Security paper detection device capable of avoiding ambient environmental noise

Abstract

The present invention relates to an electromagnetic security paper detection gate for preventing leakage of security paper and, more specifically, to a security paper detection device for detecting an amorphous micro-wire inserted into security paper. The security paper detection device, according to an embodiment of the present invention, comprises: a magnetic field frequency varying means; a Tx antenna connected to the magnetic field frequency varying means; an Rx antenna positioned to be spaced apart from and correspond to the Tx antenna; an amplifier connected to the Rx antenna; and a signal processing means connected to the amplifier, wherein the signal processing means provides a feedback signal to the magnetic field frequency varying means and changes a multiplication (detection) frequency, and the magnetic field frequency varying means changes a magnetic field frequency according to the feedback signal provided from the signal processing means.

Description

Security paper detection device capable of avoiding ambient environmental noise

[0001] The present invention relates to an electromagnetic (EM) type security paper detection gate and a handy security detector for preventing leakage of security paper, and more specifically, to a security paper detection device for detecting amorphous micro-wires contained in security paper.

[0002] In the present invention, this is collectively referred to as a security paper detection device, and the 'security paper detection device' in the present invention includes a security paper detection gate that detects whether a person is carrying a security paper and sounds an alarm when passing through the gate while carrying a security paper, and a handy security paper detector that allows a security guard to search in more detail whether an entrant is carrying a security paper.

[0003] This is a technology for a physical security solution that prevents external leakage of printed paper documents (printouts) containing key information requiring security. It is a printout leakage prevention solution that detects and generates an alarm when an illegal leakage attempt is made on printed security paper using security paper with a special alloy material embedded. Since it uses EM (Electro-magnetic) technology, which is a technology that is generally applied, it has security vulnerabilities such as detection interference or detection errors caused by electromagnetic noise generated in the surrounding environment and various alloy materials used as the technology of portable products becomes more advanced.

[0004] In the prior art, U.S. Patent No. 5,414,410 discloses a technology for a transmitter for generating two alternating magnetic fields through a single transmitting coil supplied with a transmitting signal current, and a receiver for detecting harmonics and intermodulation signals of the alternating magnetic fields through a receiving coil for generating a receiving signal current.

[0005] Also, U.S. Patent No. 5,894,270 relates to an electronic security element monitoring device within an interrogation area, comprising a transmitter that emits at least one periodic magnetic field signal into a detection area, the signal causing the security element to generate a specific signal, a receiving device that receives the specific signal, and a technique for evaluating the signal received from the receiving device and generating an alarm when the presence of the security element is established.

[0006] In addition, U.S. Patent No. 5,969,611 relates to an electronic security element monitoring device within an investigation area, wherein a transmitting device emits a transmitting signal to a detection area, and the transmitting signal causes a security element to generate a characteristic signal, and a receiving device receives the characteristic signal generated from the security element by the transmitting signal, evaluates the characteristic signal, and generates an alarm when the presence of the security element is confirmed, and discloses a technique for removing a spike signal when the received signal includes a spike signal during the evaluation.

[0007] However, in the above conventional technologies, if the frequency to be detected overlaps with the frequency of noise generated externally, there is a high possibility that a detection error will occur because the signal to be detected and the noise are not separated.

[0008]

[0009] Prior art literature

[0010] (Patent Document 0001) U.S. Patent No. 5,414,410

[0011] (Patent Document 0002) U.S. Patent No. 5,894,270

[0012] (Patent Document 0003) U.S. Patent No. 5,969,611

[0013] The present invention aims to provide a security paper detection device that solves the problems of the prior art, and more specifically, to reduce the possibility of detection errors that may occur due to the above-mentioned surrounding noise by avoiding power noise generated around a detection gate that overlaps with the detection frequency coming into a receiver (RX antenna) and noise generated from other surrounding electronic equipment.

[0014] According to one embodiment of the present invention, a security paper detection device includes: a magnetic field frequency variable means; a TX antenna connected to the magnetic field frequency variable means; an RX antenna positioned corresponding to the TX antenna; an amplifier connected to the RX antenna; and a signal processing means connected to the amplifier; wherein the signal processing means provides a feedback signal to the magnetic field frequency variable means and changes a multiplication (detection) frequency, and the magnetic field frequency variable means changes a magnetic field frequency according to the provided feedback signal.

[0015] According to an embodiment of the present invention, the multiplication (detection) frequency distribution is adjusted to be separated from the surrounding environmental noise, thereby minimizing the influence of power noise or noise from surrounding electronic devices, thereby minimizing detection errors of the security paper detection device.

[0016] Figure 1 is a diagram showing the process by which Barkhausen noise occurs.

[0017] FIG. 2 is a drawing showing a basic concept of a security paper detection device according to an embodiment of the present invention.

[0018] Figure 3 is a drawing showing the result of avoiding ambient noise according to an embodiment of the present invention.

[0019] Figure 4 is a block diagram of a security paper detection device according to one embodiment of the present invention.

[0020] Figure 5 is a detailed block diagram of a security paper detection device according to one embodiment of the present invention.

[0021] A security paper detection device according to one embodiment of the present invention comprises: a magnetic field frequency variable means; a TX antenna connected to the magnetic field frequency variable means; an RX antenna positioned corresponding to the TX antenna; an amplifier connected to the RX antenna; and a signal processing means connected to the amplifier; wherein the signal processing means provides a feedback signal to the magnetic field frequency variable means and changes a multiplication (detection) frequency, and the magnetic field frequency variable means changes a magnetic field frequency according to the provided feedback signal.

[0022] Additionally, the magnetic field frequency variable means includes a signal generator and a power amplifier connected to the signal generator.

[0023] In addition, the signal processing means includes a filter connected to the amplifier, an AD converter connected to the filter, and a digital signal processing means (DSP: Digital Signal Processing) connected to the AD converter and providing a feedback signal to the magnetic field frequency variable means and changing a multiplication (detection) frequency.

[0024] In addition, the security paper detection device further includes an alarm means connected to the signal processing means.

[0025] A security paper detection device according to the present invention is described below based on the attached drawings. The following description describes a preferred embodiment of the present invention.

[0026] Fig. 1 is a diagram showing the process of generating Barkhausen noise, which is the core of the basic principle of a security paper detection device. When an AC sinusoidal current such as B in Fig. 1 is passed through the TX antenna of Fig. 2 to form an AC magnetic field around the TX antenna and the RX antenna, when a security paper containing an amorphous metal passes through the formed AC magnetic field, a BH curve for the amorphous metal, such as A in Fig. 1, is formed. At this time, the magnetic domain arrangement in the amorphous metal changes along the AC magnetic field due to the AC magnetic field, generating noise such as C in Fig. 1, which is called Barkhausen noise. Such Barkhausen noise has a frequency spectrum with unique characteristics in the frequency domain. When the frequency spectrum with such unique characteristics is analyzed and is the same as the spectrum of the amorphous metal, it is determined to be security paper and an alarm is sounded.

[0027] However, as shown in the frequency spectrum of Fig. 3, the frequency spectrum of Barkhausen noise is expressed as a multiple of the magnetic field formation frequency. At this time, the presence of security paper, i.e., the presence of amorphous metal, is determined through spectrum analysis of the multiple frequencies (f1, f2, f3...) excluding the magnetic field formation frequency (f0). However, as shown in Fig. 3 (a), when noise from the external environment occurs close to f2, which is one of the multiple frequencies, it causes an error in the analysis of the multiple frequencies, resulting in an error in determining whether or not there is amorphous metal.

[0028] FIG. 4 and FIG. 5 are block diagrams and detailed configuration diagrams of a security paper detection device according to one embodiment of the present invention for resolving errors in the above-described multiplication frequency analysis.

[0029] Referring to FIGS. 4 and 5, a security paper detection device (100) according to one embodiment of the present invention includes a magnetic field frequency variable means (110), a TX antenna (120) connected to the magnetic field frequency variable means (110), an RX antenna (130) positioned corresponding to the TX antenna (120), an amplifier (140) connected to the RX antenna (130), and a signal processing means (150) connected to the amplifier (140).

[0030] Here, the magnetic field frequency variable means (110) includes a signal generator (111) that generates a magnetic field frequency and a power amplifier (112) connected to the signal generator (111), and the signal generator (111) of the magnetic field frequency variable means (110) changes and outputs the magnetic field frequency according to a feedback signal provided from a digital signal processing means (153) of a signal processing means (150).

[0031] And, the signal processing means (150) includes a filter (151) connected to the amplifier (140), an AD converter (152) connected to the filter (151), and a digital signal processing means (153) connected to the AD converter (152) and providing a feedback signal to the signal generator (111) of the magnetic field frequency variable means (110) and changing the multiplication (detection) frequency. Meanwhile, the digital signal processing means (153: DSP) is generally composed of a digital signal processor and a control unit that receives a processed signal and performs subsequent processing.

[0032] In addition, the security paper detection device (100) further includes an alarm means (160) connected to a signal processing means (150), and when the signal processing means (150) detects security paper, it controls the alarm means (160) so that the alarm means (160) can give an alarm through light or a warning sound via an LED.

[0033] Looking at the operation according to the above configuration, in a state where there is no metal object including security paper around the TX antenna (120) and the RX antenna (130), the signal generator (111) of the magnetic field frequency variable means (110) generates a signal of a preset magnetic field formation frequency (f0), amplifies this signal through a power amplifier (112), and inputs it to the TX antenna (120), so that an alternating magnetic field is formed around the TX antenna (120) and the RX antenna (130), and the signal processing means (150) passes only a certain band of the signal input from the RX antenna (130) through the amplifier (140) through a filter (151), and then changes this into a digital signal through an AD converter (152), and then analyzes this in the digital signal processing means (153). If the frequency of the signal input through the amplifier (140) overlaps with the multiplication (detection) frequency range, the digital signal processing means (153) determines that the frequency of external noise caused by the surrounding environment overlaps with the multiplication (detection) frequency range, and to resolve this, the digital signal processing means (153) provides a feedback signal to the signal generator (111) of the magnetic field frequency variable means (110) based on the analyzed result.

[0034] In the signal generator (111) of the magnetic field frequency variable means (110), the magnetic field formation frequency (f0) is changed to f0+a according to the feedback signal provided from the digital signal processing means (153) and inputted to the TX antenna (120), thereby forming a new alternating magnetic field around the TX antenna (120) and the RX antenna (130). Then, the digital signal processing means (153) of the signal processing means (150) changes the multiplication frequency to f1+2a, f2+3a, f3+4a, etc., and then analyzes the new signal inputted from the RX antenna (130) through the amplifier (140) again to determine whether the frequency of the external noise overlaps with the changed multiplication (detection) frequency range, and if the frequency of the signal inputted through the amplifier (140) overlaps again with the multiplication (detection) frequency range, the above process is continuously repeated so that the frequency of the external noise and the multiplication (detection) frequency do not overlap.

[0035] That is, when the frequency of formation of the alternating magnetic field f0 is changed by a by a feedback signal provided from the signal processing means (150) in the magnetic field frequency variable means (110), the signal processing means (150) must also change the multiplication (detection) frequency range from f1 to f1+2a, from f2 to f2+3a, and from f3 to f3+4a. The signal processing means (150) provides a feedback signal to the magnetic field frequency variable means (110) and also changes the multiplication (detection) frequency.

[0036] By continuously changing the magnetic field formation frequency (f0) through the above process, the magnetic field formation frequency with the smallest influence of noise is found and changed as shown in (b) of FIG. 3, and at the same time, the signal processing means (150) changes the multiplication (detection) frequency distribution, thereby adjusting the multiplication (detection) frequency distribution to be separated from the surrounding environmental noise, so that the security paper can be detected without being affected by the surrounding environmental noise when detecting the security paper. Therefore, since the multiplication (detection) frequency analysis is facilitated by the security paper detection device (100) according to one embodiment of the present invention, security paper detection errors can be reduced.

[0037] As described above, the present invention is not limited to the specific preferred embodiments described above, and anyone having ordinary skill in the art to which the invention pertains can make various modifications without departing from the gist of the present invention claimed in the claims, and such modifications are within the scope of the claims.

[0038] According to an embodiment of the present invention, a security paper detection device can be provided that can reduce the possibility of detection errors that may occur due to the above-mentioned ambient noise by avoiding power noise and noise generated from other peripheral electronic equipment.

Claims

1. Magnetic field frequency variable means; A TX antenna connected to the above magnetic field frequency variable means; An RX antenna positioned corresponding to the above TX antenna; An amplifier connected to the above RX antenna; A signal processing means connected to the above amplifier; The above signal processing means provides a feedback signal to the magnetic field frequency variable means and changes the multiplication (detection) frequency. A security paper detection device characterized in that the magnetic field frequency variable means changes the magnetic field frequency according to the feedback signal provided from the signal processing means.

2. In paragraph 1, A security paper detection device characterized in that the magnetic field frequency variable means includes a signal generator and a power amplifier connected to the signal generator.

3. In paragraph 1 or 2, A security paper detection device characterized in that the signal processing means includes a filter connected to the amplifier, an AD converter connected to the filter, and a digital signal processing means (DSP) connected to the AD converter and providing a feedback signal to the magnetic field frequency variable means.

4. In paragraph 3, A security paper detection device characterized in that it further includes an alarm means connected to the signal processing means.

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