CN116800352B - Two-way full duplex air-water cross-medium relay-free communication method - Google Patents

Abstract

A bidirectional full-duplex air-water cross-medium non-relay communication method belongs to the technical field of air-water cross-medium communication. The present invention is to solve the problem that the existing air-water cross-domain communication needs to be realized by means of a relay buoy, which has poor timeliness and low communication efficiency. It includes: in the communication uplink, the uplink modulated audio signal is amplified and converted into and released into the underwater acoustic channel by a transmitting transducer, and microwave vibrations consistent with the frequency of the uplink acoustic wave signal are generated on the water surface; a millimeter-wave radar is used to transmit a frequency-modulated continuous wave radio frequency signal to the water surface, and an echo signal is received and processed to obtain the information transmitted by the uplink modulated audio signal; in the communication downlink, the downlink communication signal is encoded to obtain a downlink coded signal, a laser is used to transmit a laser beam carrying the downlink coded signal to the water surface, and the receiving transducer receives the signal and then decodes it to obtain a decoded signal of the downlink communication signal. The present invention is used for bidirectional full-duplex air-water cross-medium communication.

Description

Bidirectional full-duplex air-water cross-medium non-relay communication method

Technical Field

The invention relates to a bidirectional full-duplex air-water cross-medium non-relay communication method, belonging to the technical field of air-water cross-medium communication.

Background technique

Experiments have found that sound waves have little attenuation in complex ocean environments and can propagate over tens of kilometers, so they have been used for underwater communications. However, sound waves cannot propagate in the air; electromagnetic waves can propagate well in the air with fast propagation speed and low latency; but due to the strong conductivity of the ocean, electromagnetic waves have great attenuation in the ocean and a short propagation distance, with the longest reaching only tens of meters, so they can only be used for short-distance cross-medium communications.

The most widely used and common air-sea cross-media communication method is the relay communication method. Its aerial nodes use electromagnetic waves/lasers/magnetism and other media as information carriers, and underwater nodes use sound/visible light and other media to transmit signals. The communication between the aerial nodes and the underwater nodes relies on a combination of relay equipment such as sea surface buoys and ships.

Relay buoys play a vital role in the cross-media communication loop. However, the cross-media communication channel established using relay buoys has a long two-way communication time and a large delay. In addition, the buoys are easily affected by the environment and weather (wind, snow, rain, etc.), are easily exposed, and have a low safety factor. At the same time, in cross-media communication, multiple buoys are needed on the ocean to establish a robust communication relay network, which has high maintenance costs.

In view of the many problems of cross-domain communication between air and sea, the existing cross-domain communication system does not meet the requirements of communication convenience, security and non-relay.

Summary of the invention

In view of the problem that the existing air-water cross-domain communication needs to be realized with the help of relay buoys, has poor timeliness and low communication efficiency, the present invention provides a bidirectional full-duplex air-water cross-medium relay-free communication method.

A bidirectional full-duplex air-water cross-medium non-relay communication method of the present invention comprises a communication uplink and a communication downlink;

In the communication uplink, the uplink modulated audio signal sent by the computer is amplified by a power amplifier, converted into an uplink acoustic wave signal by a transmitting transducer, and released into the underwater acoustic channel; the uplink acoustic wave signal hits the water surface, generating microwave vibrations on the water surface that are consistent with the frequency of the uplink acoustic wave signal;

The millimeter wave radar is used to transmit a frequency modulated continuous wave radio frequency signal to the water surface. After being reflected by the water surface, an echo signal carrying microwave vibration information is obtained. The echo signal is processed by a computer to obtain the information transmitted by the uplink modulated audio signal, thus completing the uplink communication.

In the communication downlink, the downlink communication signal is encoded by computer 2 to obtain a downlink coded signal, and a laser is used to emit a laser beam carrying the downlink coded signal to the water surface. The laser beam penetrates the water surface to form a downlink sound wave signal, which is received by the receiving transducer and converted into a downlink audio signal. The downlink audio signal is decoded by computer 1 to obtain a decoded signal of the downlink communication signal, thereby completing the downlink communication.

According to the bidirectional full-duplex air-to-water cross-medium non-relay communication method of the present invention, in the uplink communication, the millimeter wave radar sends a frequency modulated continuous wave lasting 1.28s to the water surface during each detection process, each frequency modulated continuous wave includes 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 includes 128 linear frequency modulation signals, and the sweep period Ts of each linear frequency modulation signal is 160μs, including a total of 4096 sweeps; the frequency of the linear frequency modulation signal is 77GHz-81GHz.

According to the bidirectional full-duplex air-water cross-medium non-relay communication method of the present invention, the process of computer 2 processing the echo signal includes:

The echo signal obtained by each frequency sweep is mixed with the frequency modulated continuous wave radio frequency signal in the mixer to obtain an intermediate frequency signal;

The data acquisition card collects the intermediate frequency signal and digitizes it to obtain a digital intermediate frequency signal in the form of real and imaginary parts;

Performing fast Fourier transform on 128 linear frequency modulation signals included in each frame of frequency modulation continuous wave radio frequency signal to obtain a spectrum diagram of the linear frequency modulation signal;

The intermediate frequency signal frequency and the actual distance between the water surface and the millimeter wave radar at the acoustic disturbance point are extracted from the digitized intermediate frequency signal;

The spectrum diagram is subjected to coordinate transformation using the intermediate frequency signal frequency and the actual distance to obtain a 1.28s time and distance diagram; the distance unit of the echo signal with the strongest energy is determined from the time and distance diagram, and a distance gate between the millimeter wave radar and the water surface is obtained; the phase of the range gate is extracted to obtain a time and phase diagram, and the phase in the time and phase diagram is warped; the phase in the time and phase diagram is then unwound to obtain water surface phase change information; blind source signal separation is performed on the acoustic disturbance and water disturbance contained in the water surface phase change information, the water disturbance caused by the water surface clutter is filtered out, and the phase change information of the acoustic disturbance is obtained; Fourier transform is performed on the phase change information of the acoustic disturbance, the frequency point information is extracted, and the information transmitted by the uplink modulated audio signal is obtained.

According to the bidirectional full-duplex air-water cross-medium non-relay communication method of the present invention, the laser beam carrying the downlink coding signal is a laser beam below 250KHz.

According to the bidirectional full-duplex air-water cross-medium non-relay communication method of the present invention, the self-interference signal generated by the transducer during the full-duplex synchronous co-frequency communication is suppressed and offset by means of spatial domain and digital domain assisting analog domain.

According to the bidirectional full-duplex air-water cross-medium non-relay communication method of the present invention, in the spatial domain, a sound barrier is set between the transmitting transducer and the receiving transducer; the transmitting transducer adopts a directional transmitting transducer; and the receiving transducer is a vector hydrophone.

According to the bidirectional full-duplex air-water cross-medium non-relay communication method of the present invention, in the analog domain, a local reference signal is set to suppress and offset the self-interference signals of the two transducers;

The local reference signal adjusts the phase by using a fixed tap with fixed delay and amplitude to match the self-interference signal. The local reference signal and the self-interference signal are superimposed by a combiner to suppress and offset the self-interference signal.

According to the bidirectional full-duplex air-to-water cross-medium relay-free communication method of the present invention, in the digital domain, the residual self-interference signal in the analog domain is introduced into the digital domain through an auxiliary link, and the least squares algorithm is used to estimate and model the auxiliary anti-interference signal, and the auxiliary anti-interference signal is canceled with the residual self-interference signal to achieve self-interference suppression and cancellation in the digital domain.

According to the bidirectional full-duplex air-water cross-medium non-relay communication method of the present invention, the laser comprises a laser with a high divergence angle;

The method for obtaining a laser beam carrying a downlink coded signal includes:

The modulator is placed in the optical path outside the laser resonant cavity. When the laser beam emitted by the laser passes through the modulator, the modulator changes the amplitude, phase and frequency of the laser beam by modulating the voltage to obtain a laser beam carrying a downlink coded signal.

The energy density of the laser beam carrying the downlink coded signal at the focusing point on the water surface is much greater than the dielectric breakdown threshold of water.

According to the bidirectional full-duplex air-water cross-medium non-relay communication method of the present invention, a laser beam carrying a downlink coded signal generates plasma bubbles at the focal point of the water surface, and after the plasma bubbles burst, they decay into downlink sound wave signals and are received by a receiving transducer.

Beneficial effects of the present invention: The method of the present invention uses FMCW radar to measure the microwave vibration of the water surface in the uplink to obtain underwater transmission information, uses laser-induced acoustic technology in the downlink to realize data transmission, and realizes full-duplex communication by sending and receiving sound wave signals underwater through a group of transducers. In the uplink, a transducer is used to receive and transmit sound wave signals, and the water-air cross-medium communication is completed after decoding the water surface vibration; in the downlink, a laser is used to cause the water surface to break down and generate sound waves, which are received by the receiving transducer (hydrophone) to complete the air-water cross-medium communication.

The method of the present invention completes air-to-water data transmission by measuring the water surface microwave vibration caused by underwater sound waves and the underwater sound waves caused by aerial lasers, thereby realizing two-way full-duplex relay-free communication between underwater nodes and surface nodes across air-water media. By utilizing the different transmission media of the communication uplink and downlink and the different carrier frequency bands, information can be sent and received at the same time; and there is no need to use relay equipment, thereby improving communication convenience, communication efficiency and timeliness of ocean exploration.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a communication principle diagram of the bidirectional full-duplex air-water cross-medium non-relay communication method of the present invention;

FIG2 is a simplified flowchart of self-suppression of interference in the spatial domain and the digitally assisted analog domain;

FIG3 is a simple communication model for measuring microwave vibrations in a communication uplink;

FIG4 is a simplified communication model for measuring laser-induced acoustics in a communication downlink.

Detailed ways

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

Specific implementation method 1, in conjunction with Figures 1 to 4, the present invention provides a bidirectional full-duplex air-water cross-medium relay-free communication method, including a communication uplink and a communication downlink;

In the communication uplink, the uplink modulated audio signal sent by the computer is amplified by a power amplifier, converted into an uplink acoustic wave signal by a transmitting transducer, and released into the underwater acoustic channel; the uplink acoustic wave signal hits the water surface, generating microwave vibrations on the water surface that are consistent with the frequency of the uplink acoustic wave signal;

A millimeter wave radar is used to transmit a frequency modulated continuous wave radio frequency signal to the water surface, and an echo signal carrying microwave vibration information is obtained after being reflected by the water surface. The echo signal is received by the radar receiving antenna; a computer is used to process the echo signal to obtain the information transmitted by the uplink modulated audio signal, thereby completing the uplink communication;

In the communication downlink, the downlink communication signal is encoded by computer 2 to obtain a downlink coded signal, and a laser is used to emit a laser beam carrying the downlink coded signal to the water surface. The laser beam penetrates the water surface, and the powerful energy forms a downlink sound wave signal below the water surface, which is received by the receiving transducer and converted into a downlink audio signal. The downlink audio signal is decoded and filtered by computer 1 to obtain a decoded signal of the downlink communication signal, thereby completing the downlink communication.

In this embodiment, there is a modulated audio signal in computer one, computer one is connected to a power amplifier, the power amplifier is connected to a transmitting transducer placed underwater, the transmitting transducer converts the electrical signal into a sound wave signal, the sound wave signal is released into the underwater acoustic channel, hits the water surface, and the water surface vibrates, and the water surface vibration frequency is consistent with the sound wave frequency emitted by the transmitting transducer; in the air, the FMCW millimeter wave radar fixed on the water surface receives the water surface reflection information and sends it to computer two, and after processing the intermediate frequency signal, the information transmitted underwater is obtained.

The downlink uses laser-induced acoustic technology. The laser is placed above the water surface, and the communication information is encoded and sent to the laser through computer 2.

Furthermore, in the uplink communication, the millimeter-wave radar sends a frequency-modulated continuous wave lasting 1.28s to the water surface during each detection process. Each frequency-modulated continuous wave includes 32 frames of frequency-modulated continuous wave RF signals, and the duration of each frame of frequency-modulated continuous wave RF signals is 40ms; each frame of frequency-modulated continuous wave RF signals includes 128 linear frequency modulation signals, and the sweep period Ts of each linear frequency modulation signal is 160μs, including a total of 4096 sweeps; the frequency of the linear frequency modulation signal is 77GHz-81GHz.

In this implementation manner, the process of computer 2 processing the echo signal includes:

The echo signal obtained by each frequency sweep is coherently mixed with the frequency modulated continuous wave radio frequency signal in the mixer to obtain an intermediate frequency signal about the distance and speed of the surface target position;

The data acquisition card collects the intermediate frequency signal and digitizes it to obtain a digital intermediate frequency signal in the form of real and imaginary parts;

Performing fast Fourier transform on 128 linear frequency modulation signals included in each frame of frequency modulation continuous wave radio frequency signal to obtain a spectrum diagram of the linear frequency modulation signal;

The intermediate frequency signal frequency and the actual distance between the water surface and the millimeter wave radar at the acoustic disturbance point are extracted from the digitized intermediate frequency signal;

The spectrum diagram is subjected to coordinate transformation using the intermediate frequency signal frequency and the actual distance to obtain a 1.28s time and distance diagram; the distance unit of the echo signal with the strongest energy is determined from the time and distance diagram, and a distance gate between the millimeter wave radar and the water surface is obtained; the phase of the range gate is extracted to obtain a time and phase diagram, and the phase in the time and phase diagram is warped; the phase in the time and phase diagram is then unwound to obtain water surface phase change information; blind source signal separation is performed on the acoustic disturbance and water disturbance contained in the water surface phase change information, the water disturbance caused by the water surface clutter is filtered out, and the phase change information of the acoustic disturbance is obtained; Fourier transform is performed on the phase change information of the acoustic disturbance, the frequency point information is extracted, and the information transmitted by the uplink modulated audio signal is obtained.

The calculation formula of the distance resolution d _res of millimeter wave radar is:

d _res = c/2Bsweep,

Where c is the speed of light and Bsweep is the sweep bandwidth.

The calculation formula of velocity resolution V _res is:

V _res ＝2π/N，

Wherein N is the number of linear frequency modulation signals transmitted by one frame of frequency modulation continuous wave radio frequency signal, and in this embodiment, N=128.

The receiving waveform and transmitting waveform of the millimeter wave radar are the same. As shown in Figure 2, the distance between the radar and the object is d. The millimeter electromagnetic wave propagates at the speed of light. There is a time delay difference between the receiving signal and the transmitting signal. Because the frequency changes with time, a frequency difference will be generated. The difference frequency signal is filtered, sampled, processed, and then Fourier transformed to obtain the acoustic disturbance frequency information. 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 multiple sound sources, interference and noise in different spatial positions. When obtaining the disturbance caused by the sound wave, it is necessary to filter out the surface clutter in advance. In this implementation, a blind source signal separation algorithm is used to effectively separate and denoise the target signal from multiple interference sources when multiple underwater array elements/sensors are working in different scenarios.

As an example, the laser beam carrying the downlink coding signal is a laser beam below 250 KHz.

Furthermore, in combination with what is shown in FIG2 , this embodiment suppresses and cancels the self-interference signal generated by the transducer during the full-duplex synchronous co-frequency communication process by means of spatial domain and digital domain assisting analog domain.

In the spatial domain, a sound baffle is set between the transmitting transducer and the receiving transducer; the transmitting transducer adopts a directional transmitting transducer; and the receiving transducer is a vector hydrophone.

In the analog domain, a local reference signal is set to suppress and cancel the self-interference signals of the two transducers;

The local reference signal adjusts the phase by using a fixed tap with fixed time delay and amplitude to match the self-interference signal. The local reference signal and the self-interference signal are superimposed by a combiner to suppress and offset the self-interference signal.

In the digital domain, more filter taps are provided according to the residual self-interference signal in the analog domain, and the residual self-interference signal in the analog domain is introduced into the digital domain through an auxiliary link. The least squares algorithm is used to estimate and model the auxiliary anti-interference signal, and the auxiliary anti-interference signal is canceled with the residual self-interference signal to achieve self-interference suppression and cancellation in the digital domain.

In this embodiment, the laser includes a laser with a high divergence angle, which can provide a wide beam with a large coverage area to relax strict alignment constraints;

The method for obtaining a laser beam carrying a downlink coded signal includes:

The modulator is placed in the optical path outside the laser resonant cavity. When the laser beam emitted by the laser passes through the modulator, the modulator changes the amplitude, phase and frequency of the laser beam by modulating the voltage to obtain a laser beam carrying a downlink coded signal.

A laser beam carrying a downlink coded signal is directed toward the water surface. The powerful laser energy forms a focal point on the water surface. The energy density of the focal point on the water surface is much greater than the dielectric breakdown threshold of water.

In this embodiment, the laser beam carrying the downlink coded signal generates plasma bubbles at the focal point of the water surface, and the plasma bubbles decay into downlink sound wave signals after bursting, which are received by the receiving transducer. The downlink sound wave signals received by the receiving transducer are sampled to obtain digital signals, which are demodulated by computer 1.

When the underwater sends information to the air, the air can selectively reply to the information; it can choose unilateral communication, that is, the air does not communicate with the underwater; it can also choose to reply and complete the cross-medium dialogue between the air and the underwater. The method of the present invention makes cross-air-water medium communication no different from using electromagnetic wave communication in the air, and can complete full-duplex communication within a very low delay, and both air and water nodes receive information at the same time; conversely, the dialogue is initiated by the air, and the method steps are the same.

The method of the present invention adopts frequency division technology to realize full-duplex communication, and different frequency bands are used for uplink and downlink, and different transmission carriers are used above and below the water surface. The radio frequency signal in the uplink is a high-frequency electromagnetic wave belonging to 77GHz-81GHz, and all types of laser energy used in the downlink are below 250KHz, and the laser and radio frequency signals occupy different frequency bands respectively; sound waves are used for signal transmission underwater; for the serious self-interference generated by the transmitting transducer to the receiving transducer, the self-interference signal can be well suppressed and offset by the multi-domain self-suppression interference elimination method of the transceiver transducer.

The two-way communication of the method of the present invention is information communication with feedback, which can improve the accuracy of communication and shorten the communication time;

The method of the present invention is upgraded to duplex communication on the basis of bidirectional communication, so that both parties can send and receive information at the same time, which greatly improves the work efficiency; it saves information transmission time, has a fast rate, and a small delay, improves the efficiency of information interaction, and meets the needs of cross-media information interaction;

The laser-induced sound used in the method of the present invention increases the security of communication to a certain extent, avoids a series of influences brought about by the use of buoy relay, and increases the possibility of cross-media communication.

The method of the present invention can be applied to many scenarios, such as marine resource exploration, oil development, fishery production, frogman communication, natural disaster warning, military confrontation, etc.

The cross-medium communication method of the present invention is two natural channels above the water surface, and the underwater acoustic channel uses frequency division technology to complete the full-duplex of the underwater part, so that the surface and underwater are seamlessly combined to realize communication.

The following is described by two specific embodiments:

Specific embodiment 1: The aerial unmanned equipment carries millimeter wave radar, acquisition card, laser, laser modulator, computer and other devices to perform the task of transmitting information in the air, and the AUV working underwater carries computers, transceiver transducers, power amplifiers and other devices to perform the task of transmitting information underwater.

In underwater computer 1, the modulated signal is transmitted to the transmitting transducer through the power amplifier. After the signal is FSK modulated (binary digital frequency modulation), two different frequencies _f0 and _f1 are set. _f0 represents binary "0" and _f1 represents binary "1". The transducer converts the audio signal into a sound wave signal. The sound wave propagates underwater in the form of a mechanical wave. When it propagates to the water surface, it will cause the water surface to oscillate, and the oscillation frequency is the same as the sound wave signal frequency. The lower the sound signal frequency, the greater the water surface amplitude caused. The millimeter wave radar sends a radio frequency signal to the water surface, which carries the water surface microwave vibration information after being reflected by the water surface. After the echo signal is received, it is subtracted from a part of the transmitted signal in the mixer, and the obtained intermediate frequency signal is displayed in computer 2.

After obtaining 256 sampling points at an ADC sampling rate of 10 ⁶ for each linear frequency modulation signal, FFT is performed on the digitized signal to obtain the information transmitted from underwater to air. The simple communication model of the uplink is shown in Figure 3.

In the air, external modulation is used to separate the generation and modulation of the laser. After the laser is formed, the modulation signal is loaded, that is, the modulator is placed in the optical path outside the laser resonant cavity, and the modulation signal voltage is added to the modulator to change the physical properties of the modulator accordingly; when the laser passes through the modulator, some parameters are modulated, thereby changing the intensity, frequency and other parameters of the laser. The modulated laser is emitted to the water surface, and the energy density at the focal point on the water surface is much greater than the dielectric breakdown threshold of water, so the water body at the focus will undergo optical breakdown to generate plasma bubbles, which will become sound waves after bursting, and the stronger the laser energy, the closer the frequency of the sound waves generated is to the modulation signal; the sound waves are received by the receiving transducer underwater, and after the audio signal is collected by the computer, the signal is processed to obtain the communication information from the air to the underwater, and the downlink communication model is shown in Figure 4.

Compared with the technology of using relay equipment for two-way communication, this embodiment greatly improves the efficiency of information return, ensures the real-time and accuracy of communication information, and is conducive to solving the problems of high latency and slow transmission rate brought about by previous communication technologies; since the UAV has a short endurance and a limited combat radius, the use of the method of the present invention for air-to-water communication can greatly shorten the communication time, quickly issue mission instructions, and realize the highest use value of the UAV; this embodiment has high safety performance, and its relay-free communication technology can greatly protect the safety of underwater unmanned submersibles, greatly reduce the possibility of unmanned submersibles being discovered, and enable them to complete conversations with the air without surfacing, thereby improving the self-survival ability of the unmanned boat and increasing the success rate of the mission; this embodiment greatly reduces the risk of interference by the enemy or other equipment and increases network security.

Specific embodiment 2: Based on the method of the present invention, unmanned aerial vehicle equipment is used in conjunction with underwater submersibles, etc., and sensors are used to detect geological, biological anomalies, and abnormal environmental changes; some disasters come from deep in the earth's crust, such as earthquakes, volcanic eruptions, tsunamis, and other disasters that are difficult to detect. When the underwater vehicle finds that an abnormal situation in the ocean has occurred, it can immediately send a warning message to the aerial working drone to indicate the location and source, so as to take emergency measures in the shortest time and reduce personnel and financial losses; because some disasters are more predictable in the air than under the ocean, aerial unmanned equipment can shoot information lasers underwater to inform underwater working equipment of alarm information, so that other underwater working equipment can take safety precautions. The air and underwater can also return information to each other after communication, increase exchanges, and understand early warning measures.

Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary 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 various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It will also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims (8)

1. A bidirectional full-duplex air-water cross-medium non-relay communication method, characterized by comprising a communication uplink and a communication downlink; In the communication uplink, the uplink modulated audio signal sent by the computer is amplified by a power amplifier, converted into an uplink acoustic wave signal by a transmitting transducer, and released into the underwater acoustic channel; the uplink acoustic wave signal hits the water surface, generating microwave vibrations on the water surface that are consistent with the frequency of the uplink acoustic wave signal; The millimeter wave radar is used to transmit a frequency modulated continuous wave radio frequency signal to the water surface. After being reflected by the water surface, an echo signal carrying microwave vibration information is obtained. The echo signal is processed by a computer to obtain the information transmitted by the uplink modulated audio signal, thus completing the uplink communication. In the communication downlink, the downlink communication signal is encoded by computer 2 to obtain a downlink coded signal, and a laser beam carrying the downlink coded signal is emitted to the water surface by a laser. The laser beam penetrates the water surface to form a downlink sound wave signal, which is received by the receiving transducer and converted into a downlink audio signal. The downlink audio signal is decoded by computer 1 to obtain a decoded signal of the downlink communication signal, thereby completing the downlink communication. In uplink communication, the millimeter wave radar sends a frequency modulated continuous wave lasting 1.28s to the water surface during each detection process. Each frequency modulated continuous wave includes 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 signals includes 128 linear frequency modulation signals, and the sweep period Ts of each linear frequency modulation signal is 160μs, including 4096 sweeps in total; the frequency of the linear frequency modulation signal is 77GHz-81GHz; The process of computer 2 processing the echo signal includes: The echo signal obtained by each frequency sweep is mixed with the frequency modulated continuous wave radio frequency signal in the mixer to obtain an intermediate frequency signal; The data acquisition card collects the intermediate frequency signal and digitizes it to obtain a digital intermediate frequency signal in the form of real and imaginary parts; Performing fast Fourier transform on 128 linear frequency modulation signals included in each frame of frequency modulation continuous wave radio frequency signal to obtain a spectrum diagram of the linear frequency modulation signal; The intermediate frequency signal frequency and the actual distance between the water surface and the millimeter wave radar at the acoustic disturbance point are extracted from the digitized intermediate frequency signal; The spectrum diagram is transformed by using the intermediate frequency signal frequency and the actual distance to obtain a 1.28s time and distance diagram; the distance unit of the echo signal with the strongest energy is determined from the time and distance diagram, and the distance gate between the millimeter wave radar and the water surface is obtained; the phase of the range gate is extracted to obtain a time and phase diagram, and the phase in the time and phase diagram is warped; the phase in the time and phase diagram is then unwound to obtain water surface phase change information; blind source signal separation is performed on the acoustic disturbance and water disturbance contained in the water surface phase change information, the water disturbance caused by the water surface clutter is filtered out, and the phase change information of the acoustic disturbance is obtained; the phase change information of the acoustic disturbance is Fourier transformed, the frequency point information is extracted, and the information transmitted by the uplink modulated audio signal is obtained. 2. The bidirectional full-duplex air-water cross-medium non-relay communication method according to claim 1, characterized in that: The laser beam carrying the downlink coding signal is a laser beam below 250KHz. 3. The bidirectional full-duplex air-water cross-medium non-relay communication method according to claim 2, characterized in that: The self-interference signal generated by the transducer during full-duplex synchronous co-frequency communication is suppressed and offset by means of spatial domain and digital domain assisted analog domain. 4. The bidirectional full-duplex air-water cross-medium non-relay communication method according to claim 3, characterized in that: In the spatial domain, a sound baffle is set between the transmitting transducer and the receiving transducer; the transmitting transducer adopts a directional transmitting transducer; and the receiving transducer is a vector hydrophone. 5. The bidirectional full-duplex air-water cross-medium non-relay communication method according to claim 4, characterized in that: In the analog domain, a local reference signal is set to suppress and cancel the self-interference signals of the two transducers; The local reference signal adjusts the phase by using a fixed tap with fixed time delay and amplitude to match the self-interference signal. The local reference signal and the self-interference signal are superimposed by a combiner to suppress and offset the self-interference signal. 6. The bidirectional full-duplex air-water cross-medium non-relay communication method according to claim 5, characterized in that: In the digital domain, the residual self-interference signal in the analog domain is introduced into the digital domain through an auxiliary link, and the least squares algorithm is used to estimate and model the auxiliary anti-interference signal, which is then canceled out from the residual self-interference signal to achieve self-interference suppression and cancellation in the digital domain. 7. The bidirectional full-duplex air-water cross-medium non-relay communication method according to claim 1, characterized in that: The laser comprises a laser with a high divergence angle; The method for obtaining a laser beam carrying a downlink coded signal includes: The modulator is placed in the optical path outside the laser resonant cavity. When the laser beam emitted by the laser passes through the modulator, the modulator changes the amplitude, phase and frequency of the laser beam by modulating the voltage to obtain a laser beam carrying a downlink coded signal. The energy density of the laser beam carrying the downlink coded signal at the focusing point on the water surface is much greater than the dielectric breakdown threshold of water. 8. The bidirectional full-duplex air-water cross-medium non-relay communication method according to claim 7, characterized in that: The laser beam carrying the downlink coded signal generates plasma bubbles at the focal point on the water surface. After the plasma bubbles burst, they decay into downlink acoustic wave signals and are received by the receiving transducer.