CN109727362B - Banknote magnetic signal identification method based on discrete Fourier transform - Google Patents
Banknote magnetic signal identification method based on discrete Fourier transform Download PDFInfo
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Abstract
The invention discloses a banknote magnetic signal identification method based on discrete Fourier transform, which comprises the following steps: carrying out discrete Fourier transform on standard magnetic signal data of each channel of a preset number of banknotes to obtain a coefficient array, and removing invalid signals in the coefficient array to obtain a valid coefficient array; obtaining the value range of each modular length of the effective coefficient array through data experiments, and recording the value range as a threshold array; storing the effective coefficient array and the threshold value array into a memory of the banknote identification module; and when identifying the bank notes, comparing the modular length difference value of each item of the array to be detected and the effective coefficient array stored in the memory, and outputting the judgment result of the magnetic signal of the bank notes according to the comparison result. The invention can realize the rapid analysis of the collected magnetic signals of the bank notes so as to judge whether the magnetic signals have problems, thereby realizing the rapid detection of the magnetic signals of the bank notes and realizing the counterfeit discrimination of the bank notes.
Description
Technical Field
The invention relates to the technical field of signal processing, in particular to a banknote magnetic signal identification method based on discrete Fourier transform.
Background
With the progress and development of science and technology, the counterfeit identification characteristics of the bank notes are more and more comprehensive, and the magnetic characteristics are important components of the counterfeit identification of the bank notes. At present, magnetic sensors in the banknote recognition module all adopt magnetic signal sensors, and common algorithms mainly adopt logic judgment. This method is complex to implement and does not have versatility between different types of banknote magnetic signals.
Disclosure of Invention
The invention aims to provide a banknote magnetic signal identification method based on discrete Fourier transform, which has clear structure and strong universality and aims at overcoming the technical defects in the prior art.
The technical scheme adopted for realizing the purpose of the invention is as follows:
a banknote magnetic signal identification method based on discrete Fourier transform comprises the following steps:
s1, performing discrete Fourier transform on standard magnetic signal data of each channel of the preset number of banknotes to obtain a coefficient array, and then removing invalid signals in the coefficient array through threshold judgment to obtain a valid coefficient array;
s2, obtaining the value range of each modular length of the effective coefficient array through data experiments, and recording the value range as a threshold array;
s3, storing the effective coefficient array and the threshold value array into a memory of a banknote identification module;
and S4, comparing the module length difference value of the array to be detected and each item of the effective coefficient array stored in the memory when identifying the bank note, and outputting the judgment result of the magnetic signal of the bank note according to the comparison result.
In step S4, if the difference between the lengths of the two patterns is greater than the corresponding threshold, it is determined that the magnetic signal of the banknote is faulty.
In step S4, the array to be detected is obtained by performing discrete fourier transform on the magnetic signal data of the banknote obtained in the banknote recognition.
Before the step of step S1, the method further includes the following steps:
preprocessing the collected magnetic signals of the banknotes with the preset number to obtain standard magnetic signal data.
The magnetic signal is preprocessed by interference removal and averaging.
The invention can realize the rapid analysis of the collected magnetic signals of the bank notes so as to judge whether the magnetic signals have problems, thereby realizing the rapid detection of the magnetic signals of the bank notes and realizing the counterfeit discrimination of the bank notes.
Drawings
Fig. 1 is a schematic flow chart of a banknote magnetic signal identification method based on discrete fourier transform;
FIG. 2 is a graph of magnetic signals;
fig. 3 shows a fourier transform spectrogram.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, the banknote magnetic signal identification method based on discrete fourier transform of the present invention comprises:
s1 selecting a plurality of banknotes to collect magnetic signal data, each banknote magnetic signal data comprising m data channels, each channel comprising n data points.
S2 analyzes and processes several pieces of banknote magnetic signal Data, including interference elimination and averaging operation, to obtain standard magnetic signal Data [ m, n ] of banknote.
S3 performs discrete Fourier transform on each channel magnetic signal, and decomposes the signal into n triangular waves, and the coefficient array obtained by i (i ═ 0 to m-1) th channel Data i [1, n ] transform is denoted as Fourier1 i [1, n ],
the meaning of the coefficient array Fourier1 i [1, n ] is the coefficient of the ith wave function when the curve corresponding to Data i [1, n ] is expressed as the superposition of trigonometric functions. Wherein, the discrete Fourier transform formula is as follows:
where x (N) is the input data of length N,
w N is the root of the total of the N subunits,
x (k) is the result of discrete Fourier transform of x (n).
S4 takes an appropriate threshold ValidThres i (Thres i >0) for each channel i (i ═ 0 to m-1), sets the term with a length smaller than ValidThres i in Fourier1 i [1, n ] as an invalid signal to 0, and records the resulting significant coefficient array as Fourier2 i [1, n ].
S5 standard magnetic signal Data [ m, n ] of the bank note, and after the operation is carried out on each channel Data signal, a Fourier transform effective coefficient array Fourier2[ m, n ] is obtained.
S6, carrying out data experiment to obtain the value range of each modular length of the effective coefficient array Fourier2[ m, n ], and recording the value range as a threshold array Fourier threes 2[ m, n ].
S7 stores Fourier2[ m, n ] and Fourier thres2[ m, n ] in the internal memory of the banknote recognition module.
S8, when identifying the bank note, the magnetic signal data of the bank note is recorded as NoteData [ i, j ], the discrete Fourier transform is carried out on the data, and the array obtained after the transform is recorded as NoteFourier [ m, n ].
S9 compares the modulus length difference of NoteFourier2 m, n with stored Fourier2 m, n in memory, if the difference is larger than the corresponding threshold FourierThres2 m, n, it judges that there is a problem in magnetic signal of bank note.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (3)
1. A banknote magnetic signal identification method based on discrete Fourier transform is characterized by comprising the following steps:
s1, performing discrete Fourier transform on standard magnetic signal data of each channel of the preset number of banknotes to obtain a coefficient array, and then removing invalid signals in the coefficient array through threshold judgment to obtain a valid coefficient array;
s2, obtaining the value range of each modular length of the effective coefficient array through data experiments, and recording the value range as a threshold array;
s3, storing the effective coefficient array and the threshold value array into a memory of a banknote identification module;
s4, when identifying the bank note, comparing the module length difference value of the array to be detected and each item of the effective coefficient array stored in the memory, and outputting the judgment result of the magnetic signal of the bank note according to the comparison result; the array to be detected is obtained by performing discrete Fourier transform on banknote magnetic signal data obtained during banknote identification; and if the module length difference value is larger than the corresponding threshold value, judging that the banknote magnetic signal has a problem.
2. A method for identifying a magnetic signal of a banknote based on discrete fourier transform as claimed in claim 1, wherein said step of S1 is preceded by the steps of:
preprocessing the collected magnetic signals of the banknotes with the preset number to obtain standard magnetic signal data.
3. A method of banknote magnetic signal identification based on discrete fourier transform as claimed in claim 2 wherein said magnetic signal preprocessing comprises interference rejection, averaging.
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| WO1985002928A1 (en) * | 1983-12-27 | 1985-07-04 | Bergstroem Arne | Apparatus for authenticating bank notes |
| GB9413413D0 (en) * | 1994-07-04 | 1994-08-24 | At & T Global Inf Solution | Apparatus and method for testing bank-notes |
| US6892871B2 (en) * | 2002-03-11 | 2005-05-17 | Cummins-Allison Corp. | Sensor and method for discriminating coins of varied composition, thickness, and diameter |
| JP2005092712A (en) * | 2003-09-19 | 2005-04-07 | Matsushita Electric Ind Co Ltd | Paper money identification apparatus |
| CN100415022C (en) * | 2004-12-02 | 2008-08-27 | 乐金电子(中国)研究开发中心有限公司 | CeU phone with magnetic detection function and magnetic bar code identifying method |
| GB2466465B (en) * | 2008-12-19 | 2011-02-16 | Ingenia Holdings | Authentication |
| CN104813369B (en) * | 2012-10-25 | 2018-01-12 | 魅股份有限公司 | By the system of valuable taxonomy of goods |
| US20150302677A1 (en) * | 2012-12-07 | 2015-10-22 | Sicpa Holding Sa | Non-periodic tiling document security element |
| CN105139509B (en) * | 2015-08-13 | 2017-08-29 | 深圳怡化电脑股份有限公司 | A kind of method and device of magnetic data filtering |
| CN105184954B (en) * | 2015-08-14 | 2018-04-06 | 深圳怡化电脑股份有限公司 | A kind of method and banknote tester for detecting bank note |
| CN105427446A (en) * | 2015-11-06 | 2016-03-23 | 东方通信股份有限公司 | Authentic identification method for paper money based on magnetic signal |
| CN108198322B (en) * | 2018-02-07 | 2020-03-27 | 深圳怡化电脑股份有限公司 | Magnetic stripe positioning method and device |
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