CN101873145A - Method and device for interfering passive wireless headphone by audio electromagnetic field - Google Patents
Method and device for interfering passive wireless headphone by audio electromagnetic field Download PDFInfo
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- CN101873145A CN101873145A CN201010180673A CN201010180673A CN101873145A CN 101873145 A CN101873145 A CN 101873145A CN 201010180673 A CN201010180673 A CN 201010180673A CN 201010180673 A CN201010180673 A CN 201010180673A CN 101873145 A CN101873145 A CN 101873145A
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Abstract
The invention relates to a method and a device for interfering a passive wireless headphone by an audio electromagnetic field. Cheating in conventional large-scale exams is very difficult to prevent. The passive wireless headphone is directly driven by the audio electromagnetic field so as to send an interference signal to interfere the passive wireless headphone; the interference signal comprises ordered wave and noise which are sent simultaneously; the ordered wave is frequency-hopping positive/negative pulse wave, square wave and sine wave which are alternately sent; and the sine wave and the information transmitted by the passive wireless headphone produce beat frequency. The device for realizing the method comprises an audio and noise generating device, a power amplifier and a power coil, wherein the audio and noise generating device comprises a singlechip, a D/A conversion module, a filtering module, three input resistors, a comparator OP1 and an adder OP2; the output end of the adder OP2 is the output end of the audio and noise generating device. The method has the advantages of maturity, reliability, easy operation, and capability of directly utilizing an audio voice classroom or laboratory facility.
Description
Technical field
The invention belongs to the control technology field, relate to a kind of method and device thereof of interference of electromagnetic field passive wireless headphone, particularly disturb, suppress method and electromagnetic field generation device as miniature (perhaps being called stealth) Audio frequency radio earphone of cheating instrument.
Background technology
Stealthy wireless headset on the market comprises several parts compositions of strong magnetic earplug, audio frequency amplifier, Necklet-type electromagnetic field transmitting antenna coil, battery and tone frequency channel wire.Along with development of technology, rare earth material makes that the magnetic field of permanent magnetic material is very powerful, and " passive rare earth earphone (earplug) " structure of making is smaller and more exquisite, and is disguised better, removes to be used to special requirement such as broadcasting occasion, usually utilized as the cheating instrument by the people.This class " earphone " is passive, does not promptly use power supply, is placed on the higher-strength electromagnetic field signal that produces by transmitting coil in the duct and drives and vibrate, and can conduct sound by otica.The Head and Neck that supporting power emission equipment---coil cover is worn over the people is sent out acoustic information, but operating distance is not far.In order to receive cheating information, the cribber often with on be in various types of mobile phones of mute state, as the telecommunication instrument, even can utilize various commercially available speech players, recording pen to prerecord down cheating information as the 3G mobile of Global Link GSM, code division multiple access CDMA or the 3rd third-generation mobile communication, Personal Handyphone System, intercom as the play signal source.
Stealthy wireless headset places in the duct fully, and very hidden, volume is small and exquisite, conveniently carries, and sound is clear, and its portability, disguise become the public hazards utensil of all kinds of examinations.The stealthy wireless headset of domestic ZL200620120305.7 in addition etc.The common ground of this class equipment is the concealed earphone (earplug) of wireless connections, and size as earplug external form such as the soya bean need not to use the physics lead-in wire, wears to be difficult for being discovered by other people.
Mobile phone interference unit or mobile phone shielding device can shield various types of mobile phones.The signal bandwidth of all kinds of mobile phone shielding/interference units is different with frequency range, as code division multiple access CDMA:869～894MHz, 2110～2170MHz, Global Link GSM:925～960MHz, DCS:1805～1880MHz, Personal Handyphone System PHS:1900～1990MHz, the 3rd third-generation mobile communication 3G:2015～2105MHz etc.The interference unit that has can cover 2010～2025MHz of 3G, 2110～2125MHz, 2130～2145MHz.3G mobile is in emerging communications band, and based on CDMA technology, the mobile phone shielding device that use in early stage examination hall does not all contain the 3G frequency range, has caused the concern to 3G mobile of cribber and related industry chain.Stealthy wireless headset cheating tool making is simple, as long as the cheating wireless headset signal input part that will connect inserts the handset earphone delivery outlet.Traditional High-frequency Interference, shielding leave the neutral of many frequency ranges, the frequency range, frequency modulated transmitter that also has intercom with FM receiver/broadcast receiver frequency range, Wi-Fi communicates by letter and the Wi-Fi mobile phone all can be utilized by lawless molecule.The 4th kind of 3G standard WiMAX and mobile phone thereof passing through in recent years, and the frequency uncertainty of this technology employing, existing manufacturer provides the base station of 3.7GHz, and indivedual telecom operators use in the ISM band test; Also have blue-tooth device to have 10～20 meters communication distance.The method of this employing high frequency transfer phase blocking-up is because frequency range is many, and new technology continues to bring out, and is hard to guard against.At present, even common civilian technology also adopts code division multiple access (CDMA) technology with anti-interference in a large number, need to strengthen the interference signal energy and could suppress conveying function.And disturb rejection directly relevant with spectral energy density, and need the frequency range of interference many more, the spectrum energy that can be assigned to is low more, has directly reduced the strick precaution effect.The covering radius of commercially available mobile phone shielding device is less, has only 10～20 meters, makes that the anti-cheating work of large-scale examination is very difficult.
Summary of the invention
Purpose of the present invention is exactly at the deficiencies in the prior art, and a kind of technological means and corresponding enforceable technique device that cuts off the cheating approach is provided.
The inventive method specifically is to adopt audio electromagnetic field directly to drive passive wireless headphone, sends interference signal passive wireless headphone is disturbed.Described interference signal comprises orderly ripple and the noise that sends simultaneously.
Frequency hopping positive negative pulse stuffing ripple, square wave and the sine wave of described orderly ripple for alternately sending;
Described frequency hopping positive negative pulse stuffing wave frequency is 20～200Hz;
The frequency of described square wave is 400 ± Δ fHz, Δ f=50～100Hz;
Described sinusoidal wave frequency is 900 ± Δ fHz, Δ f=50～100Hz;
The beat frequency that the sinusoidal wave information that transmits with passive wireless headphone produces.
The flat top of described noise is 600～1200Hz, and the following 1200Hz that reaches of 600Hz is with each frequency doubling attenuation 1.8dB of top.
The interfering passive wireless headphone by audio electromagnetic field device comprises audio frequency and noise-producing equipment, power amplifier and power coil.
Audio frequency and noise-producing equipment comprise single-chip microcomputer, D/A modular converter, filtration module, the first input resistance R1, the second input resistance R2, the 3rd input resistance R7, first resistance R 3, second resistance R 4, the 3rd resistance R 5, feedback resistance R6, comparator OP1, adder OP2.
An I/O pin in the I/O mouth of single-chip microcomputer is connected with the end of the first input resistance R1, another I/O pin is connected with the end of the second input resistance R2, and another I/O mouth of single-chip microcomputer is connected with the input of D/A modular converter; The positive input terminal of comparator OP1 is connected with the other end of the first input resistance R1, negative input end is connected with the other end of the second input resistance R2, and the output of comparator OP1 is connected with an end of first resistance R 3; The output of D/A modular converter is divided into two-way, wherein one the tunnel is connected with an end of second resistance R 4, another road is connected with the input of filtration module 1-3, and the output of filtration module is connected with an end of the 3rd resistance R 5; The end of the other end of the other end of the other end of first resistance R 3, second resistance R 4, the 3rd resistance R 5, feedback resistance R6 is connected with the negative input end of adder OP2, the positive input terminal of adder OP2 is connected with the end of the 3rd input resistance R7, the other end ground connection of the 3rd input resistance R7, the other end of feedback resistance R6 is connected with the output of adder OP2, and the output of adder OP2 is the output of audio frequency and noise-producing equipment.
The output of audio frequency and noise-producing equipment is connected with the input of power amplifier, and the left and right sound channels output of power amplifier is connected with two power coils by the audio power line respectively.
The inventive method can provide extremely strong magnetic field, and the electromagnetic field of change directly promotes earphone reed sounding through the enrichment of the magnetic material in the wireless headset.The electromagnetic field scope that the audio driven necklace that the present invention's employing itself carries with miniature stealthy wireless headset more than cheating produces is much bigger, utilize such stealthy wireless headset to have the ability of the high enrichment magnetic line of force, thus the Strength Changes that the is enriched to change electromagnetic field magnetic line of force bigger than ordinary audio earphone; Drive stealthy wireless headset and send noise, perhaps utilize the aliasing characteristic in physics and the acoustics---the relation of first-harmonic and (high order) harmonic wave, and " bat " phenomenon, perhaps drive stealthy wireless headset reed motion competitively, particularly adopting the shock pulse form to drive reed moves near extreme position, suppress as the concealed earphone reed range of movement of the instrument of cheating and the magnetic saturation situation in the permanent magnet, reach the hearing of disturbing the cribber and suppress equipment transmission cheating information.
The present invention adopts audio frequency large power, electrically magnetic field directly to drive stealthy wireless headset sounding, disturb and suppress and transmit cheating information as the passive micro radio earphone of cheating instrument, operation principle mature and reliable, equipment obtain easily and install, can directly utilize audio speech classroom or laboratory site facility, easy operating; The frequency band of audio frequency is narrow, the spectral power density height, and technological means is with low uncertainty, is a kind of anti-efficiently cheat method.Equipment such as alternative mobile phone shielding device are counter practises fraud, and perhaps unites use with it, remedies it and is difficult to the covering of high frequency full range band, leaves over the drawback of communication channel easily.
Description of drawings
Fig. 1 is the method schematic diagram of interfering passive wireless headphone by audio electromagnetic field of the present invention;
Fig. 2 is an apparatus structure schematic diagram of the present invention;
Fig. 3 is the structural representation of Fig. 2 sound intermediate frequency and noise-producing equipment;
Fig. 4 is a frequency hopping positive negative pulse stuffing ripple oscillogram;
Fig. 5 is square-wave waveform figure;
Fig. 6 is the curve chart of noise.
Embodiment
Below in conjunction with accompanying drawing further to the present invention's explanation.
In the method schematic diagram of the interfering passive wireless headphone by audio electromagnetic field that Fig. 1 provides, loop A, coil B pass to alternating current, have produced alternating electromagnetic field C in the centre of two coils.In the diagram mark magnetic induction direction of electric current when a direction flows.The wireless headset D that is placed in the large-area change electromagnetic field can suppress the vibration of the reed of stealthy wireless headset with the cheating voice by driving the electromagnetic field signal sounding, and the sound of irrelevant information disturbs the cribber strongly, makes it can't not hear the information of cheating.
This method adopts audio electromagnetic field directly to drive passive wireless headphone exactly, sends interference signal passive wireless headphone is disturbed.Described interference signal comprises orderly ripple and the noise that sends simultaneously.
Frequency hopping positive negative pulse stuffing ripple, square wave and the sine wave of described orderly ripple for alternately sending;
The frequency of described square wave is 400 ± Δ fHz, Δ f=50～100Hz;
Described sinusoidal wave frequency is 900 ± Δ fHz, Δ f=50～100Hz;
The beat frequency that the sinusoidal wave information that transmits with passive wireless headphone produces.
The flat top of described noise is 600～1200Hz, and the following 1200Hz that reaches of 600Hz is with each frequency doubling attenuation 1.8dB of top.
Fig. 2 provides apparatus structure schematic diagram of the present invention.
The interfering passive wireless headphone by audio electromagnetic field device comprises audio frequency and noise-producing equipment 1, power amplifier 2 and power coil 4.
The structure of audio frequency and noise-producing equipment is as shown in Figure 3: comprise single-chip microcomputer 1-1, D/A modular converter 1-2, filtration module 1-3, the first input resistance R1, the second input resistance R2, the 3rd input resistance R7, first resistance R 3, second resistance R 4, the 3rd resistance R 5, feedback resistance R6, comparator OP1, adder OP2.
An I/O pin in the I/O mouth of single-chip microcomputer 1-1 is connected with the end of the first input resistance R1, another I/O pin is connected with the end of the second input resistance R2, and another I/O mouth of single-chip microcomputer 1-1 is connected with the input of D/A modular converter 1-2; The positive input terminal of comparator OP1 is connected with the other end of the first input resistance R1, negative input end is connected with the other end of the second input resistance R2, and the output of comparator OP1 is connected with an end of first resistance R 3; The output of D/A modular converter 1-2 is divided into two-way, wherein one the tunnel is connected with an end of second resistance R 4, another road is connected with the input of filtration module 1-3, and the output of filtration module 1-3 is connected with an end of the 3rd resistance R 5; The end of the other end of the other end of the other end of first resistance R 3, second resistance R 4, the 3rd resistance R 5, feedback resistance R6 is connected with the negative input end of adder OP2, the positive input terminal of adder OP2 is connected with the end of the 3rd input resistance R7, the other end ground connection of the 3rd input resistance R7, the other end of feedback resistance R6 is connected with the output of adder OP2, and the output of adder OP2 is the output of audio frequency and noise-producing equipment.
Wherein single-chip microcomputer, D/A modular converter and filtration module all adopt mature technique, can purchase obtain.For example single-chip microcomputer adopts 8 single-chip microcomputers such as 80C51, AVR or PIC; The D/A modular converter adopts the DAC0832 chip; Frequency-the amplitude relation of filtration module control output noise adopts ripe RLC filter circuit.
The output of audio frequency and noise-producing equipment 1 is connected with the input of power amplifier 2, power amplifier adopts matured product, the interference signal of several milliwatts that audio frequency and noise-producing equipment can be produced is amplified to the audio signal of several hectowatts, for example uses the DF-A audio transmitter or the sound amplifier of 100 watts or 200 watts.The left and right sound channels output of power amplifier 2 is connected with two power coils 4 by audio power line 3 respectively.Should note the output impedance of power amplifier and the impedance matching of the power coil that sends as audio electromagnetic field, adopt the series and parallel connection according to the impedance decision of power coil.
Import the audio signal of various selected frequencies and frequency spectrum by the multichannel voice frequency input jack, amplify through power amplifier is inner, the signal after the power amplification is exported by the audio power delivery outlet; One ending connecting audio power delivery outlet of audio power line, another termination power coil.
Power coil adopts large-scale coil, coil can be embedded indoor metope.Tell on for improving electromagnetic field, can place ferromagnetic material such as ferrite at hub of a spool.The equipment in the combination of the equipment of these several parts and audio frequency hearing classroom and installation, use are close.
Fig. 4 provides pulse shock waveform and formation thereof: positive pulse duration t1 forces reed to move to the range that this pulse electromagnetic field energy reaches it; The direct impulse extinction time is t2 at interval, reed under the effect of restoring force, return motion; Negative pulse duration t3 forces reed to move to extreme position in the other direction; Select t1=t3.T4 is the blanking time after the positive negative pulse stuffing, and the total time τ of t1+t2+t3+t4 is the one-period time, its 1/ τ reciprocal=frequency f.The frequency 20-200Hz of strobe pulse surge waveform adopts random device to generate the cycle time of each shock pulse.
Accompanying drawing 5 is the pulse square wave waveform, and wherein t5 is the time of forward waveform, and t6 is the negative sense waveform time, t5=t6.The period tau 1=t5+t6 of pulse square wave.Square wave is rich in the high order harmonic component composition, selects square wave frequency 400 ± Δ f Hz, Δ f=50～100Hz.
Accompanying drawing 6 provided high segment by every frequency doubling attenuation 1.8dB and in the every frequency multiplication of low segment increase the noise amplitude curve of 1.8dB.
Two I/O pin follow procedures in the I/O mouth of single-chip microcomputer 1-1 are provided with sequential output high-low level, export positive negative level by comparator OP1, and comparator OP1 can export as the waveform of Fig. 4 or the square wave of Fig. 5, forms positive negative pulse stuffing.Another I/O mouth of single-chip microcomputer 1-1 is connected with the input of D/A modular converter 1-2, and control D/A modular converter 1-2 forms sine wave and white noise, and the white noise of generation produces specific audio-frequency noise through filter module.
The reference parameter of each equipment is as follows:
Power coil adopts multiturn, and being embedded in the metope or being placed on separately needs to shield the place that cheating may occur with wireless headset; Frequency response 20～the 15000Hz of power amplifier, power be more than or equal to 100 watts, note its output impedance will with the impedance matching of power coil; Audio frequency and noise-producing equipment select to send the sound of 20～20000Hz, have white noise generation function.Can directly utilize the equipment in the audio frequency hearing classroom of power coil, power amplifier composition to produce interference special audio electromagnetic field, as long as increase an audio frequency and noise-producing equipment.
Audio frequency and noise-producing equipment produce the pulse shock waveform of Fig. 4: positive pulse duration t1＜1.5ms, time interval t2＜0.5ms between the positive and negative pulse, negative pulse duration t3=t1, t4 random device blanking time after the positive negative pulse stuffing generates, one-period total time τ=t1+t2+t3+t4,5ms≤τ≤50ms; The energy random frequency hopping; The positive half cycle t5=of the square wave of Fig. 5 negative half period t6, the Automatic Frequency conversion.
Claims (2)
1. the method for interfering passive wireless headphone by audio electromagnetic field is characterized in that this method adopts audio electromagnetic field directly to drive passive wireless headphone, sends interference signal passive wireless headphone is disturbed;
Described interference signal comprises orderly ripple and the noise that sends simultaneously;
Frequency hopping positive negative pulse stuffing ripple, square wave and the sine wave of described orderly ripple for alternately sending; The beat frequency that the sinusoidal wave information that transmits with passive wireless headphone produces;
Described frequency hopping positive negative pulse stuffing wave frequency is 20～200Hz;
The frequency of described square wave is 400 ± Δ fHz, Δ f=50～100Hz;
Described sinusoidal wave frequency is 900 ± Δ fHz, Δ f=50～100Hz;
The flat top of described noise is 600～1200Hz, and the following 1200Hz that reaches of 600Hz is with each frequency doubling attenuation 1.8dB of top.
2. the device of interfering passive wireless headphone by audio electromagnetic field comprises audio frequency and noise-producing equipment, power amplifier and power coil, it is characterized in that:
Described audio frequency and noise-producing equipment comprise single-chip microcomputer, D/A modular converter, filtration module, the first input resistance R1, the second input resistance R2, the 3rd input resistance R7, first resistance R 3, second resistance R 4, the 3rd resistance R 5, feedback resistance R6, comparator OP1, adder OP2;
An I/O pin in the I/O mouth of single-chip microcomputer is connected with the end of the first input resistance R1, another I/O pin is connected with the end of the second input resistance R2, and another I/O mouth of single-chip microcomputer is connected with the input of D/A modular converter; The positive input terminal of comparator OP1 is connected with the other end of the first input resistance R1, negative input end is connected with the other end of the second input resistance R2, and the output of comparator OP1 is connected with an end of first resistance R 3; The output of D/A modular converter is divided into two-way, wherein one the tunnel is connected with an end of second resistance R 4, another road is connected with the input of filtration module 1-3, and the output of filtration module is connected with an end of the 3rd resistance R 5; The end of the other end of the other end of the other end of first resistance R 3, second resistance R 4, the 3rd resistance R 5, feedback resistance R6 is connected with the negative input end of adder OP2, the positive input terminal of adder OP2 is connected with the end of the 3rd input resistance R7, the other end ground connection of the 3rd input resistance R7, the other end of feedback resistance R6 is connected with the output of adder OP2, and the output of adder OP2 is the output of audio frequency and noise-producing equipment;
The output of audio frequency and noise-producing equipment is connected with the input of power amplifier, and the left and right sound channels output of power amplifier is connected with two power coils by the audio power line respectively.
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| Application Number | Priority Date | Filing Date | Title |
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| CN 201010180673 CN101873145B (en) | 2010-05-21 | 2010-05-21 | Method and device for interfering passive wireless headphone by audio electromagnetic field |
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| Application Number | Priority Date | Filing Date | Title |
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| CN 201010180673 CN101873145B (en) | 2010-05-21 | 2010-05-21 | Method and device for interfering passive wireless headphone by audio electromagnetic field |
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| CN101873145A true CN101873145A (en) | 2010-10-27 |
| CN101873145B CN101873145B (en) | 2013-03-27 |
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| CN 201010180673 Expired - Fee Related CN101873145B (en) | 2010-05-21 | 2010-05-21 | Method and device for interfering passive wireless headphone by audio electromagnetic field |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105101007A (en) * | 2014-05-21 | 2015-11-25 | 胡建人 | Method and apparatus for suppressing passive wireless earphones through pulsed magnet field |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4061972A (en) * | 1973-12-03 | 1977-12-06 | Victor Robert Burgess | Short range induction field communication system |
| US5774791A (en) * | 1993-07-02 | 1998-06-30 | Phonic Ear Incorporated | Low power wireless communication system employing magnetic control zones |
| US6137379A (en) * | 1996-09-23 | 2000-10-24 | Morrill; Russell C. | Universal noise controller |
| CN2924978Y (en) * | 2006-06-19 | 2007-07-18 | 高远瞩 | Concealed wireless earphone |
| CN201051742Y (en) * | 2007-04-17 | 2008-04-23 | 顾然 | Examination room and conference room detection prevention shielding scheduling combiner |
| CN201409118Y (en) * | 2009-05-25 | 2010-02-17 | 卢满常 | Wireless invisible earpiece shielding device |
-
2010
- 2010-05-21 CN CN 201010180673 patent/CN101873145B/en not_active Expired - Fee Related
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4061972A (en) * | 1973-12-03 | 1977-12-06 | Victor Robert Burgess | Short range induction field communication system |
| US5774791A (en) * | 1993-07-02 | 1998-06-30 | Phonic Ear Incorporated | Low power wireless communication system employing magnetic control zones |
| US6137379A (en) * | 1996-09-23 | 2000-10-24 | Morrill; Russell C. | Universal noise controller |
| CN2924978Y (en) * | 2006-06-19 | 2007-07-18 | 高远瞩 | Concealed wireless earphone |
| CN201051742Y (en) * | 2007-04-17 | 2008-04-23 | 顾然 | Examination room and conference room detection prevention shielding scheduling combiner |
| CN201409118Y (en) * | 2009-05-25 | 2010-02-17 | 卢满常 | Wireless invisible earpiece shielding device |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105101007A (en) * | 2014-05-21 | 2015-11-25 | 胡建人 | Method and apparatus for suppressing passive wireless earphones through pulsed magnet field |
| CN105101007B (en) * | 2014-05-21 | 2019-12-24 | 胡建人 | Method for suppressing passive wireless earphone by pulse magnetic field |
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| CN101873145B (en) | 2013-03-27 |
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Granted publication date: 20130327 Termination date: 20170521 |