CA1187155A - Combined radio and magnetic energy responsive surveillance marker and system - Google Patents
Combined radio and magnetic energy responsive surveillance marker and systemInfo
- Publication number
- CA1187155A CA1187155A CA000410639A CA410639A CA1187155A CA 1187155 A CA1187155 A CA 1187155A CA 000410639 A CA000410639 A CA 000410639A CA 410639 A CA410639 A CA 410639A CA 1187155 A CA1187155 A CA 1187155A
- Authority
- CA
- Canada
- Prior art keywords
- marker
- signal
- ribbon
- marker according
- impedance element
- 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.)
- Expired
Links
- 239000003550 marker Substances 0.000 title claims abstract description 43
- 230000005291 magnetic effect Effects 0.000 title claims abstract description 13
- 239000000463 material Substances 0.000 claims abstract description 16
- 230000035699 permeability Effects 0.000 claims abstract description 8
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims abstract 4
- 230000005672 electromagnetic field Effects 0.000 claims description 7
- 239000000696 magnetic material Substances 0.000 claims description 7
- 238000001514 detection method Methods 0.000 claims description 6
- 230000011664 signaling Effects 0.000 claims 2
- 230000001419 dependent effect Effects 0.000 claims 1
- 229910000889 permalloy Inorganic materials 0.000 abstract description 4
- 239000004065 semiconductor Substances 0.000 abstract description 3
- 239000004020 conductor Substances 0.000 abstract 1
- 238000009877 rendering Methods 0.000 abstract 1
- 238000010276 construction Methods 0.000 description 6
- 230000005294 ferromagnetic effect Effects 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 230000009849 deactivation Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- 241001464057 Electroma Species 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 230000005347 demagnetization Effects 0.000 description 1
- 230000005686 electrostatic field Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 230000005415 magnetization Effects 0.000 description 1
- NJPPVKZQTLUDBO-UHFFFAOYSA-N novaluron Chemical compound C1=C(Cl)C(OC(F)(F)C(OC(F)(F)F)F)=CC=C1NC(=O)NC(=O)C1=C(F)C=CC=C1F NJPPVKZQTLUDBO-UHFFFAOYSA-N 0.000 description 1
- 238000004382 potting Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000001702 transmitter Effects 0.000 description 1
- 230000001960 triggered effect Effects 0.000 description 1
- 229910000586 vicalloy Inorganic materials 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B13/00—Burglar, theft or intruder alarms
- G08B13/22—Electrical actuation
- G08B13/24—Electrical actuation by interference with electromagnetic field distribution
- G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
- G08B13/2405—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used
- G08B13/2422—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used using acoustic or microwave tags
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B13/00—Burglar, theft or intruder alarms
- G08B13/22—Electrical actuation
- G08B13/24—Electrical actuation by interference with electromagnetic field distribution
- G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
- G08B13/2428—Tag details
- G08B13/2437—Tag layered structure, processes for making layered tags
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B13/00—Burglar, theft or intruder alarms
- G08B13/22—Electrical actuation
- G08B13/24—Electrical actuation by interference with electromagnetic field distribution
- G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
- G08B13/2428—Tag details
- G08B13/2448—Tag with at least dual detection means, e.g. combined inductive and ferromagnetic tags, dual frequencies within a single technology, tampering detection or signalling means on the tag
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B13/00—Burglar, theft or intruder alarms
- G08B13/22—Electrical actuation
- G08B13/24—Electrical actuation by interference with electromagnetic field distribution
- G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
- G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
- G08B13/2468—Antenna in system and the related signal processing
- G08B13/2471—Antenna signal processing by receiver or emitter
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B13/00—Burglar, theft or intruder alarms
- G08B13/22—Electrical actuation
- G08B13/24—Electrical actuation by interference with electromagnetic field distribution
- G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
- G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
- G08B13/2468—Antenna in system and the related signal processing
- G08B13/2474—Antenna or antenna activator geometry, arrangement or layout
Abstract
ABSTRACT OF THE DISCLOSURE
A surveillance marker has a semiconductor connected between arms of a dipole antenna, one arm being of non-ferrous conductive material and the other of high permeability low coer-civity material such as permalloy. Higher coercivity magnetiz-able pieces are disposed adjacent the low coercivity arm, and all is sandwiched between paper or other insulating layers. The marker is detected by a combination of RF field and low frequency magnetic field generating and receiving units that energize a master alarm only when both units simultaneously detect the marker signals. Magnetizing the higher coercivity pieces suppresses a signal that would otherwise be reradiated by the marker from the high permeability arm thereby rendering the marker undetectable.
A surveillance marker has a semiconductor connected between arms of a dipole antenna, one arm being of non-ferrous conductive material and the other of high permeability low coer-civity material such as permalloy. Higher coercivity magnetiz-able pieces are disposed adjacent the low coercivity arm, and all is sandwiched between paper or other insulating layers. The marker is detected by a combination of RF field and low frequency magnetic field generating and receiving units that energize a master alarm only when both units simultaneously detect the marker signals. Magnetizing the higher coercivity pieces suppresses a signal that would otherwise be reradiated by the marker from the high permeability arm thereby rendering the marker undetectable.
Description
l BACKGROUND OF THE INVENTION
The present invention relates to markers for surveil-lance or control and to systems employing the same. Such markers and systems are now used extensively to prevent shoplifting and S similar unauthorized removal of articles from a controlled area.
~~ The known marker systems tend to fall into one or the ,other of two general categories; One category makes use of radio 1, - - . I
,jfrequency signals, usually in the microwave range, and is typified ,by the system disclosed in United States patent No. 4,063,229, issued on December 13, 1977, to John Welsh and Rlchard N. Vaughan for "Article Surveillance." There is described therein a system `wherein sensor-emitter labeis or tags containing a semiconductor diode or the like are applied to articles for the purpose of ,i . , surveillance. Said patent also describes the construction of special tags containing layers of ferrite material that can be magnetized or demagnetized by a suitable magnetic field for altering the operating characteristic of the tag and thereby ,deactivatiny the same.
,i An improved RF system, one that combines a microwave 'carrier signal wi-th a low frequency signal that is used to estab-llsh an electrostatic field, is described in United States paten-c No. 3,895,368, issued July 15, 1975, to Lloyd L. Gordon and Robert D. Williamson for "Surveillance System and Method Utill-zing Both Elect:rostatic and Electromagnetic Fields."
The present invention relates to markers for surveil-lance or control and to systems employing the same. Such markers and systems are now used extensively to prevent shoplifting and S similar unauthorized removal of articles from a controlled area.
~~ The known marker systems tend to fall into one or the ,other of two general categories; One category makes use of radio 1, - - . I
,jfrequency signals, usually in the microwave range, and is typified ,by the system disclosed in United States patent No. 4,063,229, issued on December 13, 1977, to John Welsh and Rlchard N. Vaughan for "Article Surveillance." There is described therein a system `wherein sensor-emitter labeis or tags containing a semiconductor diode or the like are applied to articles for the purpose of ,i . , surveillance. Said patent also describes the construction of special tags containing layers of ferrite material that can be magnetized or demagnetized by a suitable magnetic field for altering the operating characteristic of the tag and thereby ,deactivatiny the same.
,i An improved RF system, one that combines a microwave 'carrier signal wi-th a low frequency signal that is used to estab-llsh an electrostatic field, is described in United States paten-c No. 3,895,368, issued July 15, 1975, to Lloyd L. Gordon and Robert D. Williamson for "Surveillance System and Method Utill-zing Both Elect:rostatic and Electromagnetic Fields."
2~ l' The second category makes use of electromagnetic fields inductively coupled to the marker which contains a high perm~
eability low coercivity material having the ability of producing detecta~le harmonic frequencies when i,mmersed in an al~ternating ,,magnetic field of sufficient intensity. A refined system falling !
linto this second category is described in e~p~ ~q United States ¦
I!
,, 1 ~1 ~
patent No. 4,309,697 which issued on January 5, l982 to Jon N. Weaver. That patent also con-tains a good review of the prior work in the area of this category. The above-mentioned patents are assigned to the same assignee as the present inven-tion and application.
One of -the patents mentioned in United States Patent 4,309,697 is that of Bakeman, Jr. et al., United States patent No. 3,983,552, issued September 28, 1976. There is disclosed -therein a pilferage deterrent marker of laminated construc-tion containing an easily magnetized layer of permalloy and a con-trol layer of difficult to magne-tiæe vicalloy or remendur.
Such marker, when the control layer is magnetlzed, ls detec-ted by a circuit responding to -the amplitude and phase of the re-ceived second harmonic signal. When the control layer is de-magnetized -the marker is permitted -to pass undetected.
A reverse deactivation arrangement wherein the marker is detected only when demagnetized as described in United S-tates pa-ten-t No. 3,820,104, issued on June 25, 1974, -to Edward R.
Fearon for "Methods and System for Detecting an Object Wi-thin ~ Magnetic Field Interroga-tion Zone." The abstract in said patent describes the marker as including a first elongated ferromagnetic element for being secured to the object. The first ferromagnetic element has a relatively low coercivi-ty and is operable -to genera-te a detectable signal containing harmonics of the fundamen-tal frequency when placed in the in-terrogation zone. The marker further includes a second ferro-magnetic elemen-t disposed adjacent to the first element and having a coercivity greater than the firs-t element. Deac-tiva-tion structure is provided to selectively magnetize the second ferromagnetic element -to impose a plurali-ty of pairs of alter-nate magnetic poles on the first element in order to deac-tivate , ~ ,, the marker. The deactivated marker does not generate a detec-table signal containing the desired harmonics when the object passes through the interrogation zone.
An analysis of the development history of bo-th cate-gories of marker systems reveals a continuing effort to improve sensitivity while reducing Ealse alarms due to triggering of the detection equipment by components other than the markers for which the system was designed. Early RF systems were trig-gered by transistor radios, an obvious potential problem be-cause of the diodes and other non-linear devices normally in-corporated therein, and by the less obvious such as a baby carriage with a rusty oxidic junction therein. Comparable problems have also confronted the magnetic systems.
SUMMAR~ OF THE INVENTION
~ ith the foregoing in mind, it is the aim of the present invention to provide a marker and system with greater reliability and increased versatility. In effec-t, the present invention makes use of the best of both worlds.
In accordance with one aspect of the present inven-tion, there is provided a marker comprising in combinationa non-linear impedance element connected to means including at least a body of high permeability and low coercivity mater-ial, said body being dimensioned and configured to reradiate a separately detectable signal when immersed in a low frequency electromagnetic field, said non-linear impedance element with said means being responsive to the energy in a field of radio waves when immersed therein for reradiating a portion of said energy as a detectable and distinguishable radio signal, said element, means and body being united in a single structure.
~'' 1 1~ In accordance with another aspect of the present inven-tion there is provided a system including the foregoing marker which system is characterized by an RF transmitter and receiver connected to electromagnetic eneryy radiating and receiving means lfor establishing in a surveillance zone a field of radio waves and for detecting any radio signa1 in said zone from said marker, an electroma.gnetic low frequency transmi-tter and receiver con-nected to magnetic field generating and receiving means for ~establishing in said zone an electromagnetic field of low re-quency and for detecting said separately detectable signal from said mar]ier whenever said detectable signal is present in said zone, and means for providing a signal responsive to simultaneous detec-tion in said zone of said radio signal and said separately detectable signal from said marker.
'I
BRIEF DESCRIPTION OF THE DRAWINGS
~¦ The invention will be better understood after reading the following detailed description of the presently preferred 'embodiments thereof with reference to the appended drawings in 'which: l , I
i' Figure l is a schematic block diagram of a system im-ljplementing -the present invention;
Figure 2 is a pérspective view of a doorway provided iwith surveillance equipment as illustrated schematically in Fig.
~I Figure 3 is a plan view, with the covering layer removed, of a marker constructed in accordance with the present invention;
¦ Figure 4 is a side view of the marker of Fig. 3 as seen from the right side;
Figure 5 is a transverse sectional view taken along the li~e 5~5 in Fig. 3;
lS~i 1 Figure 6 is a transverse sectional view taken along the line 6-6 in Fig. 3;
Figure 7 is a transverse sectional view -taken along the line 7-7 in Fig. 3;
Figure 8 is a transverse sectional view -taken along the line 8-8 in Fig. 3;
Figure 9 is an enlarged fragmentary perspective view of a portion of the marker of ~ig. 3 illustrating a detail thereof;
l! Figure 10 is a block diagram of a deactivating device in accordance with the subject invention;
Figure 11 is a view similar to Fig. 3 but showing a modification thereof; and ' ,. I
Figure 12 is a transverse sectional view taken along the line 12-12 in Fig. 11.
lS The same reference numerals are used throughout the drawings to designate the same or similar parts.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
;, Referring now to Fig. 1 there is shown therein designa-2Q -ted generally by the reference numeral 10 an RF transmitter and receiver connected to foil elements 11 and 12 and microwave antenna elements 13, 14, 15 and 16 mounted in two pedestal struc-. . ~
tures shown diagramatically by-the phantom boxes 17 and 18.
Merely by way o~ example, the transmitter and receiver 10 may be implemented by the circuit described with reference to Fig. 4 of said Gordon and Williamson patent identified above.
The circuit of Fig. 1 also includes an electromagnetic low frequency transmitter and receiver 19 connected to a series of windings 20, 21, 22 and 23 mounted in two panels 2~ and 25.
The construction of the transmitter and receiver lg with windings _ 5 _ !
1 l20 through 23 can be as disclosed in the Weaver copending applica-Ition identified above.
I secause the details in construction of the transrnitter receiver devices lO and l9 form no part of the present invention, S and because they are fully disclosed in the referenced patent and application, no further discussion is deemed necessary herein.
Reference to said documents should be had if further description . . ;~
is desired.
As described in the referenced documents, a signal is provided in each system from a detection circu1t to a respective alarm circuit. In accordance with the present invention the connection within the RF transmitter and receiver lO between its detection circuit and independent alarm (not shown) is tapped and brought out as an output over lead 26 to one input of an AND gate 27. Similarly, the connection within electromagnetic transmitter , and receiver l9 between its detection circuit and independent alarm (not shown) is tapped and brought out as an output over lead 28 to a second input to the AND gate 27. The output from ~ND gate 27 is coupled over lead 29 to a master alarm 30O
When operating, the circuit of Fig. l requires both devices lO and l9 to provide a positive signal to AND gate 27 in order that the latter activate the master alarm 30. If either , one of the signals over leads-26 and 28 from the respective devices lO and l9 is absentt the master alarm 30 will remain ~5 inactive. However, if the respective devices lO and l9 are provided with their independent alarms (not shown) then each respective alarm will be independently actuated when the asso-ciated receiver detects a signal from a marker of the type with which it has been designed to operate.
.
1 ¦ Re~erring to Fig. 2, a typical installation is shown of the system described with reference to Fig. 1. Thus the pedestals 17 and 18 will house the elements 10 to 16, inclusive while the panels 24 and 25 will house the coils 20 -to 23, inclusive. The S component 19 may be housed in one of the pedestals 17 or 18. The AND gate 27 and master alarm 30 may be suitably located either in the pedestals or externally thereto;
Re~erence now should be hàd to Figs. 3 to 9 wherein there is illustrated a marker incorporating the present invention.
As seen therein the marker is in the form of a tag structure 31 having a paper or other insulating substrate 32 on which is mounted, by bonding, two rectangular strips o~ magnetic material 33 and 34 with a gap 35 therebetween, and over which is placed one generally J-shaped conductive antenna element 36 which with a complemental antenna element 37 constitutes a dipole antenna.
The elements 36 and 37 are provided with respective wings 33 and 39 facing each other with a small gap 40 therebetween across which is connected a diode consisting o~ a semiconductor chip 41 and a lead 42, best seen in Fig. 9. The chip 41 is bonded in known manner to the wing 33 while the lead 42 is connected in ~known manner to the wing 39. The diode and its lead may be encapsulated in a suitable epoxy or other potting medium not shown. Finally, a cover layer of paper or other insulating material is applied at 43 in order to protect and enclose the entire structure. The cover layer 43 has been omitted from Fig.
;3 in order to reveal the details of the interior of the tag 31.
Moreover, the sec-tional views shown in FigsO 5 to ~ have been greatly enlarged and exaggerated for clarity of illustrationO
The ac-tual layers of material r particularly the metallic elementsl, will be extremely th3n neas~ring only a féw mils in thic~ness.
!
lt~'7155 In a presently preferred embodiment of tay 31 the antenna element 37 may be formed from aluminum foil while the antenna element 36 may be formed from a high permeability and low coercivity material such as that known as "permalloy". The S elements 33 and 34 should consist of pieces of magnetic material of higher coercivlty than the material in element 36. Carbon steel has been found satisfactor~ for this purpose. The wire 42 may be of aluminum of one mil diameter.
It has been found that materials such as permalloy have sufficient conductivity that they can function as antenna elements for the RF energy involved in the RF systems while at the same time can produce the necessary harmonics when exposed to the low frequenc~ electromagnetic field for operating in that type of system. However, in the present structure the harmonics for operation of the low frequency system are produced only when the magnetic pieces 33 and 34 remain demagneti~ed. If pieces 33 and 34 are magneti7ed by exposing them to a magnetizing field from a suitable source such as the deactivating magnetizing field generator and coil assembly 50 shown in Fig. 10, tag 31 will fail to activate the transmitter receiver 19 of Fig~ 1 to produce an alarm signal. Hence, neither the local alarm signal (when present) nor the master alarm 30 will be actuated.
"
Figs. 11 and 12 illustrate a modification of -the tag construction wherein the antenna elements 36 and 37 are now 2S located both immediately adjacent the substrate 32 while the pieces of higher coercivity magnetic material 52 and 53 are located on top of antenna element 36, as shown. A notch 53 may be cut in the edge of piece 52 in order -to clear the semicon~
ductor chip 41. The advantage of the embodiment of Figs. 11 and ;12 over that of Figs. 3 through ~ is that it provides a somewhat 7~L55 1 ,'smoother surface to which the covering insulating layer ~3 may be applied. This embodiment may also be slightly easier to fabri-cate then that shown in E'igs. 3 to 8.
Some of the advantages flowing from the subject in-S vention should now be evident. Providing a combined tag that xequires both the diode characteristic as well as the high permeability magnetic characterlstic to occur simultaneously before an alarm is actuated~insures to a greater degree against false actuation. The tags can be readily activated or deacti-vated by magnetization or demagnetization, as desired. Thus, the subject tags can be used interchangeably in expendable and nonexpendable operations. fn fact, for lower levels of security it is possible to use the same tags as described herein with either the RF system or the low frequency electromagnetic system operating independently.
Having described the presently preferred embodiments of the subject invention, it should be apparent to those skilled in the subject art that various changes in construction can be incorporated without departing from the true spirit of the in-vention as defined in the appended claims.
. .
,'~
..
_ g _
eability low coercivity material having the ability of producing detecta~le harmonic frequencies when i,mmersed in an al~ternating ,,magnetic field of sufficient intensity. A refined system falling !
linto this second category is described in e~p~ ~q United States ¦
I!
,, 1 ~1 ~
patent No. 4,309,697 which issued on January 5, l982 to Jon N. Weaver. That patent also con-tains a good review of the prior work in the area of this category. The above-mentioned patents are assigned to the same assignee as the present inven-tion and application.
One of -the patents mentioned in United States Patent 4,309,697 is that of Bakeman, Jr. et al., United States patent No. 3,983,552, issued September 28, 1976. There is disclosed -therein a pilferage deterrent marker of laminated construc-tion containing an easily magnetized layer of permalloy and a con-trol layer of difficult to magne-tiæe vicalloy or remendur.
Such marker, when the control layer is magnetlzed, ls detec-ted by a circuit responding to -the amplitude and phase of the re-ceived second harmonic signal. When the control layer is de-magnetized -the marker is permitted -to pass undetected.
A reverse deactivation arrangement wherein the marker is detected only when demagnetized as described in United S-tates pa-ten-t No. 3,820,104, issued on June 25, 1974, -to Edward R.
Fearon for "Methods and System for Detecting an Object Wi-thin ~ Magnetic Field Interroga-tion Zone." The abstract in said patent describes the marker as including a first elongated ferromagnetic element for being secured to the object. The first ferromagnetic element has a relatively low coercivi-ty and is operable -to genera-te a detectable signal containing harmonics of the fundamen-tal frequency when placed in the in-terrogation zone. The marker further includes a second ferro-magnetic elemen-t disposed adjacent to the first element and having a coercivity greater than the firs-t element. Deac-tiva-tion structure is provided to selectively magnetize the second ferromagnetic element -to impose a plurali-ty of pairs of alter-nate magnetic poles on the first element in order to deac-tivate , ~ ,, the marker. The deactivated marker does not generate a detec-table signal containing the desired harmonics when the object passes through the interrogation zone.
An analysis of the development history of bo-th cate-gories of marker systems reveals a continuing effort to improve sensitivity while reducing Ealse alarms due to triggering of the detection equipment by components other than the markers for which the system was designed. Early RF systems were trig-gered by transistor radios, an obvious potential problem be-cause of the diodes and other non-linear devices normally in-corporated therein, and by the less obvious such as a baby carriage with a rusty oxidic junction therein. Comparable problems have also confronted the magnetic systems.
SUMMAR~ OF THE INVENTION
~ ith the foregoing in mind, it is the aim of the present invention to provide a marker and system with greater reliability and increased versatility. In effec-t, the present invention makes use of the best of both worlds.
In accordance with one aspect of the present inven-tion, there is provided a marker comprising in combinationa non-linear impedance element connected to means including at least a body of high permeability and low coercivity mater-ial, said body being dimensioned and configured to reradiate a separately detectable signal when immersed in a low frequency electromagnetic field, said non-linear impedance element with said means being responsive to the energy in a field of radio waves when immersed therein for reradiating a portion of said energy as a detectable and distinguishable radio signal, said element, means and body being united in a single structure.
~'' 1 1~ In accordance with another aspect of the present inven-tion there is provided a system including the foregoing marker which system is characterized by an RF transmitter and receiver connected to electromagnetic eneryy radiating and receiving means lfor establishing in a surveillance zone a field of radio waves and for detecting any radio signa1 in said zone from said marker, an electroma.gnetic low frequency transmi-tter and receiver con-nected to magnetic field generating and receiving means for ~establishing in said zone an electromagnetic field of low re-quency and for detecting said separately detectable signal from said mar]ier whenever said detectable signal is present in said zone, and means for providing a signal responsive to simultaneous detec-tion in said zone of said radio signal and said separately detectable signal from said marker.
'I
BRIEF DESCRIPTION OF THE DRAWINGS
~¦ The invention will be better understood after reading the following detailed description of the presently preferred 'embodiments thereof with reference to the appended drawings in 'which: l , I
i' Figure l is a schematic block diagram of a system im-ljplementing -the present invention;
Figure 2 is a pérspective view of a doorway provided iwith surveillance equipment as illustrated schematically in Fig.
~I Figure 3 is a plan view, with the covering layer removed, of a marker constructed in accordance with the present invention;
¦ Figure 4 is a side view of the marker of Fig. 3 as seen from the right side;
Figure 5 is a transverse sectional view taken along the li~e 5~5 in Fig. 3;
lS~i 1 Figure 6 is a transverse sectional view taken along the line 6-6 in Fig. 3;
Figure 7 is a transverse sectional view -taken along the line 7-7 in Fig. 3;
Figure 8 is a transverse sectional view -taken along the line 8-8 in Fig. 3;
Figure 9 is an enlarged fragmentary perspective view of a portion of the marker of ~ig. 3 illustrating a detail thereof;
l! Figure 10 is a block diagram of a deactivating device in accordance with the subject invention;
Figure 11 is a view similar to Fig. 3 but showing a modification thereof; and ' ,. I
Figure 12 is a transverse sectional view taken along the line 12-12 in Fig. 11.
lS The same reference numerals are used throughout the drawings to designate the same or similar parts.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
;, Referring now to Fig. 1 there is shown therein designa-2Q -ted generally by the reference numeral 10 an RF transmitter and receiver connected to foil elements 11 and 12 and microwave antenna elements 13, 14, 15 and 16 mounted in two pedestal struc-. . ~
tures shown diagramatically by-the phantom boxes 17 and 18.
Merely by way o~ example, the transmitter and receiver 10 may be implemented by the circuit described with reference to Fig. 4 of said Gordon and Williamson patent identified above.
The circuit of Fig. 1 also includes an electromagnetic low frequency transmitter and receiver 19 connected to a series of windings 20, 21, 22 and 23 mounted in two panels 2~ and 25.
The construction of the transmitter and receiver lg with windings _ 5 _ !
1 l20 through 23 can be as disclosed in the Weaver copending applica-Ition identified above.
I secause the details in construction of the transrnitter receiver devices lO and l9 form no part of the present invention, S and because they are fully disclosed in the referenced patent and application, no further discussion is deemed necessary herein.
Reference to said documents should be had if further description . . ;~
is desired.
As described in the referenced documents, a signal is provided in each system from a detection circu1t to a respective alarm circuit. In accordance with the present invention the connection within the RF transmitter and receiver lO between its detection circuit and independent alarm (not shown) is tapped and brought out as an output over lead 26 to one input of an AND gate 27. Similarly, the connection within electromagnetic transmitter , and receiver l9 between its detection circuit and independent alarm (not shown) is tapped and brought out as an output over lead 28 to a second input to the AND gate 27. The output from ~ND gate 27 is coupled over lead 29 to a master alarm 30O
When operating, the circuit of Fig. l requires both devices lO and l9 to provide a positive signal to AND gate 27 in order that the latter activate the master alarm 30. If either , one of the signals over leads-26 and 28 from the respective devices lO and l9 is absentt the master alarm 30 will remain ~5 inactive. However, if the respective devices lO and l9 are provided with their independent alarms (not shown) then each respective alarm will be independently actuated when the asso-ciated receiver detects a signal from a marker of the type with which it has been designed to operate.
.
1 ¦ Re~erring to Fig. 2, a typical installation is shown of the system described with reference to Fig. 1. Thus the pedestals 17 and 18 will house the elements 10 to 16, inclusive while the panels 24 and 25 will house the coils 20 -to 23, inclusive. The S component 19 may be housed in one of the pedestals 17 or 18. The AND gate 27 and master alarm 30 may be suitably located either in the pedestals or externally thereto;
Re~erence now should be hàd to Figs. 3 to 9 wherein there is illustrated a marker incorporating the present invention.
As seen therein the marker is in the form of a tag structure 31 having a paper or other insulating substrate 32 on which is mounted, by bonding, two rectangular strips o~ magnetic material 33 and 34 with a gap 35 therebetween, and over which is placed one generally J-shaped conductive antenna element 36 which with a complemental antenna element 37 constitutes a dipole antenna.
The elements 36 and 37 are provided with respective wings 33 and 39 facing each other with a small gap 40 therebetween across which is connected a diode consisting o~ a semiconductor chip 41 and a lead 42, best seen in Fig. 9. The chip 41 is bonded in known manner to the wing 33 while the lead 42 is connected in ~known manner to the wing 39. The diode and its lead may be encapsulated in a suitable epoxy or other potting medium not shown. Finally, a cover layer of paper or other insulating material is applied at 43 in order to protect and enclose the entire structure. The cover layer 43 has been omitted from Fig.
;3 in order to reveal the details of the interior of the tag 31.
Moreover, the sec-tional views shown in FigsO 5 to ~ have been greatly enlarged and exaggerated for clarity of illustrationO
The ac-tual layers of material r particularly the metallic elementsl, will be extremely th3n neas~ring only a féw mils in thic~ness.
!
lt~'7155 In a presently preferred embodiment of tay 31 the antenna element 37 may be formed from aluminum foil while the antenna element 36 may be formed from a high permeability and low coercivity material such as that known as "permalloy". The S elements 33 and 34 should consist of pieces of magnetic material of higher coercivlty than the material in element 36. Carbon steel has been found satisfactor~ for this purpose. The wire 42 may be of aluminum of one mil diameter.
It has been found that materials such as permalloy have sufficient conductivity that they can function as antenna elements for the RF energy involved in the RF systems while at the same time can produce the necessary harmonics when exposed to the low frequenc~ electromagnetic field for operating in that type of system. However, in the present structure the harmonics for operation of the low frequency system are produced only when the magnetic pieces 33 and 34 remain demagneti~ed. If pieces 33 and 34 are magneti7ed by exposing them to a magnetizing field from a suitable source such as the deactivating magnetizing field generator and coil assembly 50 shown in Fig. 10, tag 31 will fail to activate the transmitter receiver 19 of Fig~ 1 to produce an alarm signal. Hence, neither the local alarm signal (when present) nor the master alarm 30 will be actuated.
"
Figs. 11 and 12 illustrate a modification of -the tag construction wherein the antenna elements 36 and 37 are now 2S located both immediately adjacent the substrate 32 while the pieces of higher coercivity magnetic material 52 and 53 are located on top of antenna element 36, as shown. A notch 53 may be cut in the edge of piece 52 in order -to clear the semicon~
ductor chip 41. The advantage of the embodiment of Figs. 11 and ;12 over that of Figs. 3 through ~ is that it provides a somewhat 7~L55 1 ,'smoother surface to which the covering insulating layer ~3 may be applied. This embodiment may also be slightly easier to fabri-cate then that shown in E'igs. 3 to 8.
Some of the advantages flowing from the subject in-S vention should now be evident. Providing a combined tag that xequires both the diode characteristic as well as the high permeability magnetic characterlstic to occur simultaneously before an alarm is actuated~insures to a greater degree against false actuation. The tags can be readily activated or deacti-vated by magnetization or demagnetization, as desired. Thus, the subject tags can be used interchangeably in expendable and nonexpendable operations. fn fact, for lower levels of security it is possible to use the same tags as described herein with either the RF system or the low frequency electromagnetic system operating independently.
Having described the presently preferred embodiments of the subject invention, it should be apparent to those skilled in the subject art that various changes in construction can be incorporated without departing from the true spirit of the in-vention as defined in the appended claims.
. .
,'~
..
_ g _
Claims (14)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A marker comprising in combination a non-linear impedance element connected to means including at least a body of high permeability and low coercivity material, said body being dimensioned and configured to reradiate a separately detectable signal when immersed in a low frequency electromagnetic field, said non-linear impedance element with said means being respon-sive to the energy in a field of radio waves when immersed therein for reradiating a portion of said energy as a detectable and distinguishable radio signal, said element, means and body being united in a single structure.
2. A marker according to claim 1, characterized in that said means includes at least one conductive antenna element connected to said impedance element.
3. A marker according to claim 1, characterized in that said body comprises a ribbon-like structure of said material shaped and dimensioned to function both as an antenna for radio frequency waves and as a harmonic generator for low frequency magnetic waves.
4. A marker according to claim 2, characterized in that said one conductive antenna element consists of a ribbon-like structure of non-ferrous material that cooperates with said body, also ribbon-like, as a dipole antenna for said impedance element.
5. A marker according to claim 1, characterized in that pieces of higher coercivity magnetic material are disposed adjacent said body of high permeability material for altering in a detec-table and distinguishable manner the signal reradiating character of said body when said pieces of magnetic material are magnetized.
6. A marker according to claim 5, characterized in that said means includes at least one conductive antenna element connected to said impedance element.
7. A marker according to claim 6, characterized in that said one conductive antenna element consists of a ribbon-like structure of non-ferrous material that cooperates with said body, also ribbon-like, as a dipole antenna for said impedance element.
8. A system including a marker according to claim 1, characterized by an RF transmitter and receiver connected to elec-tromagnetic energy radiating and receiving means for establishing in a surveillance zone a field of radio waves and for detecting any radio signal in said zone from said marker, an electromagnetic low frequency transmitter and receiver connected to magnetic field generating and receiving means for establishing in said zone an electromagnetic field of low frequency and for detecting said separately detectable signal from said marker whenever said detectable signal is present in said zone, and means for providing a signal responsive to simultaneous detection in said zone of said radio signal and said separately detectable signal from said marker.
9. A system according to claim 8, further characterized in that at least one of said receivers is provided with an in-dependent signalling device for providing an indication whenever such receiver detects the signal that it was constructed to receive.
10. A marker according to claim 8, characterized in that pieces of higher coercivity magnetic material are disposed adjacent said body of high permeability material for altering in a detectable and distinguishable manner the signal reradiating character of said body when said pieces of magnetic material are magnetized.
11. A marker according to claim 8, characterized in that said means includes at least one conductive antenna element connected to said impedance element.
12. A marker according to claim 11, characterized in that said one conductive antenna element consists of a ribbon-like structure of non-ferrous material that cooperates with said body, also ribbon-like, as a dipole antenna for said impedance element.
13. A marker according to claim 11, characterized in that said body comprises a ribbon-like structure of said material shaped and dimensioned to function both as an antenna for radio frequency waves and as a harmonic generator for low frequency magnetic waves.
14. A system according to claim 13, further characterized in that at least one of said receivers is provided with an independent signalling device for providing an indication whenever such receiver detects the signal that it was constructed to receive.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/299,304 US4413254A (en) | 1981-09-04 | 1981-09-04 | Combined radio and magnetic energy responsive surveillance marker and system |
| US299,304 | 1981-09-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1187155A true CA1187155A (en) | 1985-05-14 |
Family
ID=23154224
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000410639A Expired CA1187155A (en) | 1981-09-04 | 1982-09-02 | Combined radio and magnetic energy responsive surveillance marker and system |
Country Status (14)
| Country | Link |
|---|---|
| US (1) | US4413254A (en) |
| JP (1) | JPS5853782A (en) |
| AR (1) | AR229279A1 (en) |
| BE (1) | BE894301A (en) |
| BR (1) | BR8205178A (en) |
| CA (1) | CA1187155A (en) |
| DE (1) | DE3231595A1 (en) |
| ES (1) | ES515482A0 (en) |
| FR (1) | FR2512557B1 (en) |
| GB (1) | GB2110506B (en) |
| IT (1) | IT1192503B (en) |
| MX (1) | MX152708A (en) |
| NL (1) | NL8203454A (en) |
| SE (1) | SE456703B (en) |
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-
1981
- 1981-09-04 US US06/299,304 patent/US4413254A/en not_active Expired - Fee Related
-
1982
- 1982-08-25 DE DE19823231595 patent/DE3231595A1/en active Granted
- 1982-08-31 GB GB08224841A patent/GB2110506B/en not_active Expired
- 1982-09-02 CA CA000410639A patent/CA1187155A/en not_active Expired
- 1982-09-03 BE BE0/208950A patent/BE894301A/en not_active IP Right Cessation
- 1982-09-03 IT IT09506/82A patent/IT1192503B/en active
- 1982-09-03 NL NL8203454A patent/NL8203454A/en not_active Application Discontinuation
- 1982-09-03 JP JP57152819A patent/JPS5853782A/en active Pending
- 1982-09-03 MX MX194289A patent/MX152708A/en unknown
- 1982-09-03 BR BR8205178A patent/BR8205178A/en unknown
- 1982-09-03 ES ES515482A patent/ES515482A0/en active Granted
- 1982-09-03 SE SE8205025A patent/SE456703B/en not_active IP Right Cessation
- 1982-09-03 FR FR8215069A patent/FR2512557B1/en not_active Expired
- 1982-09-03 AR AR290537A patent/AR229279A1/en active
Also Published As
| Publication number | Publication date |
|---|---|
| GB2110506A (en) | 1983-06-15 |
| MX152708A (en) | 1985-10-18 |
| BR8205178A (en) | 1983-08-16 |
| US4413254A (en) | 1983-11-01 |
| GB2110506B (en) | 1986-05-14 |
| SE8205025L (en) | 1983-03-05 |
| DE3231595A1 (en) | 1983-03-17 |
| ES8401653A1 (en) | 1983-12-16 |
| BE894301A (en) | 1983-01-03 |
| FR2512557B1 (en) | 1985-11-15 |
| AR229279A1 (en) | 1983-07-15 |
| NL8203454A (en) | 1983-04-05 |
| SE456703B (en) | 1988-10-24 |
| FR2512557A1 (en) | 1983-03-11 |
| DE3231595C2 (en) | 1992-02-06 |
| IT1192503B (en) | 1988-04-20 |
| ES515482A0 (en) | 1983-12-16 |
| JPS5853782A (en) | 1983-03-30 |
| IT8209506A0 (en) | 1982-09-03 |
| SE8205025D0 (en) | 1982-09-03 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |