Security paper detection device capable of avoiding ambient environmental noise

Abstract

The present disclosure relates to a security paper detection device 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 disclosure 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 multiplied (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

Technical Field

[0001] The present disclosure relates to an electromagnetic security paper detection gate and handheld security paper detector 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.

[0002] In the present disclosure, this is collectively referred to as a security paper detection device, and the term "security paper detection device" as used herein refers to both a security paper detection gate that detects whether or not a person is carrying security paper and sounds an alarm when the person carrying security paper passes through the gate and a handheld security paper detector that allows security personnel to search people going in and out more thoroughly whether they are carrying security paper.Background Art

[0003] As a technology for a physical security solution for preventing external leakage of printed paper documents (printouts) containing key information requiring security, electromagnetic (EM) technology is generally applied as a printout leakage prevention solution that issues an alarm upon detecting an attempt to illegally leak security paper which is printed using security paper containing special alloy material, thus leading to inherent security vulnerabilities such as detection interference or detection errors caused by electromagnetic noise generated in the surroundings and various alloy materials that are used along with the advance of the technology of portable products.

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

[0005] Also, U.S. Patent No. 5,894,270 relates to an electronic security element monitoring apparatus within an interrogation zone, which discloses a technology in which the apparatus includes a transmitting device that emits at least one periodic magnetic field signal to a detection zone, causing the security element to generate a specific signal, and a receiving device that receives the specific signal, and the signal received from the receiving device is evaluated and an alarm is generated 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 apparatus within an investigation zone, which discloses a technology in which a transmitting device emits a transmission signal to a detection zone, the transmission signal causing the security element to generate a characteristic signal, and a receiving device receives the characteristic signal generated from the security element by the transmission signal, evaluates the characteristic signal, generates an alarm when the presence of the security element is established, and removes a spike signal during evaluation if the received signal contains the spike signal.

[0007] However, in the above conventional technologies, when the frequency to be detected overlaps with the frequency of externally generated noise, the signal to be detected and the noise are not separated, thereby increasing the likelihood of detection errors.Prior art literature

[0008] (Patent Document 0001) US Patent No. 5414410 (Patent Document 0002) US Patent No. 5894270 (Patent Document 0003) US Patent No. 5,969,611 DETAILED DESCRIPTION OF THE INVENTION Technical Problem

[0009] The present disclosure aims to provide a security paper detection device that overcomes the problems of the prior art, and more specifically, it seeks to avoid power noise generated around a detection gate that overlaps with a detection frequency coming into a receiver (RX antenna) and other noise generated from surrounding electronic equipment, thereby reducing the likelihood of detection errors that may be caused by such ambient noise.Technical Solution

[0010] According to an embodiment of the present disclosure, a security paper detection device includes: a magnetic field frequency varying means; a TX antenna connected to the magnetic field frequency varying means; an RX antenna positioned to 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 multiplied (detection) frequency, and the magnetic field frequency varying means changes a magnetic field frequency according to the provided feedback signal.Effects of the Invention

[0011] According to an embodiment of the present disclosure, the distribution of multiplied (detection) frequencies is adjusted such that they are separated from ambient noise, thereby minimizing the influence of power noise or noise from surrounding electronic devices and reducing detection errors in the security paper detection device.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a diagram illustrating a process in which Barkhausen noise is produced. FIG. 2 is a diagram showing the basic concept of a security paper detection device according to an embodiment of the present disclosure. FIG. 3 is a diagram showing the result of avoiding ambient noise according to an embodiment of the present disclosure. FIG. 4 is a block diagram of a security paper detection device according to an embodiment of the present disclosure. FIG. 5 is a detailed block diagram of a security paper detection device according to an embodiment of the present disclosure. Best Mode for Implementing the Invention

[0013] According to an embodiment of the present disclosure, a security paper detection device includes: a magnetic field frequency varying means; a TX antenna connected to the magnetic field frequency varying means; an RX antenna positioned to 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 multiplied (detection) frequency, and the magnetic field frequency varying means changes a magnetic field frequency according to the provided feedback signal.

[0014] In addition, the magnetic field frequency varying means includes a signal generator and a power amplifier connected to the signal generator.

[0015] Furthermore, the signal processing means includes a filter connected to the amplifier, an AD converter connected to the filter, and a digital signal processing (DSP) means connected to the AD converter, that provides a feedback signal to the magnetic field frequency varying means and changes a multiplied (detection) frequency.

[0016] Moreover, the security paper detection device further includes an alarm means connected to the signal processing means.Mode for Implementing the Invention

[0017] Hereinafter, a security paper detection device according to the present disclosure will be described with reference to the accompanying drawings. The following description describes a preferred embodiment of the disclosure.

[0018] FIG. 1 is a diagram showing a process in which Barkhausen noise is produced, which is the core of the basic principle of the security paper detection device. Once an alternating sinusoidal current such as in B of FIG. 1 is passed through the TX antenna of FIG. 2 and forms an AC magnetic field around the TX antenna and the RX antenna, when security paper containing amorphous metal passes through the formed AC magnetic field, a B-H curve for the amorphous metal is formed as shown in A of FIG. 1. At this time, the AC magnetic field causes the domain arrangement within the amorphous metal to change along the AC magnetic field, thereby generating noise as shown in C of FIG. 1. This noise is referred to as Barkhausen noise. Such Barkhausen noise has a frequency spectrum with unique characteristics in the frequency domain. By analyzing the unique frequency spectrum with unique characteristics and determining that it matches the spectrum of amorphous metal, security paper is detected, and an alarm is sounded.

[0019] By the way, as shown in the frequency spectrum of FIG. 3, the frequency spectrum of Barkhausen noise is expressed as multiples of a magnetic field formation frequency. In this case, the presence of security paper, i.e., the presence of amorphous metal, is determined by analyzing the multiplied frequencies (f1, f2, f3...) but not the magnetic field formation frequency (f0). However, as illustrated in the left graph of FIG. 3, when external ambient noise occurs close to f2, which is one of the multiplied frequencies, it may cause an error in the analysis of multiplied frequencies, thereby resulting in an error in determining the presence of amorphous metal.

[0020] FIGS. 4 and 5 are block diagrams of a security paper detection device according to an embodiment of the present disclosure and a detailed configuration thereof, for resolving the above errors occurring in the analysis of multiplied frequencies.

[0021] Referring to FIGS. 4 and 5, the security paper detection device 100 according to one embodiment of the present disclosure includes: a magnetic field frequency varying means 110; a TX antenna 120 connected to the magnetic field frequency varying means 110; an RX antenna 130 positioned to correspond 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.

[0022] Here, the magnetic field frequency varying means 110 includes a signal generator 111 that generates a magnetic field frequency and a power amplifier 112 connected to the signal generator 111. The signal generator 111 of the magnetic field frequency varying means 110 outputs a signal by changing the magnetic field frequency according to a feedback signal provided from the digital signal processing means 153 of the signal processing means 150.

[0023] Also, 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, that provides a feedback signal to the signal generator 111 of the magnetic field frequency varying means 110 and changes a multiplied (detection) frequency. Meanwhile, the digital signal processing means (DSP) 153 is generally composed of a digital signal processor and a control unit that receives a processed signal and performs subsequent processing.

[0024] In addition, the security paper detection device 100 further includes an alarm means 160 connected to the signal processing means 150. When the signal processing means 150 detects security paper, it controls the alarm means 160 so that an alarm can be indicated by light through an LED or by a warning sound.

[0025] The operation according to the above configuration is as follows. In a state where no security paper or other metallic object is present around the TX antenna 120 and the RX antenna 130, the signal generator 111 of the magnetic field frequency varying means 110 generates a preset magnetic field formation frequency (f0) signal. This signal is amplified through the power amplifier 112 and input to the TX antenna 120, thereby forming an AC magnetic field around the TX antenna 120 and the RX antenna 130. The signal processing means 150 allows only a certain band of the signal input from the RX antenna 130 through the amplifier 140 to pass through the filter 151, converts it into a digital signal through the AD converter 152, and then analyzes it in the digital signal processing means 153. If the frequency of the signal input through the amplifier 140 overlaps with a multiplied (detection) frequency region, the digital signal processing means 153 determines that the frequency of external noise from the surroundings overlaps with the multiplied (detection) frequency region. To resolve this, the digital signal processing means 153 provides a feedback signal to the signal generator 111 of the magnetic field frequency varying means 110 based on the analysis result.

[0026] In the signal generator 111 of the magnetic field frequency varying 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 the signal is input to the TX antenna 120. Once a new AC magnetic field is formed around the TX antenna 120 and the RX antenna 130, the digital signal processing means 153 of the signal processing means 150 changes the multiplied frequencies to f1+2a, f2+3a, f3+4a, and so forth. It then re-analyzes the new signal input from the RX antenna 130 through the amplifier 140 to determine whether the frequency of external noise overlaps with the changed multiplied (detection) frequency region. If the frequency of the signal input through the amplifier 140 overlaps with the multiplied (detection) frequency region, the above process is continuously repeated so that the frequency of external noise does not overlap with the multiplied (detection) frequencies.

[0027] That is, when the magnetic field frequency varying means 110 changes the AC magnetic field formation frequency f0 by an amount a according to the feedback signal provided from the signal processing means 150, the signal processing means 150 also has to change the multiplied (detection) frequency region 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 varying means 110 and at the same time changes the multiplied (detection) frequencies.

[0028] Through this process, the magnetic field formation frequency (f0) is continuously changed, and, as shown in the right graph of FIG. 3, the frequency with the least influence from noise is found and changed. At the same time, the signal processing means 150 changes the distribution of the multiplied (detection) frequencies so that the distribution of the multiplied (detection) frequencies is adjusted such that they are separated from ambient noise. As a result, security paper can be detected without being affected by ambient noise. Therefore, the security paper detection device 100 according to an embodiment of the present disclosure facilitates the analysis of multiplied (detection) frequencies, thereby reducing errors in detecting security paper.

[0029] As described above, the present disclosure is not limited to the specific preferred embodiments described above, and anyone having ordinary skill in the art to which the present invention pertains can make various modifications without departing from the gist of the present disclosure claimed in the claims, and such modifications are within the scope of the claims.Industrial Applicability

[0030] According to the embodiments of the present disclosure, it is possible to avoid power noise and other noise generated from surrounding electronic equipment, thereby reducing the likelihood of detection errors that may be caused by such ambient noise.

Claims

1. A security paper detection device comprising: a magnetic field frequency varying means; a TX antenna connected to the magnetic field frequency varying means; an Rx antenna positioned to 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 multiplied (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.

2. The security paper detection device of claim 1, wherein the magnetic field frequency varying means includes a signal generator and a power amplifier connected to the signal generator.

3. The security paper detection device of claim 1 or 2, wherein 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, that provides a feedback signal to the magnetic field frequency varying means.

4. The security paper detection device of claim 3, further comprising an alarm means connected to the signal processing means.

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