CN112910885A - Secure communication system and method based on Wheatstone bridge balance method - Google Patents

Secure communication system and method based on Wheatstone bridge balance method Download PDF

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Publication number
CN112910885A
CN112910885A CN202110122904.1A CN202110122904A CN112910885A CN 112910885 A CN112910885 A CN 112910885A CN 202110122904 A CN202110122904 A CN 202110122904A CN 112910885 A CN112910885 A CN 112910885A
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signal
sound
noise
wheatstone bridge
source
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刘三军
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Hubei University for Nationalities
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Hubei University for Nationalities
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L63/00—Network architectures or network communication protocols for network security
    • H04L63/04—Network architectures or network communication protocols for network security for providing a confidential data exchange among entities communicating through data packet networks
    • H04L63/0428—Network architectures or network communication protocols for network security for providing a confidential data exchange among entities communicating through data packet networks wherein the data content is protected, e.g. by encrypting or encapsulating the payload

Abstract

The invention belongs to the technical field of communication, and discloses a secret communication system and method based on a huygens bridge balance method. The invention uses wired mode to transmit signal, the signal only spreads in the specified wired area, and the confidentiality of telephone communication system is greatly improved from the physical layer by releasing the target signal and strong power co-frequency self-interference signal in the transmission line. The secret communication method of the invention prevents the risk of stealing the transmitted information from the physical layer in a mode of simultaneously releasing the target signal and the strong-power same-frequency self-interference signal in the transmission line, thereby realizing the aim of secret communication, and simultaneously, the trusted party can easily acquire the target information due to the Wheatstone bridge balance principle.

Description

Secure communication system and method based on Wheatstone bridge balance method
Technical Field
The invention belongs to the technical field of communication, and particularly relates to a secure communication system and method based on a Wheatstone bridge balance method.
Background
At present, in the internet era, information becomes an important wealth of people, and the loss of people caused by stealing information just like stealing private property of people, so that how to effectively resist private signals from being leaked becomes an important research direction of secret communication.
At present, the security of communication is realized by mainly performing encryption transmission or common key and key ways through a very complex upper layer encryption technology.
However, these techniques have some problems: the complex upper layer encryption technology does greatly improve the security of information transmission, but with the rapid increase of the computing power of computer devices in recent years, the possibility that the upper layer encryption method based on the complex computing amount is damaged gradually increases. The secret key of the secret communication risks being deciphered or stolen and leaked, so that the confidentiality is lost.
The above problem is difficult to overcome fundamentally in the upper layer encryption mode, and therefore the present invention proceeds to solve the problem from the physical layer transfer mode.
The physical layer transmission mode of the signal comprises a wireless transmission mode and a wired transmission mode, the wireless transmission mode is easier to steal from the physical layer by a third party because electromagnetic waves are released towards a wide free space, and the signal to noise ratio obtained by an eavesdropper is higher when the eavesdropper is closer to a transmitting information source, and is possibly far greater than a target receiver, so that the eavesdropper is easier to leak from the perspective of Shannon's theorem. Therefore, the invention uses a wired mode to transmit signals, and the signals only propagate in a specified wired area, thereby avoiding the problem of wireless transmission.
Instead of using the common encryption algorithm, the physical layer method is used to implement secure communication, and a new design of the whole communication circuit structure and a communication method matched with the new design are required. How to solve the problem skillfully and make the circuit simple and low in cost, which makes the application of the circuit possible, is a difficult problem to be solved. The invention discloses a secure communication system based on a Wheatstone bridge balance method and a secure communication method for communication by using the circuit.
The invention can realize the secret communication which is absolutely safe theoretically on the physical layer and solve the safety problem of the encryption technology.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a secure communication system and method based on a Wheatstone bridge balance method.
The present invention is achieved in this way, and a secure communication system based on a wheatstone bridge balance method includes:
the device comprises a combined Wheatstone bridge module, two signal source modules and two signal demodulation processing unit modules, wherein the combined Wheatstone bridge module is a bridge arm;
the two signal source modules are respectively connected with the input ends of two signal sources in the combined Wheatstone bridge modules which are mutually bridge arms through respective power amplifier output ends;
the two signal demodulation processing unit modules are respectively connected to the input ends of the two signal demodulation processing units 1 and 2 in the combined Wheatstone bridge module which is a bridge arm through the output ends of the emitter followers 1 and 2.
Further, the circuit connection of the combined wheatstone bridge modules of the bridge arms is as shown in fig. 1:
firstly, ports of two identical port networks are connected through a twisted pair to form a loop circuit, wherein the used port network is a port network obtained by a Wheatstone bridge circuit which lacks a bridge arm resistor and is open-circuited from the branch, and a-c and h-f branches of a combined Wheatstone bridge module which mutually form bridge arms are respectively connected with a signal source 1 and a signal source 2 with extremely small input resistors;
then, the two port networks can be equivalent to an equivalent resistor in the opposite circuit network, and the equivalent resistor is used as a bridge arm resistor which is lacked in the opposite bridge network, so that the two port networks respectively form a complete Wheatstone bridge circuit;
finally, the emitter followers 1 and 2 in the two signal demodulation processing unit modules are respectively connected in parallel at the b-d and e-g ends of the two Wheatstone bridges, and when the two signal sources drive the circuit through power amplification, the terminal voltage U of the Wheatstone bridge is obtainedbdAnd Ueg。
Further, the mutually bridge arm joint wheatstone bridge module circuit connection further comprises:
constant value resistors R are respectively connected among the nodes a-b, c-d, e-f and g-h1、R3、R4、R6Sliding rheostats R are respectively connected between the nodes b-c and f-g2、R5(ii) a The output impedances of the signal source 1 and the signal source 2 are extremely small and are Rr1And Rr2(ii) a Wherein the constant value resistor is selected to satisfyRelation R1、R3、R4And R6The resistance values of the fixed value resistors are far greater than Rr1And Rr2(ii) a The selection of the slide rheostat satisfies R2The resistance value has a variation range of
Figure BDA0002922721860000031
R5The resistance value has a variation range of
Figure BDA0002922721860000032
Further, the two signal source modules are shown in fig. 2, and include: the device comprises a power amplifier 1, a power amplifier 2, a signal modulator 1, a signal demodulator 2, a signal modulator 3, a signal modulator 4, an up-converter 1, an up-converter 2 and two summers;
signal modulator 1 for modulating "S1Sound source, i.e. the sound emitted by the user, is modulated to obtain a sound signal S1；
Signal modulator 2 for modulating' N1The noise source is modulated to obtain a noise signal N1；
A signal modulator 3 for modulating "S2Sound source, i.e. the sound emitted by the user, is modulated to obtain a sound signal S2；
Signal modulator 4 for modulating' N2The noise source is modulated to obtain a noise signal N2；
The signal modulator 1 and the signal modulator 4 adopt the same modulation method, and the signal modulator 2 and the signal modulator 3 adopt the same modulation method;
up-converter 1 for converting noise signal N1And carrier fc1Performing up-mixing to obtain a noise signal' N1Up ";
an up-converter 2 for converting the sound signal S2And carrier fc2Performing up-mixing to obtain a noise signal S2Up ";
adder and power amplifier 1 for adding N1Upper and S1Carrying out power amplification;
adder and power amplifier2 for to N2And "S2Carrying out power amplification;
the noise signal "N1Noise source and sound signal S1All are in the frequency range of 20HZ to 20KHZ, and the carrier wave fc1>60 KHZ; the noise signal N2With the sound signal "S2The frequency range of the sound source is 20 HZ-20 KHZ; the carrier wave fc2>60KHZ；
The sound signal "S2Upper output and noise signal after power amplification of power amplifier 21The signal-to-noise ratio between the outputs amplified by the power amplifier 1 is less than or equal to-20 dB;
the sound signal S1Output and noise signal N after power amplification of power amplifier 12The signal-to-noise ratio between the outputs amplified by the power amplifier 2 is less than or equal to-20 dB.
The connection of two signal source modules in a combined wheatstone bridge module that are legs of each other is shown in fig. 3.
Further, as shown in fig. 4, the two signal demodulation processing unit modules include: an emitter follower 1, an emitter follower 2, a band-pass filter, a low-pass filter, a down converter 1, a demodulator 3, a horn 1 and a horn 2;
emitter follower 1 for picking up sound signal "S2Up and noise signal N2And transmits it to the center frequency fcdA bandwidth of W3The band-pass filter of (1);
emitter follower 2 for picking up sound signal S1And noise signal "N1And transmits it to the center frequency fcaA bandwidth of W4The low-pass filter of (1);
the band-pass filter is used for filtering the noise signal N2Keeping the sound signal "S2Up ";
the low-pass filter is used for filtering the noise signal N1Up', preserving the sound signal S1；
Down converter 1 for processing sound signal "S2Up mixing downObtaining a sound signal S2；
A demodulator 1 corresponding to the signal modulator 1 for demodulating the sound signal S1Demodulating to obtain S1Sound source ";
a demodulator 3 corresponding to the signal modulator 3 for the sound signal S2Demodulating to obtain S2Sound source ";
a horn 1 for pairing "S2Playing the sound source;
a horn 2 for the pair "S1Sound source "plays.
The connection of the two signal demodulation processing unit modules and the two signal source modules in the combined huygens bridge module with the bridge arms of each other is shown in fig. 5.
Another object of the present invention is to provide a wheatstone bridge balance method-based secure communication method applied to the wheatstone bridge balance method-based secure communication system, the wheatstone bridge balance method-based secure communication method including:
connecting two communication terminal nodes 1 and 2 through twisted-pair wires; a, B two channels are used for the information transmission of node 1 and node 2.
Further, the information transmission between the node 1 and the node 2 by using A, B two channels includes:
node 1 sends a sound signal S via signal source 11And noise signal "N1Upper ", the node 2 sends a sound signal" S "via the signal source 22Up and noise signal N2(ii) a Let noise signal N2With the sound signal S1Are transmitted on the same frequency band, i.e. channel a; simultaneously by pairs of "N1Noise source ", fc1、“S2Sound source ″, fc2Selection order of "S2Upper and N1The upper "is communicated on the same frequency band, channel B.
Further, the channel A and the channel B are not overlapped and have a certain margin; the center frequency of the channel A is 10KHZ, and the bandwidth of the channel is W1(W120 KHZ); channel B center frequency fcbChannel bandwidth of W2(W220KHZ), the frequency range of channel B is fcb-0.5W2，fcb+0.5W2]The channel A, B satisfies the relationship
Figure BDA0002922721860000051
Wherein
Figure BDA0002922721860000052
A certain margin of separation between the channels A, B.
Further, the secret communication method based on the Wheatstone bridge balance method comprises the following steps:
the signal encryption method comprises the following steps:
signal source 1 module in node 1, will "S1The sound source is "modulated into a sound signal S by a signal modulator 11(ii) a N at the human voice frequency range of 20 HZ-20 KHZ1Noise source "is modulated into noise signal N by signal modulator 21And will noise signal N1And carrier fc1Up-mixing by up-converter 1 to obtain noise signal "N1Up "; noise signal' N1Upper and sound signal S1After passing through the adder, the power is amplified through a power amplifier 1 and then transmitted;
the signal source 2 module in the node 2 is used for generating noise N in the human voice frequency range of 20 HZ-20 KHZ2The sound source is' modulated into a noise signal N by a signal modulator 42(ii) a Will be "S2The sound source is' modulated into a sound signal S by a signal modulator 32And the sound signal S2And carrier fc2Up-mixing by means of an up-converter 2 to obtain an acoustic signal "S2Up "; will be "S2Upper and N2After passing through the adder, the power is amplified through a power amplifier 2 and then transmitted;
let the sound signal "S2Upper output and noise signal after power amplification of power amplifier 21The signal-to-noise ratio of the output after power amplification by the power amplifier 1 is less than or equal to-20 dB; let the sound signal S1Output and noise signal N after power amplification of power amplifier 12The signal-to-noise ratio of the output after power amplification of the power amplifier 2 is less than or equal to-20dB；
S1、“N1Upper and lower2Upper', N2Simultaneously transmitting on twisted pair: sound signal "S2Up sum noise signal N1Upper "in the channel B, the acoustic signal S1And noise signal N2Spread in channel a;
the signal receiving method comprises the following steps:
emitter follower 1 in signal demodulation processing unit 1 detects equivalent resistance R of Wheatstone bridge of node 1 in node 23Obtaining the sound signal "S" emitted by the node 22Up and noise signal N2；
The emitter follower 2 in the signal demodulation processing unit 2 detects the equivalent resistance R of the Wheatstone bridge of the node 2 in the node 16Obtaining the sound signal S emitted by the node 11And noise signal "N1Up ";
the signal processing method comprises the following steps:
emitter follower 1 of signal demodulation processing unit 1 in node 1 acquires sound signal "S2Up and noise signal N2(ii) a Using the acquired signal with a center frequency fcdA bandwidth of W3The band-pass filter for filtering the noise signal N2Keeping the sound signal "S2Up "; convert the sound signal "S2Up-conversion by a down-converter 1 to obtain an acoustic signal S2(ii) a The sound signal S is demodulated using a demodulator 3 corresponding to the modulator 32Demodulating to obtain "S2Sound source "and played through the loudspeaker 1;
emitter follower 2 of signal demodulation processing unit 2 in node 2 acquires noise signal "N1Up and sound signal S1(ii) a Using the acquired signal with a center frequency fcaA bandwidth of W4Low pass filter for filtering noise signal' N1Up', preserving the sound signal S1(ii) a The sound signal S is demodulated using a demodulator 1 corresponding to the modulator 11Demodulating to obtain "S1Sound source "and played through the speaker 2.
By combining all the technical schemes, the invention has the advantages and positive effects that: the invention uses the wired mode to transmit signals, the signals are only transmitted in the specified wired area, and simultaneously, the risk of stealing the transmitted information is prevented from the physical layer by simultaneously releasing the target signals and the strong-power co-frequency self-interference signals in the transmission line, thereby realizing the purpose of secret communication, and simultaneously, the target information can be easily obtained by a receiving party due to the Wheatstone bridge balance principle.
The circuit communication structure of the invention is simple, easy to realize and the safety achieved is very high.
The invention is not limited to the secrecy in the aspect of voice communication, and can realize other secrecy of information communication through signal transmission, such as text information transmission, picture information transmission and the like. But it is pointed out that the core points are to be followed:
(1) the destination information transferred by the node 1 and the noise signal sent by the node 2 are located in the same frequency band, the destination information transferred by the node 2 and the noise signal sent by the node 1 are located in the same frequency band, and the two frequency bands are not overlapped.
(2) Self-interference signal with same frequency for releasing target signal and strong power in transmission line and self-interference elimination by Wheatstone bridge balance
Drawings
For clarity of explanation, the invention will be further described with reference to the drawings of embodiments, it being understood that the drawings described below are merely examples of the present application and that other drawings may be derived from those figures by a person skilled in the art without inventive step.
Fig. 1 is a schematic diagram of a combined huyghen bridge module with bridge arms according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of two signal source modules according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of two signal source modules connected in a wheatstone bridge module circuit according to an embodiment of the present invention.
Fig. 4 is a schematic diagram of two signal processing units according to an embodiment of the present invention.
Fig. 5 is a schematic circuit diagram of a method for implementing secure communication by utilizing bridge balancing principle to eliminate interference according to an embodiment of the present invention.
Fig. 6 is a flowchart of a secure communication method based on a wheatstone bridge balancing method according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In view of the problems in the prior art, the present invention provides a secure communication system and method based on the wheatstone bridge balancing method, and the present invention is described in detail below with reference to the accompanying drawings.
The embodiment of the invention provides a secret communication system based on a Wheatstone bridge balance method, which comprises the following steps:
the device comprises a combined Wheatstone bridge module, two signal source modules and two signal demodulation processing unit modules, wherein the combined Wheatstone bridge module is a bridge arm;
the two signal source modules are respectively connected with the input ends of two signal sources in the combined Wheatstone bridge modules which are mutually bridge arms through respective power amplifier output ends;
the two signal demodulation processing unit modules are respectively connected to the input ends of two signal demodulation processing units in the combined Wheatstone bridge module which is a bridge arm through the output ends of the emitter followers.
As shown in fig. 1, the combined wheatstone bridge modules of the bridge arms provided by the embodiment of the present invention are connected as follows:
firstly, ports of two identical port networks are connected through a twisted pair to form a loop circuit, wherein the used port network is a port network obtained by a Wheatstone bridge circuit which lacks a bridge arm resistor and is open-circuited from the branch, and a-c and h-f branches of a combined Wheatstone bridge module which mutually form bridge arms are respectively connected with a signal source 1 and a signal source 2 with extremely small input resistors;
then, the two port networks are equivalent to an equivalent resistor in the opposite circuit network, and are used as bridge arm resistors which are lacked in the opposite bridge network, so that the two port networks respectively form a complete Wheatstone bridge circuit;
finally, the emitter followers 1 and 2 in the two signal demodulation processing unit modules are respectively connected in parallel at the b-d and e-g ends of the two Wheatstone bridges, and when the two signal sources drive the circuit through power amplification, the terminal voltage U of the Wheatstone bridge is obtainedbdAnd Ueg。
Constant value resistors R are respectively connected among the nodes a-b, c-d, e-f and g-h1、R3、R4、R6Sliding rheostats R are respectively connected between the nodes b-c and f-g2、R5(ii) a The output impedances of the signal source 1 and the signal source 2 are extremely small and are Rr1And Rr2(ii) a Wherein the selection of the constant value resistor satisfies the relation R1、R3、R4And R6The resistance values of the fixed value resistors are far greater than Rr1And Rr2(ii) a The selection of the slide rheostat satisfies R2The resistance value has a variation range of
Figure BDA0002922721860000081
R5The resistance value has a variation range of
Figure BDA0002922721860000082
As shown in fig. 2 to fig. 3, a signal source module provided in an embodiment of the present invention includes: the device comprises a power amplifier 1, a power amplifier 2, a signal modulator 1, a signal demodulator 2, a signal modulator 3, a signal modulator 4, an up-converter 1, an up-converter 2 and two summers;
signal modulator 1 for modulating "S1Sound source, i.e. the sound emitted by the user, is modulated to obtain a sound signal S1；
Signal modulator 2 for modulating' N1The noise source is modulated to obtain a noise signal N1；
Signal modulationA device 3 for converting "S2Sound source, i.e. the sound emitted by the user, is modulated to obtain a sound signal S2；
Signal modulator 4 for modulating' N2The noise source is modulated to obtain a noise signal N2；
The signal modulator 1 and the signal modulator 4 adopt the same modulation method, and the signal modulator 2 and the signal modulator 3 adopt the same modulation method;
up-converter 1 for converting noise signal N1And carrier fc1Performing up-mixing to obtain a noise signal' N1Up ";
an up-converter 2 for converting the sound signal S2And carrier fc2Performing up-mixing to obtain a noise signal S2Up ";
adder and power amplifier 1 for adding N1Upper and S1Carrying out power amplification;
adder and power amplifier 2 for adding N2And "S2Carrying out power amplification;
said "N1Noise source and sound signal S1All are in the frequency range of 20HZ to 20KHZ, and the carrier wave fc1>60 KHZ; the noise signal N2And "S2The frequency range of the sound source is 20 HZ-20 KHZ; the carrier wave fc2>60KHZ；
The sound signal "S2Upper output and noise signal after power amplification of power amplifier 21The signal-to-noise ratio between the outputs amplified by the power amplifier 1 is less than or equal to-20 dB;
the sound signal S1Output and noise signal N after power amplification of power amplifier 12The signal-to-noise ratio between the outputs amplified by the power amplifier 2 is less than or equal to-20 dB.
As shown in fig. 4, the signal demodulation processing unit module provided in the embodiment of the present invention includes: an emitter follower 1, an emitter follower 2, a band-pass filter, a low-pass filter, a down converter 1, a demodulator 3, a horn 1 and a horn 2;
emitter follower 1 ofObtaining a sound signal "S2Up and noise signal N2And transmits it to the center frequency fcdA bandwidth of W3The band-pass filter of (1);
emitter follower 2 for picking up sound signal S1And noise signal "N1And transmits it to the center frequency fcaA bandwidth of W4The low-pass filter of (1);
the band-pass filter is used for filtering the noise signal N2Keeping the sound signal "S2Up ";
the low-pass filter is used for filtering the noise signal N1Up', preserving the sound signal S1；
A down converter 1 for down-mixing to obtain an acoustic signal S2；
A demodulator 1 corresponding to the signal modulator 1 for demodulating the sound signal S1Demodulating to obtain S1Sound source ";
a demodulator 3 corresponding to the signal modulator 3 for performing the sound signal S2Demodulating to obtain "S2Sound source ";
a horn 1 for pairing "S2Playing the sound source;
a horn 2 for the pair "S1Sound source "plays.
Fig. 5 is a complete diagram of the two signal source modules and the two signal demodulation processing unit modules connected to the combined wheatstone bridge with the bridge arms of each other according to the present invention.
As shown in fig. 6, the secure communication method based on the wheatstone bridge balancing method according to the embodiment of the present invention includes the following steps:
s101, connecting two communication terminal nodes 1 and 2 through twisted-pair lines;
and S102, adopting A, B two channels to respectively transmit information of the node 1 and the node 2.
The information transmission of the node 1 and the node 2 by adopting A, B two channels respectively provided by the embodiment of the invention comprises the following steps:
node 1 sends sound via signal source 1Signal S1And noise signal "N1Upper ", the node 2 sends a sound signal" S "via the signal source 22Up and noise signal N2(ii) a Let noise signal N2With the sound signal S1Located in the same frequency band, channel a; simultaneously by pairs of "N1Noise source ", fc1、“S2Sound source ″, fc2Selection order of "S2Upper and N1The upper "is located in the same frequency band, i.e., channel B.
In the embodiment of the invention, the channel A and the channel B are not overlapped and have a certain margin at intervals; the center frequency of the channel A is 10KHZ, and the bandwidth of the channel is W1(W120 KHZ); channel B center frequency fcbChannel bandwidth of W2(W220KHZ), the frequency range of channel B is fcb-0.5W2，fcb+0.5W2]The channel A, B satisfies the relationship
Figure BDA0002922721860000101
Wherein
Figure BDA0002922721860000102
A certain margin of separation between the channels A, B.
The embodiment of the invention provides a secret communication method based on a Wheatstone bridge balance method, which comprises the following steps:
the signal encryption method comprises the following steps:
signal source 1 module in node 1, will "S1The sound source is "modulated into a sound signal S by a signal modulator 11(ii) a N at the human voice frequency range of 20 HZ-20 KHZ1Noise source "is modulated into noise signal N by signal modulator 21And will noise signal N1And carrier fc1Up-mixing by up-converter 1 to obtain noise signal "N1Up "; noise signal' N1Upper and sound signal S1After passing through the adder, the power is amplified through a power amplifier 1 and then transmitted;
the signal source 2 module in the node 2 is used for generating noise N in the human voice frequency range of 20 HZ-20 KHZ2The sound source is' modulated into noise by a signal modulator 4Acoustic signal N2(ii) a Will be "S2The sound source is' modulated into a sound signal S by a signal modulator 32And the sound signal S2And carrier fc2Up-mixing by means of an up-converter 2 to obtain an acoustic signal "S2Up "; the sound signal "S2Up and noise signal N2After passing through the adder, the power is amplified through a power amplifier 2 and then transmitted;
let the sound signal "S2Upper output and noise signal after power amplification of power amplifier 21The signal-to-noise ratio of the output after power amplification of the power amplifier 1 is less than or equal to-20 dB;
let the sound signal S1Output and noise signal N after power amplification of power amplifier 12The signal-to-noise ratio of the output after power amplification by the power amplifier 2 is less than or equal to-20 dB;
S1、“N1upper and lower2Upper', N2Simultaneously transmitting on twisted pair: sound signal S1And noise signal N2Propagating on channel A, the acoustic signal "S2Up sum noise signal N1Upper "is located in channel B propagation;
the signal receiving method comprises the following steps:
emitter follower 1 in signal demodulation processing unit 1 detects equivalent resistance R of Wheatstone bridge of node 1 in node 23Obtaining the sound signal "S" emitted by the node 22Up and noise signal N2；
The emitter follower 2 in the signal demodulation processing unit 2 detects the equivalent resistance R of the Wheatstone bridge of the node 2 in the node 16Obtaining the sound signal S emitted by the node 11And noise signal "N1Up ";
the signal processing method comprises the following steps:
emitter follower 1 of signal demodulation processing unit 1 in node 1 acquires sound signal "S2Up and noise signal N2(ii) a Using the acquired signal with a center frequency fcdA bandwidth of W3The band-pass filter for filtering the noise signal N2Keeping the sound signal "S2Up "; convert the sound signal "S2Up-conversion by a down-converter 1 to obtain an acoustic signal S2(ii) a The sound signal S is demodulated using a demodulator 3 corresponding to the modulator 32Demodulating to obtain "S2Sound source "and played through the loudspeaker 1;
emitter follower 2 of signal demodulation processing unit 2 in node 2 acquires noise signal "N1Up and sound signal S1(ii) a Using the acquired signal with a center frequency fcaA bandwidth of W4Low pass filter for filtering noise signal' N1Up', preserving the sound signal S1(ii) a The sound signal S is demodulated using a demodulator 1 corresponding to the modulator 11Demodulating to obtain "S1Sound source "and played through the speaker 2.
The technical effects of the present invention will be further described with reference to specific embodiments.
Example 1:
the invention designs a communication system with excellent confidentiality by adopting the principle of a Wheatstone bridge method. The circuit design of the system comprises three parts: the device comprises a combined Wheatstone bridge module, two signal source modules and two signal demodulation processing unit modules, wherein the combined Wheatstone bridge module is a bridge arm.
As shown in fig. 1, the ports of two identical port networks are connected by twisted pair wires to form a loop circuit, which is the main circuit of the present invention, wherein the used port network is a port network obtained from a huygens bridge circuit lacking a bridge arm resistor and having an open circuit from the branch, and simultaneously, the a-c and h-f branches of the mutually-bridge arm combined huygens bridge module are respectively connected with a signal source 1 and a signal source 2 having extremely small input resistors. Then, due to the characteristics of the circuit structure design, the two one-port networks can be equivalent to an equivalent resistor in the other circuit network and used as a bridge arm resistor which is lacked in the other bridge network, so that the two one-port networks respectively form a complete Wheatstone bridge circuit. Finally, the emitter follower 1 and the emitter follower 2 are respectively connected in parallel with b-d and b-d of two Wheatstone bridgese-g terminal for obtaining terminal voltage U of Wheatstone bridge when two signal sources drive circuit through power amplifierbdAnd Ueg. The two signal demodulation processing unit modules 1 and 2 are respectively connected to the input ends of the two signal demodulation processing units 1 and 2 in the combined Wheatstone bridge module which is a bridge arm through the output ends of the emitter followers. The structural design is characterized in that under the driving of the power amplifiers of the two signal sources, when the two Wheatstone bridges reach the bridge balance state, the terminal voltage U of the two bridgesbd、Ueg0v, the voltage detected by the emitter follower connected in parallel with the bridge is only the voltage information in the opposite bridge circuit when the bridge is equivalent to the bridge arm resistance in the opposite bridge circuit. When the circuit is applied to communication, the follower can acquire the information transmitted by the other party according to the detected voltage without receiving the information transmitted by the other party, so that the aim of automatically filtering the information transmitted by the other party from the physical layer is fulfilled.
The resistors used in the combined Wheatstone bridge module with the bridge arms of each other are shown in FIG. 1, and constant value resistors R are respectively connected among the nodes a-b, c-d, e-f and g-h1、R3、R4、R6Sliding rheostats R are respectively connected between the nodes b-c and f-g2、R5. The output impedances of the signal source 1 and the signal source 2 are extremely small and are Rr1And Rr2. Wherein the selection of the constant value resistor satisfies the relation R1、R3、R4And R6The resistance values of the resistors are all larger than 10K omega, so that the resistance value of the constant value resistor is far larger than Rr1And Rr2. The selection of the slide rheostat satisfies R2The resistance value has a variation range of
Figure BDA0002922721860000131
R5The resistance value has a variation range of
Figure BDA0002922721860000132
Viewed from the Wheatstone bridge end of the node 1 in the combined Wheatstone bridge modules of the bridge arms, the node 2 is equivalent to the Wheatstone bridge in the node 1The equivalent bridge arm resistance of (1). Due to the input resistance R of the signal source 2r2Extremely small, so that the voltage value actually measured by the emitter follower 2 in the signal processing unit 2 and the constant value resistor R6Has almost the same voltage value, and since the node 2 is equivalent to the equivalent resistance of the Wheatstone bridge in the node 1
Figure BDA0002922721860000133
Figure BDA0002922721860000134
Is almost equal to the constant value resistor R6Of equal resistance, i.e. R6≈Req1The equivalent resistance can be regarded as R6So when the Wheatstone bridge at node 2 reaches an equilibrium state, the emitter follower 2 will measure the equivalent bridge arm resistance R of the Wheatstone bridge at node 16Thereby acquiring the information sent by node 1.
In the combined wheatstone bridge modules of the bridge arms, viewed from the wheatstone bridge end of the node 2, the node 1 is equivalent to the equivalent bridge arm resistance of the wheatstone bridge in the node 2. Due to the input resistance R of the signal source 1r1Extremely small, so that the voltage value actually measured by the emitter follower 1 in the signal processing unit 2 and the constant value resistor R3Has almost the same voltage value, and because the node 1 is equivalent to the equivalent resistance of the Wheatstone bridge in the node 2
Figure BDA0002922721860000135
Figure BDA0002922721860000136
Is almost equal to the constant value resistor R3Of equal resistance, i.e. R3≈Req2The equivalent resistance can be regarded as R3So when the Wheatstone bridge at node 1 reaches an equilibrium state, the emitter follower 1 will measure the equivalent bridge arm resistance R of the Wheatstone bridge at node 23Thereby acquiring the information sent by node 2.
Adjustable slide rheostat R2To make the Wheatstone bridge in the node 1 reach the bridge balance, the formula of the bridge balance
Figure BDA0002922721860000137
Can obtain the product
Figure BDA0002922721860000138
Adjustable slide rheostat R5The Wheatstone bridge in node 2 is balanced by the bridge balance formula
Figure BDA0002922721860000141
Can obtain the product
Figure BDA0002922721860000142
Besides the combined Wheatstone bridge modules which are mutually bridge arms, the combined Wheatstone bridge module also comprises two signal source modules and two signal processing unit modules.
The signal source module is shown in fig. 2 and includes: the device comprises a power amplifier 1, a power amplifier 2, a signal modulator 1, a signal demodulator 2, a signal modulator 3, a signal modulator 4, an up-converter 1, an up-converter 2 and two summers;
in FIG. 2(a), S1For the sound signal, the signal modulator 1 will "S1The sound source "is modulated by the sound emitted by the user. N is a radical of1For noise signals, N is modulated by the signal modulator 21A noise source is modulated to obtain a noise signal N1And carrier fc1Up-mixing the signals by an up-converter 1 to obtain a noise signal' N1Upper ". Wherein the noise signal "N1Noise source selection assurance and sound signal S1Is in the frequency range of 20HZ to 20KHZ, fc1>60KHZ。“N1Upper and S1And the power amplification is carried out through the power amplifier 1 after passing through the adder.
In FIG. 2(b), N2For noise signals, N is modulated by the signal modulator 42The noise source "is modulated. S2For sound signals, the signal modulator 3 will send "S2Sound source "is the sound emitted by the user, modulated, the sound signal S2And carrier fc2The up-frequency mixing is carried out by an up-converter 2 to obtain an acoustic signal S2Wherein the noise signal N2Is selected to ensure the audio signal "S2The frequency range of the sound source is in the frequency range of 20 HZ-20 KHZ, fc2>60KHZ。“S2Upper and N2The power amplification is carried out through the power amplifier 2 after passing through the adder.
Let the sound signal "S2Upper output and noise signal after power amplification of power amplifier 21The output signal-to-noise ratio after the power amplification of the power amplifier 1 is less than or equal to-20 dB.
Let the sound signal S1Output and noise signal N after power amplification of power amplifier 12The output signal-to-noise ratio after power amplification by the power amplifier 2 is less than or equal to-20 dB.
Wherein the signal modulator 1 and the signal modulator 4 adopt the same modulation method, and the signal modulator 2 and the signal modulator 3 adopt the same modulation method. Fig. 2 shows that the signal source modules (a) and (b) are respectively connected to the input terminals of the signal sources 1 and 2 in the combined huygens bridge module, which is a bridge arm of each other, through their respective power amplifier output terminals, as shown in fig. 3.
The secret communication method is adopted.
(1) As shown in fig. 3, node 1 and node 2 represent two communication terminals, connected by a twisted pair.
(2) The information transmission of the node 1 and the node 2 adopts A, B two channels for transmission. Node 1 sends a sound signal S via signal source 11And noise signal "N1Upper ", the node 2 sends a sound signal" S "via the signal source 22Up and noise signal N2. Wherein the noise signal "N1Is formed by a noise signal N1And carrier fc1Performing up-mixing to obtain; sound signal "S2Upper is formed by the sound signal S2And carrier fc2And performing up-mixing to obtain the final product.
(3) Noise signal N2Is selected according to the sum of1The sound sources being "in substantially the same frequency band", i.e. noise signals N2And "S1The frequency of the sound source is in the range of 20 HZ-20 KHZ, thereby ensuring the noise signalNumber N2With the sound signal S1Located in the same frequency band, which is called channel a.
(4) By pair of "N1Noise source ", fc1、“S2Sound source ″, fc2Is selected so that "S" is2Upper and N1The upper "is located in channel B. Specifically, let' N1Noise source AND S2The frequency of the sound source is in the range of 20 HZ-20 KHZ, and the carrier wave fc1≈fc2>60 KHZ. Thereby ensuring a noise signal "N1Up AND Sound Signal S2The upper "is located in the same frequency band, which is called channel B.
(5) And ensuring that the channel A and the channel B do not overlap and the interval has a certain margin. The center frequency of the channel A is 10KHZ, and the bandwidth of the channel is W1(W120 KHZ). Channel B center frequency fcbChannel bandwidth of W2(W220KHZ), the frequency range of channel B is fcb-0.5W2，fcb+0.5W2]. Therefore, in order to satisfy the condition that "the channel a should not overlap with the channel B and there is a certain margin between the channels" in this embodiment, it is ensured
Figure BDA0002922721860000151
Wherein
Figure BDA0002922721860000152
A certain margin of separation between the channels A, B.
(6) According to the design, the sound signal S is provided on the twisted pair wire1Noise signal N2Transmitted over channel A, the sound signal "S2Up ", noise signal" N1The up "is transmitted over channel B. When an illegal eavesdropper tries to steal information, the method can simultaneously acquire A, B channels of four transmitted signals in total, however, noise signals are interfered in each channel, and noise N is generated1Upper and sound signal S1Signal to noise ratio and noise N2With the sound signal "S2The signal-to-noise ratios of the above are all lower than-20 dB, so that the signal-to-noise ratio of the signal acquired by an illegal stealer is very low, and the signal-to-noise ratio is completely lowUseful information can not be obtained at all, and finally stealing fails.
(7) For the nodes 1 and 2, due to the circuit structure design characteristic of utilizing the Wheatstone bridge balance method to eliminate interference, when the respective Wheatstone bridges of the two nodes are balanced, the two emitter followers only detect the voltage information in the node of the other party, so that only the information sent by the node of the other party is acquired in communication, namely the node 1 acquires the sound signal S2Up ", noise signal N2On channels B and a, respectively, node 2 acquires a sound signal S1Noise signal "S1And the signals are respectively positioned on the channel A and the channel B, and the noise signals can be easily eliminated only by processing through the signal demodulation processing unit in the invention, so that the sound signals sent by the nodes of the opposite side are obtained.
The signal processing unit is shown in fig. 4 and comprises: an emitter follower 1, an emitter follower 2, a band-pass filter, a low-pass filter, a down converter 1, a demodulator 3, a horn 1 and a horn 2;
(1) in FIG. 4(a), the emitter follower 1 is made to pick up the sound signal "S2Up and noise signal N2To a central frequency fcdA bandwidth of W3Band pass filter (f)cd≈fcb，W320KHZ) to filter out the noise signal N2Keeping the sound signal "S2Up ", which is then mixed down by a down-converter 1 to obtain an acoustic signal S2Finally, the S is obtained by demodulating through a demodulator 3 corresponding to the modulator 32Sound source "and played through the speaker 1.
(2) In FIG. 4(b), the emitter follower 2 is made to pick up the noise signal "N1Up and sound signal S1To a central frequency fcaA bandwidth of W4Low pass filter (f)ca≈10KHZ，W420KHZ) to filter out the noise signal "N1Up', preserving the sound signal S1Finally, the S is obtained by demodulating through a demodulator 1 corresponding to the modulator 11Sound source ", and finally played through the speaker 2.
The invention realizes the secret communication from the physical layer, and the secret degree is very high. The power amplifier and signal generating module, the signal receiving and processing module and the main circuit are connected as shown in fig. 5.
Example 2:
the basic operating principle of the circuit of the present invention will be explained in more detail. The method can be divided into three processes of signal encryption, signal reception and signal decryption, as shown in fig. 5.
The signal encryption process specifically comprises the following steps:
(1) signal source 1 module in node 1, will "S1The sound source is "modulated into a sound signal S by a signal modulator 11(ii) a N at the human voice frequency range of 20 HZ-20 KHZ1Noise source "is modulated into noise signal N by signal modulator 21And will noise signal N1And carrier fc1Up-mixing by up-converter 1 to obtain noise signal "N1Upper "(f)c1>60 KHZ); will be "N1Upper and S1After the adder, the power amplifier 1 amplifies the power and transmits the power.
(2) The same is true. The signal source 2 module in the node 2 is used for generating noise N in the human voice frequency range of 20 HZ-20 KHZ2The sound source is' modulated into a noise signal N by a signal modulator 42(ii) a Will be "S2The sound source is' modulated into a sound signal S by a signal modulator 32And the sound signal S2And carrier fc2Up-mixing by means of an up-converter 2 to obtain an acoustic signal "S2Upper "(f)c2≈fc1) (ii) a Will be "S2Upper and N2After the adder, the power amplifier 2 amplifies the power and transmits the power.
(3) Let the sound signal "S2Upper output and noise signal after power amplification of power amplifier 21The signal-to-noise ratio of the output after the power amplification of the power amplifier 1 is less than or equal to-20 dB.
(4) Let the sound signal S1Output and noise signal N after power amplification of power amplifier 12The signal-to-noise ratio of the output after power amplification by the power amplifier 2 is less than or equal to-20 dB.
(5)S1、“N1Upper and lower2Upper', N2Will be transmitted simultaneously over the twisted pair of wires. Guarantee fc2≈fc1>60KHZ, making the sound signal "S2Up sum noise signal N1The upper "is propagated on channel B, which has a center frequency fcbBandwidth of W2(W220 KHZ). Sound signal S1And noise signal N2Is located in a channel A for propagation, the center frequency of the channel A is 10KHZ, and the bandwidth is W1(W1＝20KHZ)。
(6) Channel A and channel B satisfy the formula
Figure BDA0002922721860000171
With a certain margin so that channels a and B are separated from each other without intersection.
The signal receiving process specifically comprises the following steps:
(1) in the combined Wheatstone bridge module with the bridge arms mutually, when viewed from the Wheatstone bridge end of the node 1, the equivalent resistance of the node 2 in the Wheatstone bridge of the node 1 is Req1Wherein R iseq1≈R6Regulating the sliding rheostat R in the node 12Has a resistance value of
Figure BDA0002922721860000172
Bringing the wheatstone bridge of node 1 to a bridge balance condition:
Figure BDA0002922721860000173
so that the emitter follower 1 detects the voltage difference U across the wheatstone bridge of node 1db0v, i.e. the sound signal S emitted by the node 11And noise signal "N1The upper "is not captured by the emitter follower 1. And emitter follower 2 can detect the equivalent resistance R of the Wheatstone bridge of node 2 in node 16Thereby obtaining the sound signal S emitted by the node 11And noise signal "N1Upper ".
(2) In the combined Wheatstone bridge module with the bridge arms mutually, when viewed from the Wheatstone bridge end of the node 1, the equivalent resistance of the Wheatstone bridge of the node 1 in the node 2 is Req2Wherein R iseq2≈R3Regulating the sliding rheostat R in the node 25Has a resistance value of
Figure BDA0002922721860000181
Bringing the wheatstone bridge of node 2 to a bridge balance condition:
Figure BDA0002922721860000182
so that the emitter follower 2 detects the voltage difference U across the wheatstone bridge at node 2eg0v, i.e. the sound signal "S" emitted by the node 22Up and noise signal N2Is not captured by the emitter follower 2. And emitter follower 1 can detect the equivalent resistance R of the Wheatstone bridge of node 1 in node 23Thereby obtaining the sound signal "S" emitted by the node 22Up and noise signal N2。
The signal processing process comprises the following steps:
(1) emitter follower 1 in node 1 picks up sound signal "S2Up and noise signal N2. Using the acquired signal with a center frequency fcdA bandwidth of W3Band pass filter (f)cd≈fcb，W320KHZ) to filter out the noise signal N2Keeping the sound signal "S2Upper ". Then the sound signal "S2Up-conversion by a down-converter 1 to obtain an acoustic signal S2. Finally, the sound signal S is demodulated by using a demodulator 3 corresponding to the modulator 32Demodulating to obtain "S2Sound source "and played through the speaker 1.
(2) Similarly, first, the emitter follower 2 in the node 2 acquires the noise signal "N1Up and sound signal S1. The acquired signal is then used with a center frequency fcaA bandwidth of W4Low pass filter (f)ca≈10KHZ，W420KHZ) to filter out the noise signal "N1Up', preserving the sound signal S1. Finally, the sound signal S is demodulated by using a demodulator 1 corresponding to the modulator 11Demodulating to obtain "S1Acoustic source "and pass through loudspeakerThe horn 2 plays.
Thus, the whole process of generating, transmitting, receiving and processing the signals is completed.
The foregoing embodiments are merely illustrative of the present invention, but not limited to the foregoing embodiments, for example, in the core point "(1) the destination information transferred by the node 1 and the noise signal transmitted by the node 2 are located in the same frequency band, the destination information transferred by the node 2 and the noise signal transmitted by the node 1 are located in the same frequency band, and the two frequency bands do not overlap. (2) Based on the self-interference signal with the same frequency which releases the target signal and strong power in the transmission line and the self-interference which is eliminated by the Wheatstone bridge balance, the following embodiments are also possible but not limited.
Example 3
Based on the example for explanation of the present invention, the sound signal S of the node 1 can be used to make the selection of the channel more free according to the bandwidth resource1And noise signal N of node 22The same up-mixing is also carried out, and corresponding down-mixing processing is added in the signal demodulation processing unit module, so that the channel is not limited to 20 HZ-20 KHZ, but the principle that the channels are not overlapped and a certain margin is left is still followed, and the selection of the channel can be flexibly adjusted according to the distribution of channel resources.
Example 4
The present invention is not limited to the transmission of voice communication, and on the basis of the example shown in the explanation of the present invention, the sound signals of the node 1 and the node 2 may be replaced by text information signals, image information signals or other information-transmittable signals, and it should be noted that the frequency band range of the corresponding noise signal is selected according to the frequency band range of the information signal of transmission purpose, that is, the self-interference signal complying with the strong power of the target signal released in the transmission line is selected.
The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.

Claims (10)

1. A wheatstone bridge balance based secure communication system, comprising:
the device comprises a combined Wheatstone bridge module, two signal source modules and two signal demodulation processing unit modules, wherein the combined Wheatstone bridge module is a bridge arm;
the two signal source modules are respectively connected with the input ends of two signal sources in the combined Wheatstone bridge modules which are mutually bridge arms through respective power amplifier output ends;
the two signal demodulation processing unit modules are respectively connected to the input ends of two signal demodulation processing units in the combined Wheatstone bridge module which is a bridge arm through the output ends of the emitter followers.
2. The wheatstone bridge balancing-based secure communication system of claim 1, wherein the combined wheatstone bridge module circuits of the legs of each other comprise:
firstly, ports of two identical port networks are connected through a twisted pair to form a loop circuit, wherein the used port network is a port network obtained by a Wheatstone bridge circuit which lacks a bridge arm resistor and is open-circuited from the branch, and a-c and h-f branches of a combined Wheatstone bridge module which mutually form bridge arms are respectively connected with a signal source 1 and a signal source 2 with extremely small input resistors;
then, the two port networks are equivalent to an equivalent resistor in the opposite circuit network, and are used as bridge arm resistors which are lacked in the opposite bridge network, so that the two port networks respectively form a complete Wheatstone bridge circuit;
finally, the emitter followers 1 and 2 in the two signal demodulation processing unit modules are respectively connected in parallel at the b-d and e-g ends of the two Wheatstone bridges, and when the two signal sources drive the circuit through power amplification, the terminal voltage U of the Wheatstone bridge is obtainedbdAnd Ueg。
3. The wheatstone bridge balancing-based secure communication system of claim 2, wherein the combined wheatstone bridge module circuits of the legs of each other further comprise:
constant value resistors R are respectively connected among the nodes a-b, c-d, e-f and g-h1、R3、R4、R6Sliding rheostats R are respectively connected between the nodes b-c and f-g2、R5(ii) a The output impedances of the signal source 1 and the signal source 2 are extremely small and are Rr1And Rr2(ii) a Wherein the selection of the constant value resistor satisfies the relation R1、R3、R4And R6The resistance values of the fixed value resistors are far greater than Rr1And Rr2(ii) a The selection of the slide rheostat satisfies R2The resistance value has a variation range of
Figure FDA0002922721850000021
R5The resistance value has a variation range of
Figure FDA0002922721850000022
4. The wheatstone bridge balancing-based secure communication system of claim 1, wherein the signal source module comprises: the device comprises a power amplifier 1, a power amplifier 2, a signal modulator 1, a signal modulator 2, a signal modulator 3, a signal modulator 4, an up-converter 1, an up-converter 2 and two summers;
signal modulator 1 for modulating "S1Sound source, i.e. the sound emitted by the user, is modulated to obtain a sound signal S1；
Signal modulator 2 for modulating' N1The noise source is modulated to obtain a noise signal N1；
A signal modulator 3 for modulating "S2Sound source, i.e. the sound emitted by the user, is modulated to obtain a sound signal S2；
Signal modulator 4 for modulating' N2The noise source is modulated to obtain a noise signal N2；
The signal modulator 1 and the signal modulator 4 adopt the same modulation method, and the signal modulator 2 and the signal modulator 3 adopt the same modulation method;
up-converter 1 for converting noise signal N1And carrier fc1Performing up-mixing to obtain a noise signal' N1Up ";
an up-converter 2 for converting the sound signal S2And carrier fc2Performing up-mixing to obtain a noise signal S2Up ";
adder and power amplifier 1 for adding N1Upper and S1Carrying out power amplification;
adder and power amplifier 2 for adding N2And "S2Carrying out power amplification;
said "N1Noise source and sound signal S1All are in the frequency range of 20HZ to 20KHZ, and the carrier wave fc1Is more than 60 KHZ; the noise signal N2With the sound signal "S2The frequency range of the sound source is 20 HZ-20 KHZ; the carrier wave fc2＞60KHZ；
The sound signal "S2Upper output and noise signal after power amplification of power amplifier 21The output signal-to-noise ratio after the power amplification of the power amplifier 1 is less than or equal to-20 dB;
the sound signal S1Output and noise signal N after power amplification of power amplifier 12The output signal-to-noise ratio after power amplification by the power amplifier 2 is less than or equal to-20 dB.
5. The wheatstone bridge balancing-based secure communication system according to claim 1, wherein the signal demodulation processing unit module includes: an emitter follower 1, an emitter follower 2, a band-pass filter, a low-pass filter, a down converter 1, a demodulator 3, a horn 1 and a horn 2;
emitter follower 1 for picking up sound signal "S2Up and noise signal N2And transmits it to the center frequency fcdA bandwidth of W3Band pass ofA filter;
emitter follower 2 for picking up sound signal S1And noise signal "N1And transmits it to the center frequency fcaA bandwidth of W4The low-pass filter of (1);
the band-pass filter is used for filtering the noise signal N2Keeping the sound signal "S2Up ";
the low-pass filter is used for filtering the noise signal N1Up', preserving the sound signal S1；
Down converter 1 for processing sound signal "S2Up mixing down to obtain sound signal S2；
A demodulator 1 corresponding to the signal modulator 1 for demodulating the sound signal S1Demodulating to obtain S1Sound source ";
a demodulator 3 corresponding to the signal modulator 3 for performing the sound signal S2Demodulating to obtain "S2Sound source ";
a horn 1 for pairing "S2Playing the sound source;
a horn 2 for the pair "S1Sound source "plays.
6. A secure communication method based on a wheatstone bridge balance method for a secure communication system, the secure communication method based on the wheatstone bridge balance method comprising:
connecting two communication terminal nodes 1 and 2 through twisted-pair wires; a, B two channels are used for the information transmission of node 1 and node 2 respectively.
7. The wheatstone bridge balancing-based secure communication method as claimed in claim 6, wherein said employing A, B two channels for information transmission of node 1 and node 2 respectively comprises:
node 1 sends a sound signal S via signal source 11And noise signal "N1Upper ", the node 2 sends a sound signal" S "via the signal source 22Up and noise signal N2(ii) a Let noise signal N2With the sound signal S1Located in the same frequency band, channel a; simultaneously by pairs of "N1Noise source ", fc1、“S2Sound source ″, fc2Is selected to make the sound signal "S2Up sum noise signal N1The upper "is located in the same frequency band, i.e., channel B.
8. The wheatstone bridge balancing-based secure communication method as claimed in claim 7, wherein the channel a and the channel B do not overlap and have a margin; the center frequency of the channel A is 10KHZ, and the bandwidth of the channel is W1(W120 KHZ); channel B center frequency fcbChannel bandwidth of W2(W220KHZ), the frequency range of channel B is fcb-0.5W2，fcb+0.5W2]The channel A, B satisfies the relationship
Figure FDA0002922721850000041
Wherein
Figure FDA0002922721850000042
A certain margin of separation between the channels A, B.
9. The wheatstone bridge balance based secure communication method as claimed in claim 6, wherein the wheatstone bridge balance based secure communication method comprises the steps of:
the signal encryption method comprises the following steps:
(1) signal source 1 module in node 1, will "S1The sound source is "modulated into a sound signal S by a signal modulator 11(ii) a N at the human voice frequency range of 20 HZ-20 KHZ1Noise source "is modulated into noise signal N by signal modulator 21And will noise signal N1And carrier fc1Up-mixing by up-converter 1 to obtain noise signal "N1Up "; noise signal' N1Upper and sound signal S1After passing through the adder, the power is amplified through a power amplifier 1 and then transmitted;
(2) the signal source 2 module in the node 2 is used for generating noise N in the human voice frequency range of 20 HZ-20 KHZ2The sound source is' modulated into a noise signal N by a signal modulator 42(ii) a Will be "S2The sound source is' modulated into a sound signal S by a signal modulator 32And the sound signal S2And carrier fc2Up-mixing by means of an up-converter 2 to obtain an acoustic signal "S2Up "; the sound signal "S2Up and noise signal N2After passing through the adder, the power is amplified through a power amplifier 2 and then transmitted;
(3) let the sound signal "S2Upper output and noise signal after power amplification of power amplifier 21The signal-to-noise ratio of the output after power amplification of the power amplifier 1 is less than or equal to-20 dB; let the sound signal S1Output and noise signal N after power amplification of power amplifier 12The signal-to-noise ratio of the output after power amplification by the power amplifier 2 is less than or equal to-20 dB;
(4)S1、“N1upper and lower2Upper', N2Four signals are transmitted simultaneously over the twisted pair: sound signal "S2Up sum noise signal N1Upper "in the channel B, the acoustic signal S1And noise signal N2Spread in channel a;
the signal receiving method comprises the following steps:
emitter follower 1 in signal demodulation processing unit 1 detects equivalent resistance R of Wheatstone bridge of node 1 in node 23Obtaining the sound signal "S" emitted by the node 22Up and noise signal N2；
The emitter follower 2 in the signal demodulation processing unit 2 detects the equivalent resistance R of the Wheatstone bridge of the node 2 in the node 16Obtaining the sound signal S emitted by the node 11And noise signal "N1Up ";
the signal processing method comprises the following steps:
(1) emitter follower 1 of signal demodulation processing unit 1 in node 1 acquires sound signal "S2Up and noise signal N2(ii) a Using the acquired signalCenter frequency of fcdA bandwidth of W3The band-pass filter for filtering the noise signal N2Keeping the sound signal "S2Up "; convert the sound signal "S2Up-conversion by a down-converter 1 to obtain an acoustic signal S2(ii) a The sound signal S is demodulated using a demodulator 3 corresponding to the signal modulator 32Demodulating to obtain "S2Sound source "and played through the loudspeaker 1;
(2) emitter follower 2 of signal demodulation processing unit 2 in node 2 acquires noise signal "N1Up and sound signal S1(ii) a Using the acquired signal with a center frequency fcaA bandwidth of W4Low pass filter for filtering noise signal' N1Up', preserving the sound signal S1(ii) a The sound signal S is demodulated using a demodulator 1 corresponding to the signal modulator 11Demodulating to obtain "S1Sound source "and played through the speaker 2.
10. A communication information data processing terminal, characterized in that the communication information data processing terminal is used for implementing the secret communication method based on the wheatstone bridge balance method according to any one of claims 6 to 9.
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