CN111064543A - Hidden interference signal generating device and method based on ultrasonic parametric array - Google Patents
Hidden interference signal generating device and method based on ultrasonic parametric array Download PDFInfo
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- H—ELECTRICITY
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Abstract
The invention discloses a hidden interference signal generating device and method based on an ultrasonic parametric array. The method mainly comprises the following steps: firstly, a low-frequency broadband noise signal is generated and modulated to obtain an ultrasonic interference signal, the ultrasonic interference signal is amplified by an amplifying module and matched by a matching module and then is transmitted by an ultrasonic transducer array, and the ultrasonic interference signal is self-demodulated at a receiving end due to the inherent nonlinear defect of an acoustic device to cover a voice signal, so that the function of hiding interference recording is realized. The invention overcomes the defects of the existing anti-eavesdropping method and can realize the hidden interference on all the recording devices.
Description
Technical Field
The invention relates to the field of information security maintenance, in particular to a hidden interference signal generating device and method based on an ultrasonic parametric array.
Background
Information leakage is a problem which puzzles people for a long time, and with the rapid development of intelligent equipment, means for stealing information by utilizing some advanced recording equipment such as a smart phone, a recording pen and the like are more convenient and more concealed, so that hidden dangers exist for individuals, enterprises and even countries.
In order to solve the problem, the recording and eavesdropping prevention technology which is common in the current engineering comprises an audio interference technology and an electromagnetic wave interference technology: the audio interference technology annihilates the voice signal by playing some background noise, but the mode generates audible noise signals in the air, so that great interference and inconvenience are brought to a speaker; the electromagnetic wave interference is that the high-power electromagnetic wave is emitted to cause interference signals generated by the digital equipment due to electromagnetic coupling so as to prevent normal recording. However, most of the existing digital recording devices are provided with anti-interference circuits, the circuits of the existing digital recording devices are difficult to sense corresponding electromagnetic signals, meanwhile, the effective acting distance of electromagnetic interference is only tens of centimeters, the types of mobile phones capable of effectively interfering are very limited, the interference function is greatly restricted, the interference distance is short, the interference effect is poor, and the application range is narrow.
Disclosure of Invention
The purpose of the invention is as follows: in order to overcome the defects of the existing scheme and effectively conceal and shield the recording equipment, the invention provides a concealed interference signal generating device and method based on an ultrasonic parametric array, which are used for solving the increasingly serious problem of information leakage caused by eavesdropping of the recording equipment.
The technical scheme is as follows: the technical scheme adopted by the invention is as follows:
the invention provides a hidden interference signal generating device based on an ultrasonic parametric array, which is composed of a signal processing platform, a signal amplification module, a matching circuit module and an ultrasonic array module on the circuit structure; the signal processing platform comprises a single chip microcomputer and a filter in signal connection with the single chip microcomputer; the signal amplification module comprises a plurality of power amplifiers forming a power amplifier matrix; the matching circuit module comprises a plurality of transformers and inductive elements connected with each transformer; wherein the output port of the signal processing platform is connected with the power signal amplification module; the power amplification module is connected with a transformer in the matching circuit module; the inductive element is connected with the ultrasonic transducer; the signal processing platform sends out multiple paths of ultrasonic interference signals, and the connection method of each path is the same, so that an ultrasonic array is formed.
The signal processing platform generates a noise signal and a digital sinusoidal signal with specified frequency, and outputs an ultrasonic interference signal generated after the noise signal and a carrier signal are modulated after smoothing processing by a filter. The signal amplification module amplifies and outputs the ultrasonic interference signal generated by the signal processing platform by using a power amplifier. The matching circuit module realizes the functions of tuning matching and impedance matching: the active resistance of the transducer is changed by adopting a transformer, so that the active resistance is close to the output resistance of a power amplifier, and the optimal transmission power matching is achieved; the input reactance of the transducer is adjusted by switching in the inductive element so that the equivalent impedance input phase angle is 0. The ultrasonic array module converts the ultrasonic interference signals into sound waves to be transmitted in the air from electric signals, a plurality of ultrasonic transducers can generate a plurality of difference frequency components and low-frequency primary wave signals after self-demodulation at a receiving end, and meanwhile, the design of the array enables energy to be more concentrated, directivity to be stronger and interference distance to be farther.
A method for generating hidden interference signals based on ultrasonic parametric array includes generating low-frequency broadband noise signals, modulating the signals to obtain ultrasonic interference signals, amplifying the ultrasonic interference signals by an amplifying module and matching the ultrasonic interference signals by a matching module, and self-demodulating the ultrasonic interference signals at receiving end due to inherent nonlinearity of acoustic devices to realize the function of hidden interference recording. The method specifically comprises the following steps:
a) generating an initial seed and an initial key by adopting a multiplication congruence algorithm: let initial value x0Is a 256-bit value, multiply congruenceThe algorithm formula is as follows:
xn+1＝xn*k(modM)
where k and M are constants, xnIs the iteration result of the nth round. The final output is obtained after 1000 rounds. And taking the output first 128bit value as an initial key, and taking the output second 128bit value as an initial seed.
b) And encrypting the generated initial seed by using the generated initial key by using an SM4 cryptographic algorithm to obtain a final pseudo-random number noise sequence.
wherein L isFTaking values for tuning inductance, C0Is the static capacitance of a single transducer, f0The frequency of the primary wave generated inside the channel signal generator.
The output resistance of the power amplifier is recorded as R0And the equivalent load impedance of the energy converter after tuning matching is R, and in order to realize impedance matching, the transformation ratio N of the transformer should meet the following conditions:
1:N2＝R0:R
and 150, outputting an ultrasonic interference signal by the ultrasonic transducer array, wherein the ultrasonic interference signal is self-demodulated at a receiving end due to the inherent nonlinear defect of the acoustic device, and the noise signal covers the voice signal. The arrangement of the ultrasonic transducer array can be reasonably arranged into a one-dimensional linear matrix, an arc matrix, a circular matrix, a honeycomb matrix, a multi-dimensional matrix and the like according to the appearance requirement. The distance d between adjacent transducers should satisfy:
d≤λ/2
where λ is the wavelength of the signal transmitted by the ultrasonic transducer.
For self demodulation at the receiving end: due to the inherent non-linear defect of an acoustic device in the recording equipment, an ultrasonic interference signal can be automatically demodulated in the ultrasonic interference signal according to an acoustic parametric array theory, high-frequency components are filtered by a filter of the recording equipment, and low-frequency components are left in the recording.
Westervelt dual-frequency parametric array theory: two high-frequency initial waves with the same propagation direction can generate frequency spectrum components such as difference frequency, sum frequency and frequency multiplication in a nonlinear receiving system.
Primary wave:
second order quantity:
only the difference frequency component is left after filtering.
The Westervelt double-frequency parametric array theory only explains the situation that two frequency components exist in the original wave, but more low-frequency components exist in the original wave under the actual condition, and Berktay reasonably explains the situation.
Berktay broadband parametric array theory:
assume that the signal directly transmitted by the physical sound source is:
second order quantity:
after filtering, the low-frequency broadband signal remains as a noise signal of interference.
The invention has the beneficial effects that: the low-frequency broadband signal is modulated to obtain an ultrasonic interference signal, the ultrasonic interference signal is sent in the air in a concealed mode, due to the inherent nonlinear defect of an acoustic device, the ultrasonic interference signal is self-demodulated at a receiving end, the voice signal is covered, and therefore the effect of shielding the recording equipment is achieved. The invention skillfully utilizes the inaudibility of ultrasonic waves and the inherent nonlinearity of an acoustic device, and combines an acoustic parametric array theory to effectively shield the recording interception by sending the shielding interference signal.
Drawings
FIG. 1 is a flow chart of a method for generating a concealed interference signal based on an ultrasonic parametric array according to the present invention;
FIG. 2 is a hardware structure diagram of a hidden interference signal generating device based on an ultrasonic parametric array according to the present invention;
Detailed Description
The present invention will be further described with reference to the accompanying drawings.
FIG. 1 is a flow chart of a method for generating a concealed interference signal based on an ultrasonic parametric array according to the present invention.
The invention provides a method for generating a concealed interference signal based on an ultrasonic parametric array, which comprises the steps of firstly generating a low-frequency broadband noise signal, modulating the low-frequency broadband noise signal to obtain an ultrasonic interference signal, amplifying the ultrasonic interference signal by an amplifying module, matching the ultrasonic interference signal by a matching module, and then sending the ultrasonic interference signal out by an ultrasonic transducer array. The method specifically comprises the following steps:
110. generating a low frequency broadband noise signal: firstly, a pseudo-random number sequence is generated to be used as a noise signal, and then spread spectrum modulation is carried out on an original binary sequence by adopting a spread spectrum modulation technology to generate a broadband signal.
1110. Generating a pseudo-random number sequence: firstly, generating an initial seed and an initial key by adopting a multiplication-congruence algorithm; and encrypting the initial seed by using an initial key by adopting an encryption algorithm to obtain a pseudo-random number noise sequence. The method comprises the following specific steps:
1111. generating an initial seed and an initial key by adopting a multiplication congruence algorithm: let initial value x0Is composed of
A 256bit value, multiply-congruence algorithm is formulated as follows:
xn+1＝xn*k(modM)
where k and M are constants, xnIs the iteration result of the nth round. The final output is obtained after 1000 rounds. And taking the output first 128bit value as an initial key, and taking the output second 128bit value as an initial seed.
1112. And encrypting the generated initial seed by using the generated initial key by using an SM4 cryptographic algorithm to obtain a final pseudo-random number noise sequence.
1120. Spreading the pseudo-random number sequence by adopting a direct sequence spread spectrum modulation technology, and carrying out XOR operation on the signal code and the pseudo-random number sequence to widen the frequency spectrum of a baseband so as to obtain a low-frequency broadband noise signal.
120. Generating an ultrasonic interference signal: generating an ultrasonic sine signal with a specified frequency as a carrier wave for modulation, and modulating the low-frequency broadband noise signal generated in the step 1 to generate an ultrasonic interference signal. The method specifically comprises the following steps:
1210. the direct digital synthesis technology is adopted to generate digital sinusoidal signal ultrasonic waves with specified frequency as carrier waves for modulation.
1220. And (2) modulating the sine wave of the generated digital signal and the low-frequency broadband noise signal sequence in the step (1) by adopting a certain communication modulation method to obtain a digital ultrasonic interference signal, and converting the binary discrete sequence into a continuous analog signal by a digital-to-analog converter. A common modulation method is BASK modulation but is not limited to this modulation method.
1230. Smoothing the step-type ultrasonic interference signal output by the upper stage (digital-to-analog converter) by using a filter, filtering out aliasing and useless stray components, smoothing the waveform and obtaining the ultrasonic interference signal.
130. Amplifying the ultrasonic interference signal: and amplifying the ultrasonic interference signal generated in the step 2 by using a power amplification module for better signal transmission.
140. And (3) performing tuning matching and impedance matching on the system: and the inductive device is used for tuning and matching the ultrasonic transducer, so that reactive loss in power transmission is reduced. The output impedance of the power amplification module is matched with the load impedance to be equal or close to each other, so that the output power of the power amplifier reaches or is close to the maximum.
1410. And (3) performing tuning matching: the ultrasonic transducer is a capacitive load, if a driving signal is directly loaded to the transducer, phase difference occurs between a voltage signal and a current signal, so that the signal power loaded to the load is weakened, and the input reactance of the transducer is adjusted by adopting a method of externally connecting an inductive element, so that the input phase angle of the equivalent reactance tends to 0. Common external methods are, but not limited to, series or parallel tuning inductors. The inductance value in the series tuning inductance method is calculated as follows:
wherein L isFTaking values for tuning inductance, C0Is the static capacitance of a single transducer, f0The frequency of the primary wave generated inside the channel signal generator.
1420. And (3) performing impedance matching: the output power of the power amplifier may be maximized when the output impedance of the power amplifier is equal to the input impedance of the load. The active resistance of the transducer is changed by connecting the transformer, so that the active resistance is equal to or close to the output resistance of the power amplifier, the optimal power transmission matching is achieved, and the transducer obtains the maximum output power.
The output resistance of the power amplifier is recorded as R0And the equivalent load impedance of the energy converter after tuning matching is R, and in order to realize impedance matching, the transformation ratio N of the transformer should meet the following conditions:
1:N2＝R0:R
150. the ultrasonic interference signal is output by the ultrasonic transducer array, the ultrasonic interference signal is self-demodulated at a receiving end due to the inherent nonlinear defect of the acoustic device, and the noise signal covers the voice signal. The arrangement of the ultrasonic transducer array can be reasonably arranged into a one-dimensional linear matrix, an arc matrix, a circular matrix, a honeycomb matrix, a multi-dimensional matrix and the like according to the appearance requirement. The distance d between adjacent transducers should satisfy:
d≤λ/2
where λ is the wavelength of the signal transmitted by the ultrasonic transducer.
For self demodulation at the receiving end: due to the inherent non-linear defect of an acoustic device in the recording equipment, an ultrasonic interference signal can be automatically demodulated in the ultrasonic interference signal according to an acoustic parametric array theory, high-frequency components are filtered by a filter of the recording equipment, and low-frequency components are left in the recording.
Westervelt dual-frequency parametric array theory:
two high-frequency initial waves with the same propagation direction can generate frequency spectrum components such as difference frequency, sum frequency and frequency multiplication in a nonlinear receiving system.
Primary wave:
second order quantity:
only the difference frequency component is left after filtering.
The Westervelt double-frequency parametric array theory only explains the situation that two frequency components exist in the original wave, but more low-frequency components exist in the original wave under the actual condition, and Berktay reasonably explains the situation.
Berktay broadband parametric array theory:
assume that the signal directly transmitted by the physical sound source is:
second order quantity:
after filtering, the low-frequency broadband signal remains as a noise signal of interference.
According to the embodiment, the low-frequency broadband signal is modulated to obtain the ultrasonic interference signal and the ultrasonic interference signal is sent in the air in a concealed mode, due to the inherent nonlinear defect of the acoustic device, the ultrasonic interference signal is self-demodulated at the receiving end, the voice signal is covered, and therefore the effect of shielding the recording equipment is achieved. The invention skillfully utilizes the inaudibility of ultrasonic waves and the inherent nonlinearity of an acoustic device, and combines an acoustic parametric array theory to effectively shield the recording interception by sending the shielding interference signal.
Claims (7)
1. The utility model provides a conceal interference signal generating device based on ultrasonic wave parametric array which characterized in that: the circuit structure is composed of a signal processing platform, a signal amplification module, a matching circuit module and an ultrasonic array module; the signal processing platform comprises a single chip microcomputer and a filter in signal connection with the single chip microcomputer; the signal amplification module comprises a plurality of power amplifiers forming a power amplifier matrix; the matching circuit module comprises a plurality of transformers and inductive elements connected with each transformer; wherein the output port of the signal processing platform is connected with the power signal amplification module; the power amplification module is connected with a transformer in the matching circuit module; the inductive element is connected with the ultrasonic transducer; the signal processing platform sends out multiple paths of ultrasonic interference signals, and the connection method of each path is the same, so that an ultrasonic array is formed.
2. A hidden interference signal generating method based on an ultrasonic parametric array is characterized in that firstly, a signal processing platform generates a low-frequency broadband noise signal, the low-frequency broadband noise signal is modulated to obtain an ultrasonic interference signal, the ultrasonic interference signal is amplified by an amplifying module and matched by a matching module and then is emitted by an ultrasonic transducer array, and the ultrasonic interference signal is self-demodulated at a receiving end due to inherent nonlinearity of an acoustic device, so that the function of hidden interference recording is realized;
the method comprises the following steps:
step 110, generating a low-frequency broadband noise signal: firstly, generating a pseudo-random number sequence as a noise signal, and then performing spread spectrum modulation on an original binary sequence by adopting a spread spectrum modulation technology to generate a broadband signal;
step 120, generating an ultrasonic interference signal: generating an ultrasonic sinusoidal signal with a specified frequency as a carrier for modulation, and modulating the low-frequency broadband noise signal generated in step 110 to generate an ultrasonic interference signal;
step 130, amplifying the ultrasonic interference signal: amplifying the ultrasonic interference signal generated in the step 2 by using a power amplification module for better signal transmission;
step 140, performing tuning matching and impedance matching on the system: and the inductive device is used for tuning and matching the ultrasonic transducer, so that reactive loss in power transmission is reduced. Matching the output impedance of the power amplification module with the load impedance to make the output impedance equal to or close to the load impedance, so that the output power of the power amplifier reaches or is close to the maximum;
and 150, outputting an ultrasonic interference signal by the ultrasonic transducer array, wherein the ultrasonic interference signal is self-demodulated at a receiving end due to the inherent nonlinear defect of the acoustic device, and the noise signal covers the voice signal.
3. The method for generating the concealed interference signal based on the ultrasonic parametric array according to claim 2, characterized in that: the step 110 is performed according to the following steps:
step 1110, generating a pseudo-random number sequence: firstly, generating an initial seed and an initial key by adopting a multiplication-congruence algorithm; encrypting the initial seed by using an initial key by adopting an encryption algorithm to obtain a pseudo-random number noise sequence;
and 1120, performing XOR operation on the signal code and the pseudo-random number sequence by adopting a direct sequence spread spectrum modulation technology to spread the spectrum of the pseudo-random number sequence, so as to widen the baseband spectrum and obtain a low-frequency broadband noise signal.
4. The method of generating a concealed interference signal based on an ultrasonic parametric array according to claim 3, wherein: the specific steps for generating the pseudo-random number sequence in step 1110 are as follows:
a) generating an initial seed and an initial key by adopting a multiplication congruence algorithm: let initial value x0Is one 25The 6bit value, the multiply-congruence algorithm formula is as follows:
xn+1＝xn*k(mod M)
where k and M are constants, xnIs the iteration result of the nth round; obtaining final output after 1000 rounds; taking the output first 128bit value as an initial key, and taking the output second 128bit value as an initial seed;
b) and encrypting the generated initial seed by using the generated initial key by using an SM4 cryptographic algorithm to obtain a final pseudo-random number noise sequence.
5. The method for generating the concealed interference signal based on the ultrasonic parametric array according to claim 2, characterized in that: the step 120 is performed according to the following steps:
step 1210, generating a digital ultrasonic sine signal with specified frequency as a carrier for modulation by adopting a direct digital synthesis technology;
step 1220, a certain communication modulation method is adopted to modulate the sine wave of the generated digital signal and the low-frequency broadband noise signal sequence in step 110 to obtain a digital ultrasonic interference signal, and the binary discrete sequence is converted into a continuous analog signal through a digital-to-analog converter. The common modulation mode is BASK modulation but is not limited to the modulation method;
step 1230, using a filter to carry out filter pair on the previous stage; a digital-to-analog converter; and smoothing the output step-type ultrasonic interference signal, and filtering out aliasing and useless stray components to enable the waveform to be smoother so as to obtain the ultrasonic interference signal.
6. The method for generating the concealed interference signal based on the ultrasonic parametric array according to claim 2, characterized in that: the step 140 is performed according to the following steps:
step 1410, tuning and matching: adjusting the input reactance of the transducer by adopting a method of externally connecting an inductive element to enable the input phase angle of the equivalent reactance to tend to 0; a common external method is to tune the inductance in series but is not limited thereto; the inductance value in the series tuning inductance method is calculated as follows:
wherein L isFTaking values for tuning inductance, C0Is the static capacitance of a single transducer, f0The frequency of the primary wave generated inside the channel signal generator.
Step 1420, impedance matching: the active resistance of the transducer is changed by connecting a transformer, so that the active resistance is equal to or close to the output resistance of a power amplifier, the optimal power transmission matching is achieved, and the transducer obtains the maximum output power; the output resistance of the power amplifier is recorded as R0And the equivalent load impedance of the energy converter after tuning matching is R, and in order to realize impedance matching, the transformation ratio N of the transformer should meet the following conditions:
1:N2＝R0:R 。
7. the method for generating the concealed interference signal based on the ultrasonic parametric array according to claim 2, characterized in that: when the distance d between adjacent transducers in the step 150 satisfies:
d≤λ/2
where λ is the wavelength of the signal transmitted by the ultrasonic transducer.
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| CN101594165A (en) * | 2009-06-19 | 2009-12-02 | 中国科学院微电子研究所 | A kind of mixed spread spectrum communication system and method for work thereof |
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