An evaporation duct profile inversion method based on non-cooperative marine radar signals

Abstract

The present application relates to a kind of evaporation waveguide profile inversion methods based on non-cooperative marine radar signal, using the method of spatial diversity of monitoring point, in the key monitoring sea area is laid multiple sets of monitoring system and forms monitoring network, jointly using the method of amplitude direction finding, time delay lock, frequency division multiple access, detect and track the same marine radar target signal of monitoring, combine the signal intensity difference of monitoring point at different receiving height, the evaporation waveguide profile distribution in monitoring area is inverted;With the evaporation waveguide inversion result of short-range link as initial value, further combined with the monitoring result of different marine radar signal, link from near to far, using assimilation, interpolation algorithm, the evaporation waveguide distribution of large-scale sea area is inverted.The marine radar of monitoring area periphery ship is reasonably used, real-time passive reception signal is inverted, the evaporation waveguide profile in large-scale sea area is inverted, the environmental characteristics of electromagnetic wave propagation on sea is obtained, and the needs of over-the-horizon work of electromagnetic system on sea are ensured.

Description

Technical Field

[0001] This invention belongs to the technical fields of near-sea evaporating waveguides, marine atmosphere, and ocean physics. It relates to a method for inverting evaporating waveguide profiles based on non-cooperative marine radar signals. This method inverts evaporating waveguide profiles over a large sea area, obtains the environmental characteristics of marine electromagnetic wave propagation, and ensures the over-the-horizon operation requirements of marine electromagnetic systems. It can be used for evaporating waveguide model calibration, data comparison, inversion optimization, and scientific research. Background Technology

[0002] Evaporation waveguides are a common atmospheric waveguide phenomenon at sea, frequently occurring within the troposphere. This phenomenon arises from the interaction between meteorological factors such as temperature, humidity, and pressure in the atmosphere. Due to seawater evaporation, sea-vapor interaction occurs at the sea surface. The vapor continuously diffuses, and as the diffusion altitude increases, the atmospheric refractive index decreases. At a certain altitude, the refractive index becomes less than the curvature of the Earth's sea surface, trapping electromagnetic waves within this layer and enabling beyond-line-of-sight propagation.

[0003] Currently, active inversion methods for evaporating waveguides require the transmitter to emit electromagnetic signals, and calculations are performed using received path loss data, increasing the complexity and difficulty of monitoring. Marine radar is a commonly used detection device on naval vessels, possessing high signal strength, and the radio frequency of X-band marine radar falls within the optimal frequency band for evaporating waveguides. While passive inversion methods using marine radar to retrieve evaporating waveguide profiles have inherent technical advantages, the sheer number of naval vessels often makes it impossible to obtain prior information from the transmitter. Therefore, there is an urgent need for an evaporating waveguide profile inversion method based on non-cooperative marine radar signals.

[0004] Current methods for obtaining evaporating waveguide profiles have limitations, failing to provide long-term, real-time, covert, efficient, and wide-range high-precision real-world evaporating waveguide profiles at sea. Furthermore, the sheer number of ships at sea makes it impossible to acquire prior information from all maritime radar transmitters. This invention proposes an evaporating waveguide profile inversion method based on maritime radar signals, filling the gap in passive evaporating waveguide inversion methods and providing auxiliary decision-making support for maritime electromagnetic systems. It is applicable to evaporating waveguide profile inversion, comparative testing of evaporating waveguide monitoring experimental data, and feasibility prediction of evaporating waveguide communication, offering advantages such as long-term real-time capability, covert efficiency, and wide coverage. Summary of the Invention

[0005] Technical problems to be solved

[0006] To overcome the shortcomings of existing technologies, this invention proposes an evaporation waveguide profile inversion method based on non-cooperative marine radar signals.

[0007] Technical solution

[0008] A method for inverting evaporating waveguide profiles based on non-cooperative marine radar signals, characterized by the following steps:

[0009] Step 1: Extraction and classification of marine radar signals:

[0010] From A1 to A n The evaporation waveguide observation network receives signals from marine navigation radar. The omnidirectional antennas at each monitoring point determine the pulse signals SD1 to SD2 from different directions using amplitude comparison direction finding. m ;

[0011] According to the rotation principle of marine radar, the time delay difference between different monitoring points in two adjacent radar cycles is the same, that is: τ a (T1)=τ a (T2)=t A -t B T1 and T2 represent the rotation period of the marine radar, t A and t B This indicates the arrival time of the signal determined by the maximum beam, and the received marine radar signals are classified according to the type of monitoring point within the evaporating waveguide observation network;

[0012] Step 2: Calculate the measured path loss difference corresponding to the different receiving antenna height differences Δh at time t. That is, the difference between the signal received at different antenna heights and the reference signal:

[0013]

[0014] in, For height h q The signal level received by the antenna at that location. The signal level received by the antenna at height h3; This represents the measured path loss.

[0015] Step 3: Evaporated waveguide inversion of single-ship target signal:

[0016] Since the transmission parameters of the non-cooperative marine radar are unknown, the signal strength received at an antenna height of 3m is used as a benchmark. The difference between the signals received at different antenna heights and the benchmark signal is used to invert the evaporation waveguide distribution.

[0017] The objective function for the inversion is:

[0018]

[0019] in: N is a performance metric for optimization algorithms, used to represent the degree of optimization of the objective during the inversion process; ΔhN represents the number of searches for different receiving antenna height differences Δh, and its size is the same as the data size of the copy field database; t The number of searches at time t is the product of the monitoring duration in step 2 and the sampling rate of the device.

[0020] This represents the simulated path loss difference corresponding to different antenna height differences Δh in the copy field database;

[0021] Step 4: Unidirectional evaporation waveguide profile inversion:

[0022] Let [S1, S2...Sn] represent signals of different intensities from the navigation radars of different ships in the same direction. The signal strength from the nearest to the monitoring point to the farthest point is S1>S2...>Sn;

[0023] The non-uniform evaporation waveguide distribution inverted from signal S1 is used as the initial value M for the inversion of signal S2, and so on, to obtain the evaporation waveguide distribution in long-distance, non-uniform environments;

[0024] The distribution of evaporation waveguides over a large area of ​​sea was obtained by using assimilation and difference algorithms.

[0025] The types of monitoring points within the evaporation waveguide observation network include shore-based, island / reef, and mobile observation points.

[0026] The establishment of the copy field database involves calculating the atmospheric corrected refractive index distribution at 0.1-meter intervals from 0 to 50 m in height of the evaporation waveguide. Where: M0 and M(z) are the atmospheric corrected refractive indices at the sea surface and altitude z, respectively, with M0 taking a value of 330; h t =z EDH Where is the height of the evaporation waveguide, and the roughness length z0 = 1.5 × 10⁻⁶. -4 ΔM=M(h1)-M0 is the intensity of the evaporation waveguide, and M(h1) is the corrected refractive index at the height of the evaporation waveguide.

[0027] The simulation path loss difference Calculation: By inputting the transmitter antenna height and resolution, distance and resolution into the high-level propagation model, the path loss of the corresponding evaporating waveguide profile is calculated; the simulated path loss difference corresponding to different antenna height differences Δh is calculated. Where, Δh=h q -h3,h q The height is represented by q, where q ranges from 3 to 30m. This represents the difference between the signal received at different antenna heights and the reference signal.

[0028] The height of the transmitting antenna is 3 to 25 meters, and the resolution is 1 meter.

[0029] The distance is less than or equal to 300km, and the resolution is 0.5km.

[0030] The measured path loss For, the unit is dB; PL fs is the free space loss, measured in dB, and is an intermediate value used to calculate path loss; h is the antenna height; F is the propagation factor, obtained through an advanced propagation model.

[0031] The advanced propagation model has the following forms of expression:

[0032] In the space of parabolic equations calculate;

[0033] Ray space calculation is as follows:

[0034]

[0035] The flat Earth space is calculated as follows:

[0036]

[0037] The super-optical space extends far beyond the evaporated waveguide layer and is calculated approximately using ray space.

[0038] Where: |u(x,z)| represents the electromagnetic field strength distribution in the evaporating waveguide environment calculated using the parabolic equation model; x represents the propagation distance in meters; F d and F r Let Ω and β represent the antenna direction factors for the direct and refracted rays, respectively, and let Ω represent the total phase angle of the direct and refracted rays. d and β r R and R represent the propagation angles of the direct and refracted rays, respectively. These represent the Fresnel reflection coefficient level and lag phase, respectively; α is the receiving elevation angle; α1 and α0 represent the angles at the beginning and end of each ray tracing step, respectively; X represents the calculation distance; S represents the spherical propagation factor; D represents the optical path length difference; r1 and r2 are the path lengths of the direct and refracted rays, respectively; a represents the average radius of the Earth; and k... e This represents the effective sphere radius coefficient.

[0039] When calculating the advanced propagation model, the flat Earth space is used when the antenna elevation angle is greater than 5° or the distance is less than 2.5km, the ray space is used when the antenna elevation angle is less than 5° but greater than 2° and the distance is greater than 2.5km, the low-altitude region outside the ray space is the parabolic equation space, and the high-altitude region is the super-optical space.

[0040] The amplitude comparison direction finding method in step 1 uses adjacent beams of the antenna to receive the same marine radar signal. By comparing the amplitude of the received signal, the direction is determined by a function of direction finding. The point where the directions determined by two receivers in different azimuths intersect in space is the specific location of the radar signal radiation source.

[0041] Beneficial effects

[0042] This invention proposes an evaporating waveguide profile inversion method based on non-cooperative marine radar signals. It employs a spatial diversity approach, deploying multiple monitoring systems in key monitoring areas to form a monitoring network. These systems utilize amplitude comparison direction finding, time delay locking, and frequency division multiple access (FDMA) to detect and track the same marine radar target signal. By combining the signal strength differences at different receiving altitudes, the evaporating waveguide profile distribution within the monitoring area is inverted. Using the evaporating waveguide inversion results from near-range links as initial values, and further combining monitoring results from different marine radar signals (links from near to far), assimilation and interpolation algorithms are used to invert the evaporating waveguide distribution over a large area of ​​sea. By rationally utilizing the marine radars of ships surrounding the monitoring area to passively receive signals in real time, the evaporating waveguide profile over a large area of ​​sea can be inverted, obtaining the environmental characteristics of marine electromagnetic wave propagation and ensuring the over-the-horizon operation requirements of marine electromagnetic systems.

[0043] This invention proposes an evaporating waveguide profile inversion method based on non-cooperative marine radar signals. By monitoring the marine radar signals of ships at sea, the evaporating waveguide distribution is obtained by utilizing the signal level difference. This method directly utilizes the signals from ships at sea without actively transmitting signals, thus avoiding frequency interference between devices. Furthermore, the passive reception method has inherent stealth, solving the problem that existing evaporating waveguide channel monitoring methods are difficult to apply in a long-term, real-time, covert, efficient, and large-scale manner. It can serve as an auxiliary decision-making tool for marine electromagnetic systems. Attached Figure Description

[0044] Figure 1 This is a flowchart of the method of the present invention. Figure 2 This is a schematic diagram of path loss when the evaporation waveguide has a non-uniform distribution. Figure 3 This is a schematic diagram showing the difference in path loss at different antenna heights. Figure 4 This is a conceptual diagram of marine radar signal reception, extraction, and classification. Figure 5 This is a schematic diagram of a non-uniform evaporation waveguide distribution on a single link. Detailed Implementation The present invention will now be further described in conjunction with the embodiments and accompanying drawings: A method for inverting evaporative waveguide profiles based on non-cooperative marine radar signals is characterized by using a spatial diversity method of shore-based monitoring points, utilizing the time delay of signals from horizontal monitoring points, and combining amplitude comparison direction finding to determine the target signal to be inverted; utilizing the signal strength difference of vertical monitoring points to invert the evaporative waveguide distribution of a single target monitoring area; and utilizing the time-division and frequency-division characteristics of different marine radars, combined with data assimilation and interpolation methods, to invert the evaporative waveguide distribution over a large sea area. The steps are as follows: Step 1: Establish a copy field database. Use Equation (1) to calculate the atmospheric corrected refractive index distribution from 0 to 50 m in height of the evaporation waveguide with an interval of 0.1 m, and establish a horizontally uniform evaporation waveguide environment.

[0045]

[0046] In equation (1), M0 and M(z) are the atmospheric corrected refractive indices at the sea surface and height z, respectively, with M0 taking a value of 330; h t =z EDH Where is the height of the evaporation waveguide, and the roughness length z0 = 1.5 × 10⁻⁶. -4 ΔM=M(h1)-M0 is the intensity of the evaporation waveguide, and M(h1) is the corrected refractive index at the height of the evaporation waveguide.

[0047] Step 2: Path loss simulation. The transmitter antenna height is set to 15–25 m with a resolution of 1 m, and the calculation distance is set to 0–300 km with a resolution of 0.5 km. These values ​​are then substituted into the high-level propagation model to calculate the path loss for the corresponding evaporation waveguide profile.

[0048] Step 3: Calculate the simulated path loss difference. Use equation (2) to calculate the simulated path loss difference corresponding to different antenna height differences Δh.

[0049]

[0050] Where, Δh=h q -h3,h q The height is represented by q, where q ranges from 3 to 30m. This represents the difference between the signal received at different antenna heights and the reference signal.

[0051] Step 4: Extraction and classification of marine radar signals. This includes signals from shore-based, island / reef, and moving observation points A1 to A2. n The evaporation waveguide observation network receives signals from marine navigation radar. The omnidirectional antennas at each monitoring point determine the pulse signals SD1 to SD2 from different directions using amplitude comparison direction finding. m According to the rotation principle of marine radar, the time delay difference between different monitoring points in two adjacent radar cycles is the same, that is: τ a (T1)=τa (T2)=t A -t B T1 and T2 represent the rotation period of the marine radar, t A and t B This indicates the arrival time of the signal determined by the maximum beam, and it is used to classify a large number of received marine radar signals.

[0052] Step 5: Calculate the measured path loss difference corresponding to the different receiving antenna height differences Δh at time t using equation (3).

[0053]

[0054] in, For height h q The signal level received by the antenna at that location. The signal level received by the antenna at height h3.

[0055] Step 6: Evaporated waveguide inversion of single-ship target signal. Since the transmission parameters of the non-cooperative marine radar are unknown, the evaporated waveguide distribution is inverted by using the signal strength received at an antenna height of 3m as a reference and the difference between the signals received at different antenna heights and the reference signal. The target function for inversion is determined by equation (4).

[0056]

[0057] Where, N Δh N represents the number of height difference searches, and its size is related to the copy field database established in step 1. t This indicates the number of time searches, and its size is related to the monitoring duration in step 4.

[0058] Step 7: Unidirectional Evaporated Waveguide Profile Inversion. Signals of different intensities in the same direction come from the navigation radars of different ships. The signal intensities from near to far from the monitoring point are represented as [S1, S2...Sn], then S1>S2...>Sn. The non-uniform evaporated waveguide distribution inverted from signal S1 is used as the initial value M for the inversion of signal S2, and so on, to obtain the evaporated waveguide distribution in a long-distance, non-uniform environment. Combined with assimilation and difference algorithms, the evaporated waveguide distribution over a large area of ​​the sea is obtained.

[0059] The aforementioned marine radar includes two types: X-band and C-band. X-band radar is more suitable for inversion of evaporation waveguide profiles because its radio frequency signal is in the optimal frequency band of the evaporation waveguide. Therefore, X-band navigation radar signal is selected as the inversion target.

[0060] The amplitude comparison direction finding method described above uses adjacent beams of the antenna to receive the same marine radar signal. By comparing the amplitude of the received signal, the direction is determined by a function of direction finding. The point where the directions determined by two receivers in different azimuths intersect in space is the specific location of the radar signal radiation source. Specific implementation examples:

[0062] By employing a spatial diversity method based on shore-based monitoring points, utilizing the time delay of signals from horizontal monitoring points, and combining this with amplitude comparison direction finding, the target signal to be inverted is determined. The evaporation waveguide distribution of a single target monitoring area is inverted using the signal strength difference between vertical monitoring points. Finally, by utilizing the time-division and frequency-division characteristics of different marine radars, combined with data assimilation and interpolation methods, the evaporation waveguide distribution over a large sea area is inverted. Figure 1 This is a flowchart of the method of the present invention.

[0063] The steps of this method embodiment are as follows:

[0064] Step 1: Establish a copy field database. Use Equation (1) to calculate the atmospheric corrected refractive index distribution from 0 to 50 m in height of the evaporation waveguide with an interval of 0.1 m, and establish a horizontally uniform evaporation waveguide environment.

[0065] Step 2: Calculate the path loss of the corresponding evaporation waveguide profile using formulas (5) to (10). In this embodiment, it is assumed that the height of the receiving antenna is 3m and 15m respectively. Figure 2 This is a schematic diagram of path loss when the transmitting antenna is 20 meters high and the evaporation waveguide is 15 meters and 20 meters high, respectively, with uneven distribution.

[0066] PL fs =32.45+20logf+20logr (5)

[0067]

[0068] In equations (5) to (6), f is the frequency in MHz, r is the distance between the transmitting and receiving antennas in km, and PL fs This is free space loss, measured in dB. The path loss is calculated in dB, and F is the propagation factor. In the advanced propagation model, F has two forms: in parabolic space, it is calculated by equation (7); in ray space, it is calculated by equations (8) and (9); in flat Earth space, it is calculated by equations (8) and (10); and in super-optical space, which extends far beyond the evaporating waveguide layer, it is approximated by ray space. Among these, flat Earth space is used when the antenna elevation angle is greater than 5° or the distance is less than 2.5km; ray space is used when the antenna elevation angle is less than 5° but greater than 2° and the distance is greater than 2.5km; the low-altitude region outside the ray space is parabolic space, and the high-altitude region is super-optical space.

[0069]

[0070]

[0071]

[0072]

[0073] In formulas (7) to (10), |u(x,z)| represents the electromagnetic field strength distribution in the evaporation waveguide environment calculated using the parabolic equation model; x represents the propagation distance in meters; F d and F r Let Ω and β represent the antenna direction factors for the direct and refracted rays, respectively, and let Ω represent the total phase angle of the direct and refracted rays. d and β r R and R represent the propagation angles of the direct and refracted rays, respectively. These represent the Fresnel reflection coefficient level and lag phase, respectively; α is the receiving elevation angle; α1 and α0 represent the angles at the beginning and end of each ray tracing step, respectively; X represents the calculation distance; S represents the spherical propagation factor; D represents the optical path length difference; r1 and r2 are the path lengths of the direct and refracted rays, respectively; a represents the average radius of the Earth; and k... e This represents the effective sphere radius coefficient.

[0074] Step 3: Calculate the path loss difference in the simulation using equation (11). Figure 3 This is a schematic diagram showing the difference in path loss at different antenna heights when the receiving point is 50km away.

[0075]

[0076] Where, Δh=h 15 -h3,h 15 This indicates a height of 15m. This represents the difference between the signal received at different antenna heights and the reference signal.

[0077] Step 4: Extraction and Classification of Marine Radar Signals. An evaporative waveguide observation network consisting of shore-based, island / reef, and mobile observation points A1 and A2 receives marine radar signals. The omnidirectional antennas at each monitoring point use amplitude comparison direction finding to determine the pulse signals SD1 to SD5 from different directions. Based on the rotation principle of marine radar, the large number of received marine radar signals are classified. Figure 4 This is a conceptual diagram of marine radar signal reception, extraction, and classification.

[0078] Step 5: Calculate the measured path loss difference corresponding to the different receiving antenna height differences Δh at time t using equation (9). In this embodiment, it is assumed that the receiving antenna height is 15m.

[0079] Step 6: Evaporated waveguide inversion of single-ship target signal. Combining the results of Steps 4 and 5, the non-uniform evaporated waveguide profile is obtained through inversion, as shown in the figure. Figure 5 As shown.

[0080] Step 7: Unidirectional evaporation waveguide profile inversion. Using multiple ship targets in the same direction, the unidirectional non-uniform evaporation waveguide distribution is obtained through inversion. Combined with assimilation and difference algorithms, the evaporation waveguide distribution over a large area of ​​the sea is obtained.

[0081] This invention fills a gap in passive inversion methods for evaporating waveguides and can provide auxiliary decision-making for marine electromagnetic systems. It is applicable to evaporating waveguide profile inversion, comparative testing of evaporating waveguide monitoring experimental data, and prediction of evaporating waveguide communication feasibility, and has advantages such as long-term real-time operation, covert efficiency, and wide range.

Claims

1. A method for inverting evaporating waveguide profiles based on non-cooperative marine radar signals, characterized in that... The steps are as follows: Step 1: Extraction and classification of marine radar signals: From A1 to A n The evaporation waveguide observation network receives signals from marine navigation radar. The omnidirectional antennas at each monitoring point determine the pulse signals SD1 to SD2 from different directions using amplitude comparison direction finding. m ; According to the rotation principle of marine radar, the time delay difference between different monitoring points in two adjacent radar cycles is the same, that is: τ a (T1)=τ a (T2)=t A -t B T1 and T2 represent the rotation period of the marine radar, t A and t B This indicates the arrival time of the signal determined by the maximum beam, and the received marine radar signals are classified according to the type of monitoring point within the evaporating waveguide observation network; Step 2: Calculate the measured path loss difference corresponding to the different receiving antenna height differences Δh at time t. That is, the difference between the signal received at different antenna heights and the reference signal: in, For height h q The signal level received by the antenna at that location. The signal level received by the antenna at height h3; This represents the measured path loss. Step 3: Evaporated waveguide inversion of single-ship target signal: Since the transmission parameters of the non-cooperative marine radar are unknown, the signal strength received at an antenna height of 3m is used as a benchmark. The difference between the signals received at different antenna heights and the benchmark signal is used to invert the evaporation waveguide distribution. The objective function for the inversion is: in: N is a performance metric for optimization algorithms, used to represent the degree of optimization of the objective during the inversion process; Δh N represents the number of searches for different receiving antenna height differences Δh, and its size is the same as the data size of the copy field database; t The number of searches at time t is the product of the monitoring duration in step 2 and the sampling rate of the device. This represents the simulated path loss difference corresponding to different antenna height differences Δh in the copy field database; Step 4: Unidirectional evaporation waveguide profile inversion: Let [S1, S2...Sn] represent signals of different intensities from the navigation radars of different ships in the same direction. The signal strength from the nearest to the monitoring point to the farthest point is S1>S2...>Sn; The non-uniform evaporation waveguide distribution inverted from signal S1 is used as the initial value M for the inversion of signal S2, and so on, to obtain the evaporation waveguide distribution in long-distance, non-uniform environments; The distribution of evaporation waveguides over a large area of ​​sea was obtained by using assimilation and difference algorithms.

2. The method for inverting evaporating waveguide profiles based on non-cooperative marine radar signals according to claim 1, characterized in that: The types of monitoring points within the evaporation waveguide observation network include shore-based, island / reef, and mobile observation points.

3. The method for inverting evaporating waveguide profiles based on non-cooperative marine radar signals according to claim 1, characterized in that: The establishment of the copy field database involves calculating the atmospheric corrected refractive index distribution at 0.1-meter intervals from 0 to 50 m in height of the evaporation waveguide. Where: M0 and M(z) are the atmospheric corrected refractive indices at the sea surface and altitude z, respectively, with M0 taking a value of 330; h t =z EDH Where is the height of the evaporation waveguide, and the roughness length z0 = 1.5 × 10⁻⁶. -4 ΔM=M(h1)-M0 is the intensity of the evaporation waveguide, and M(h1) is the corrected refractive index at the height of the evaporation waveguide.

4. The method for inverting evaporating waveguide profiles based on non-cooperative marine radar signals according to claim 1, characterized in that: The simulation path loss difference The calculation involves inputting the transmitter antenna height and resolution, distance and resolution into the advanced propagation model to calculate the path loss of the corresponding evaporating waveguide profile. Calculate the simulated path loss difference corresponding to different antenna height differences Δh. Where, Δh=h q -h3,h q The height is represented by q, where q ranges from 3 to 30m. This represents the difference between the signal received at different antenna heights and the reference signal.

5. The method for inverting evaporating waveguide profiles based on non-cooperative marine radar signals according to claim 4, characterized in that: The height of the transmitting antenna is 3 to 25 meters, and the resolution is 1 meter.

6. The method for inverting evaporating waveguide profiles based on non-cooperative marine radar signals according to claim 4, characterized in that: The distance is less than or equal to 300km, and the resolution is 0.5km.

7. The method for inverting evaporating waveguide profiles based on non-cooperative marine radar signals according to claim 1, characterized in that: The measured path loss The unit is dB; PL fs is the free space loss, measured in dB, and is an intermediate value used to calculate path loss; h is the antenna height; F is the propagation factor, obtained through an advanced propagation model.

8. The method for inverting evaporating waveguide profiles based on non-cooperative marine radar signals according to claim 1 or 4, characterized in that: The advanced propagation model has the following forms of expression: In the space of parabolic equations calculate; Ray space calculation is as follows: The flat Earth space is calculated as follows: The super-optical space extends far beyond the evaporated waveguide layer and is calculated approximately using ray space. Where: |u(x,z)| represents the electromagnetic field strength distribution in the evaporating waveguide environment calculated using the parabolic equation model; x represents the propagation distance in meters; F d and F r Let Ω and β represent the antenna direction factors for the direct and refracted rays, respectively, and let Ω represent the total phase angle of the direct and refracted rays. d and β r R and R represent the propagation angles of the direct and refracted rays, respectively. These represent the Fresnel reflection coefficient level and lag phase, respectively; α is the receiving elevation angle; α1 and α0 represent the angles at the beginning and end of each ray tracing step, respectively; X represents the calculation distance; S represents the spherical propagation factor; D represents the optical path length difference; r1 and r2 are the path lengths of the direct and refracted rays, respectively; a represents the average radius of the Earth; and k... e This represents the effective sphere radius coefficient.

9. The method for inverting evaporating waveguide profiles based on non-cooperative marine radar signals according to claim 8, characterized in that: When calculating the advanced propagation model, the flat Earth space is used when the antenna elevation angle is greater than 5° or the distance is less than 2.5km, the ray space is used when the antenna elevation angle is less than 5° but greater than 2° and the distance is greater than 2.5km, the low-altitude region outside the ray space is the parabolic equation space, and the high-altitude region is the super-optical space.

10. The method for inverting evaporating waveguide profiles based on non-cooperative marine radar signals according to claim 1, characterized in that: The amplitude comparison direction finding method in step 1 uses adjacent beams of the antenna to receive the same marine radar signal. By comparing the amplitude of the received signal, the direction is determined by a function of direction finding. The point where the directions determined by two receivers in different azimuths intersect in space is the specific location of the radar signal radiation source.

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