MXPA00003875A - Anti-theft detecting system - Google Patents

Abstract

An anti-theft detection system. A target (11) comprising a frequency multiplier is affixed to goods in a retail store. A low power radio frequency source (21) is placed near the exits to the retail store, and the target (11) emits harmonics of the frequency transmitted by the radio frequency source (21) when located near the radio frequency source (21). A detector (37) also located near the exits to the retail store detects the harmonics and commands an alarm (43), thereby allowing for an apprehension of shoplifters.

Description

BACKGROUND OF THE INVENTION The present invention is generally concerned with anti-theft detection systems and more in particular with an electronic anti-theft security system using a frequency multiplier. Electronic security systems are known for the detection of unauthorized removal of products from warehouses and other facilities. These detection systems 10 are beneficial in that the presence of such detection systems prevents theft in stores and allows the apprehension of thieves from shops not detained. These detection systems are found in a variety of locations, including retail stores, particularly those that sell clothing, books, videotapes, and the like. The detection system often comprises a magnetic strip attached to a good together with a detector that verifies magnetic fields to determine when the magnetic strip passes through an area 20 < next to the detector. The detection system also sometimes includes plastic labels attached to clothing and the like, also together with a magnetic field detector. The plastic labels contain a resonant circuit that, when passed through a magnetic field, resonates and alters the magnetic field of a magnetic field.

REF .: 119740 detectable way. Detection systems of this type have been installed in a wide variety of locations and are widely used. Those detection systems are not without problems, however. The magnetic strip or label containing a resonant circuit, both of which can generally be described as a target, is generally joined (and sometimes withdrawn) by a retailer in a labor intensive operation. The objectives are also often too large to be easily accommodated by many retail items or too expensive to justify use with certain items, particularly those found in food stores and retail medications. These detection systems also do not allow the placement of assets near the detectors, since such assets would activate the detection alarm. This decreases the amount of floor space available for product display. These detection systems are also adversely affected by the presence of nearby metal objects, such as by noise generators, such as laser product scanners and the like. Additionally, there is evidence that some detection systems affect the operations of pacemakers and therefore possibly pose health risks for individuals who require the use of a pacemaker.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides an anti-theft detection system using small frequency multipliers. A low-power radio frequency source that transmits radio signals to a first frequency is placed near an outlet of a retail establishment. Items for sale in the retail establishment are marked with a miniature frequency multiplier. When the frequency multiplier passes the radio frequency source, a detector detects the harmonics of the first frequency emitted by the frequency multiplier and causes an alarm to be issued.

DESCRIPTION OF THE DRAWINGS Many of the concurrent features of this invention will be more readily appreciated as it is better understood by reference to the following detailed description considered in connection with the accompanying drawings in which like reference symbols designate like parts of the same. beginning to end Figure 1 is a schematic view of an object of the present invention; Figure 2 is a block diagram of an output gate of the present invention; Figure 3 is a block diagram of a deactivation system of the present invention; Figure 4 is a plan view of a product * with an objective of the present invention fixed to an inviolable seal 5 and Figure 5 is a plan view of a sale label carrying an objective of the present invention.

DETAILED DESCRIPTION OF THE INVENTION 10 Figure 1 illustrates a schematic view of a preferred objective of the present invention. The objective is a harmonic generator and in the preferred embodiment the objective comprises a diode 11. An input antenna 13 is connected to the p-junction of the diode. An output antenna 15 is attached to the n junction of the node. The first and second antennas are conductive lines of hair width. Diodes are of course non-linear devices. Therefore, when the diode is fed with an input signal at a first frequency the diode generates an output signal with a component at the same frequency as the input signal, together with components at multiples of the frequency of the input signal. Thus, the diode operates as a frequency multiplier, which is a type of harmonic generator. As with most multipliers of At the frequency, the diode generates multiple harmonics of the input signal, the higher frequency harmonics are generated to a smaller extent. Thus, when the diode is subjected to a radio frequency input signal at a frequency fi, the diode will generate an output signal with components at frequencies fi, f2, f3, ... fN. The frequency f2 is twice the frequency fi, the frequency f3 is three times the frequency fi and the frequency fN is N times the frequency fi. In general, the power loss at a frequency N times the input frequency is 1 / N for a multiplier diode frequency. Accordingly, the signal strength of the signal component at the frequency f2 will be significantly greater than the signal strength at the frequency f .... fN for a diode frequency multiplier. 15 Any diversity of types of diodes can be used as a frequency multiplier, which include tunnel diodes, stage recovery diodes ^ (SRD) and SNAP diodes. A SNAP diode is particularly suitable for use in the embedded target. A SNAP diode accumulates current for a short part of each input cycle before suddenly releasing this accumulated current. A transistor or other non-linear device can also be used as a frequency multiplier and can be used in place of the diode in the embedded target. Without However, transistors are more expensive than diodes to be manufactured. Additionally, the power loss of the transistor at a frequency f "is 1 / N :, ignoring the current gain of the transistor, while the power loss of the diode is only 1 / N. Accordingly, the use of a diode as the non-linear circuit element is more economical to manufacture and produces signal harmonics with a larger amplitude. An observer that measures the output signal generated by the embedded target at an input frequency fj. you will see an output signal with frequency components at fx and frequencies f2, f3 ... fN. However, if the embedded target moves with respect to the observer, then the observer would see an output signal with components af? D, F2D,?,,,,, Where f? D, f2D, f3D, ... ÍND they are displaced frequencies of Doppler fi, f2, ... fN. Thus, an observer would be able to determine whether a non-mobile target is within an area subjected to a radio frequency input fi by receiving and measuring signals at the frequency f2. The observer would also be able to determine whether a mobile target is within the area subjected to the RF input frequency by receiving and measuring signals at the shifted frequency of Doppler f2D. Figure 2 illustrates a diagram of blocks of a preferred output gate to generate and transmit an RF signal at the frequency fi and to measure and process the received RF signals. A low power radio frequency source 21 produces electromagnetic energy at a first frequency fi. fx is preferably in the gigahertz range to provide an appropriate resolution of signal harmonics and displaced Doppler signals. Low-power radio frequency sources of this type for radar and other applications are known in the art. These radio frequency sources generally emit signals of a few milli atts, which is of sufficiently low power that health concerns are not implicated. The signal generated by the RF source is passed through a bandpass filter 23. The purpose of bandpass filters is to eliminate the components of the signal generated by the RF source at frequencies other than fi and particularly to reduce the signal strength of any fi harmonics. Then, the filtered signal is passed through a duplexer 31 to an antenna 33 for transmission. The antenna radiates the RF signal over an appropriate area, such as an antenna surrounding an exit to an installation. The antenna is of a type suitable for transmitting and receiving radio signals in the gigahertz range and does not have a particular lobe configuration. However, the antenna can be a directional antenna or a specially designed antenna with particular lobe configurations. The antenna also receives RF signals, although separate input and output antennas can be used to reduce crosstalk and other interference problems. The antenna receives signals at frequency t \ due to reflections from the output signal and antenna signals from other nearby output gates. The antenna also receives parasitic harmonics not completely filtered by the bandpass filters of other output systems, as well as other parasitic electromagnetic signals present in the environment. More importantly, the antenna receives signals at frequencies fi, f2, f3, ... fN from non-mobile targets in the reception area of the radio source. Additionally, the input antenna receives signals that are shifted Doppler signals at frequencies f? D, f2D, f3D, ... f ^ of moving targets within the reception area. To the extent that the radio frequency source emits harmonics of the RF signal at the frequency flf the input antenna also receives reflected signals non-mobile objects at frequencies f2, f3, ... fN and reflected signals from moving objects, such as people , at frequencies f2D, f3D, ... ÍMD. With frequency fi in the range of 1 gigahertz and a mobile target at one meter per second, which is assumed to be the normal speed at which the average person walks, the Doppler shift is in the range of three to three hundred hertz, depending on the angle between the propagation of the signal and the movement of the objective. The signals received by the antenna are passed to a divider 34 by means of the duplexer. The divider divides the received signals and passes the signals to two bandpass filters 35a, b arranged in parallel. The first bandpass filter 35a filters the signal components at frequencies other than fi and the second bandpass filter 35b filters the components of the signals at frequencies other than those of about f. Because the shifted frequency of Doppler f2D is close to the frequency f2, the second bandpass filter allows the signal components at both frequencies f2 and f2D to be passed. The filtered signals are combined in a combiner 36 and fed at frequencies fi, f2 and f2D. The detector also determines the frequency fD. Indicator values of the signal strength of the signal components at these frequencies, also as a frequency indicator value f2D, are input to a computer 39. The computer stores in memory values indicating an expected signal strength of signal components at frequencies fi and f2 due to the RF source of the detection system. Additionally, the computer stores in memory values indicating the expected signal strength of signal components at frequency f2D for reflective objects and for irradiating objects. The computer also stores an average of C operation of the indicator values of the intensity of signal received from the components of the signals at frequencies fi and f2. The received signal strength of the signals at frequencies fi and f are both from the RF source and any non-mobile targets within the reception area. Thus, the computer maintains information concerning the signal levels expected from the source of RF and actual received signal levels which may include signs of display items placed near the exit gate. With this information and the detector inputs of the signal intensity indicator values of the signal components at frequencies fi, f2, and f2D, also as the indicator value of the frequency f2D, the computer is able to determine when to activate a _ alarm circuit 43. Alarm circuits are conventional in the art and may include lights flashes and audible alarms. When a target moves in and through the receiving area, the indicator value of the received signal strength of the signal component at frequency f2D is increased. Thus, in the preferred embodiment, the computer activates the alarm circuit when an increase in signal strength at frequency f2D is recorded by the computer. In another embodiment, the computer activates the alarm circuit when an increase in the intensity of the signal at frequency fD approximates the expected signal strength due to a moving target or an increase other than that which would occur due to reflection of a mobile object is registered by the computer. In another embodiment, the computer activates the alarm circuit when either an increase in the signal strength at the frequency fi or f2 or both or an increase in the signal strength at the frequency f2D is recorded by the computer. In yet another mode, the computer activates the alarm circuit when an increase in signal strength at the frequency f2o +, 15 with f2D + greater than f2D is first recorded, followed by an increase in signal strength at the frequency f2D- , with fD. less than f2D. Such a received signal strength configuration is indicative of a target approaching first P to the exit gate and then away from the exit gate. In still other modalities, the computer activates the alarm circuit using a combination of the methods described above. The output gate additionally has a . back-up power supply 41 to power the output gate during periods of interruption of the normal supply circuits, that is, "blackouts". Due to the low power requirements of the source of RF and other components of the detection system, it can be 1 ^ 1 Use a small NiCad battery or other battery to Energize the backup power supply. This allows a full operation of the system during blackouts, thus increasing the operability and versatility of the system. Figure 3 is a block diagram of a preferred system for deactivating the targets, a source 45 of pulses provides a pulse signal of very short duration at frequency fi. The amplitude of this short duration pulse is sufficient to destroy the pn junction of the target. Alternatively, the pulse source can be used to destroy fuse links 16, 17 (shown in figure 1) on the input and output terminals of diode 11 (also shown in figure 1) of the objective. As with the RF source of the output gate, the signal from the source - RF of the deactivation system is passed through a bandpass filter 47 to reduce, the intensity of global signal and eliminate parasitic harmonics, particularly those at frequency or greater than frequency f2. A deactivation antenna 49 for the deactivation system is located within an apparatus of , scanning or barcode scanner (not shown) that are common in retail stores. The antenna can also be located on a separate manual rod or other movable article. Figure 4 shows an embedded target 57 i used with a small bottle of aspirin 51. The bottle of aspirin is sealed with a bottle cap 53. The bottle cap and the bottle are additionally sealed by an inviolable seal 55. The inviolable seal is a band that can be thermally shrunk from PVC. The inviolable stamps are commonly used with a variety of small retail goods and the uses of such stamps are well known. The circuits of the lens are formed on a substrate. Then the substrate is attached to the inviolable seal by gluing, printing, deposition or other appropriate techniques. 15 The objective can also be applied to a wide variety of articles, in which a price label is included. Figure 5 illustrates a price tag 61 that incorporates the purpose of the present invention. The price tag has varied printed information 64, in which bar code information 63 is included, on the price label. An objective 65 is fixed to the price tag. The label can also be part of the barcode information without affecting the usefulness of the barcode. Thus, the goal can be applied to 25 price tags, clothing labels and a variety of other items.

The tag can be hidden in a variety of ways in many of these items due to the small size of the tag and store thieves will be stopped by being unable to determine with certainty whether a target is present in any item. Thus, the anti-theft detection system of the present invention provides a simple and adaptable anti-theft control system. The low power output signal of the output gate presents a minimal health risk and the objective provides a small and economical theft control marker. Although this invention has been described in certain specific embodiments, many modifications and additional variations will be apparent to those skilled in the art. Accordingly, it will be understood that this invention may be practiced in another manner unless specifically described herein. Thus, the embodiments present in the invention should be considered in all respects as illustrative and not restrictive, the scope of the invention will be indicated by the appended claims in lieu of the foregoing description. It is noted that, in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it refers.

Claims (18)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. An anti-theft detection system, characterized in that it comprises: a radiofrequency source that emits a source signal at a first frequency; an objective that emits an objective signal with a component at a second frequency when it is subjected to the signal at the first frequency; a detector for detecting the component of the target signal at the second frequency and for detecting a component of a displaced Doppler target signal approximated to the second frequency; an alarm activated when the detector detects the component of the target signal at the second frequency and the component of the shifted Doppler target signal approximated to the second frequency; the objective comprises a frequency multiplier; the first frequency is a frequency fi and the "second frequency is a frequency f2 and f2 is a multiple, of fi; wherein the detector detects the signals at frequencies approximating the frequency f2, the signals at frequencies approximating the frequency of f are signals C displaced from Doppler at frequency f2; 5 an alarm processor, the alarm processor receives information from the signal level of the detector; wherein the alarm processor controls the alarm when the alarm processor determines that the detector has detected the component of the target signal at the frequency 10 f and the component of the approximate Doppler shifted target signal f; wherein the alarm processor stores predefined indicators of the signal strength at frequencies fi, f2 and the shifted frequencies of Doppler 15 of f2 and the alarm processor controls the alarm when the alarm processor determines that the detector has detected an increase in the signal strength above the indicator values of the signal strength at frequencies P fi, f2 and the displaced Doppler frequencies of f2.
2. 2. The anti-theft detection system according to claim 1, characterized in that the target comprises a diode.
3. The anti-theft detection system according to claim 2, characterized in that the diode has an input antenna connected to an input_ of the diode and an output antenna connected to an output of the diode.
4. 4. The anti-theft detection system according to claim 3, characterized in that the input antenna includes a fusible link.
5. 5. The anti-theft detection system according to claim 4, characterized in that the output antenna includes a fusible link.
6. 6. The anti-theft detection system according to claim 3, characterized in that the frequency multiplier is attached to an inviolable seal.
7. The anti-theft detection system according to claim 3, characterized in that the frequency multiplier is' attached to a price tag., 8.
8. The anti-theft detection system according to claim 6, characterized in that the tamper-evident seal It comprises a band that can be thermally shrunk.
9. The anti-theft detection system according to claim 8, characterized in that the thermally shrinkable band is composed of a polyvinyl chloride material.
10. 10. An anti-theft detection system, characterized in that it comprises: a radiofrequency source that emits a source signal at a first frequency; an objective that emits an objective signal with a component at a second frequency when it is subjected to the signal at the first frequency; a detector for detecting a component of a shifted Doppler target signal approximated to the second frequency; an alarm activated when the detector detects the component of the displaced Doppler target signal approximated to the second frequency, the alarm is not "activated only by detecting the detector of a component of the target signal at the second frequency; the objective comprises a frequency multiplier; the first frequency is a frequency fi and the second frequency is a frequency f2 and f2 is a multiple of fi; where the detector detects signals at approximate frequencies at the frequency f2, signals at frequencies approximating the frequency of f are signals shifted by Doppler at frequency f2; an alarm processor, the alarm processor receives information from the signal level of the detector; wherein the alarm processor controls the alarm when the alarm processor determines that the detector has detected the component of the shifted Doppler target signal approximating f2; and wherein the alarm processor stores predefined values of signal strength at shifted Doppler frequencies of f and the alarm processor controls the alarm when the alarm processor determines that the detector has detected an increase in signal strength above of the signal values indicating the signal intensity at displaced Doppler frequencies of f2. / 11.
11. The anti-theft detection system according to claim 10, characterized in that the target comprises a diode.
12. The anti-theft detection system according to claim 11, characterized in that the diode has an input antenna connected to an input of the diode and an output antenna connected to an output of the diode.
13. The anti-theft detection system according to claim 12, characterized in that the input antenna includes a fusible link.
14. The anti-theft detection system according to claim 13, characterized in that the output antenna includes a fusible link.
15. 15. The anti-theft detection system according to claim 12, characterized in that the diode is attached to an inviolable seal.
16. 16. The anti-theft detection system of fc 5 according to claim 15, characterized in that the tamper-evident seal comprises a strip that can be thermally shrunk.
17. 17. The anti-theft detection system according to claim 16, characterized in that the The strip that can be thermally contracted is composed of a polyvinyl chloride material.
18. 18. The anti-theft detection system according to claim 12, characterized in that the frequency multiplier is attached to a tag of 15 prices.