CN113156426B

CN113156426B - Novel marine surface waveguide passive monitoring method based on AIS signal level

Info

Publication number: CN113156426B
Application number: CN202110454284.1A
Authority: CN
Inventors: 田斌; 唐文龙; 察豪
Original assignee: Naval University of Engineering PLA
Current assignee: Naval University of Engineering PLA
Priority date: 2021-04-26
Filing date: 2021-04-26
Publication date: 2023-07-21
Anticipated expiration: 2041-04-26
Also published as: CN113156426A

Abstract

The invention discloses a novel marine surface waveguide passive monitoring method based on AIS signal level, which comprises the following steps: s1, constructing an atmosphere basic environment; s2, constructing an AIS signal propagation environment database; s3, developing a matched monitoring device; s4, preprocessing actual measurement AIS signal propagation environment data; and S5, establishing a reasonable objective function and a quick search algorithm to obtain a relatively accurate inversion monitoring result. According to the invention, the characteristic quantity of the surface waveguide is inverted by utilizing the VHF signal sent by the AIS modulated by the surface waveguide, so that the problem that the traditional method for inverting the surface waveguide based on radar sea clutter and the like is easily influenced by evaporation and the surface waveguide is solved, and more pure surface waveguide data is obtained; meanwhile, due to the large AIS installation quantity and high signal space-time resolution, richer data sources can be provided for surface waveguide inversion monitoring, the requirement of passive monitoring of the surface waveguide is met, and the defect that electromagnetic waves are required to radiate outwards in the traditional method based on radar sea clutter inversion of the surface waveguide and the like is overcome.

Description

Novel marine surface waveguide passive monitoring method based on AIS signal level

Technical Field

The invention relates to the technical field of information and communication, in particular to a novel marine surface waveguide passive monitoring method based on AIS signal level.

Background

The atmospheric waveguide has important military and civil application values due to the characteristic of being capable of obviously influencing the use efficiency of the coverage range of a radio system and the like, and is always a hot spot problem of concern of military and national countries in the world. In military application, the offshore atmospheric waveguide environment is critical to offshore operations, can influence the efficiency of electronic equipment such as radars, communication and the like, further directly influence the capability of offshore beyond-line-of-sight striking, and is an offshore environment factor which must be considered and mastered by commanders to make operation plans; in civil application, the atmospheric waveguide can influence indexes such as transmission capacity, call quality and the like of a mobile communication system, and can also cause performance synergy or energy reduction phenomena of equipment such as a civil ship Automatic Identification System (AIS) and the like which are related to civil traffic safety.

The surface waveguide in the atmospheric waveguide is also a type of waveguide with high occurrence probability, the occurrence probability is about 14% worldwide, and the occurrence probability of the surface waveguide can be raised to about 58% in the fjord seas such as the bose bay. In addition to having significant "capture" capability for electromagnetic radiation sources such as radar, surface waveguides also have a strong effect on VHF (very high frequency) signals emitted by, for example, AIS systems, which are less affected by the evaporating waveguide.

Disclosure of Invention

The invention provides a novel marine surface waveguide passive monitoring method based on AIS signal level, which effectively solves the problem.

In order to achieve the above purpose, the invention adopts the following technical scheme:

an AIS signal level-based marine surface waveguide passive monitoring new method comprises the following steps:

s1, constructing an atmosphere basic environment, and generating an atmosphere correction refractive index three-dimensional profile data set meeting a certain spatial resolution index according to the accuracy requirement of electromagnetic wave propagation model calculation;

s2, constructing an AIS signal propagation environment database associated with the atmospheric correction refractive index three-dimensional profile data set, and generating the AIS signal propagation environment database by utilizing information such as an electromagnetic wave propagation model, the atmospheric correction refractive index three-dimensional profile data set, AIS signal radiation source parameters and the like which are matched with the VHF signal;

s3, developing a matched monitoring device, wherein the existing AIS equipment does not have the capability of analyzing AIS signal propagation environment data, so that the matched device meeting passive inversion monitoring needs to be developed;

s4, preprocessing actually measured AIS signal propagation environment data, wherein the AIS signal propagation environment data acquired by the matched monitoring device has huge data quantity, and the acquired AIS signal propagation environment data can be screened by considering the hardware condition of the matched monitoring device and the time requirement of monitoring output products, so that the timeliness of the invention is improved;

s5, a reasonable objective function and a quick search algorithm are established, a relatively accurate inversion monitoring result is obtained, the value of the objective function is a standard for measuring the matching degree between the actually observed AIS signal propagation environment data and the AIS signal propagation environment data obtained through modeling simulation, the quick search algorithm is responsible for optimizing the established objective function, data which enable the objective function to be minimum are found in an AIS signal propagation environment database in the shortest time, and waveguide parameters which are related to the data and comprise three-dimensional profile data of the atmospheric correction refractive index are used as final output results.

As a preferable mode of the above-mentioned scheme, in step S1, an atmospheric base environment is constructed by adopting a profile modeling method based on atmospheric data assimilation, specifically including:

s11, atmosphere data assimilation

Substituting the driving data into a mesoscale mode, judging whether shore-based and shipborne platform observation data exist in a time window, and assimilating the data through a data assimilation algorithm if the shore-based and shipborne platform observation data exist in the time window, so as to generate a final data assimilation product for profile modeling; if no observation data exists, taking the result of the mesoscale mode output as the input of profile modeling;

s12, modeling of profile

And encrypting the air pressure, the relative humidity, the air temperature and the air speed of the low-level atmosphere by using a similar theorem to obtain data of the air pressure, the relative humidity, the air temperature and the air speed of the low-level atmosphere with high vertical resolution, and fully fusing the meteorological data of the low-level atmosphere and the high-level atmosphere by using a fusion algorithm to further calculate a complete atmosphere correction refractive index profile.

As a preferable aspect of the above-described aspect, in step S2, AIS signal propagation environment data is calculated based on the surface waveguide propagation loss model, the expression of which is as follows:

L＝32.44+20lg(f)-Z _y +20lg(r)-L _d (1)

where L is propagation loss, r is propagation distance, Z _y Is a high gain function of the receiving antenna, L _d Is the antenna pattern loss term and f is the electromagnetic frequency.

As a preference to the above, for the receiving antenna height Z, the height gain Z _y Is a function of the wave frequency f and the surface waveguide height d, and since AIS device frequencies are 161.975MHz and 162.025MHz, the height gain function is expressed as:

as a preferable aspect of the above-described aspect, in step S3, the mating monitoring device includes: AIS receiver, ultrashort wave antenna and matched cable;

the AIS receiver comprises a limiter, a radio frequency and terminal module, wherein the limiter is used for completing amplitude suppression of space useless signals, the radio frequency and terminal module is used for completing filtering, frequency conversion and amplification of AIS signals and then sending the AIS signals to a baseband demodulation chip for demodulating AIS information, and a central processing unit processes the demodulated AIS information and forms AIS messages according to a protocol and reports the AIS messages to an upper computer through an RS422 serial port;

the ultra-short wave antenna is connected with the AIS receiver through a cable and is used for receiving space signals.

As a preferable mode of the above scheme, the radio frequency and terminal module includes a radio frequency unit and a terminal processing unit;

the radio frequency unit comprises a first amplifier and a power divider which are sequentially connected, wherein the power divider divides an AIS signal into two paths, and each path is sequentially connected with a narrow-band filter, a second amplifier, a mixer and a demodulation chip;

the terminal processing unit comprises a processor, a demodulation chip, a reset chip, an EEPROM, a temperature sensor, an isolation chip and an external interface chip which are respectively connected with the processor.

As an optimization of the scheme, the terminal processing unit comprises a data receiving and transmitting module, a data analyzing module, a protocol processing module and an encapsulation and packaging module;

the data receiving and transmitting module is used for receiving the demodulated data;

the data analysis module is used for analyzing the received data, converting the received data into an internally agreed data structure and transmitting the internally agreed data structure to the processing module;

the protocol processing module of the embedded software is used for processing the data analyzed by the analysis module, analyzing whether the data is required to be packaged, processing the command issued by the application program and outputting a corresponding response result;

the packaging and packaging module is used for packaging AIS local data meeting the requirements into a special self-defined format for output.

In step S4, preferably, in the screening process, the vessel data near the matched monitoring device is obtained less than the vessel data far from the matched monitoring device, and the demarcation point uses the line of sight calculated by using the height of the matched monitoring device as a reference.

As a preferable aspect of the above, in step S5, an objective function Φ based on the least square method is adopted:

φ(m)＝e ^T e (3)

wherein the method comprises the steps of

In the method, in the process of the invention,is the actual observed power value, P _c And (m) is the power value of the modeling simulation.

As an optimization of the above scheme, in step S5, the fast search algorithm selects the LFQPSO algorithm, and the main flow of the algorithm includes:

s51, initializing population size, initial position and initial speed of particles and maximum iteration times;

s52, calculating fitness values of all particles in the population;

s53, updating the individual optimal position and the global optimal position of each particle in the population;

s54, utilizeUpdating the position of each particle;

s55, throughUpdating the position of the particles;

s56, if the iteration termination condition is met, continuing to perform the next step, otherwise returning to S52;

s57, outputting an optimal solution.

The invention has the beneficial effects that:

according to the invention, the VHF signal emitted by the AIS system subjected to surface waveguide modulation is utilized to invert the surface waveguide characteristic quantity, so that the problem that the traditional method for inverting the surface waveguide based on radar sea clutter is easily affected by evaporation and surface two kinds of waveguide is solved, and more pure surface waveguide data is obtained; meanwhile, due to the fact that the automatic ship identification system (AIS) is large in installation quantity and high in signal space-time resolution, richer data sources can be provided for surface waveguide inversion monitoring, the requirement of passive surface waveguide monitoring can be met, and the defect that electromagnetic waves need to be radiated outwards in the traditional method of inverting surface waveguides based on radar sea clutter is overcome.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the description of the embodiments will be briefly described below.

FIG. 1 is a workflow diagram of the present invention;

FIG. 2 is a flow chart of the atmospheric data assimilation of the present invention;

FIG. 3 is a flow chart of the profile modeling of the present invention;

FIG. 4 is a block diagram of a matched monitoring device of the present invention;

FIG. 5 is a functional block diagram of a radio frequency and terminal module according to the present invention;

FIG. 6 is a functional block diagram of a radio frequency unit according to the present invention;

FIG. 7 is a functional block diagram of a terminal processing unit according to the present invention;

FIG. 8 is a flow chart illustrating the process of the data transceiver module of the present invention;

FIG. 9 is a software flow chart of the parsing module of the present invention;

FIG. 10 is a flow chart of a protocol processing module of the present invention;

FIG. 11 is a software flow diagram of the encapsulation and packaging module of the present invention.

Detailed Description

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

Referring to fig. 1 to 11, the present embodiment provides a new method for passive monitoring of a marine surface waveguide based on AIS signal level, which has the following overall concept:

The specific flow is as follows:

s1, constructing an atmosphere basic environment

In step S1, an atmospheric basic environment is constructed by adopting a profile modeling method based on atmospheric data assimilation, and the method specifically comprises the following two steps:

s11, assimilation of atmospheric data

As shown in fig. 2, the driving data is substituted into the mesoscale mode, and different steps are performed according to whether there is land-based or ship-borne platform observation data in the time window. If the observed data exist, assimilating the observed data through different data assimilation algorithms to generate a final data assimilation product for modeling the profile; if no data is observed, the result of the mesoscale mode output is used as input to the profile modeling.

S12, profile modeling method

As shown in fig. 3, the air pressure (P in the corresponding diagram), the relative humidity (H in the corresponding diagram), the air temperature (T in the corresponding diagram), and the wind speed (u, v in the corresponding diagram) of the lower atmosphere are encrypted by using the similarity theorem to obtain data of the air pressure, the relative humidity, the air temperature, and the wind speed of the lower atmosphere with high vertical resolution. And fully fusing the meteorological data of the low-level atmosphere and the high-level atmosphere through a fusion algorithm, and further calculating a complete atmosphere correction refractive index profile.

Wherein, the assimilation algorithm, the encryption algorithm and the fusion algorithm can all adopt the prior art.

S2, constructing AIS signal propagation environment database

In step S2, in the building process, the present embodiment uses a surface waveguide propagation loss model to calculate AIS signal propagation environment data, and the expression is as follows:

L＝32.44+20lg(f)-Z _y +20lg(r)-L _d (1)

For a receiving antenna height Z, a height gain Z _y Is a function of the wave frequency f and the surface waveguide height d, since AIS device frequencies are 161.975MHz and 162.025MHz, the height gain function can be expressed as:

s3, development of matched monitoring device

In step S3, in order to solve the problem of data acquisition of the actual AIS signal propagation environment, a matched monitoring device needs to be developed. The device comprises an AIS receiver, an ultrashort wave antenna and a matched cable, wherein the AIS receiver comprises an amplitude limiter, a radio frequency and a terminal module. In the AIS receiver, the amplitude limiter mainly completes the amplitude suppression of space useless signals, the radio frequency and terminal module completes the filtering and frequency conversion of AIS signals, the AIS signals are amplified and then sent to the baseband demodulation chip to demodulate AIS information, the central processing unit processes the AIS information after demodulation, AIS messages are formed according to a protocol, and the AIS messages are reported through an RS422 serial port. And the ultrashort wave antenna receives the space signal. A scheme block diagram of the matched monitoring device is shown in fig. 4.

A. Working principle and working flow of matched monitoring device

After the matched monitoring device is electrified, a central processing unit in the AIS receiver reports a self-checking working state, judges whether the working state is normal or not, and enters the normal working state after the self-checking is successful.

The VHF radio frequency signal is passed through an ultrashort wave antenna to an AIS receiver. The AIS receiver filters, amplifies, mixes and demodulates the signals, then sends the baseband signals to the baseband demodulation chip for demodulation, then carries out NRZI decoding, HDLC data unpacking and other processes, and the central processing unit sends AIS messages to the upper computer according to the protocol format.

B. Hardware design of matched monitoring device

The hardware design of the matched monitoring device is mainly the design of a radio frequency and terminal module.

The radio frequency and terminal module mainly realizes the receiving function of the AIS signals of two frequency points of 161.975MHz and 162.025 MHz. Mainly comprises a radio frequency unit and a terminal processing unit. The radio frequency unit comprises functions of demodulation and reception of AIS radio frequency signals and the like. The terminal processing unit comprises functions of AIS data analysis, serial port communication and the like. The functional block diagram is shown in fig. 5.

a) Radio frequency unit

The functional block diagram of the radio frequency unit is shown in fig. 6. As shown in the figure, AIS radio frequency signals of 161.975MHz and 162.025MHz of two detection frequency points enter a radio frequency unit through an antenna, and the signal amplitude is-110 dBm to-10 dBm. The first stage device of the radio frequency unit adopts a limiter to prevent the damage of external high-power interference signals to the subsequent stage circuit. The AIS signal passes through the limiter and then is amplified by the amplifier A1 in a low noise mode. The AIS signal is divided into two paths by the power divider, and then the two paths of signals of 161.975MHz and 162.025MHz are subjected to channel selection by the narrow-band filter, and interference signals are further filtered. The processing modes of the two AIS signals are the same, so only the working principle of the AIS-A signal of 161.975MHz is explained here.

The AIS-A path signal is amplified by the amplifier A2 after being filtered by the BPF2, and is used for compensating the loss brought by the path filter and the mixer. And then down-converted to a first intermediate frequency by entering a first stage mixer. And then the intermediate frequency AIS signal enters a demodulation chip N1 integrating the functions of mixing, limiting amplification and demodulation and then outputs an analog baseband demodulation signal to a terminal module.

b) Terminal processing unit

The schematic block diagram of the terminal processing unit is shown in fig. 7.

I, description of workflow and principle of terminal processing unit

The power chip converts externally input +7.5V direct current into +5V direct current, and converts the +5V direct current into +3.3V direct current through the power chip for use by the integrated circuit chip in the module; the isolation power supply isolates the input +5V into a single +5V for 422 and 485 interface chips, and the isolated power supply supplies power to the interface chips, so that devices in the protection board can be effectively protected from external voltage impact.

The processor is a core device in the module, and peripheral devices of the processor mainly comprise a clock, an EEPROM and a reset chip. The main control chip is connected with the demodulation chip and used for controlling the demodulation of GMSK baseband signals; and the serial communication is carried out with the outside through the serial port connected with the RS485 and RS422 interface chips.

The demodulation chip receives AIS baseband signals input from the radio frequency unit, sends the AIS baseband signals to the main control chip through the bus after demodulation, and outputs AIS messages from the serial port after protocol analysis is carried out in the main control chip.

Hardware design of terminal processing unit

(1) Power supply design

The external power supply provides +7.5V+ -0.2V voltage, and the terminal module mainly uses +5.0V and +3.3V voltage. The power supply chip is used to convert the +7.5v voltage to +5.0v voltage first. The output current is 800mA, the current used by the later stage load is about 300mA, the output current requirement is met, and a margin is left.

The +5V power supply is converted into +3.3V through the power supply chip and is used by the later-stage integrated circuit. The output current is 800mA, and the current used by the later stage load is about 300mA, so that the requirement is met.

The isolation power supply part converts +5V direct current into +5V isolation direct current by using a power supply chip, and the +5V isolation direct current is used for RS422 and RS485 interface chips. And 5V isolation voltage is output, and the isolation voltage is 1500VDC. The maximum output current is 150mA, and the current required by the subsequent load is about 20mA, so that the requirement is met.

(2) Main control chip

The maximum main frequency of the main control chip can reach 120MHz. The peripheral components include up to 512KB Flash memory, 96KB data memory, 4KB internal EEPROM, 5 UART, 3 SSP controllers, 3I 2C interfaces, 8 channel 12 bit ADC, 4 general purpose timers, 6-output general PWM and up to 70 general purpose I/O pins, etc., meeting terminal module performance and interface requirements. The processor has a low power consumption mode, and each interface functional module can be turned off, and the current in the mode is only 5mA. The chip can carry out on-line debugging and program downloading of the simulator through a JTAG interface, and can also carry out program downloading through a serial port through a reserved programming control interface.

(3) Modem chip

The modem chip has 2-way receiving demodulation and 1-way transmitting modulation, wherein the 2-way receiving demodulation can receive and demodulate the AIS baseband signal and the DSC baseband signal. And simultaneously can monitor the signals of the two transmitted channels. The demodulation chip has two working modes BURST and RAW. The BURST mode of operation may be in accordance with the format prescribed by the AIS Class B on-board transponder protocol for performing data stuffing, sequence code, NRZI, CRC check, etc. related processing on the received and transmitted data. The RAW working mode is relatively free and flexible, and the received and transmitted data is not processed and is directly converted. The CPU needs to handle the related tasks such as data stuffing, sequence codes, NRZI, CRC check, etc. This allows custom transport protocols to be implemented, but requires more CPU resources. In order to save CPU resources and realize a complete AIS Class B shipborne transponder communication protocol, a BURST working mode of a chip is adopted. The power supply of the demodulation chip can be controlled by the processor, and the power supply can be turned off in a low power consumption mode.

(4) EEPROM memory

And the externally reserved EEPROM is used for storing static parameters to be stored, and the storage capacity is 1KB.

(5) External interface chip

And the 2-path RS422 interface is used for receiving and transmitting signals from and through a serial port of the processor, converting the signals into isolated 5V signals through an isolated voltage conversion chip and converting the signals into differential signals of an RS422 bus through a MAX490 chip. The serial rate may be configurable by the processor.

(6) Temperature monitoring chip

The temperature monitoring of the radio frequency and terminal module is completed by a temperature sensor chip. The temperature sensor chip provides a monitoring temperature range of-55 ℃ to +150 ℃, the measured temperature is output through a voltage of +0.6V to +2.5V, the temperature is sampled through the AD sampler, and a temperature value is calculated.

C. Software design of matched monitoring device

The AIS receiver software operates in an ARM integrated circuit of the terminal unit, after receiving AIS data, the radio frequency unit converts the AIS data into GMSK baseband signals and transmits the GMSK baseband signals to the terminal unit, an AIS demodulation chip demodulates the AIS data, the demodulated data are delivered to embedded software for processing and packaging, and the packaged data are uploaded to upper application software. The embedded software is installed in the terminal unit of the AIS receiver, and the software level is general software.

From the aspect of modularization, the embedded software is decomposed into four functional modules, namely a data receiving and transmitting module, a data analyzing module, a protocol processing module and an encapsulation and packaging module. The design of each module will be described separately below.

a) Data transceiver module

The data transceiver module is a module for receiving the demodulated data and responsible for data transceiver work with an upper layer application. The module serves as an interface of embedded software and communicates with external hardware.

The data receiving and transmitting module mainly utilizes global buffering to receive data transmitted by the external hardware module, stores the data into local buffering and informs the analysis module to work. A software flow chart of the data transceiver module is shown in fig. 8.

b) Data analysis module

The data analysis module is mainly responsible for analyzing the received data, converting the received data into an internally agreed data structure, informing the protocol processing module through a corresponding interface, and completing protocol processing by the protocol processing module.

In the embedded software, a process flow diagram of the data parsing module is shown in fig. 9.

c) Protocol processing module

The protocol processing module of the embedded software mainly completes processing of the data analyzed by the analysis module, analyzes whether the data is required to be packaged, processes the command issued by the application program and outputs a corresponding response result.

A software flow diagram of the protocol processing module is shown in fig. 10.

d) Packaging module

The packaging and packaging module is responsible for packaging AIS local data meeting the requirements into a special self-defined format for output.

A software flow diagram of the encapsulation package module is shown in fig. 11.

Aiming at specific use requirements and task characteristics, AIS information sent out by packaging and packaging can be cut, namely dynamic messages of No. 1, no. 2, no. 3, no. 18 and No. 19 and static messages of No. 5, no. 24A and No. 24B, wherein the dynamic messages comprise information such as MMSI (globally unique user identification code) of a ship, speed, course, position and the like; the static information comprises information such as ship MMSI code, cargo type, draft, ship length and width, destination port and the like, other AIS information is shielded, the upper computer is not reported, and the workload of the rear-end processing equipment on data classification, filtering and the like is reduced.

S4, preprocessing actual measurement AIS signal propagation environment data

Because the AIS signal propagation environment data volume that utilizes supporting monitoring devices to gather is huge, consider supporting monitoring devices hardware condition and monitor output product time requirement, can screen the AIS signal propagation environment data that gathers. In the screening process, the ship data close to the matched monitoring device are less, the ship data far away from the matched monitoring device are more, and the demarcation point can take the vision distance calculated by taking the using height of the matched monitoring device as a reference.

And S5, establishing a reasonable objective function and a quick search algorithm to obtain a relatively accurate inversion monitoring result.

The objective function used by the traditional method based on the radar sea clutter inversion surface waveguide and the like only considers the single-frequency and single-power conditions, however, the AIS system has the double-frequency (161.975 MHz, 162.025 MHz) and double-power (12.5W, 2W) conditions, so that the construction of the objective function is more complex than the factors to be considered based on the radar sea clutter inversion surface waveguide, and the invention adopts the objective function phi based on the least square method:

φ(m)＝e ^T e (3)

wherein the method comprises the steps of

The calculated AIS signal power has the properties of double frequency, double power and the like, so that the objective function at the moment is converted into an objective function vector, namely, the objective function vector consists of a plurality of objective functions. Therefore, in the process of performing the inversion of the AIS information, it is necessary to compose an objective function composed of a plurality of objective sub-functions according to conditions such as frequency, power, and the like.

The invention uses the LFQPSO algorithm as a quick search algorithm, and the main flow of the algorithm is described as follows:

s52, calculating fitness values of all particles in the population;

s54, utilizeUpdating the position of each particle;

s55, throughUpdating the position of the particles;

s56, if the iteration termination condition is met, continuing to carry out the next step, otherwise, returning to the step B;

s57, outputting an optimal solution.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The novel method for passively monitoring the marine surface waveguide based on the AIS signal level is characterized by comprising the following steps of:

s2, constructing an AIS signal propagation environment database associated with the atmospheric correction refractive index three-dimensional profile data set, and generating the AIS signal propagation environment database by utilizing an electromagnetic wave propagation model matched with the VHF signal, the atmospheric correction refractive index three-dimensional profile data set and AIS signal radiation source parameter information;

s3, developing a matched monitoring device;

s4, preprocessing actually measured AIS signal propagation environment data, and screening the acquired AIS signal propagation environment data;

2. The new method for passive monitoring of marine surface waveguides based on AIS signal levels according to claim 1, characterized in that in step S1, a profile modeling method based on atmospheric data assimilation is used to construct an atmospheric base environment, comprising in particular:

s11, atmosphere data assimilation

s12, modeling of profile

3. The new method of passive monitoring of marine surface waveguides based on AIS signal levels according to claim 1, wherein in step S2 AIS signal propagation environment data is calculated based on a surface waveguide propagation loss model expressed as follows:

L＝32.44+20lg(f)-Z _y +20lg(r)-L _d (1)

4. The AIS-based system of claim 3Novel method for passive monitoring of signal level by marine surface waveguide, characterized in that for the receiving antenna height Z, the height gain Z _y Is a function of the wave frequency f and the surface waveguide height d, and since AIS device frequencies are 161.975MHz and 162.025MHz, the height gain function is expressed as:

5. the new method of passive monitoring of marine surface waveguides based on AIS signal levels according to claim 1, wherein in step S3, the mating monitoring means comprises: AIS receiver, ultrashort wave antenna and matched cable;

the AIS receiver comprises a limiter and a radio frequency and terminal module, wherein the limiter is used for completing amplitude suppression of space useless signals, the radio frequency and terminal module is used for completing filtering, frequency conversion and amplification of AIS signals, demodulating AIS information, forming AIS messages according to a protocol, and reporting the AIS messages to an upper computer through a serial port;

6. The new method for passive monitoring of marine surface waveguide based on AIS signal level according to claim 5, wherein said radio frequency and terminal module comprises a radio frequency unit and a terminal processing unit;

7. The novel marine surface waveguide passive monitoring method based on the AIS signal level, as set forth in claim 6, wherein the terminal processing unit comprises a data transceiver module, a data analysis module, a protocol processing module and a packaging and packaging module;

8. The new method for passive monitoring of marine surface waveguide based on AIS signal level according to claim 1, wherein in step S4, the vessel data acquired close to the matched monitoring device is less than the vessel data acquired far from the matched monitoring device, and the demarcation point is referenced to the viewing distance calculated by using the height of the matched monitoring device as reference.

9. The new method of passive monitoring of marine surface waveguides based on AIS signal levels according to claim 1, characterized in that in step S5, the objective function Φ based on least squares method is used:

φ(m)＝e ^T e (3)

wherein the method comprises the steps of

10. The new passive monitoring method of marine surface waveguide based on AIS signal level as set forth in claim 1, wherein in step S5, the fast search algorithm is lfqPSO algorithm, and the main flow of the algorithm comprises:

s52, calculating fitness values of all particles in the population;

s54, utilizeUpdating the position of each particle;

s55, throughUpdating the position of the particles;

s57, outputting an optimal solution.