CN116800352B - Two-way full duplex air-water cross-medium relay-free communication method - Google Patents
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Abstract
A two-way full duplex air-water cross-medium relay-free communication method belongs to the technical field of air-water cross-medium communication. The invention aims to solve the problems of poor timeliness and low communication efficiency of the existing air-water cross-domain communication which is realized by means of a relay buoy. Comprising the following steps: in a communication uplink, an uplink modulation audio signal is amplified and then converted into an underwater sound channel through a transmitting transducer and released into the underwater sound channel, and microwave vibration with the frequency consistent with that of the uplink sound signal is generated on the water surface; transmitting a frequency modulation continuous wave radio frequency signal to the water surface by adopting a millimeter wave radar, receiving a return wave signal and processing the return wave signal to obtain information transmitted by an uplink modulation audio signal; in a communication downlink, a downlink communication signal is encoded to obtain a downlink encoded signal, a laser is adopted to transmit a laser beam carrying the downlink encoded signal to the water surface, and the decoded signal of the downlink communication signal is obtained after a receiving transducer receives the signal. The invention is used for bidirectional full duplex air-water cross-medium communication.
Description
Technical Field
The invention relates to a two-way full duplex air-water cross-medium relay-free communication method, and belongs to the technical field of air-water cross-medium communication.
Background
Experiments show that sound waves have small attenuation in a complex marine environment, and the propagation distance can reach tens of kilometers, so that the sound waves are always used for underwater communication, but the sound waves cannot propagate in the air; the electromagnetic wave can be well transmitted in the air, the transmission speed is high, and the delay is low; however, due to the strong conductivity of the ocean, electromagnetic waves attenuate greatly in the ocean, and the propagation distance is short, which is only tens of meters at maximum, so that the electromagnetic waves can only be used for short-distance cross-medium communication.
The most commonly used air-sea cross-medium communication method is a relay communication method at present, an air node of the method uses electromagnetic waves/lasers/magnetism and other mediums as an information carrier, an underwater node uses sound/visible light and other mediums to transmit signals, and communication between the air node and the underwater node is connected by means of a sea surface buoy, a ship and other relay equipment.
The relay buoy has a vital function in a cross-medium communication loop, but a cross-medium communication channel established by the relay buoy has long two-way communication time and large time delay, and the buoy is easily influenced by environment and weather (wind, snow, rain and the like), is easy to expose and has low safety coefficient; meanwhile, in cross-medium communication, a plurality of buoys are needed on the ocean to establish a strong communication relay network, and the maintenance cost is high.
In view of many problems of air-sea cross-domain communication, the existing cross-domain communication system does not meet the convenience, safety and no relay of communication.
Disclosure of Invention
Aiming at the problems that the existing air-water cross-domain communication needs to be realized by means of a relay buoy, the timeliness is poor and the communication efficiency is low, the invention provides a two-way full-duplex air-water cross-medium relay-free communication method.
The invention relates to a two-way full duplex empty water cross-medium relay-free communication method, which comprises a communication uplink and a communication downlink;
In the communication uplink, an uplink modulation audio signal sent by a computer is amplified by a power amplifier, converted into an uplink sound wave signal by a sending transducer and released into a water sound channel; the uplink sound wave signal impacts the water surface, and microwave vibration with the frequency consistent with that of the uplink sound wave signal is generated on the water surface;
Transmitting a frequency modulation continuous wave radio frequency signal to the water surface by adopting a millimeter wave radar, obtaining an echo signal carrying microwave vibration information after the frequency modulation continuous wave radio frequency signal is reflected by the water surface, processing the echo signal by adopting a computer II to obtain information transmitted by an uplink modulation audio signal, and completing uplink communication;
In a communication downlink, a downlink communication signal is encoded by a computer II to obtain a downlink encoding signal, a laser is adopted to transmit a laser beam carrying the downlink encoding signal to the water surface, the laser beam penetrates the water surface to form a downlink sound wave signal, the downlink sound wave signal is received by a receiving transducer and then is converted into a downlink audio signal, the downlink audio signal is decoded by the computer I to obtain a decoding signal of the downlink communication signal, and downlink communication is completed.
According to the bidirectional full duplex air-water cross-medium relay-free communication method, in uplink communication, a millimeter wave radar transmits a frequency modulation continuous wave which lasts for 1.28s to the water surface in each detection process, each frequency modulation continuous wave comprises 32 frames of frequency modulation continuous wave radio frequency signals, and the duration of each frame of frequency modulation continuous wave radio frequency signals is 40ms; each frame of frequency-modulated continuous wave radio frequency signal comprises 128 linear frequency modulation signals, the sweep frequency period Ts of each linear frequency modulation signal is 160 mu s, and the frequency sweep period Ts totally comprises 4096 times of frequency sweeps; the frequency of the linear frequency modulation signal is 77GHz-81GHz.
According to the two-way full duplex air-water cross-medium relay-free communication method, the process of processing echo signals by a second computer comprises the following steps:
Mixing an echo signal obtained by each sweep frequency with a frequency modulation continuous wave radio frequency signal in a mixer to obtain an intermediate frequency signal;
the data acquisition card acquires the intermediate frequency signal and digitizes the intermediate frequency signal to obtain a digitized intermediate frequency signal displayed in a real-imaginary part form;
Performing fast Fourier transform on 128 linear frequency modulation signals included in each frame of frequency modulation continuous wave radio frequency signals to obtain a spectrogram of the linear frequency modulation signals;
Extracting the digital intermediate frequency signal to obtain the intermediate frequency signal frequency and the actual distance between the water surface at the sound-induced disturbance point and the millimeter wave radar;
Carrying out coordinate transformation on the spectrogram by using the intermediate frequency signal frequency and the actual distance to obtain a time and distance graph of 1.28 s; determining an echo signal distance unit with the strongest energy according to the time and distance graph, and obtaining a distance gate between the millimeter wave radar and the water surface; extracting the phase of a distance gate to obtain a time and phase diagram, wherein the phase in the time and phase diagram is coiled; then, the phase in the time and phase diagram is unwound to obtain the water surface phase change information; carrying out blind source signal separation on acoustic disturbance and water disturbance contained in the water surface phase change information, and filtering water disturbance caused by water surface clutter to obtain the phase change information of the acoustic disturbance; and carrying out Fourier transform on the phase change information of the acoustic disturbance, and extracting frequency point information to obtain information transmitted by the uplink modulation audio signal.
According to the two-way full duplex air-water cross-medium relay-free communication method, the laser beam carrying the downlink coding signal is a laser beam below 250 KHz.
According to the bidirectional full-duplex air-water cross-medium relay-free communication method, self-interference signals generated by the transducer in the full-duplex synchronous same-frequency communication process are restrained and counteracted in a mode of a space domain and a digital domain auxiliary analog domain.
According to the two-way full-duplex air-water cross-medium relay-free communication method, an acoustic baffle is arranged between a transmitting transducer and a receiving transducer in a space domain; the transmitting transducer adopts a directional transmitting transducer; the receiving transducer is a vector hydrophone.
According to the bidirectional full duplex air-water cross-medium relay-free communication method, a local reference signal is arranged on an analog domain and used for restraining and counteracting self-interference signals of two transducers;
The local reference signal is matched with the self-interference signal by adjusting the phase by utilizing a fixed tap with fixed time delay and amplitude, and the local reference signal and the self-interference signal are overlapped by a combiner, so that the self-interference signal is restrained and counteracted.
According to the two-way full duplex air-water cross-medium relay-free communication method, in a digital domain, residual self-interference signals in an analog domain are introduced into the digital domain through an auxiliary link, a least square algorithm is adopted for estimation and modeling to obtain auxiliary anti-interference signals, and the auxiliary anti-interference signals and the residual self-interference signals are cancelled, so that self-interference suppression and cancellation of the digital domain are realized.
According to the two-way full-duplex air-water cross-medium relay-free communication method, the laser comprises a laser with a high divergence angle;
the method for obtaining the laser beam carrying the downlink code signal comprises the following steps:
The modulator is arranged in an optical path outside the laser resonant cavity, and when a laser beam emitted by the laser passes through the modulator, the modulator changes the amplitude, the phase and the frequency of the laser beam through modulating voltage to obtain the laser beam carrying the downlink coding signal;
the energy density of the laser beam carrying the downstream encoding signal at the focus point of the water surface is far greater than the dielectric breakdown threshold of water.
According to the bidirectional full duplex air-water cross-medium relay-free communication method, a laser beam carrying a downlink coding signal generates plasma bubbles at a focusing point of the water surface, and the plasma bubbles are attenuated into downlink sound wave signals after being broken and received by a receiving transducer.
The invention has the beneficial effects that: according to the method, FMCW radar is used for measuring water surface microwave vibration in an uplink to obtain underwater transmission information, laser sound technology is used for realizing data transmission in a downlink, and a group of transducers are used for receiving and transmitting sound wave signals in the underwater to realize full duplex communication. Transmitting sound wave signals by using a transducer in an uplink, and completing water-air cross medium communication after decoding water surface vibration; and in the downlink, laser is adopted to cause water surface breakdown to generate sound waves, and the sound waves are received by a receiving transducer (hydrophone) to complete air-water cross-medium communication.
According to the method, the underwater data transmission is completed by measuring the water surface microwave vibration caused by the underwater sound wave and the underwater sound wave caused by the aerial laser, so that the two-way full duplex relay-free communication between the underwater node and the above-water node across the empty water medium is realized, the information can be transmitted and received at the same time by utilizing the different carrier frequency bands of different communication uplink and downlink transmission media; and relay equipment is not needed, so that the communication convenience, the communication efficiency, the ocean exploration timeliness and the like are improved.
Drawings
FIG. 1 is a communication schematic diagram of a bi-directional full duplex air-water cross-medium relay-less communication method according to the present invention;
FIG. 2 is a schematic flow diagram of the spatial domain and the digital-assisted analog domain self-suppressing interference;
FIG. 3 is a simple communication model of the communication uplink for measuring microwave vibrations;
Fig. 4 is a simplified communication model of laser induced sounding measurements by the communication downlink.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
The invention is further described below with reference to the drawings and specific examples, which are not intended to be limiting.
The invention provides a two-way full-duplex air-water cross-medium relay-free communication method, which comprises a communication uplink and a communication downlink, as shown in the detailed description of the first embodiment and in combination with fig. 1 to 4;
In the communication uplink, an uplink modulation audio signal sent by a computer is amplified by a power amplifier, converted into an uplink sound wave signal by a sending transducer and released into a water sound channel; the uplink sound wave signal impacts the water surface, and microwave vibration with the frequency consistent with that of the uplink sound wave signal is generated on the water surface;
transmitting a frequency modulation continuous wave radio frequency signal to the water surface by adopting a millimeter wave radar, and obtaining an echo signal carrying microwave vibration information after the frequency modulation continuous wave radio frequency signal is reflected by the water surface, wherein the echo signal is received by a radar receiving antenna; processing the echo signals by a second computer to obtain information transmitted by uplink modulation audio signals, and completing uplink communication;
In the downlink communication, a downlink communication signal is encoded by a second computer to obtain a downlink encoding signal, a laser is used for transmitting a laser beam carrying the downlink encoding signal to the water surface, the laser beam penetrates the water surface, strong energy forms a downlink sound wave signal below the water surface, the downlink sound wave signal is received by a receiving transducer and then is converted into a downlink audio signal, and the downlink audio signal is decoded and filtered by the first computer to obtain a decoded signal of the downlink communication signal, so that downlink communication is completed.
In the embodiment, a first computer is provided with a modulated audio signal, the first computer is connected with a power amplifier, the power amplifier is connected with a transmitting transducer arranged under water, the transmitting transducer converts an electric signal into an acoustic signal, the acoustic signal is released into an underwater acoustic channel to strike the water surface, the water surface generates vibration, and the frequency of the vibration of the water surface is consistent with the frequency of the acoustic wave sent by the transmitting transducer; in the air, the FMCW millimeter wave radar fixed on the water surface receives the water surface reflection information and then sends the water surface reflection information to the second computer, and after the intermediate frequency signal is processed, the underwater transmitted information is obtained.
The downlink uses laser-induced acoustic technology. The laser is arranged above the water surface, and the communication information is encoded by the second computer and then sent to the laser.
Further, in the uplink communication, the millimeter wave radar transmits a frequency-modulated continuous wave which lasts for 1.28s to the water surface in each detection process, each frequency-modulated continuous wave comprises 32 frames of frequency-modulated continuous wave radio frequency signals, and the duration of each frame of frequency-modulated continuous wave radio frequency signals is 40ms; each frame of frequency-modulated continuous wave radio frequency signal comprises 128 linear frequency modulation signals, the sweep frequency period Ts of each linear frequency modulation signal is 160 mu s, and the frequency sweep period Ts totally comprises 4096 times of frequency sweeps; the frequency of the linear frequency modulation signal is 77GHz-81GHz.
In this embodiment, the second computer processes the echo signal, including:
carrying out coherent mixing on the echo signal obtained by each sweep frequency and the frequency-modulated continuous wave radio frequency signal in a mixer to obtain an intermediate frequency signal about the distance and the speed of the water surface target position;
the data acquisition card acquires the intermediate frequency signal and digitizes the intermediate frequency signal to obtain a digitized intermediate frequency signal displayed in a real-imaginary part form;
Performing fast Fourier transform on 128 linear frequency modulation signals included in each frame of frequency modulation continuous wave radio frequency signals to obtain a spectrogram of the linear frequency modulation signals;
Extracting the digital intermediate frequency signal to obtain the intermediate frequency signal frequency and the actual distance between the water surface at the sound-induced disturbance point and the millimeter wave radar;
Carrying out coordinate transformation on the spectrogram by using the intermediate frequency signal frequency and the actual distance to obtain a time and distance graph of 1.28 s; determining an echo signal distance unit with the strongest energy according to the time and distance graph, and obtaining a distance gate between the millimeter wave radar and the water surface; extracting the phase of a distance gate to obtain a time and phase diagram, wherein the phase in the time and phase diagram is coiled; then, the phase in the time and phase diagram is unwound to obtain the water surface phase change information; carrying out blind source signal separation on acoustic disturbance and water disturbance contained in the water surface phase change information, and filtering water disturbance caused by water surface clutter to obtain the phase change information of the acoustic disturbance; and carrying out Fourier transform on the phase change information of the acoustic disturbance, and extracting frequency point information to obtain information transmitted by the uplink modulation audio signal.
The calculation formula of the distance resolution d res of the millimeter wave radar is as follows:
dres＝c/2Bsweep，
Where c is the speed of light and Bsweep is the swept bandwidth.
The calculation formula of the velocity resolution V res is:
Vres＝2π/N，
Where N is the number of chirps transmitted by a frame of fm continuous wave rf signal, n=128 in this embodiment.
The received waveform and the transmitted waveform of the millimeter wave radar are the same, and as shown in fig. 2, the distance between the radar and the object is d, the millimeter electromagnetic wave propagates at the speed of light, and there is a time delay difference between the received signal and the transmitted signalAnd because the frequency is changed along with time, a frequency difference is generated, and the obtained difference frequency signal is utilized to carry out filtering, sampling and processing, and then the acoustic disturbance frequency information is obtained after Fourier transformation. Where d is the distance between the millimeter wave radar and the detection target and c is the speed of light.
The intermediate frequency signal obtained by the millimeter wave radar carries a plurality of sound sources, interference and noise at different spatial positions, and when the disturbance caused by the sound waves is obtained, water surface clutter needs to be filtered in advance. In the embodiment, a blind source signal separation algorithm is adopted, so that noise is effectively separated under the condition that a plurality of underwater array elements/sensors work under different scenes, and target signals are obtained from a plurality of interference sources.
As an example, the laser beam carrying the downstream encoding signal is a laser beam below 250 KHz.
Still further, as shown in fig. 2, the present embodiment suppresses and cancels the self-interference signal generated by the transducer during the full duplex synchronous co-frequency communication by means of the spatial domain and the digital domain auxiliary analog domain.
In the spatial domain, an acoustic baffle is disposed between the transmitting transducer and the receiving transducer; the transmitting transducer adopts a directional transmitting transducer; the receiving transducer is a vector hydrophone.
Setting a local reference signal in an analog domain for suppressing and canceling self-interference signals of two transducers;
The local reference signal is matched with the self-interference signal by adjusting the phase by utilizing a fixed tap with fixed time delay and amplitude, and the local reference signal and the self-interference signal are overlapped by a combiner, so that the self-interference signal is restrained and counteracted.
In the digital domain, according to the residual self-interference signals in the analog domain, a greater number of filter taps are provided, the residual self-interference signals in the analog domain are introduced into the digital domain through an auxiliary link, a least square algorithm is adopted for estimation and modeling to obtain auxiliary anti-interference signals, the auxiliary anti-interference signals and the residual self-interference signals are cancelled, and self-interference suppression and cancellation in the digital domain are realized.
In this embodiment, the laser comprises a high divergence angle laser that can provide a broad beam with a large footprint to relax strict alignment constraints;
the method for obtaining the laser beam carrying the downlink code signal comprises the following steps:
The modulator is arranged in an optical path outside the laser resonant cavity, and when a laser beam emitted by the laser passes through the modulator, the modulator changes the amplitude, the phase and the frequency of the laser beam through modulating voltage to obtain the laser beam carrying the downlink coding signal;
The laser beam carrying the downlink coding signal is irradiated to the water surface, the strong laser energy forms a focusing point on the water surface, and the energy density of the focusing point on the water surface is far greater than the dielectric breakdown threshold of the water.
In this embodiment, the laser beam carrying the downlink code signal generates a plasma bubble at the focusing point on the water surface, and the plasma bubble is attenuated into a downlink sound wave signal after being broken and received by the receiving transducer. The downlink sound wave signals received by the receiving transducer are sampled to obtain digital signals, and the digital signals are demodulated by a first computer.
After the underwater sends information to the air, the air can selectively reply the information; one-way communication, i.e. no over-the-air talk with underwater deployment, may be selected; the reply can also be selected to finish the cross-medium dialogue between the air and the underwater. The method ensures that the communication of the air-crossing water medium is not different from the communication of electromagnetic waves in the air, can complete full duplex communication in extremely low time delay, and can simultaneously receive information by both air-water nodes; otherwise, the dialogue is initiated by the air, and the method steps are the same.
The method adopts a frequency division technology to realize full duplex communication, the uplink and the downlink use different frequency bands, different transmission carriers are used above and below the water surface, the radio frequency signals in the uplink are high-frequency electromagnetic waves belonging to 77GHz-81GHz, all types of laser energy used in the downlink are below 250KHz, and the laser and the radio frequency signals occupy different frequency bands respectively; transmitting signals underwater by using sound waves; for severe self-interference generated by the transmitting transducer and the receiving transducer, the self-interference signal can be well restrained and counteracted by the multi-domain self-restraining interference elimination method of the receiving transducer.
The two-way communication of the method is feedback information communication, so that the accuracy of communication can be improved, and the communication time is short;
The method is upgraded to duplex communication on the basis of two directions, and can send and receive information simultaneously, thereby greatly improving the working efficiency; the method saves information transmission time, has high speed and small time delay, improves information interaction efficiency and meets the requirement of cross-medium information interaction;
the laser induced sound used by the method increases the safety of communication to a certain extent, avoids a series of influences brought by using buoy relay, and increases the possibility of cross-medium communication.
The method of the invention can be suitable for various scenes, such as ocean resource detection, petroleum development, fishery production, frogman communication, natural disaster early warning, military countermeasure and the like.
The cross-medium communication method of the invention is characterized in that two natural channels are arranged above the water surface, the underwater acoustic channel utilizes the frequency division technology to complete the full duplex of the underwater part, and the communication is realized by the seamless combination of the underwater and the water.
The following is described by two specific examples:
First embodiment: the unmanned aerial vehicle carries devices such as millimeter wave radar, acquisition card, laser modulator, computer and the like to execute the task of transmitting information in the air, and the AUV working underwater carries devices such as computer, transceiver transducer, power amplifier and the like to execute the task of transmitting information in the underwater.
After the signal is subjected to FSK modulation (binary digital frequency modulation), two different frequencies f 0,f1,f0 are set to represent binary 0, f 1 represents binary 1, the transducer converts an audio signal into an acoustic wave signal, the acoustic wave propagates under water in a mechanical wave mode, the acoustic wave propagates to the water surface to cause water surface oscillation, the oscillation frequency is the same as the frequency of the acoustic wave signal, the lower the frequency of the acoustic signal is, the larger the caused water surface amplitude is, the millimeter wave radar transmits a radio frequency signal to the water surface, the water surface microwave vibration information is carried after the signal is reflected by the water surface, the echo signal is received and then is subjected to difference with a part of a transmitting signal in a mixer, and the obtained intermediate frequency signal is displayed in the second computer.
After 256 sampling points are obtained at the ADC sampling rate of each chirp signal 10 6, the digitized signal is subjected to FFT to obtain the information transferred from underwater to air, and the simple communication model of the uplink is shown in fig. 3.
In the air, external modulation is used to separate the generation and modulation of laser, and after the laser is formed, a modulation signal is loaded, namely, a modulator is arranged in an optical path outside a laser resonant cavity, and modulation signal voltage is added on the modulator, so that the physical characteristics of the modulator are correspondingly changed; when the laser passes through the modulator, certain parameters are modulated, so that the parameters such as the intensity, the frequency and the like of the laser are changed. The modulated laser is emitted to the water surface, the energy density of a focusing point on the water surface is far greater than the dielectric breakdown threshold of the water, so that the water body at the focus can generate light breakdown to generate plasma bubbles, the bubbles become sound waves after being broken, and the stronger the laser energy is, the closer the frequency of the generated sound waves is to a modulation signal; the receiving transducer receives sound waves underwater, the computer collects audio signals, the signals are processed to obtain communication information from the air to the underwater, and the downlink communication model is shown in fig. 4.
Compared with the technology of two-way communication by using relay equipment, the information feedback efficiency is greatly improved, the real-time performance and accuracy of communication information are ensured, and the problems of high time delay, slow transmission rate and the like brought by the traditional communication technology are solved; because the unmanned aerial vehicle has short endurance capacity and limited operational radius, the communication time can be greatly shortened by adopting the method for carrying out the air-water communication, the task instruction can be rapidly issued, and the strongest use value of the unmanned aerial vehicle can be realized; the embodiment has high safety performance, the relay-free communication technology can greatly protect the safety of the unmanned underwater vehicle, greatly reduce the possibility that the unmanned underwater vehicle is found, enable the unmanned underwater vehicle to finish the conversation with the air without being out of the water, improve the self-viability of the unmanned ship and increase the success rate of tasks; the embodiment greatly reduces the risk of interference by enemies or other devices and increases the network security.
Specific embodiment II: based on the method, unmanned plane equipment is matched with an underwater vehicle and the like, and the sensor is used for detecting geological, biological abnormality and environmental abnormality changes; some disasters come from deep earth crust, such as disasters which are not easy to detect, such as earthquake, volcanic eruption, tsunami and the like, when an underwater vehicle finds that the marine abnormal situation occurs, warning information can be immediately sent to an aerial work unmanned plane, the site source is described, emergency measures are made in the shortest time, and personnel and financial losses are reduced; because some disasters have higher predictability in the air than in the ocean, the aerial unmanned equipment can send information laser to the underwater, inform the underwater working equipment of alarm information, and enable other underwater working equipment to take safety precautions. The air and the water can also return information after communication, so that communication is increased, and early warning measures are known.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein may be combined in ways other than as described in the original claims. It is also to be understood that features described in connection with separate embodiments may be used in other described embodiments.
Claims (8)
1. A bidirectional full duplex air-water cross-medium relay-free communication method is characterized by comprising a communication uplink and a communication downlink;
In the communication uplink, an uplink modulation audio signal sent by a computer is amplified by a power amplifier, converted into an uplink sound wave signal by a sending transducer and released into a water sound channel; the uplink sound wave signal impacts the water surface, and microwave vibration with the frequency consistent with that of the uplink sound wave signal is generated on the water surface;
Transmitting a frequency modulation continuous wave radio frequency signal to the water surface by adopting a millimeter wave radar, obtaining an echo signal carrying microwave vibration information after the frequency modulation continuous wave radio frequency signal is reflected by the water surface, processing the echo signal by adopting a computer II to obtain information transmitted by an uplink modulation audio signal, and completing uplink communication;
In a communication downlink, a downlink communication signal is encoded through a computer II to obtain a downlink encoding signal, a laser is adopted to transmit a laser beam carrying the downlink encoding signal to a water surface, the laser beam penetrates the water surface to form a downlink sound wave signal, the downlink sound wave signal is received by a receiving transducer and then is converted into a downlink audio signal, the downlink audio signal is decoded through the computer I to obtain a decoding signal of the downlink communication signal, and downlink communication is completed;
In uplink communication, the millimeter wave radar transmits a frequency-modulated continuous wave which lasts for 1.28s to the water surface in each detection process, wherein each frequency-modulated continuous wave comprises 32 frames of frequency-modulated continuous wave radio frequency signals, and the duration of each frame of frequency-modulated continuous wave radio frequency signal is 40ms; each frame of frequency-modulated continuous wave radio frequency signal comprises 128 linear frequency modulation signals, the sweep frequency period Ts of each linear frequency modulation signal is 160 mu s, and the frequency sweep period Ts totally comprises 4096 times of frequency sweeps; the frequency of the linear frequency modulation signal is 77GHz-81GHz;
the second computer processes the echo signals, which comprises the following steps:
Mixing an echo signal obtained by each sweep frequency with a frequency modulation continuous wave radio frequency signal in a mixer to obtain an intermediate frequency signal;
the data acquisition card acquires the intermediate frequency signal and digitizes the intermediate frequency signal to obtain a digitized intermediate frequency signal displayed in a real-imaginary part form;
Performing fast Fourier transform on 128 linear frequency modulation signals included in each frame of frequency modulation continuous wave radio frequency signals to obtain a spectrogram of the linear frequency modulation signals;
Extracting the digital intermediate frequency signal to obtain the intermediate frequency signal frequency and the actual distance between the water surface at the sound-induced disturbance point and the millimeter wave radar;
Carrying out coordinate transformation on the spectrogram by using the intermediate frequency signal frequency and the actual distance to obtain a time and distance graph of 1.28 s; determining an echo signal distance unit with the strongest energy according to the time and distance graph, and obtaining a distance gate between the millimeter wave radar and the water surface; extracting the phase of a distance gate to obtain a time and phase diagram, wherein the phase in the time and phase diagram is coiled; then, the phase in the time and phase diagram is unwound to obtain the water surface phase change information; carrying out blind source signal separation on acoustic disturbance and water disturbance contained in the water surface phase change information, and filtering water disturbance caused by water surface clutter to obtain the phase change information of the acoustic disturbance; and carrying out Fourier transform on the phase change information of the acoustic disturbance, and extracting frequency point information to obtain information transmitted by the uplink modulation audio signal.
2. The method of two-way full duplex air-water cross-medium relay-less communication of claim 1,
The laser beam carrying the downlink code signal is a laser beam below 250 KHz.
3. The method of two-way full duplex air-water cross-medium relay-less communication of claim 2, wherein,
And the self-interference signals generated by the transducer in the full duplex synchronous same-frequency communication process are restrained and counteracted by a mode of assisting an analog domain in a space domain and a digital domain.
4. The method for two-way full duplex air-water cross-medium relay-less communication of claim 3,
In the spatial domain, an acoustic baffle is disposed between the transmitting transducer and the receiving transducer; the transmitting transducer adopts a directional transmitting transducer; the receiving transducer is a vector hydrophone.
5. The method of two-way full duplex air-water cross-medium relay-less communication of claim 4, wherein,
Setting a local reference signal in an analog domain for suppressing and canceling self-interference signals of two transducers;
The local reference signal is matched with the self-interference signal by adjusting the phase by utilizing a fixed tap with fixed time delay and amplitude, and the local reference signal and the self-interference signal are overlapped by a combiner, so that the self-interference signal is restrained and counteracted.
6. The method of two-way full duplex air-water cross-medium relay-less communication of claim 5,
In the digital domain, the residual self-interference signal in the analog domain is introduced into the digital domain through an auxiliary link, the auxiliary anti-interference signal is obtained by estimating and modeling through a least square algorithm, and the auxiliary anti-interference signal and the residual self-interference signal are cancelled, so that the self-interference suppression and cancellation of the digital domain are realized.
7. The method of two-way full duplex air-water cross-medium relay-less communication of claim 1,
The laser comprises a laser with a high divergence angle;
the method for obtaining the laser beam carrying the downlink code signal comprises the following steps:
The modulator is arranged in an optical path outside the laser resonant cavity, and when a laser beam emitted by the laser passes through the modulator, the modulator changes the amplitude, the phase and the frequency of the laser beam through modulating voltage to obtain the laser beam carrying the downlink coding signal;
the energy density of the laser beam carrying the downstream encoding signal at the focus point of the water surface is far greater than the dielectric breakdown threshold of water.
8. The method of two-way full duplex air-water cross-medium relay-less communication of claim 7,
The laser beam carrying the downlink code signal generates plasma bubbles at a focusing point on the water surface, and the plasma bubbles are attenuated into downlink sound wave signals after being broken and received by the receiving transducer.
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| CN114629567A (en) * | 2020-12-08 | 2022-06-14 | 军事科学院系统工程研究院网络信息研究所 | Photoacoustic interconnection bidirectional communication method for air and underwater mobile platform |
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