CN116318436A - Manchester code-based air-to-water cross-medium laser induced acoustic communication method - Google Patents
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- H—ELECTRICITY
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- H04B—TRANSMISSION
- H04B13/00—Transmission systems characterised by the medium used for transmission, not provided for in groups H04B3/00 - H04B11/00
- H04B13/02—Transmission systems in which the medium consists of the earth or a large mass of water thereon, e.g. earth telegraphy
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- H—ELECTRICITY
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- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
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- H04B10/516—Details of coding or modulation
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- H—ELECTRICITY
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- H04L25/4904—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems using self-synchronising codes, e.g. split-phase codes
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Abstract
The application belongs to the technical field of cross-medium communication, and particularly relates to an air-to-water cross-medium laser sound-making communication method based on Manchester codes, wherein a signal transmitting end acquires data information, binary conversion is carried out on the acquired data information, manchester coding is carried out, OOK modulation is carried out, the data information is transmitted into a laser in a square wave form, the laser generates laser pulse signals, the laser pulse signals output by the laser are vertically incident to a water-gas interface in the light emitting direction controlled by a light guide arm, and thermal expansion effect is generated by focusing of laser energy, so that the laser pulse signals are converted into acoustic signals to be transmitted in all directions under water; the acoustic signals are received by a hydrophone at a signal receiving end and converted into electric signals, and the electric signals are transmitted to an acquisition system; the acquisition system acquires the original signal information and completes the cross-medium communication from air to water. The method and the device can meet the communication requirements between the air platform and the underwater target, and remarkably improve the performance of a communication system.
Description
Technical Field
The application belongs to the technical field of cross-medium communication, and particularly relates to an air-to-water cross-medium laser induced sound communication method based on Manchester codes.
Background
The sea-air integrated communication is increasingly prominent in future war and national economy production, and the laser acoustic communication technology between the air platform and the underwater target is an important component for constructing the sea-air integrated communication, can remove a water surface communication relay and realizes direct communication between the air platform and the underwater target. The existing cross-medium communication mode between the air platform and the underwater target is limited by the high loss of the air-water interface to communication signals, the complexity of the underwater environment, the concealment of a communication system and other application scenes, and the downlink communication application of the air-water cross-medium is not completely realized.
Disclosure of Invention
In order to achieve the above purpose, the technical scheme adopted in the application is as follows: the air-to-water cross-medium laser induced sound communication method based on Manchester codes comprises the following steps of:
the Manchester code-based air-to-water cross-medium laser induced sound communication method is characterized by comprising the following steps of: the method comprises the following steps:
step 1: the signal transmitting terminal acquires data information, performs binary conversion on the acquired data information, and performs Manchester coding to obtain a coded signal;
step 2: the coded signal is conducted on OOK modulation and is transmitted into a laser in a square wave form, the laser is controlled to emit a signal with repetition frequency, and then a laser pulse signal is generated;
step 3: the laser pulse signals output by the laser are vertically incident to the water-air interface through the light guide arm, and the thermal expansion effect is generated by focusing the laser energy, so that the laser pulse signals are converted into acoustic signals to be transmitted in various directions under water;
step 4: the acoustic signals are transmitted through the underwater acoustic channel, received by the hydrophone at the signal receiving end, converted into electric signals and transmitted to the acquisition system;
step 5: the acquisition system demodulates the OOK signal in a non-coherent envelope detection mode, converts the OOK signal into a square wave signal through threshold selection, performs sampling judgment, generates a binary digital signal, and obtains a demodulated signal;
step 6: the demodulated signal is decoded to obtain the original signal information, and the cross-medium communication from air to water is completed.
Alternatively, in step 1, the Manchester code uses positive and negative square waves of one period to represent "0" and "1";
the coding rule of Manchester code is that "0" code is denoted by "01" and "1" code is denoted by "10".
Alternatively, in step 1, the Manchester code is a bipolar NRZ waveform comprising two levels of opposite polarity, and there is a level jump at the center point of each symbol interval.
Optionally, in step 2, OOK modulation is performed on the encoded signal, and two paths of signals are required to be input for the external triggering mode of the pulse laser;
one path is a CLKin signal, the frequency is 500Hz, the duty cycle is 50%,
the second path is a Q-switched signal, which is an externally coded signal;
the CLKin signal and the Q-switched signal are input in the form of square waves, the low level is 0V, and the high level is 5V.
Alternatively, the laser is controlled to generate laser light, the rising edge of the square wave of the Q-switched signal is required to be in the high level of the CLKin signal, and the positive square wave and the negative square wave of the Manchester code are expressed by using the high level of the CLKin signal as one period, so that the actual coding effect is that the "0" code is expressed by "0001", and the "1" code is expressed by "0010", thereby controlling the laser to emit laser pulse signals.
Optionally, in step 3, when the pulse incident liquid intensity of the laser pulse signal is lower than 80mJ, the excited liquid molecules radiate a pulse sound wave into the surrounding medium;
when the effects of sound attenuation and heat conduction are not considered, the range of values of the beam radius and the laser pulse width is expressed by the formula (1):
wherein r is the radius of the laser beam, which is used for representing the geometric dimension of the photo-acoustic source; τ L Is the pulse width of the laser pulse;
k. d, C and ρ 0 The heat conductivity, the thermal diffusivity, the specific heat and the density of the liquid are respectively; c 0 Is the speed of sound in the liquid; eta/p 0 Is the dynamic viscosity of the liquid.
Alternatively, the photoacoustic wave equation of the laser excited underwater acoustic wave is formula (2):
wherein ,
p is sound pressure; c 0 The sound velocity is the sound velocity, and x, y and z are the space coordinate direction distances; t is time; alpha is the absorption coefficient of water; e (E) 0 Is the surface laser energy density; c p Constant pressure specific heat per unit mass; h is absorbed in unit timeAn electromagnetic energy density converted to heat; beta is the volume thermal expansion coefficient of the liquid, and T is the temperature; assuming that T is unchanged in the process, β is a constant.
Optionally, in step 5, the acquisition system completes the demodulation of the OOK signal, and restores the signal by using an envelope detection mode of incoherent demodulation, where the specific steps of the envelope detection incoherent demodulation are as follows:
step 5-1: the hydrophone receives the underwater acoustic signals and converts the underwater acoustic signals into electric signals, and the electric signals are transmitted to the acquisition system;
step 5-2: the acquisition system carries out band-pass filtering on the input electric signals to remove power frequency noise;
step 5-3: performing envelope detection on the filtered electric signals, and extracting upper envelope information;
step 5-4: judging the upper envelope information according to the selected threshold value, judging that the upper envelope information is higher than the threshold value and is 1, judging that the upper envelope information is lower than the threshold value and is 0, and converting the upper envelope information into square wave signals;
step 5-5: and sampling judgment is carried out on the square wave signal, and decoding is carried out, so that the original data information is obtained.
Optionally, in step 1, the signal sending end includes an upper computer and a signal generator;
the upper computer is used for inputting data information, converting the data information into binary data and carrying out Manchester coding;
the signal generator is used for carrying out OOK modulation on the Manchester encoded signal to generate a square wave signal.
Optionally, in step 4, the hydrophone is an optical fiber hydrophone; in step 2, the laser is a pump solid state laser.
The air-to-water cross-medium laser induced sound communication method based on Manchester codes can meet the communication requirements between an air platform and an underwater target, and the performance of a communication system is remarkably improved. In the application, when the laser emission energy is within the range of 30-63mJ, the laser repetition frequency is within 100Hz, and the communication error rate can be controlled below 0.01; when the communication is carried out at the laser repetition frequency of 500Hz, the communication rate can reach 150bits/s, and the communication rate is mainly limited by the hardware parameters of the laser, such as the increase of the laser repetition frequency, so that the communication rate can be further increased.
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In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required for the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a process step diagram of the present application;
FIG. 2 is a schematic structural view of the present application;
FIG. 3 is a waveform diagram of an external trigger square wave signal of the laser in the present application;
fig. 4 is a diagram of the signal processing after the hydrophone in the present application receives a signal.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved by the present application more clear, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.
The air-to-water cross-medium laser induced acoustic communication method based on Manchester codes provided by the embodiment of the application is described. Referring to fig. 1 to 4, the Manchester code-based air-to-water cross-medium laser induced acoustic communication method comprises the following steps:
step 1: the signal transmitting end acquires data information, performs binary conversion on the acquired data information, and then performs Manchester encoding.
Step 2: and (3) performing OOK modulation on the encoded signal, transmitting the OOK modulated signal into a laser in a square wave form, and controlling the laser to emit a repetition frequency to generate a laser pulse signal.
Step 3: the laser pulse signals output by the laser are vertically incident to the water-air interface through the light guide arm, and the thermal expansion effect is generated by focusing the laser energy, so that the laser pulse signals are converted into acoustic signals to be transmitted in various directions under water;
the light guide arm is used for controlling the incident direction of the laser pulse signal.
Step 4: the acoustic signals are transmitted through the underwater acoustic channel, received by the hydrophone at the signal receiving end, converted into electric signals and transmitted to the acquisition system.
Step 5: the acquisition system demodulates the OOK signal in a non-coherent envelope detection mode, and the OOK signal is converted into a square wave signal through threshold selection, sampling judgment is carried out, and a binary digital signal is generated.
Step 6: and decoding the demodulated signal to obtain original signal information, and completing cross-medium communication from air to water.
In step 1, the Manchester code is a method for representing 0 and 1 by positive and negative square waves of one period. The coding rule is that a "0" code is denoted by "01", and a "1" code is denoted by "10". The Manchester code is a bipolar NRZ waveform, only has two levels with opposite polarities, and has level jump at the center point of each symbol interval, so the Manchester code contains abundant timing information, has no direct current component, has simple coding process and can macroscopically detect errors.
In step 2, the coded signal is subjected to OOK modulation, and two paths of signals are required to be input aiming at the external triggering mode of the pulse laser, one path of CLKin signal has the frequency of 500Hz, the duty ratio of 50%, and the other path of Q-switched signal is the signal after external coding. The input square wave has a low level of 0V and a high level of 5V, so that the Manchester code is transmitted in a unipolar RZ code mode. The laser is controlled to generate laser, the rising edge of the square wave of the Q-switched signal is required to be in the high level of the CLKin signal, the positive square wave and the negative square wave of the Manchester code are expressed by taking the high level of the CLKin signal as one period, so that the actual coding effect is that a '0' code is expressed by 0001 ', a' 1 'code is expressed by 0010', and the light pulse emission frequency of the laser is controlled. By the method, the frequency band utilization rate can be improved without changing the communication rate, and the device contains abundant timing information and can macroscopically detect errors.
In step 3, when the laser pulse incidence liquid intensity is lower than 80mJ, the excited liquid molecules undergo a non-radiative relaxation process, the liquid medium is instantaneously heated and expanded due to absorption of light energy, so as to radiate pulse sound waves into surrounding medium, and the process of generating elastic stress and displacement change of substances by utilizing a thermal expansion mechanism is also called as a thermoelastic effect.
Assuming that the sound attenuation and heat conduction are not considered, when the heat conduction time is far longer than the time of the sound wave crossing the photo-acoustic source, the liquid can be approximated as a non-viscous liquid, and based on the above assumption, the range of values of the beam radius and the laser pulse width is expressed by the formula (1):
wherein r is the radius of the laser beam, which is used for representing the geometric dimension of the photo-acoustic source; τ L Is the pulse width of the laser pulse;
k. d, C and ρ 0 The heat conductivity, the thermal diffusivity, the specific heat and the density of the liquid are respectively; c 0 Is the speed of sound in the liquid; eta/p 0 Is the dynamic viscosity of the liquid.
The generation of sound waves can be described in the linear theory category when the thermal expansion rate of the heated liquid volume is much less than the speed of sound. Under the above assumption, the photoacoustic wave equation of the laser excited underwater acoustic wave is formula (2):
wherein ,
p is sound pressure; c 0 The sound velocity is the sound velocity, and x, y and z are the space coordinate direction distances; t is time; alpha is the absorption coefficient of water; e (E) 0 Is the energy density of surface laser；c p Constant pressure specific heat per unit mass; h is the electromagnetic energy density absorbed per unit time and converted to heat; beta is the volumetric thermal expansion coefficient of the liquid, T is the temperature (assuming T is constant during the process).
The light signal is controlled by the light guide arm to vertically enter the water-gas interface in the light emitting direction, and the laser energy is focused to generate a thermal expansion effect, so that the laser pulse signal is converted into an acoustic signal to be transmitted in various directions under water.
In step 5, the signal processing module completes the demodulation of the OOK signal, and restores the signal by the envelope detection mode of incoherent demodulation, wherein the specific steps of the envelope detection incoherent demodulation are as follows:
step 5-1: the hydrophone receives the underwater acoustic signals and converts the underwater acoustic signals into electric signals, and the electric signals are transmitted to the acquisition system;
step 5-2: the acquisition system carries out band-pass filtering on the input electric signals to remove power frequency noise;
step 5-3: performing envelope detection on the filtered electric signals, and extracting upper envelope information;
step 5-4: judging the upper envelope signal according to the selected threshold value, judging that the upper envelope signal is higher than the threshold value and is 1, judging that the upper envelope signal is lower than the threshold value and is 0, and converting the upper envelope signal into a square wave signal;
step 5-5: and sampling judgment is carried out on the square wave signal, and decoding is carried out, so that the original data information is obtained.
The hydrophone in the application is a fiber optic hydrophone (DFB-FL), and the laser is a pumped solid state laser.
In the application, the signal transmitting end comprises an upper computer and a signal generator, the upper computer inputs text information, converts the text information into binary data, carries out Manchester coding, and the "0" code is represented by "01" and the "1" code is represented by "10". The signal generator is converted into square wave signals to be used as external trigger Q-switched signals of the laser to be transmitted, and meanwhile, another square wave signal with the frequency of 500Hz is required to be transmitted as external trigger CLKin signals of the laser to be transmitted, and the two signals are transmitted at the high level of 5V and the low level of 0V. The rising edge of the Q-switched signal is ensured to be positioned at the high level of CLKin, and the laser is controlled to emit pulses through the rising edge of the Q-switched signal. The pulse laser signal is incident to the water surface through the air through the light guide arm, and laser energy is gathered at one point of the water surface to generate a thermal expansion effect. And then the optical signals are converted into acoustic signals which are transmitted in all directions under water, and the acoustic signals are received by the hydrophone at any position under water. The hydrophone receives the acoustic signals and transmits the acoustic signals to the acquisition system, and the acquisition system comprises a data processing module and a data acquisition card. The data acquisition card receives the electric signals transmitted by the hydrophone; the data processing module carries out band-pass filtering on the electric signals received by the data acquisition card to remove power frequency noise, extracts an upper envelope, selects a proper threshold value and generates square wave signals. And sampling and judging the square wave signal, decoding "0001" to represent "0" and "0010" to represent "1", and finally converting binary data into text information to complete cross-medium communication from air to water.
The air-to-water cross-medium laser induced sound communication method based on Manchester codes can meet the communication requirements between an air platform and an underwater target, and the performance of a communication system is remarkably improved. In the application, when the laser emission energy is within the range of 30-63mJ, the laser repetition frequency is within 100Hz, and the communication error rate can be controlled below 0.01; when the communication is carried out at the laser repetition frequency of 500Hz, the communication rate can reach 150bits/s, and the communication rate is mainly limited by the hardware parameters of the laser, such as the increase of the laser repetition frequency, so that the communication rate can be further increased.
The foregoing description of the preferred embodiments of the present application is not intended to be limiting, but is intended to cover any and all modifications, equivalents, and alternatives falling within the spirit and principles of the present application.
Claims (10)
1. The Manchester code-based air-to-water cross-medium laser induced sound communication method is characterized by comprising the following steps of: the method comprises the following steps:
step 1: the signal transmitting terminal acquires data information, performs binary conversion on the acquired data information, and performs Manchester coding to obtain a coded signal;
step 2: the coded signal is conducted on OOK modulation and is transmitted into a laser in a square wave form, the laser is controlled to emit a signal with repetition frequency, and then a laser pulse signal is generated;
step 3: the laser pulse signals output by the laser are vertically incident to the water-air interface through the light guide arm, and the thermal expansion effect is generated by focusing the laser energy, so that the laser pulse signals are converted into acoustic signals to be transmitted in various directions under water;
step 4: the acoustic signals are transmitted through the underwater acoustic channel, received by the hydrophone at the signal receiving end, converted into electric signals and transmitted to the acquisition system;
step 5: the acquisition system demodulates the OOK signal in a non-coherent envelope detection mode, converts the OOK signal into a square wave signal through threshold selection, performs sampling judgment, generates a binary digital signal, and obtains a demodulated signal;
step 6: the demodulated signal is decoded to obtain the original signal information, and the cross-medium communication from air to water is completed.
2. The Manchester code based air-to-water cross-media laser induced acoustic communication method of claim 1, wherein: in step 1, the Manchester code uses positive and negative square waves of one period to represent '0' and '1';
the coding rule of Manchester code is that "0" code is denoted by "01" and "1" code is denoted by "10".
3. The Manchester code based air-to-water cross-media laser induced acoustic communication method of claim 2, wherein: in step 1, the Manchester code is a bipolar NRZ waveform comprising two levels of opposite polarity, and there is a level jump at the center point of each symbol interval.
4. The Manchester code based air-to-water cross-media laser induced acoustic communication method of claim 1, wherein: in the step 2, the coded signals are subjected to OOK modulation, and two paths of signals are required to be input aiming at the external triggering mode of the pulse laser;
one path is a CLKin signal, the frequency is 500Hz, the duty cycle is 50%,
the second path is a Q-switched signal, which is an externally coded signal;
the CLKin signal and the Q-switched signal are input in the form of square waves, the low level is 0V, and the high level is 5V.
5. The Manchester code based air-to-water cross-media laser induced acoustic communication method of claim 4, wherein: the laser is controlled to generate laser, the rising edge of the square wave of the Q-switched signal is required to be in the high level of the CLKin signal, the positive square wave and the negative square wave of the Manchester code are expressed by taking the high level of the CLKin signal as one period, so that the actual coding effect is that the "0" code is expressed by 0001, the "1" code is expressed by 0010, and the laser is controlled to emit laser pulse signals.
6. The Manchester code based air-to-water cross-media laser induced acoustic communication method of claim 1, wherein: in the step 3, when the pulse incidence liquid intensity of the laser pulse signal is lower than 80mJ, excited liquid molecules radiate pulse sound waves into surrounding media;
when the effects of sound attenuation and heat conduction are not considered, the range of values of the beam radius and the laser pulse width is expressed by the formula (1):
wherein r is the radius of the laser beam, which is used for representing the geometric dimension of the photo-acoustic source; τ L Is the pulse width of the laser pulse;
k. d, C and ρ 0 The heat conductivity, the thermal diffusivity, the specific heat and the density of the liquid are respectively; c 0 Is the speed of sound in the liquid; eta/p 0 Is the dynamic viscosity of the liquid.
7. The Manchester code based air-to-water cross-media laser induced acoustic communication method of claim 6, wherein:
the photoacoustic wave equation of the laser excited underwater acoustic wave is the formula (2):
wherein ,
p is sound pressure; c 0 The sound velocity is the sound velocity, and x, y and z are the space coordinate direction distances; t is time; alpha is the absorption coefficient of water; e (E) 0 Is the surface laser energy density; c p Constant pressure specific heat per unit mass; h is the electromagnetic energy density absorbed per unit time and converted to heat; beta is the volume thermal expansion coefficient of the liquid, and T is the temperature; assuming that T is unchanged in the process, β is a constant.
8. The Manchester code based air-to-water cross-media laser induced acoustic communication method of claim 1, wherein: in step 5, the acquisition system completes the demodulation of the OOK signal, and restores the signal by an envelope detection mode of incoherent demodulation, wherein the specific steps of the envelope detection incoherent demodulation are as follows:
step 5-1: the hydrophone receives the underwater acoustic signals and converts the underwater acoustic signals into electric signals, and the electric signals are transmitted to the acquisition system;
step 5-2: the acquisition system carries out band-pass filtering on the input electric signals to remove power frequency noise;
step 5-3: performing envelope detection on the filtered electric signals, and extracting upper envelope information;
step 5-4: judging the upper envelope information according to the selected threshold value, judging that the upper envelope information is higher than the threshold value and is 1, judging that the upper envelope information is lower than the threshold value and is 0, and converting the upper envelope information into square wave signals;
step 5-5: and sampling judgment is carried out on the square wave signal, and decoding is carried out, so that the original data information is obtained.
9. The Manchester code based air-to-water cross-media laser induced acoustic communication method of claim 1, wherein: in the step 1, a signal transmitting end comprises an upper computer and a signal generator;
the upper computer is used for inputting data information, converting the data information into binary data and carrying out Manchester coding;
the signal generator is used for carrying out OOK modulation on the Manchester encoded signal to generate a square wave signal.
10. The Manchester code based air-to-water cross-media laser induced acoustic communication method of claim 1, wherein: in the step 4, the hydrophone is an optical fiber hydrophone; in step 2, the laser is a pump solid state laser.
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