ detQctable event 1~ prodUcQd wlthln the r~calv~r. ~hi~ i~ then u~d to producQ an approprlat~ alar~.
Systems ol~ thl~ g~narnl typa are available Pro~ manu~arkurers such a3 Chackpolnt SystQ~, Inc., oi~ Thoro~re, New Jersey, among oth~rs .
Although ~uch ~y~tam~ h~VQ provdn 9~ 0c1:iv~ in both sacurlty an woll a~ inventory ~nd proc~s~ ~anaga~0nt, it ha- been round th~t c~rtain ~nhancem6~nts to ~uch ~yst~ would bs de~irablo. Porhap~ ~ore~o~t i5 th~ avar-pr~sent de~ir~ to r~duca to tha extent pos~ibla any arror~ (~.g., ~ 8~ al~ ) which ar~
produced by ~uch ~yo1~ , particul~rly ln t~:lll8 0:1~ k~-ir dl~crim-~ nation b~tw~n tho pr~ nc~ o~ ~ tag ( ~igni~ying th~ pr~ nce o~
a ~rotact~d articl~) and o~ lnt~r~r~rlc~ ~hich ~ny b- pr~ent in ths vicinlty o~ ctronic artlcl~ ~ur~illanc~ ~ystom.
Any ~tepa whlch can b~ taksn to ~rihanc~ th~ accuracy oi the ~y~ will t~n~ to ~duc~ ~uch und~6irab1- re~ul~. How~v~r, coD~pl1c~ting thi~ tha corr~spondlng ~nd ~t tlm~ con~llc~lng requirQ~nt that any ~l-ld~ which ~r~ produced by th~ sy~to~ ~u~t me0t prev~ q FCC r~gul~tlon~ itinq th~ nzltur~ ncy, int~na~lty, ~tc.) o~ th~ ld~ whlch m~y b~ u~sd lr~ ~klng ~uch d~t~ ainatlon~,.
On~ f~ tor which contributod to t~i~ rolat~ tc3 th~
~00~ 9 antenna ~tructures wh~ ch are u~ed ln con~unctlon wlth the sy~tem' ~ tran~ltter and recaiver, in ordar to dQvelop and pick up th~ partlcular r~dlo-~r~s~uancy ~iqnals whlch are utlllz~d l ~uch syst~m~. In partlcular, th~ knowrl ~ntenna ~tructurQI3 had re~pons~ chllracteristlc~, wlthln the r~ngel o~ radio ~requencie~
typlcally employ~d, whlch could lntroduce amplitud~ and/or phasQ
di~tortiorl~ lnto th~ lgnala whlch ware su~Siclontly pronour~c~d to contrlbut~ to ~al8e al~
It i~ thOEro~or~ a prl~ary ob~ct o~ tho proaent lnv~ntlon to provldo an el~ctronlc artlcle sunr-lllanc~ ~yl~te~ o~
i~proved accuracy and r~ bllity.
It 1~ ~180 an ob~sct o~ th~ ~rl~s~rlt lnv0ntion to provlda an 31~ctronlc a~tlcl~ ~ur~illanco ~y~t~ whlch can Pccurat~ly and reliably reacl: to ~n lncr~a~d proportion o~ tho la}: ells or tag~ which it ~Jacounterei.
It i~ ~180 an ob~ ~ct oi~ pr~ont lnvont~on to provld~
an improvod ant~nna con~ r~tlon i~or ~n ~l~ctronl¢ articl~
sur~roillanc~ yl~ whlch p~rnita thn sy~to~ to 30re~ e~ ectiYely dl~c~imln~ato b~ltw~ ignal produc~d by ~ ~g p~lng in thQ
viclnity Og th~ ~leatronic: ~rtlcla E~ur~rsiïlanc~ ~y~te~, ~nd potential E~OU~C~ o~ in~er~rancn.
:Et i~ o ~n ob~ ~ct o~ ~hQ pr~snt in~n~ion to pro~ide ;~o~
an antonn~ ay~to~ o~ improved amplltUd~ ro~ponso ~or usa ln con~unction wlth electron~c artlcle surv~illanca ~y~te~ or oth~r applicationa haviny similar op~ratin~ require~Qnts.
It i~ ~urthor an ob~oct Or ths presant invontion to provide an antenn~ ~yst~ og thls gen~ral typ~ which can increa~e the 3~n itlvlty o~ t~e sy~te~ to tag ~i~n~l co~ponent~, whils decrea~ing it~ ~onaitivity ~o und~slrabl~ ~ignal compon~nt~.
It 1- ~urth~r an ob~ct o~ tho pre~ont inv~ntion to provld~ an antonna 4y~t~ whlch 1~ cs~abl~ o~ op~r~tln~ with a co~p~ratlv~ly con~tant (or ~lat) amplltud~ r~spon~a Acro~
prod~tar~ln-d ~roquency rang~ wlthln which lt i~ to op~r~t~.
It 1- ~urthe~ n ob~ect o,~ th- pres~n~ in~ntion t provid~ an ~ ~y~te~ ~ c~ ia capa ~ op~rat ~ th a~
co~p3r ~ oly con~t~n ~ r ~lat) ~ tud~ r~po ~ acro~
pr ~ t~r~in~d ~r~ ~ ncy r~ng- ~ ln which 1 ~ 9 to op~t~.J
Th~ and other o~-cts ar~ ~chi-v~d ln accordanc- wlth t~ pres~nt lnventlon by providing an el~ctronic ~rticl~
~urY~lllanc~ ~y~t~ with an l~prov~d Antanna con~igur~tion, a~
tollow~ Th~ tr~n~lttlng antenna ~or th- sy~t-~ utlllzes, ln plac~ o~ th~ hlngl--le~d or ~lngl- co~xlal-cabl~ loop antonn~ o~
th~ prior art, ~ "p~ir~d-l~ad~ loop ant~nna conglguratlon. Tho t~r~ ~pair~ sd~ includ~ nok only th~ twin-axl~l c~bl~ whloh i~ curr~ntly pr~arr~d ~or u~, but al~o oth~r ~rrang~ment~ o~
~ o -two parAllol le~ds, ~uch ~pair~d coaxlal ~ nd th~ like.!
Wlt~in ~ach ~t ~ palrad-l~ads, on~ l~ad ~or~ an ~actl~
z~o~
antsnna loop, 1.-. ono which la drivon by th~ tran~ltter clrcultry, in th~ cas~ o~ the kran~ittlng antann~, and whlch driv~s the xacelvar clrcultry in the ca~e o~ tho rec~iver antenna. The other l~ad ~orma a "p~lve" loop, l.e. on~ which i~ not drlven or drlvlng, but rather inter~ct~ wlth th~
re3pective ~ctlv~ loop only through mutual coupllng bstwQQn t~m.
Th~ pas~iv~ loop can th~n b~ ~pproprlat~ly p~ol~Qly loaded, and th~ combinatlon o~ actlv~ ~nd pasolve loop will then ~xhlblt the de~lrsd ~latt~n~d amplltud~ nd lln~rlz~d pha~ r~pon~.
~ow~v~r, thl~ ~n~lcl~l ~rr~ct wlll b~ obt~ln-d without ~u~stanti~lly dotractlng ~ro~ th~ lcl~ncy Or th- ~ntenn~ whlch 1~ ~o con~lgurod.
In addition, on~ Or th~ p~ir~d l-ad~, pr~arably th~
pa~sive ono, can ~upply 6n~r~izlng ~ignal~ rrOa th- r~c~iv~r circultry to th~ ~lar~ d~ic~ o~ tho ~yot~ .g., wnrnlng light or buzzor~, wh~n-vor ~ tag 1- d-t~ct~d.
~ urth0r d~tail r~gardlng an ~nt~nnA ~y~t~ havlng tho~e capabiliti~ ~ay b~ had with r~r~nco to th~ d~tall~d dsscription ~hich i~ provided bolow, tak~n ln con~unction wlth th~ acco~Anyln~ drawing~.
~ Sc~lPti~n Q~_~h~D~winq~
Flgure 1 i3 a block dia~ram o~ a conventlonal slectronic article surveillance ~y~te~.
Figure~ 2~ and ~b ara diagram~atic plan vlew~ ~howing an l~proved ~ntenna 8y8te~ ~or u~o in con~unction wlth the tran~mitting and r~c~iving portl on~ o~ ~h~ c~ronlc axticl~
~urvaillanc~ 9y8te~ 0~ Figurs 1.
Figur~ 3 iq ~cheD~tic diagr~ o~ an ~quivalont clrcuit ~or tho ant~nna oy~t~m ~hown in Figur- 2~.
Flgur~ 4 ia a graph which llluatrateo the ~raquency and pha~ r~pon~ o~ the ant0nna ~ysts~ shown in Flgur~ 2.
In tho ~v~r~l vi~wa provid~d, liko ro~r~nc- nu~r~la dQno~a ~l~ll~r æle~nts.
Flguro 1 ~how~ ~ln ~lo¢~ di~qra~ ~or~3 wh~t g~rally con~titut~ th~ co~entlonal ~ on~nt- o~ ~n ~lac~ronic ~rtlclo ~urvQill~nc- ~y~to~ 1 Or ~h~ ty~ m~nu~actur~d by and ~v~llabl~
rro~ C~ckpolnt ~y~t~m~, ~nc., o~ Thoro~ra, ~w J~r~y. ~hi~
~y~tQ~ 1 ln~lud-~ a tn~ 2, which can b- appli~d to ~ny variaty o~ dl~r~nt ~rtiGl~ in ~ccord~nc~ with known t~chni~u~ or ~x~mplQ, th~ ~g 2 ~ay ~ak~ th~ ~orm o~ ~ Whard"
tag wh~ch 1~ att~chabl~ to ~n artlcl~, u~ing ~hh connecting plA
with which thls type Or tag i8 generally provlded. Alt~r-natively, th~ tag 2 m~y taXe the ~or~ o~ a hang-tag whlch 13 appropriat~ly tled to th~ articla. The tag 2 ~ay al~o take t~e for~ o~ a lab~l adhe~iv~ly a~flxed ts th~ articla. ~ny Or a variQty of type~ o~ tag~ and appllcatlon t~chniqu~s may ~e u~d to accompll~h thl~ general ta~k.
Irra~pec~lYa o~ tho type or tag which 18 u~d, or it~
~anner o~ attachmsnt to tha a~ociatad articlo, th~ tag 2 incorporat~ a r~oonant clxcuit ~not ~hown) w~ich i- cap~ble Or reacting to appll~d rl~lda o~ 41~ctro~gn~tlo onargy. A
trans~itting ~ntenna 3 ls provid~d which i8 capabl- o~ devoloping thes~ appli~ ri~ld~ r~3pon~ive to th~ op~ratlon Or ~880C~ ~ted tran~mitt~r circuitry 4. A recalvinq ant~nnn 5 i8 providad ~or recqiving ~lectro~gnatic enorgy bot~ ~ro~ th~ tr~n~ittlng antQnna 3 and th~ r6~0nant circult o~ th~ tag 2 to dnvolop 3ignal which i~ ln turn ~p~ d to r~c~iv~r clr~uitry 6~ Th~
rec~iver 6 th~n op~rat48 upon thi~ rec~lv~d ~lgnal to d~ter~ine whather tag 2 i~ pr~ent in th~ viclnlty o~ ~h~ tran~itting and r~c~iving ~nt~nna~ 3,5, an~ to glv~ ~n alar~ i~ ~uch i~ th~,~
ca~
R~rring now to Figureo 2a and 2b o~ ~h~ drawing~, thea~ ~ho~ ~ x in ~hlch ant~ ~bodying ~h~ pre~ont inv~ntion ~ay b~ con~igured and ~ounted.
Fi~ur~ 2~ ohow~ ~hi~ ~or thQ tran~ltting Ant~nna 3, Figuro 2b ~or ~h~ r~coiving ant~nna 5.
~t~0~i~7~9 In ~ch c~o, there 1~ provlded a hou~ing 7. In it~
prasently pr~erred e~bodlment, thia hou~lng 7 1~ ~da o~ a hollow ~ynth~tlc plaatlc body, ln whona int~rior all the other ale~ents ara po~ltioned. Sp~ci~ically in the ba~ portion 7a o~
FigurQ 2~, thera i~ located thQ tran~itt~r circuitry 4 (Figura 1~ while, in th~ ba~e portlon 7~ o~ Flgura 2~, th~r~ i8 loca~d th~ receiver clrcuitry 6 ~Flgur~ 1).
Each houalng 7 ha~ a pair o~ uprights 7b and 7c, which ~r~ connoct~d by cro~s-m~mber~ 7d ~nd 7~.
In ~ach hou~lng 7, tho antenna loop 15 ~tart~ at th~
baso portion 72 and ~xtend~ upwa~dly on on- ld- o~ th~ loop ~nto upright portion 7b And on th~ other ~idQ into upright portlon 7c.
Howaver, ~t cro~-na~b~r 7d, th~ sid~ o~ th- ~nt~na loop 15 changa pl~c0~, i.a. th~ portlon oxtendlng ~long uprlgh~ 7b ~wltche~ ov~r to uprlght 7g and vlca-v~r~a. ~h- ~nt~nna loop 15 la then complet~d withln cro~o-~e~ber 70.
Thla croe~lng over Or th~ upp~r and low~r portion~ or each ant~nna loop 15 t~ what creato~ ~ar~ canc~llation o~
the anterna patt~rnJ, a~ approprlat~ to ~atls~y FCC r~gulat~sn~, a~ well ~ to r~duc- lnter~erenc~ ~ro~ re~ot~ ~ourc~ o~
extraneou~ rAdio ~r~quency enorgy. ~hi~ t~¢~nlguo o~ u~ln~ one or ~ore 9ud~ cro~-ov-r~ i8 ~nown, and in 1~ , do~ no~
con~titut~ an sl~nt o~ ~h~ pr~nt invention.
What do~ con~titut-- th~ pr~ nt in~entlon 1~ that th~
~ntonna loop 15 1~ ~orD~d. o~ pa~r~d lea~ whi~:h ar~ pr~er~bly embodied ln a twin-ax~l ca~
200~ 9 Such a cable compri~ n insul~tlng ~leav~, within l,:
which extand~ a ~ bwbl pair o~ ~ep~r~te lead~, ~urrounded by a , conduc~lv~ shiRld. A conductor ~or grounding th~ ~hield 1~ also pre~id~d, and ~pacer~ ar~ twi~t~d in with th~ laads to maintain 3ub~tantlally unl~orm ~paclng o~ thQ ele~ant~ withln tha outer~o~t in~ulating ~leeve.
In Figure~ 2a and 2b, thl~ cable i8 repr2sented somawha~
dlAgr~matic~lly ~y tubular ~l~m~nt 9 ~nd by conductor p~lrs 17a, 17b snd 13a, 18b, whlch ar~ soon to ~m~rg~ ~ro~ th~ op~n low~r end~ o~ nt 9. Sp-ci~lcAlly, ~l~ment 9 r~pr~nt~ th-conductive ohl~ld o~ tho ~w~n-axlal cable; conductor p~lro 17a, 17b and 13~, 18b r~re~en~ th~ ~ep~rats l~ads in~ido ~h~ cabl~, whioh becom~ vi~ibl~ ln Flgure- 28 ~nd 2b, whDr~ ~h~y ~rgo ~rom th~ in~ldo Or ~hl~ld 9, na~r tho tran~mitt~r and r~c~lv~r clrcui~ry 4 ~nd 6, r~poctiv-ly.
Mor~ ~p~ci~ically, ~onductors 17a and 17b r~preaant th~
~o-o~ergln~ opposlt~ ends o~ th~ sa~ one o~ th~ two ~eparat~
l~ds in~ido ~hi~ld 9 7 conductor~ 18a and 18b r~pr~ent th~
oppo~lt~ end~ o~ th~ ~cond on~ o~ th~ two ~op~r~t~ l~ad~ in~ld~
shield 9.
A~ ~hown in Flguro 2a, tr~nsmltt~r clrcultry 4 i~
connectsd to that on~ le~d who~o ~rging end~ d~ign~tsd ~y r~renc~ nu~ral~ 17~, 17b 1~ Flgur- 2a, Thi~ txan~itting circui~ry thu~ csn~titu~a~ an ~c~ive~ lo~d ~or ~hl~ l~ad and thn losp which th~t l~ad for~ ~n~ shlold 16 con~tltute~ th~
actlv~ loop o~ tho tran~itting ~ntenn~.
_9_ i~0~ 7~
In Flgur~ 2b, it 1~ tha r~ceiv~r clrcuitry 6 whlch is connected to that one lead wheo2 em~rging end~ are ~imilarly de~ignated by re~Qrenc~ numQrals 17a, 17b in Figur~ 2b.
Accordingly, ln Figure ~b, it i~ ths recelving clrcult~y which con8titut3~ an "actlvQN load rOr thl~ lead and tha loop whlch that le~d ~or~ in~ide shisld 16 in Figur~ ~b con~titute3 the ~ctlve" loop o~ the rec~iving antenna.
Wa now turn to ths other lead in~lda each sh~ld 9~
nam~ly that lsad who~ e~r~ing ~nds ~r~ de~ign~tad by r~r~nce nu~rsl~ 18a, 18b in oach o~ Flgur~ 2a ~nd 2b. Th~s~ othor l~ada are not conn~cted to t~Q raspectiv- activ~ load~ (na~ly to trans~itter or ræceivar clrcuitry 4, 6). Rathor th~ e~rging portion~ 18a, 18b o~ ths~ ad~ ar~ conn~ct~d in ~ch o~ ~igur~
ANTENNA sTRucruRE FOR AN
~;Ç~IÇ~I~S~I;~a~YSTEM
B~a~ound o~ the In~
Th2 pre~ent lnvantion primarily r~late3 to ~lec~ronlc ~acurity ~y~ta~, and in particular, to an improvQd antenna structure ~or an electronlc artit:le survaillanc~ ~y~tem.
A varle~y Or el~c~ronic ~r~icl~ ~urv~llancs ~ystems h~vo b~en propo~ed and i~pl~m~nt~d ~o r~r~ct ~hla unauthoriz~d removal o~ artlcl~ roDI a partIcular promi~2~. On~ conmon ~orla of this 1~ electronic articl~ ~urvelll~nca ~y~ whlch 2~a~
coms to ba placed near the exit~ o~ rotail ~$ltabli~ nta, librar~ e~ and th~ lik~. Howover, electronio article ~ur~reill~nce ~y~t~m~ ar~ o u~d ~or purpo0~1- o~ proc~ and lnv~ntory controls, to tr~ck articl~a ~ thoy pas~ through a particular sy~tem, a~ong oth~r application~.
Irr~spectiY~ Or ~he application involved, ~uch ~31Qctronic a~tlcl~ ou~ nc~ oyst~ g~n~r~lly op4rate lpon a coDul~on principlQ. Artlcle~ to b~ ~onitor~d ~ provld~od wlth tags (o~ v~xlou~ r~nt ty~of~) whlch con~alrl a circuit ( r~onant c:l~cult) ~or r~ctlng Wl~h an appli~d rad1s-rr~aque~ncy rl~ld. A txan~itto~ ~nd a ~an~itting ant~ aro proYlded to dQV0l0p th~ appliQd ~i~ld, and a r~cei~-,r amd a rec:~iving ant~ ar~ pro~rid~d to d~t~ct disturbanc~ in th~ appli~d ~iold.
I~ th~ ~ctlva clrcult oP a tag 1~ p ~ed bst~n th~ tr~n~itting and receivlrlg antanr~ which ara generally plac~d ne~r tha polnt of exlt ~ro~ a glven prami~a~, tha applled ~iald 1~ a~ectsd ln such ~ashion ~h~t ~ detQctable event 1~ prodUcQd wlthln the r~calv~r. ~hi~ i~ then u~d to producQ an approprlat~ alar~.
Systems ol~ thl~ g~narnl typa are available Pro~ manu~arkurers such a3 Chackpolnt SystQ~, Inc., oi~ Thoro~re, New Jersey, among oth~rs .
Although ~uch ~y~tam~ h~VQ provdn 9~ 0c1:iv~ in both sacurlty an woll a~ inventory ~nd proc~s~ ~anaga~0nt, it ha- been round th~t c~rtain ~nhancem6~nts to ~uch ~yst~ would bs de~irablo. Porhap~ ~ore~o~t i5 th~ avar-pr~sent de~ir~ to r~duca to tha extent pos~ibla any arror~ (~.g., ~ 8~ al~ ) which ar~
produced by ~uch ~yo1~ , particul~rly ln t~:lll8 0:1~ k~-ir dl~crim-~ nation b~tw~n tho pr~ nc~ o~ ~ tag ( ~igni~ying th~ pr~ nce o~
a ~rotact~d articl~) and o~ lnt~r~r~rlc~ ~hich ~ny b- pr~ent in ths vicinlty o~ ctronic artlcl~ ~ur~illanc~ ~ystom.
Any ~tepa whlch can b~ taksn to ~rihanc~ th~ accuracy oi the ~y~ will t~n~ to ~duc~ ~uch und~6irab1- re~ul~. How~v~r, coD~pl1c~ting thi~ tha corr~spondlng ~nd ~t tlm~ con~llc~lng requirQ~nt that any ~l-ld~ which ~r~ produced by th~ sy~to~ ~u~t me0t prev~ q FCC r~gul~tlon~ itinq th~ nzltur~ ncy, int~na~lty, ~tc.) o~ th~ ld~ whlch m~y b~ u~sd lr~ ~klng ~uch d~t~ ainatlon~,.
On~ f~ tor which contributod to t~i~ rolat~ tc3 th~
~00~ 9 antenna ~tructures wh~ ch are u~ed ln con~unctlon wlth the sy~tem' ~ tran~ltter and recaiver, in ordar to dQvelop and pick up th~ partlcular r~dlo-~r~s~uancy ~iqnals whlch are utlllz~d l ~uch syst~m~. In partlcular, th~ knowrl ~ntenna ~tructurQI3 had re~pons~ chllracteristlc~, wlthln the r~ngel o~ radio ~requencie~
typlcally employ~d, whlch could lntroduce amplitud~ and/or phasQ
di~tortiorl~ lnto th~ lgnala whlch ware su~Siclontly pronour~c~d to contrlbut~ to ~al8e al~
It i~ thOEro~or~ a prl~ary ob~ct o~ tho proaent lnv~ntlon to provldo an el~ctronlc artlcle sunr-lllanc~ ~yl~te~ o~
i~proved accuracy and r~ bllity.
It 1~ ~180 an ob~sct o~ th~ ~rl~s~rlt lnv0ntion to provlda an 31~ctronlc a~tlcl~ ~ur~illanco ~y~t~ whlch can Pccurat~ly and reliably reacl: to ~n lncr~a~d proportion o~ tho la}: ells or tag~ which it ~Jacounterei.
It i~ ~180 an ob~ ~ct oi~ pr~ont lnvont~on to provld~
an improvod ant~nna con~ r~tlon i~or ~n ~l~ctronl¢ articl~
sur~roillanc~ yl~ whlch p~rnita thn sy~to~ to 30re~ e~ ectiYely dl~c~imln~ato b~ltw~ ignal produc~d by ~ ~g p~lng in thQ
viclnity Og th~ ~leatronic: ~rtlcla E~ur~rsiïlanc~ ~y~te~, ~nd potential E~OU~C~ o~ in~er~rancn.
:Et i~ o ~n ob~ ~ct o~ ~hQ pr~snt in~n~ion to pro~ide ;~o~
an antonn~ ay~to~ o~ improved amplltUd~ ro~ponso ~or usa ln con~unction wlth electron~c artlcle surv~illanca ~y~te~ or oth~r applicationa haviny similar op~ratin~ require~Qnts.
It i~ ~urthor an ob~oct Or ths presant invontion to provide an antenn~ ~yst~ og thls gen~ral typ~ which can increa~e the 3~n itlvlty o~ t~e sy~te~ to tag ~i~n~l co~ponent~, whils decrea~ing it~ ~onaitivity ~o und~slrabl~ ~ignal compon~nt~.
It 1- ~urth~r an ob~ct o~ tho pre~ont inv~ntion to provld~ an antonna 4y~t~ whlch 1~ cs~abl~ o~ op~r~tln~ with a co~p~ratlv~ly con~tant (or ~lat) amplltud~ r~spon~a Acro~
prod~tar~ln-d ~roquency rang~ wlthln which lt i~ to op~r~t~.
It 1- ~urthe~ n ob~ect o,~ th- pres~n~ in~ntion t provid~ an ~ ~y~te~ ~ c~ ia capa ~ op~rat ~ th a~
co~p3r ~ oly con~t~n ~ r ~lat) ~ tud~ r~po ~ acro~
pr ~ t~r~in~d ~r~ ~ ncy r~ng- ~ ln which 1 ~ 9 to op~t~.J
Th~ and other o~-cts ar~ ~chi-v~d ln accordanc- wlth t~ pres~nt lnventlon by providing an el~ctronic ~rticl~
~urY~lllanc~ ~y~t~ with an l~prov~d Antanna con~igur~tion, a~
tollow~ Th~ tr~n~lttlng antenna ~or th- sy~t-~ utlllzes, ln plac~ o~ th~ hlngl--le~d or ~lngl- co~xlal-cabl~ loop antonn~ o~
th~ prior art, ~ "p~ir~d-l~ad~ loop ant~nna conglguratlon. Tho t~r~ ~pair~ sd~ includ~ nok only th~ twin-axl~l c~bl~ whloh i~ curr~ntly pr~arr~d ~or u~, but al~o oth~r ~rrang~ment~ o~
~ o -two parAllol le~ds, ~uch ~pair~d coaxlal ~ nd th~ like.!
Wlt~in ~ach ~t ~ palrad-l~ads, on~ l~ad ~or~ an ~actl~
z~o~
antsnna loop, 1.-. ono which la drivon by th~ tran~ltter clrcultry, in th~ cas~ o~ the kran~ittlng antann~, and whlch driv~s the xacelvar clrcultry in the ca~e o~ tho rec~iver antenna. The other l~ad ~orma a "p~lve" loop, l.e. on~ which i~ not drlven or drlvlng, but rather inter~ct~ wlth th~
re3pective ~ctlv~ loop only through mutual coupllng bstwQQn t~m.
Th~ pas~iv~ loop can th~n b~ ~pproprlat~ly p~ol~Qly loaded, and th~ combinatlon o~ actlv~ ~nd pasolve loop will then ~xhlblt the de~lrsd ~latt~n~d amplltud~ nd lln~rlz~d pha~ r~pon~.
~ow~v~r, thl~ ~n~lcl~l ~rr~ct wlll b~ obt~ln-d without ~u~stanti~lly dotractlng ~ro~ th~ lcl~ncy Or th- ~ntenn~ whlch 1~ ~o con~lgurod.
In addition, on~ Or th~ p~ir~d l-ad~, pr~arably th~
pa~sive ono, can ~upply 6n~r~izlng ~ignal~ rrOa th- r~c~iv~r circultry to th~ ~lar~ d~ic~ o~ tho ~yot~ .g., wnrnlng light or buzzor~, wh~n-vor ~ tag 1- d-t~ct~d.
~ urth0r d~tail r~gardlng an ~nt~nnA ~y~t~ havlng tho~e capabiliti~ ~ay b~ had with r~r~nco to th~ d~tall~d dsscription ~hich i~ provided bolow, tak~n ln con~unction wlth th~ acco~Anyln~ drawing~.
~ Sc~lPti~n Q~_~h~D~winq~
Flgure 1 i3 a block dia~ram o~ a conventlonal slectronic article surveillance ~y~te~.
Figure~ 2~ and ~b ara diagram~atic plan vlew~ ~howing an l~proved ~ntenna 8y8te~ ~or u~o in con~unction wlth the tran~mitting and r~c~iving portl on~ o~ ~h~ c~ronlc axticl~
~urvaillanc~ 9y8te~ 0~ Figurs 1.
Figur~ 3 iq ~cheD~tic diagr~ o~ an ~quivalont clrcuit ~or tho ant~nna oy~t~m ~hown in Figur- 2~.
Flgur~ 4 ia a graph which llluatrateo the ~raquency and pha~ r~pon~ o~ the ant0nna ~ysts~ shown in Flgur~ 2.
In tho ~v~r~l vi~wa provid~d, liko ro~r~nc- nu~r~la dQno~a ~l~ll~r æle~nts.
Flguro 1 ~how~ ~ln ~lo¢~ di~qra~ ~or~3 wh~t g~rally con~titut~ th~ co~entlonal ~ on~nt- o~ ~n ~lac~ronic ~rtlclo ~urvQill~nc- ~y~to~ 1 Or ~h~ ty~ m~nu~actur~d by and ~v~llabl~
rro~ C~ckpolnt ~y~t~m~, ~nc., o~ Thoro~ra, ~w J~r~y. ~hi~
~y~tQ~ 1 ln~lud-~ a tn~ 2, which can b- appli~d to ~ny variaty o~ dl~r~nt ~rtiGl~ in ~ccord~nc~ with known t~chni~u~ or ~x~mplQ, th~ ~g 2 ~ay ~ak~ th~ ~orm o~ ~ Whard"
tag wh~ch 1~ att~chabl~ to ~n artlcl~, u~ing ~hh connecting plA
with which thls type Or tag i8 generally provlded. Alt~r-natively, th~ tag 2 m~y taXe the ~or~ o~ a hang-tag whlch 13 appropriat~ly tled to th~ articla. The tag 2 ~ay al~o take t~e for~ o~ a lab~l adhe~iv~ly a~flxed ts th~ articla. ~ny Or a variQty of type~ o~ tag~ and appllcatlon t~chniqu~s may ~e u~d to accompll~h thl~ general ta~k.
Irra~pec~lYa o~ tho type or tag which 18 u~d, or it~
~anner o~ attachmsnt to tha a~ociatad articlo, th~ tag 2 incorporat~ a r~oonant clxcuit ~not ~hown) w~ich i- cap~ble Or reacting to appll~d rl~lda o~ 41~ctro~gn~tlo onargy. A
trans~itting ~ntenna 3 ls provid~d which i8 capabl- o~ devoloping thes~ appli~ ri~ld~ r~3pon~ive to th~ op~ratlon Or ~880C~ ~ted tran~mitt~r circuitry 4. A recalvinq ant~nnn 5 i8 providad ~or recqiving ~lectro~gnatic enorgy bot~ ~ro~ th~ tr~n~ittlng antQnna 3 and th~ r6~0nant circult o~ th~ tag 2 to dnvolop 3ignal which i~ ln turn ~p~ d to r~c~iv~r clr~uitry 6~ Th~
rec~iver 6 th~n op~rat48 upon thi~ rec~lv~d ~lgnal to d~ter~ine whather tag 2 i~ pr~ent in th~ viclnlty o~ ~h~ tran~itting and r~c~iving ~nt~nna~ 3,5, an~ to glv~ ~n alar~ i~ ~uch i~ th~,~
ca~
R~rring now to Figureo 2a and 2b o~ ~h~ drawing~, thea~ ~ho~ ~ x in ~hlch ant~ ~bodying ~h~ pre~ont inv~ntion ~ay b~ con~igured and ~ounted.
Fi~ur~ 2~ ohow~ ~hi~ ~or thQ tran~ltting Ant~nna 3, Figuro 2b ~or ~h~ r~coiving ant~nna 5.
~t~0~i~7~9 In ~ch c~o, there 1~ provlded a hou~ing 7. In it~
prasently pr~erred e~bodlment, thia hou~lng 7 1~ ~da o~ a hollow ~ynth~tlc plaatlc body, ln whona int~rior all the other ale~ents ara po~ltioned. Sp~ci~ically in the ba~ portion 7a o~
FigurQ 2~, thera i~ located thQ tran~itt~r circuitry 4 (Figura 1~ while, in th~ ba~e portlon 7~ o~ Flgura 2~, th~r~ i8 loca~d th~ receiver clrcuitry 6 ~Flgur~ 1).
Each houalng 7 ha~ a pair o~ uprights 7b and 7c, which ~r~ connoct~d by cro~s-m~mber~ 7d ~nd 7~.
In ~ach hou~lng 7, tho antenna loop 15 ~tart~ at th~
baso portion 72 and ~xtend~ upwa~dly on on- ld- o~ th~ loop ~nto upright portion 7b And on th~ other ~idQ into upright portlon 7c.
Howaver, ~t cro~-na~b~r 7d, th~ sid~ o~ th- ~nt~na loop 15 changa pl~c0~, i.a. th~ portlon oxtendlng ~long uprlgh~ 7b ~wltche~ ov~r to uprlght 7g and vlca-v~r~a. ~h- ~nt~nna loop 15 la then complet~d withln cro~o-~e~ber 70.
Thla croe~lng over Or th~ upp~r and low~r portion~ or each ant~nna loop 15 t~ what creato~ ~ar~ canc~llation o~
the anterna patt~rnJ, a~ approprlat~ to ~atls~y FCC r~gulat~sn~, a~ well ~ to r~duc- lnter~erenc~ ~ro~ re~ot~ ~ourc~ o~
extraneou~ rAdio ~r~quency enorgy. ~hi~ t~¢~nlguo o~ u~ln~ one or ~ore 9ud~ cro~-ov-r~ i8 ~nown, and in 1~ , do~ no~
con~titut~ an sl~nt o~ ~h~ pr~nt invention.
What do~ con~titut-- th~ pr~ nt in~entlon 1~ that th~
~ntonna loop 15 1~ ~orD~d. o~ pa~r~d lea~ whi~:h ar~ pr~er~bly embodied ln a twin-ax~l ca~
200~ 9 Such a cable compri~ n insul~tlng ~leav~, within l,:
which extand~ a ~ bwbl pair o~ ~ep~r~te lead~, ~urrounded by a , conduc~lv~ shiRld. A conductor ~or grounding th~ ~hield 1~ also pre~id~d, and ~pacer~ ar~ twi~t~d in with th~ laads to maintain 3ub~tantlally unl~orm ~paclng o~ thQ ele~ant~ withln tha outer~o~t in~ulating ~leeve.
In Figure~ 2a and 2b, thl~ cable i8 repr2sented somawha~
dlAgr~matic~lly ~y tubular ~l~m~nt 9 ~nd by conductor p~lrs 17a, 17b snd 13a, 18b, whlch ar~ soon to ~m~rg~ ~ro~ th~ op~n low~r end~ o~ nt 9. Sp-ci~lcAlly, ~l~ment 9 r~pr~nt~ th-conductive ohl~ld o~ tho ~w~n-axlal cable; conductor p~lro 17a, 17b and 13~, 18b r~re~en~ th~ ~ep~rats l~ads in~ido ~h~ cabl~, whioh becom~ vi~ibl~ ln Flgure- 28 ~nd 2b, whDr~ ~h~y ~rgo ~rom th~ in~ldo Or ~hl~ld 9, na~r tho tran~mitt~r and r~c~lv~r clrcui~ry 4 ~nd 6, r~poctiv-ly.
Mor~ ~p~ci~ically, ~onductors 17a and 17b r~preaant th~
~o-o~ergln~ opposlt~ ends o~ th~ sa~ one o~ th~ two ~eparat~
l~ds in~ido ~hi~ld 9 7 conductor~ 18a and 18b r~pr~ent th~
oppo~lt~ end~ o~ th~ ~cond on~ o~ th~ two ~op~r~t~ l~ad~ in~ld~
shield 9.
A~ ~hown in Flguro 2a, tr~nsmltt~r clrcultry 4 i~
connectsd to that on~ le~d who~o ~rging end~ d~ign~tsd ~y r~renc~ nu~ral~ 17~, 17b 1~ Flgur- 2a, Thi~ txan~itting circui~ry thu~ csn~titu~a~ an ~c~ive~ lo~d ~or ~hl~ l~ad and thn losp which th~t l~ad for~ ~n~ shlold 16 con~tltute~ th~
actlv~ loop o~ tho tran~itting ~ntenn~.
_9_ i~0~ 7~
In Flgur~ 2b, it 1~ tha r~ceiv~r clrcuitry 6 whlch is connected to that one lead wheo2 em~rging end~ are ~imilarly de~ignated by re~Qrenc~ numQrals 17a, 17b in Figur~ 2b.
Accordingly, ln Figure ~b, it i~ ths recelving clrcult~y which con8titut3~ an "actlvQN load rOr thl~ lead and tha loop whlch that le~d ~or~ in~ide shisld 16 in Figur~ ~b con~titute3 the ~ctlve" loop o~ the rec~iving antenna.
Wa now turn to ths other lead in~lda each sh~ld 9~
nam~ly that lsad who~ e~r~ing ~nds ~r~ de~ign~tad by r~r~nce nu~rsl~ 18a, 18b in oach o~ Flgur~ 2a ~nd 2b. Th~s~ othor l~ada are not conn~cted to t~Q raspectiv- activ~ load~ (na~ly to trans~itter or ræceivar clrcuitry 4, 6). Rathor th~ e~rging portion~ 18a, 18b o~ ths~ ad~ ar~ conn~ct~d in ~ch o~ ~igur~
2~ and 2b to ~ Np~lv~n load 20 and th- loop whi~h ~ach Or th~e l~ad~ ~or~ ln~id~ it~ ~hl~ld 9 thu~ ~on~tituto~ th~ ~pas~lv~"
loop of th~ reap~ctlvo antenna.
E~ch o~ th~se passlYO loop~ i8 in turn coupled to the activo loo~ in~1d~ th~ samo dhi~ld 9 by ~ean~ o~ ~h~ ~utu~l cou~llng which ~xl~t~ b~t~n two clo~ly ad~acent la~d~. ~
Th~ l~p~danc~ o~ pA~iVo load 20 1~ so cho~-n that, wh~n it i~ ~e~l~ct-d ba~k lnto t~ re~p~ctiv~ activ~ load through th~
abov2~ tlon~ ~tual coupllng, th~ ovarall e~ct will b~
to lmpart to ~c~ ~n~nna loop 15 a ~uch ~lat~r a~plitude r~ponse and a ~uch ~or~ lln~r pha~ r~pons~ t~n could oth~rwi~ h~vo b~en obtain~d, wi~hout ~ubst~ntlally r~ducin~ the antonn~ icl~ncyO
Becau~q o~ tho diatribut~d nature o~ the mutual coupling bRtwaen th~ leadA in~ido ~ach shi~ld 9, it 1~ dl~icul~ to provid~ a preci~ equlvalent circult ~or the arra~gement. An approximatlon o~ such ~n equivalent clrcuit rOr th~ transmltter portion Or the ~y~tam i~ ~hown ln Figuro 3 within th~ brok~n lln~
rectangl~ de~ignat~d by ra~QrencQ numeral 19.
A~ illustrated in Figure 4, to whic~ re~renc~ ~ay now b- mad~, th~ u~e o~ a ~cond load ln tha ~nn~r ~bodying the pra~nt inv~ntlon chang~o th~ ant~nna a~plitud~ r~pon~ ~ro~ On9 which 1~ g~norally l~ilar to th~t ohown at ~1 ln Figuro ~, to onQ whlch 1~ g~n~rally almil~r to that shown at 22, i.~. to on~
which i~ ~ignl~icantly mor~ uni~or~ throughou~ ~ho op~ra~iv~
~rQquoncy band. Al~o illu~tratod in Flgur~ 4 i- ~ corro~ponding l~provem~nt in tha 2nt~nna' 8 pha~2 r~apon~o, ~ro~ A r~pon~a g~nerally llko th~t ~hown at 23, to a co~pa~Atlv~ly ~or~ llnoar respon~o ~uch a~ Dhown ~t 24.
By ~c rlattenlng th~ ant~nn~3~ a~plltud- r~$pono~ ~nd line~rizing tholr ph~ r~pon~, lt beco~o~ pos~lblQ to ~ectlvOEly d~toct tag algnal~ ov~r ~ wid~r rAngs o~ ~r~qu~nclo3, without cr-atlnq ~or- ~al~ alarms. ~hi~ 1~ import~nt b~caus~
~h~ re~onant circult, whlch i~ part o~ ~ch t~y 2, t~nd~ to v~ry in re~on~nt ~xoqu~ncy ~ro~ ono tag to ano~h~r. B~c3u~e o~ this, convention~l practic~ requlr~ a ~wept ~requ~ncy to b~ utiliz~d by ~hQ ~ysts~ ~.g., 8.2 ~Hz + 800 ~Xz) ao ao to ~a~tiv~ly intorac~ with ~ueh ~ag~ de~pito th~lr v~riation in r~onant ~r~qu~ncy. Ev~n ~hon, 80~ tag~ had to b~ r~ect~d iollowing ~o~
thair ~anu~actur~ becau~ they could not ~ati~y th~ toleranc~
requlre~nta ~or th~ olsctronln artlcla survoillance ayste~ with whlch they w~re to be used. By maklng it po~sibl~ to e~ectiv~ly detect a bro~der ranga o~ ~reguencies, the el~ctronic article survelllance ~y~ta~ 1 o~ th~ pre~ent lnv~ntlon wlll operate to deta~t a widar rang~ Or re~onant tag~, ln turn permittlng a ~ignl~icantly r~duced number o~ tags ~o b~ r~sctQd in the cours~
of thelr manuf~cturs.
U~ing a twln-axial cabla a~ ths r~c~lving ant~nn~ 5 provldes an Additional advantag~ ~or th~ ~y~t~ t i~ th~
prinalpnl ~unction o~ th- r~c-iv~r ~ to actlvat~ an appropria~
alarm when th~ pr~sQnc~ o~ a tag 2 i~ det~cted ~otw-on th~
txanfi~itting ant~nna 3 and th- r~c~iving antonna 5.
~ o ~hat end, th~r- ~ay b- ~ou~t~d in~ld~ thq upp~ cro~
~e~bor 73 o~ hou~ing 7 in Flguro 2b ~ Go~v~n~lon~l warni~g llght arr~nga~nt dl~gr~atlc~lly r~pr~oontod by r~ctzngl~ as- In order to onerglzs thi~ w~rning llght wh~n r~qulred, ~ d-c conn~ction noada to b~ provlded b~twe~n it and th~ r~Qiv~r 6 locat~d in th~ ba~- 7a o~ tho hou~lng 7. Tho p~31~ d (th~
ono who~o ~orglng ~nda ar4 d~lgnatad by re~er~nc~ nu~ral~ 18a and 18b in ~igur~ 2b) ~ay b~ u3~d ~or th~t pUrpO~Q.
Speci~lcally, d-c output ~ro~ rac~lver 6 ~ay b~ appll~d to th~t l~ad YiZ a co~noctlon which 1~ dlaqram~Atically r~pre~nt~d by l~ad 26 ln Figur~ 2b. At tha top o~ th- loop ~or~d by th~
twin axlal ~abl-, a conn~ction i~ ~ad~ ~o t~ 8~ p~iv~ d n~ar tha w~rnlng light arrang0m~nt 25, a~ dl~gr~n~atioally -12- .
~ ~ Ogi7 ~ 9 representad by conn~cting la~d a7 ln Flgure 2b. A~ a reault, theFe ia no need ror a 3~parat~, addition~l lead b~tweQn receiv~r 6 and warnlng light 25. Potsntial adver~a e~ect~ on ant~nn~
per~or~ance, resultlng ~ro~ th~ pre~anc~ o~ ~uch an additional lead, ar~ thereby averted.
It wlll now b~ ~eQn that the above-de~crl~od antenna ysts~ opora~a to ~atl3~y ~ho variou~ ob~ectiv~ whlch w~r2 proviou~ly ~tatod. It will ~urther be undor~tood th~t thQ~-antenna By~te~ may b~ varlod, 1~ de~lred, wlthout d~p~rting ~rom th~ spirit and ~cop~ o~ th~ pr0a~nt invontlon.
For exa~ple, ~lthough tho l~prova~nt~ o~ th~ prn~ont invQntion ar~ ~pecirically d~cribod in connection with a particular typa o~ electronic ar~iclo ~urvalllanc~ ay3te~, ~uch improvomQnt~ will ~ind aqual applicability to othor typ~ o~
~lectronic arti~ urv~lllnnc~ ~y~tQ~-, or ~von oth-r ~nt-n~
applic~tion~ wh-r~ imllar i~prov~nt~ sra d~lr~d.
A3 di~cu~ed, the pres0ntly pre~orrod i~plo~ntatlon o~
the p~lr~d~ d ant~nnas whlch a~body th~ lnv~ntlon 1~ by ~oans Or a twln-axlal a~ lo. A cabl- aultablo ~or ~ho purpoa- 1 avallabla ~ro~ B~ld~n Wlr~ S Cabl- Co~pany, P.O. Box l980 Richmond, Indian~ ~7375, und~r th~ir pr~duct nu~b~r 9271.
~ cw~v~r, lt wlll bs und~r~tood that oth~r paired-l~ad sy~te~o ~ay al~o b~ utlllzQd. For ox~plo, it 1- al~o po~ible to ~k~ u~ o~ two dl~cr~to, g~nor~lly parall~l wir~ to ~or~ tha ant~nna loop 15. Pairæ~ coaxi~l cabl~- ~ay a~oo be u~ad.
~o~t74~
In ~ny ca~e, the lndlvidual lo~d~ are pre~r~bly uni~ormly space i ~rom one another throughQut th~r length~ .
Further, lt i~ pre~erabl~ ~or the palred-l~ad~ to be unl~orD~ly twisted along thDlr length~ ~lnca thl~ reduca~ th~ e~ ct local lrregularitl~
~ en using A ~hi~lded ~t o~ paired 10ad~ ln tha ca~Q o~ twin-~xlal cabl~ previously dl~cu~od, lt 1 appropri~t~ to provide a breaX in th~t ~hield, to a~ t th~
l~ad~ in~lda th~ shi~ld in psr~or~ing th~llr ba~ic 1'unction a~
antonna ~ aan~ Such ~ br~k la repr~sen~d ~t 9~ ln Flguro 2a, wher~ lead~ in~ido ~hi~ld 9 bscoms oxpol~od. 'ro maintain ol~ctrical continuity ~or shl~ld ~, tho upp~r and low~r porl:ion-~saparatad by ~h~ br~X ar~ conductlvQly conrloc~d by conductor~
~b and 9c.
Althouqh not illu~trat~d, tho t~o bruak arr~ng~nt 1 pr~rably providfld ~or th~ ant~nna 5 oX Figur~ 2b.
In vl~w o~ all the ~or~going, lt 1~ d~aired that ths ~cop~ o~ pr~nt inve~ntion bo d~ln~d only by th~ ~pp~nded clal~s.
loop of th~ reap~ctlvo antenna.
E~ch o~ th~se passlYO loop~ i8 in turn coupled to the activo loo~ in~1d~ th~ samo dhi~ld 9 by ~ean~ o~ ~h~ ~utu~l cou~llng which ~xl~t~ b~t~n two clo~ly ad~acent la~d~. ~
Th~ l~p~danc~ o~ pA~iVo load 20 1~ so cho~-n that, wh~n it i~ ~e~l~ct-d ba~k lnto t~ re~p~ctiv~ activ~ load through th~
abov2~ tlon~ ~tual coupllng, th~ ovarall e~ct will b~
to lmpart to ~c~ ~n~nna loop 15 a ~uch ~lat~r a~plitude r~ponse and a ~uch ~or~ lln~r pha~ r~pons~ t~n could oth~rwi~ h~vo b~en obtain~d, wi~hout ~ubst~ntlally r~ducin~ the antonn~ icl~ncyO
Becau~q o~ tho diatribut~d nature o~ the mutual coupling bRtwaen th~ leadA in~ido ~ach shi~ld 9, it 1~ dl~icul~ to provid~ a preci~ equlvalent circult ~or the arra~gement. An approximatlon o~ such ~n equivalent clrcuit rOr th~ transmltter portion Or the ~y~tam i~ ~hown ln Figuro 3 within th~ brok~n lln~
rectangl~ de~ignat~d by ra~QrencQ numeral 19.
A~ illustrated in Figure 4, to whic~ re~renc~ ~ay now b- mad~, th~ u~e o~ a ~cond load ln tha ~nn~r ~bodying the pra~nt inv~ntlon chang~o th~ ant~nna a~plitud~ r~pon~ ~ro~ On9 which 1~ g~norally l~ilar to th~t ohown at ~1 ln Figuro ~, to onQ whlch 1~ g~n~rally almil~r to that shown at 22, i.~. to on~
which i~ ~ignl~icantly mor~ uni~or~ throughou~ ~ho op~ra~iv~
~rQquoncy band. Al~o illu~tratod in Flgur~ 4 i- ~ corro~ponding l~provem~nt in tha 2nt~nna' 8 pha~2 r~apon~o, ~ro~ A r~pon~a g~nerally llko th~t ~hown at 23, to a co~pa~Atlv~ly ~or~ llnoar respon~o ~uch a~ Dhown ~t 24.
By ~c rlattenlng th~ ant~nn~3~ a~plltud- r~$pono~ ~nd line~rizing tholr ph~ r~pon~, lt beco~o~ pos~lblQ to ~ectlvOEly d~toct tag algnal~ ov~r ~ wid~r rAngs o~ ~r~qu~nclo3, without cr-atlnq ~or- ~al~ alarms. ~hi~ 1~ import~nt b~caus~
~h~ re~onant circult, whlch i~ part o~ ~ch t~y 2, t~nd~ to v~ry in re~on~nt ~xoqu~ncy ~ro~ ono tag to ano~h~r. B~c3u~e o~ this, convention~l practic~ requlr~ a ~wept ~requ~ncy to b~ utiliz~d by ~hQ ~ysts~ ~.g., 8.2 ~Hz + 800 ~Xz) ao ao to ~a~tiv~ly intorac~ with ~ueh ~ag~ de~pito th~lr v~riation in r~onant ~r~qu~ncy. Ev~n ~hon, 80~ tag~ had to b~ r~ect~d iollowing ~o~
thair ~anu~actur~ becau~ they could not ~ati~y th~ toleranc~
requlre~nta ~or th~ olsctronln artlcla survoillance ayste~ with whlch they w~re to be used. By maklng it po~sibl~ to e~ectiv~ly detect a bro~der ranga o~ ~reguencies, the el~ctronic article survelllance ~y~ta~ 1 o~ th~ pre~ent lnv~ntlon wlll operate to deta~t a widar rang~ Or re~onant tag~, ln turn permittlng a ~ignl~icantly r~duced number o~ tags ~o b~ r~sctQd in the cours~
of thelr manuf~cturs.
U~ing a twln-axial cabla a~ ths r~c~lving ant~nn~ 5 provldes an Additional advantag~ ~or th~ ~y~t~ t i~ th~
prinalpnl ~unction o~ th- r~c-iv~r ~ to actlvat~ an appropria~
alarm when th~ pr~sQnc~ o~ a tag 2 i~ det~cted ~otw-on th~
txanfi~itting ant~nna 3 and th- r~c~iving antonna 5.
~ o ~hat end, th~r- ~ay b- ~ou~t~d in~ld~ thq upp~ cro~
~e~bor 73 o~ hou~ing 7 in Flguro 2b ~ Go~v~n~lon~l warni~g llght arr~nga~nt dl~gr~atlc~lly r~pr~oontod by r~ctzngl~ as- In order to onerglzs thi~ w~rning llght wh~n r~qulred, ~ d-c conn~ction noada to b~ provlded b~twe~n it and th~ r~Qiv~r 6 locat~d in th~ ba~- 7a o~ tho hou~lng 7. Tho p~31~ d (th~
ono who~o ~orglng ~nda ar4 d~lgnatad by re~er~nc~ nu~ral~ 18a and 18b in ~igur~ 2b) ~ay b~ u3~d ~or th~t pUrpO~Q.
Speci~lcally, d-c output ~ro~ rac~lver 6 ~ay b~ appll~d to th~t l~ad YiZ a co~noctlon which 1~ dlaqram~Atically r~pre~nt~d by l~ad 26 ln Figur~ 2b. At tha top o~ th- loop ~or~d by th~
twin axlal ~abl-, a conn~ction i~ ~ad~ ~o t~ 8~ p~iv~ d n~ar tha w~rnlng light arrang0m~nt 25, a~ dl~gr~n~atioally -12- .
~ ~ Ogi7 ~ 9 representad by conn~cting la~d a7 ln Flgure 2b. A~ a reault, theFe ia no need ror a 3~parat~, addition~l lead b~tweQn receiv~r 6 and warnlng light 25. Potsntial adver~a e~ect~ on ant~nn~
per~or~ance, resultlng ~ro~ th~ pre~anc~ o~ ~uch an additional lead, ar~ thereby averted.
It wlll now b~ ~eQn that the above-de~crl~od antenna ysts~ opora~a to ~atl3~y ~ho variou~ ob~ectiv~ whlch w~r2 proviou~ly ~tatod. It will ~urther be undor~tood th~t thQ~-antenna By~te~ may b~ varlod, 1~ de~lred, wlthout d~p~rting ~rom th~ spirit and ~cop~ o~ th~ pr0a~nt invontlon.
For exa~ple, ~lthough tho l~prova~nt~ o~ th~ prn~ont invQntion ar~ ~pecirically d~cribod in connection with a particular typa o~ electronic ar~iclo ~urvalllanc~ ay3te~, ~uch improvomQnt~ will ~ind aqual applicability to othor typ~ o~
~lectronic arti~ urv~lllnnc~ ~y~tQ~-, or ~von oth-r ~nt-n~
applic~tion~ wh-r~ imllar i~prov~nt~ sra d~lr~d.
A3 di~cu~ed, the pres0ntly pre~orrod i~plo~ntatlon o~
the p~lr~d~ d ant~nnas whlch a~body th~ lnv~ntlon 1~ by ~oans Or a twln-axlal a~ lo. A cabl- aultablo ~or ~ho purpoa- 1 avallabla ~ro~ B~ld~n Wlr~ S Cabl- Co~pany, P.O. Box l980 Richmond, Indian~ ~7375, und~r th~ir pr~duct nu~b~r 9271.
~ cw~v~r, lt wlll bs und~r~tood that oth~r paired-l~ad sy~te~o ~ay al~o b~ utlllzQd. For ox~plo, it 1- al~o po~ible to ~k~ u~ o~ two dl~cr~to, g~nor~lly parall~l wir~ to ~or~ tha ant~nna loop 15. Pairæ~ coaxi~l cabl~- ~ay a~oo be u~ad.
~o~t74~
In ~ny ca~e, the lndlvidual lo~d~ are pre~r~bly uni~ormly space i ~rom one another throughQut th~r length~ .
Further, lt i~ pre~erabl~ ~or the palred-l~ad~ to be unl~orD~ly twisted along thDlr length~ ~lnca thl~ reduca~ th~ e~ ct local lrregularitl~
~ en using A ~hi~lded ~t o~ paired 10ad~ ln tha ca~Q o~ twin-~xlal cabl~ previously dl~cu~od, lt 1 appropri~t~ to provide a breaX in th~t ~hield, to a~ t th~
l~ad~ in~lda th~ shi~ld in psr~or~ing th~llr ba~ic 1'unction a~
antonna ~ aan~ Such ~ br~k la repr~sen~d ~t 9~ ln Flguro 2a, wher~ lead~ in~ido ~hi~ld 9 bscoms oxpol~od. 'ro maintain ol~ctrical continuity ~or shl~ld ~, tho upp~r and low~r porl:ion-~saparatad by ~h~ br~X ar~ conductlvQly conrloc~d by conductor~
~b and 9c.
Althouqh not illu~trat~d, tho t~o bruak arr~ng~nt 1 pr~rably providfld ~or th~ ant~nna 5 oX Figur~ 2b.
In vl~w o~ all the ~or~going, lt 1~ d~aired that ths ~cop~ o~ pr~nt inve~ntion bo d~ln~d only by th~ ~pp~nded clal~s.
Claims (23)
1. An antenna formed of paired leads and including a first lead for connection to an active load, and a second lead for connection to a passive load, said second lead being mutually coupled with but not conductively connected to said first lead.
2. The antenna of claim 1 wherein said passive load 1 resistive.
3. The antenna of claim 2 wherein said passive load modifies the overall response of said antenna.
4. The antenna of claim 3 wherein said antenna exhibits a relatively constant amplitude response and relatively linear phase response over a predetermined frequency range.
5. The antenna of claim 4 wherein said predetermined frequency range corresponds to a range of resonant frequencies of the resonant circuits associated with the tags of an electronic article surveillance system.
6. The antenna of claim 1 wherein said active load is a transmitter.
7. The antenna of claim 6 wherein said transmitter forms part of an electronic article surveillance system.
8. The antenna of claim 1 wherein said active load 1 a receiver.
9. The antenna of claim 8 wherein said receiver forms part of an electronic article surveillance systems.
10. The antenna of claim 9 wherein said electronic article surveillance system includes means for reporting alarms, said means being electrically connected to said receiver by said second lead.
11. The antenna of claim 1 wherein said second lead is not conductively connected to said active load.
12. The antenna of claim 1 wherein said antenna is configured as a far-field cancelling loop antenna structure.
13. The antenna of claim 1 wherein said paired leads are formed by a twin axial cable.
14. The antenna of claim 13 wherein the paired leads of said twin-axial cable are twisted about each other.
15. The antenna of claim 1 wherein said paired lead are substantially uniformly spaced from one another along their lenght.
16. An electronic article surveillance system for interacting with tag means including a resonant circuit, comprising:
a transmitter for generating a signal having a frequency at the resonant frequency of said resonant circuit;
a first antenna first to said transmitt for producing a field exposed to said tag means;
a second antenna for receiving signals generated by said tag means responsive to said field; and a receiver connected to said second antenna for detecting the signals generated by said tag means;
wherein at least said first antenna or said second antenna is formed of paired load, including a first lead for connection to an active load, and a second lead for connection to a passive load and mutually coupled with, but not conductively connected to said first lead.
a transmitter for generating a signal having a frequency at the resonant frequency of said resonant circuit;
a first antenna first to said transmitt for producing a field exposed to said tag means;
a second antenna for receiving signals generated by said tag means responsive to said field; and a receiver connected to said second antenna for detecting the signals generated by said tag means;
wherein at least said first antenna or said second antenna is formed of paired load, including a first lead for connection to an active load, and a second lead for connection to a passive load and mutually coupled with, but not conductively connected to said first lead.
17. The system of claim 16 wherein said active load is said transmitter, and said passive load modifies the response of said first antenna to said transmitter without resistively loading said transmitter.
18. The system of claim 16 wherein said active load is said receiver, and said passive load modifies the response of said receiver to said second antenna without resistively loading said receiver.
19. The system of claim 18 wherein said electronic article surveillance system includes means for reporting alarms, electrically connected to said receiver by the second lead of said second antenna.
20. The system of claim 16 wherein said paired leads are in the form of a twin-axial cable.
21. The system of claim 20 wherein the paired leads of said twin-axial cable are twisted about each other.
22. The system of claim 20 wherein both said first antenna and said second antenna are formed of a twin-axial cable including a first lead for connection to an active load, and a second lead for connection to a passive load and mutually coupled with, but not conductively connected to said first lead.
23. The system of claim 16 wherein said first antenna and said second antenna are configured as far-field cancelling loop antennas.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/292,361 | 1988-12-30 | ||
| US07/292,361 US5103235A (en) | 1988-12-30 | 1988-12-30 | Antenna structure for an electronic article surveillance system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2006749A1 true CA2006749A1 (en) | 1990-06-30 |
Family
ID=23124336
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002006749A Abandoned CA2006749A1 (en) | 1988-12-30 | 1989-12-28 | Antenna structure for an electronic article surveillance system |
Country Status (12)
| Country | Link |
|---|---|
| US (1) | US5103235A (en) |
| EP (1) | EP0407532B1 (en) |
| JP (1) | JPH03503110A (en) |
| AT (1) | ATE120042T1 (en) |
| AU (1) | AU620679B2 (en) |
| CA (1) | CA2006749A1 (en) |
| DE (1) | DE68921745T2 (en) |
| DK (1) | DK206790D0 (en) |
| ES (1) | ES2020690A6 (en) |
| FI (1) | FI97092C (en) |
| MX (1) | MX170375B (en) |
| WO (1) | WO1990007803A1 (en) |
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-
1988
- 1988-12-30 US US07/292,361 patent/US5103235A/en not_active Expired - Fee Related
-
1989
- 1989-12-11 MX MX018672A patent/MX170375B/en unknown
- 1989-12-26 AU AU48275/90A patent/AU620679B2/en not_active Ceased
- 1989-12-26 EP EP90901501A patent/EP0407532B1/en not_active Expired - Lifetime
- 1989-12-26 JP JP2501930A patent/JPH03503110A/en active Pending
- 1989-12-26 DE DE68921745T patent/DE68921745T2/en not_active Expired - Fee Related
- 1989-12-26 AT AT90901501T patent/ATE120042T1/en not_active IP Right Cessation
- 1989-12-26 WO PCT/US1989/005872 patent/WO1990007803A1/en active IP Right Grant
- 1989-12-27 ES ES8904373A patent/ES2020690A6/en not_active Expired - Lifetime
- 1989-12-28 CA CA002006749A patent/CA2006749A1/en not_active Abandoned
-
1990
- 1990-08-27 FI FI904232A patent/FI97092C/en not_active IP Right Cessation
- 1990-08-29 DK DK206790A patent/DK206790D0/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| DE68921745T2 (en) | 1995-08-10 |
| DE68921745D1 (en) | 1995-04-20 |
| FI97092C (en) | 1996-10-10 |
| DK206790A (en) | 1990-08-29 |
| MX170375B (en) | 1993-08-18 |
| ES2020690A6 (en) | 1991-09-01 |
| EP0407532A1 (en) | 1991-01-16 |
| AU4827590A (en) | 1990-08-01 |
| DK206790D0 (en) | 1990-08-29 |
| EP0407532B1 (en) | 1995-03-15 |
| WO1990007803A1 (en) | 1990-07-12 |
| ATE120042T1 (en) | 1995-04-15 |
| FI904232A0 (en) | 1990-08-27 |
| US5103235A (en) | 1992-04-07 |
| EP0407532A4 (en) | 1991-08-21 |
| JPH03503110A (en) | 1991-07-11 |
| AU620679B2 (en) | 1992-02-20 |
| FI97092B (en) | 1996-06-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |