An atmospheric waveguide inversion method based on sea surface clutter signal monitoring data

Abstract

An embodiment of the present invention relates to an atmospheric waveguide inversion method based on sea surface clutter point signal monitoring data, comprising: setting and determining that a signal transmitting and receiving device is located in a waveguide environment; adjusting a signal transmitting elevation angle, and obtaining sea surface clutter reflection signal monitoring data through signal transmission and reception; analyzing a radio wave propagation trajectory in the atmospheric waveguide based on the sea surface clutter signal monitoring data, determining reflection point distribution data of a beam, and compiling and processing the reflection point distribution data to obtain clutter reflection characteristic points; calculating atmospheric refractive index data of the clutter reflection characteristic points at the sea surface; calculating atmospheric refractive index distribution data of the clutter reflection characteristic points in a vertical direction; and interpolating atmospheric refractive index distribution data in a horizontal space based on the atmospheric refractive index distribution data of the clutter reflection characteristic points and horizontal position data of the clutter reflection characteristic points to obtain distribution result data of the atmospheric refractive index in a spatial cross-section.

Description

Technical Field

[0001] The present invention relates to the field of radio wave propagation technology, and in particular to an atmospheric waveguide inversion method based on sea surface clutter signal monitoring data. Background Art

[0002] An atmospheric duct is a "special" atmospheric layered structure formed under specific meteorological conditions, where the atmospheric refractive index decreases rapidly with altitude within a certain altitude range. Because this internal atmospheric structure can refract radio waves, trapping them within the duct layer and allowing them to propagate beyond the horizon, the atmospheric duct environment often has a significant impact on the performance of electronic equipment.

[0003] Currently, the most accurate diagnostic method for atmospheric ducts is to make judgments based on the spatial distribution of the atmospheric refractive index combined with the atmospheric refractive index gradient characteristics within the atmospheric duct environment. However, in a real-time combat environment, the atmospheric environment in the enemy area is often impossible to directly measure, which seriously limits the diagnosis of atmospheric duct distribution. Therefore, a technical means that can conveniently perform atmospheric waveduct inversion analysis can often help expand the regional scope of atmospheric waveduct real-time analysis and seize the initiative on the battlefield.

[0004] Existing methods for inferring atmospheric ducts fall into two main categories: contact detection and remote sensing. Contact detection can be further divided into direct and indirect methods. Direct methods utilize high-precision meteorological sensors to directly measure atmospheric profiles of parameters such as temperature, humidity, pressure, and refractive index to determine whether an atmospheric duct exists. Indirect methods employ high-precision meteorological and hydrological instruments to measure atmospheric temperature, humidity, pressure, wind speed and direction, and sea temperature at a specific altitude. These parameters are then incorporated into a specific model to determine the presence of an atmospheric duct. Remote sensing methods utilize equipment and technologies such as meteorological satellites, radar, GPS, microwave radiometers, and lidar to infer atmospheric ducts.

[0005] Although the above-mentioned atmospheric waveguide inversion method has entered the application level, many problems still exist. For example, it requires a lot of manpower, material resources and high-precision instruments, and has certain financial requirements; the inversion method has poor adaptability to the environment, and the accuracy fluctuates more violently in extreme environments; the prediction speed and accuracy are closely related to the selected prediction model. Therefore, the waveguide parameters inverted based on different prediction models have large errors, and it is also impossible to predict the waveguide environment outside the detection range of the precision radar. Summary of the Invention

[0006] The purpose of the present invention is to provide an atmospheric waveguide inversion method based on sea surface clutter signal monitoring data to solve the problems of low computational efficiency, poor inversion accuracy, and limited scope of application of existing inversion methods.

[0007] To this end, an embodiment of the present invention provides an atmospheric duct inversion method based on sea surface clutter signal monitoring data, comprising:

[0008] Set up and ensure that the signal transmitting and receiving devices are within the waveguide environment;

[0009] Adjust the signal transmission elevation angle and obtain sea surface clutter reflection signal monitoring data through signal transmission and reception;

[0010] Analyze the propagation trajectory of radio waves in the atmospheric waveguide based on the sea surface clutter signal monitoring data, determine the reflection point distribution data of the beam, and compile and process the reflection point distribution data to obtain clutter reflection feature points;

[0011] Calculating atmospheric refractive index data of the clutter reflection feature point at the sea surface;

[0012] Calculating atmospheric refractive index distribution data of the clutter reflection feature point in the vertical direction;

[0013] The atmospheric refractive index distribution data in the horizontal space is interpolated according to the atmospheric refractive index distribution data of the clutter reflection feature point and the horizontal position data of the clutter reflection feature point to obtain distribution result data of the atmospheric refractive index in the spatial section.

[0014] Preferably, the method further comprises:

[0015] Performing atmospheric duct distribution diagnosis point by point based on the atmospheric refractive index distribution result data to determine whether an atmospheric duct exists;

[0016] In the presence of atmospheric ducting, determine the duct thickness, duct height, and duct strength.

[0017] Preferably, the setting and determining that the signal transmitting and receiving device is in a waveguide environment specifically includes:

[0018] The signal transmitting and receiving device is installed on a movable platform on the sea surface;

[0019] Measuring the temperature, humidity, and atmospheric pressure at different heights where the signal transmitting and receiving devices are located, and calculating the vertical distribution of the atmospheric refractive index based on the measurement results to obtain a calculation result M; wherein the calculation result M includes the atmospheric refractive index N at different heights; t is temperature, P is atmospheric pressure, and e is water vapor pressure determined by humidity;

[0020] Calculate the atmospheric refractive index gradient according to the calculation result M. When it satisfies When N nThe height of the point is compared with the height of the signal transmitting and receiving device. If the height is greater than the height of the transmitting equipment, it is determined that the signal transmitting and receiving device is in the waveguide environment, otherwise it is not in the waveguide environment; N n and N n-1 are the two atmospheric refractive indices at adjacent heights in the calculation results of the vertical distribution of atmospheric refractive index, where N n is the atmospheric refractive index at a higher altitude, N n-1 is the atmospheric refractive index at a lower altitude point, and ΔH is the height difference between the above adjacent altitudes.

[0021] Further preferably, when the signal transmitting and receiving device is not in the waveguide environment, the movable platform is moved to reset and re-determine that the signal transmitting and receiving device is in the waveguide environment.

[0022] Preferably, the adjusting the signal transmission elevation angle and obtaining sea surface clutter reflection signal monitoring data by signal transmission and reception specifically includes:

[0023] According to the half-power beam angle θ and the critical refraction angle θ0 of the transmitting antenna in the signal transmitting and receiving device, the transmitting elevation angle is set to θ / 2+θ0, and then the transmitting elevation angle is reduced by a minimum change unit allowed by the adjustment accuracy, an electromagnetic wave signal is transmitted through the signal transmitting and receiving device, and first sea surface clutter reflection signal monitoring data is collected;

[0024] Then, the transmitting elevation angle is set to -θ / 2-θ0, and then the transmitting elevation angle is increased by a minimum change unit allowed by the adjustment accuracy, an electromagnetic wave signal is transmitted through the signal transmitting and receiving device, and the second sea surface clutter reflection signal monitoring data is collected;

[0025] The sea surface clutter reflection signal monitoring data includes: azimuth, signal strength and the distance between the reflection point and the emission point.

[0026] Further preferably, the analyzing the radio wave propagation trajectory in the atmospheric waveguide according to the sea surface clutter signal monitoring data, determining the reflection point distribution data of the beam, and compiling and processing the reflection point distribution data to obtain the clutter reflection characteristic points specifically includes:

[0027] Establishing a coordinate system according to the emission direction of the electromagnetic wave signal so that the emission direction of the electromagnetic wave signal is in the first quadrant of the coordinate system;

[0028] The first sea surface clutter reflection signal monitoring data is analyzed. When the maximum distance between the reflection point and the emission point is greater than the radio wave propagation line of sight range D limitWhen the first sea surface clutter reflection signal monitoring data is used, a first one-dimensional array is generated according to the distance between the reflection point and the transmission point, and the data is sorted in ascending order by data size, and a second one-dimensional array representing the position spacing of different reflection points is formed by the data size difference between the latter and the former items of each group;

[0029] Index each data item that is a preset multiple or greater than the value of the first data item in the second one-dimensional array; if such data item exists, output the first data item obtained by the index as the position of the first feature point P1 on the horizontal coordinate of the coordinate system; if such data item does not exist, output the last data item in the second one-dimensional array as the position of the first feature point P1 on the horizontal coordinate of the coordinate system;

[0030] Analyzing the second sea surface clutter reflection signal monitoring data, generating a third one-dimensional array based on the distances between reflection points and emission points in the second sea surface clutter reflection signal monitoring data, sorting the data in ascending order by data size, and forming a fourth one-dimensional array representing the positional spacings of different reflection points based on the data size differences between the last item and the first item in each group;

[0031] Index each data that is a preset multiple or more larger than the value of the first data in the fourth one-dimensional array; output the second data obtained by the index as the position of the second feature point P2 on the horizontal coordinate of the coordinate system; output the first data obtained by the index as the position of the auxiliary point P3 of the second feature point P2 on the horizontal coordinate of the coordinate system.

[0032] Further preferably, the preset multiple is 10 times.

[0033] Further preferably, the calculating of the atmospheric refractive index data of the clutter reflection feature point at the sea surface specifically includes:

[0034] according to Calculate the atmospheric refractive index at the first feature point P1 and the second feature point P2 respectively, where n p is the atmospheric refractive index at the sea surface corresponding to the feature point, R_0 is the radius of the earth, H 天线 is the altitude of the transmitting antenna, n 天线 is the atmospheric refractive index at the location of the transmitting antenna, θ t is the signal transmission elevation angle of the beam at the corresponding feature point, θ r is the beam entry angle at the corresponding feature point;

[0035] According to n p Calculate the sea surface atmospheric refractive index N corresponding to the first feature point P1 and the second feature point P2 respectively p , N p =(n p -1)×106 +R_0*H 天线 , get the atmospheric refractive index N at the first characteristic point P1 on the sea surface p1 , and the atmospheric refractive index N at the second characteristic point P2 sea surface p2 .

[0036] Further preferably, the calculating of the atmospheric refractive index distribution data of the clutter reflection feature point in the vertical direction specifically includes:

[0037] Calculate the change in angle between the electromagnetic wave signal and the earth's surface due to the curvature of the earth during its propagation;

[0038] The atmospheric refractive index distribution data of the first feature point P1 in the vertical direction and the atmospheric refractive index distribution data of the second feature point P2 in the vertical direction are calculated according to the angle variation.

[0039] Further preferably, the atmospheric refractive index distribution data in the horizontal space is interpolated according to the atmospheric refractive index distribution data of the clutter reflection feature point and the horizontal position data of the clutter reflection feature point to obtain the distribution result data of the atmospheric refractive index in the spatial section, specifically:

[0040] Determine the position of the position to be measured in horizontal space;

[0041] When point S d1 When the corresponding position to be measured d1 is between the position of the transmitting antenna and the horizontal position of the first feature point P1 in the horizontal space, the point S with a height H above the ground d1 The atmospheric refractive index at is: N d1 =N0+(N p1 -N0) / L d1 ×(x d1 -x p0 ); where N d1 Point S d1 The atmospheric refractive index at the position of the transmitting antenna is N0, which is the atmospheric refractive index at the height H corresponding to the transmitting antenna position. p1 is the atmospheric refractive index at the height H corresponding to the first characteristic point P1, L d1 is the horizontal distance between the transmitting antenna and the first feature point P1, x d1 Point S d1 The horizontal position, x p0 is the horizontal position of the transmitting antenna;

[0042] When point S d2 When the corresponding position to be measured d2 is between the horizontal positions of the first feature point P1 and the second feature point P2 in the horizontal space, the point S with a height H from the ground d2The atmospheric refractive index at is: N d2 =N p2 +(N p2 -N p1 ) / L d2 ×(x d2 -x p1 ); where N d2 For S d2 Atmospheric refractive index at N p2 is the atmospheric refractive index at the height H corresponding to the second characteristic point P2, L d2 is the horizontal distance between the first feature point P1 and the second feature point P2, x d2 Point S d2 The horizontal position, x p1 is the horizontal position of the first feature point P1;

[0043] When point S d3 When the corresponding position to be measured d3 is outside the horizontal position of the second feature point P2 in the horizontal space, the point S with a height H from the ground d3 The atmospheric refractive index at is: N d3 =N p1 +(N p2 -N p1 ) / L d2 ×(x d3 -x p1 ); where N d3 Point S d3 Atmospheric refractive index at x d3 is the horizontal position of point d3.

[0044] The atmospheric waveguide inversion method based on sea surface clutter point signal monitoring data provided by the embodiment of the present invention starts from the perspective of atmospheric refraction effect, based on sea clutter reflection data, by analyzing the distribution of clutter reflection point positions, the relationship between the signal reflection point at the sea surface and the signal transmission elevation angle, and calculating the atmospheric refractive index distribution in space based on the principle of spherical layered atmospheric refraction, so as to generate the atmospheric refractive index distribution data required for atmospheric waveguide diagnosis. The method described in the present invention can be used to analyze and calculate the parameters used to characterize the atmospheric waveguide environment structure in areas where field atmospheric environment measurements cannot be performed, and can effectively expand the control range of the radio wave environment in different application scenarios. Compared with the existing atmospheric waveguide inversion technology, the atmospheric waveguide inversion method proposed in the present invention is based on the atmospheric refraction effect for analysis. The analysis process can better reflect the propagation characteristics of radio waves in the atmospheric waveguide and the calculation process is simpler, with higher efficiency and accuracy, better applicability, and at the same time, the device required to implement the method is simple, low cost, and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1A flow chart of the atmospheric duct inversion method provided in an embodiment of the present invention;

[0046] Figure 2 A diagram showing a test scenario setup for a signal transmitting and receiving device according to an embodiment of the present invention;

[0047] Figure 3 Calculation results and simulation diagram of the vertical profile of atmospheric refractive index provided by the embodiment of the present invention;

[0048] Figure 4 Schematic diagram of the propagation trajectory of radio waves in a waveguide environment provided by an embodiment of the present invention, where the left side Figure 4 a is the uplink beam, on the right Figure 4 b is the downlink beam;

[0049] Figure 5 A schematic diagram of a tangent line between a launch point and the Earth provided in an embodiment of the present invention;

[0050] Figure 6 A schematic diagram of the atmospheric refractive index expansion in the vertical direction of the uplink beam characteristic point provided in an embodiment of the present invention;

[0051] Figure 7 A schematic diagram of the atmospheric refractive index expansion in the vertical direction of the downlink beam characteristic point provided by an embodiment of the present invention;

[0052] Figure 8 A schematic diagram of the interpolation and expansion of the horizontal atmospheric refractive index provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0053] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0054] An embodiment of the present invention provides an atmospheric duct inversion method based on sea surface clutter signal monitoring data. The method calculates the atmospheric refractive index distribution through data monitoring, obtains parameters used to characterize the atmospheric duct environment structure, and realizes atmospheric duct inversion. Figure 1 The atmospheric waveguide inversion method based on sea surface clutter signal monitoring data provided by the embodiment of the present invention is as follows: Figure 1 The steps of this method are described in detail.

[0055] Step 110, setting and determining that the signal transmitting and receiving device is in a waveguide environment;

[0056] Step 111, a signal transmitting and receiving device is set up on a movable platform on the sea surface; the signal transmitting and receiving device can be an integrated electromagnetic wave signal transmitting device and receiving device, or a separate independent device, which is set up on a movable platform on the sea surface, such as Figure 2 As shown to facilitate adjustment of its position.

[0057] Step 112: measuring the temperature, humidity, and atmospheric pressure at different heights where the signal transmitting and receiving devices are located, and calculating the vertical distribution of the atmospheric refractive index based on the measurement results to obtain a calculation result M; wherein the calculation result M includes the atmospheric refractive index N at different heights;

[0058] T is temperature, P is atmospheric pressure, and e is the water vapor pressure determined by humidity;

[0059] The temperature, humidity and atmospheric pressure at different heights are measured by low-altitude balloons. The maximum measurement height is as low as 40m. The measurement height interval can be selected according to actual conditions. The smaller the interval, the higher the final calculation accuracy.

[0060] Water vapor pressure (WVP) determined by humidity refers to the pressure exerted by water vapor molecules in the air at a given temperature. Humidity refers to the amount of water vapor in the air and is typically expressed as relative humidity (RH), defined as the ratio of the actual amount of water vapor in the air to the saturated water vapor partial pressure at that temperature. Therefore, the parameter WVP can be determined by measuring temperature, humidity, and atmospheric pressure. At a given temperature, the amount of water vapor in the air and relative humidity are correlated. That is, when the temperature remains constant, higher relative humidity increases the amount of water vapor in the air, and the resulting WVP increases.

[0061] The calculation result M obtained by the above calculation of the vertical distribution of atmospheric refractive index can be expressed as an atmospheric refractive index profile, which refers to the distribution of the atmospheric refractive index that changes with altitude. The atmospheric refractive index is a dimensionless physical quantity that represents the ratio of the refraction angle of light when passing through the atmosphere to the refraction angle in a vacuum. Its value varies with factors such as temperature, pressure, and humidity in the atmosphere. The value of the atmospheric refractive index will change with changes in altitude and air composition, so the refractive index is different at different altitudes. This change is usually continuous, so it can be represented by a cross-sectional diagram, which is the atmospheric refractive index profile. For example Figure 3 shown.

[0062] Step 113, calculate the atmospheric refractive index gradient according to the calculation result M, and when When N n The height of the point is compared with the height of the signal transmitting and receiving device. If the height is greater than the height of the transmitting equipment, it is determined that the signal transmitting and receiving device is in the waveguide environment, otherwise it is not in the waveguide environment; N n and Nn-1 are the two atmospheric refractive indices at adjacent heights in the calculation results of the vertical distribution of atmospheric refractive index, where N n is the atmospheric refractive index at a higher altitude, N n-1 is the atmospheric refractive index at a lower altitude point, and ΔH is the height difference between the above adjacent altitudes.

[0063] In step 114, when the signal transmitting and receiving device is not within the waveguide environment, the movable platform is moved to reposition and re-establish the signal transmitting and receiving device within the waveguide environment. In other words, steps 111-113 are repeated until the signal transmitting and receiving device is properly positioned within the waveguide environment.

[0064] After confirming that the signal transmitting and receiving devices are in the waveguide environment, record this location and the corresponding atmospheric refractive index profile. The data content of the atmospheric refractive index profile is as follows:

[0065] Serial number Height (m) Atmospheric refractive index

[0066] Step 120: Adjust the signal transmission elevation angle and obtain sea surface clutter reflection signal monitoring data through signal transmission and reception;

[0067] This step is based on the half-power beam angle θ and critical refraction angle θ0 of the transmitting antenna in the signal transmitting and receiving device;

[0068] The half-power beam angle θ can be obtained from the antenna parameters and is an inherent property of the transmitting antenna.

[0069] The critical refraction angle θ0 is calculated as follows:

[0070] θ0=[(2×10 -6 )(N 天线 - Nmin )] 1 / 2 -1×10 -6 (Formula 3)

[0071] Where N1 is the atmospheric refractive index at the antenna height, N min is the minimum value in the atmospheric refractive index profile M.

[0072] The transmission elevation angle is set to θ / 2+θ0, then the transmission elevation angle is reduced by one minimum unit of change allowed by the adjustment accuracy, an electromagnetic wave signal is transmitted through the signal transmitting and receiving device, and the first sea surface clutter reflection signal monitoring data is collected, recorded as data A. The transmission elevation angle is then set to -θ / 2-θ0, then the transmission elevation angle is increased by one minimum unit of change allowed by the adjustment accuracy, an electromagnetic wave signal is transmitted through the signal transmitting and receiving device, and the second sea surface clutter reflection signal monitoring data is collected, recorded as data B. The above sea surface clutter reflection signal monitoring data includes: azimuth, signal strength, and the distance between the reflection point and the transmission point. The data content contained in data A and data B is as follows:

[0073] Serial number Azimuth (°) Signal strength Distance between reflection point and emission point (m)

[0074] Step 130: Analyze the propagation trajectory of the radio wave in the atmospheric waveguide based on the sea surface clutter signal monitoring data, determine the reflection point distribution data of the beam, and compile and process the reflection point distribution data to obtain clutter reflection feature points;

[0075] Step 131, establishing a coordinate system according to the emission direction of the electromagnetic wave signal, so that the emission direction of the electromagnetic wave signal is in the first quadrant of the coordinate system;

[0076] Step 132: Analyze the first sea surface clutter reflection signal monitoring data, extract the longest distance between the reflection point and the emission point in the data and set it as D max , and calculate the line-of-sight range of radio wave propagation, and set the calculation result as D limit .

[0077] The calculation formula is as follows:

[0078]

[0079] where h 天线 is the altitude of the transmitting antenna, in m, h 目标 is the height of the reflection point. Since the reflection point is on the sea surface, h 目标 =0.

[0080] If Dlimit max This indicates that there is a waveguide effect, and you can proceed to the next step. If Dlimi t max This means that there is no waveguide and the entire method ends.

[0081] Step 133: When the maximum distance between the reflection point and the emission point is greater than the radio wave propagation line of sight range D limitWhen the first sea surface clutter reflection signal monitoring data is used, a first one-dimensional array L1 is generated according to the distance between the reflection point and the transmission point, and the data is sorted in ascending order according to the data size. The second one-dimensional array L2 for representing the position spacing of different reflection points is composed of the data size difference between the latter and former items of each group.

[0082] Step 134: Index each data item that is a preset multiple or greater than the value of the first data item in the second one-dimensional array; if such data item exists, output the first data item obtained by the index as the position of the first feature point P1 on the horizontal coordinate of the coordinate system; if such data item does not exist, output the last data item in the second one-dimensional array as the position of the first feature point P1 on the horizontal coordinate of the coordinate system;

[0083] Specifically, the preset multiple in this embodiment is determined through experimentation and is set to 10. The second one-dimensional array L2 is analyzed, and the first value in the array is designated as a1. Numbers within the array that are ten times or greater than a1 are indexed, representing blind spots, and their positions in the array are output, i1, i2, etc. If a blind spot exists, the number at position i1 in L1 is used as the position of the first feature point used for calculation. If there is no blind spot, i.e., no result is output, the last number in the first one-dimensional array L1 is used as the position of the first feature point used for calculation; this first feature point is denoted as P1.

[0084] Step 135: Analyze the second sea surface clutter reflection signal monitoring data, generate a third one-dimensional array L3 based on the distances between the reflection points and the transmission points in the second sea surface clutter reflection signal monitoring data, sort the data in ascending order by data size, and use the data size difference between the last item and the first item in each group to form a fourth one-dimensional array L4 to represent the positional spacing of different reflection points;

[0085] Step 136, index each data that is a preset multiple or more larger than the value of the first data in the fourth one-dimensional array L4; output the second data obtained by the index as the position of the second feature point P2 on the horizontal coordinate of the coordinate system; output the first data obtained by the index as the position of the auxiliary point P3 of the second feature point P2 on the horizontal coordinate of the coordinate system.

[0086] Specifically, analyze the fourth one-dimensional array L4, set the first value in the array to a2, and index a number within the array that is ten times greater than a2. This number represents the blind spot, and the position of the first blind spot is output as i. The number at position i+1 in the fourth one-dimensional array L4 is used as the position of the second feature point used for calculation, and the second feature point is recorded as P2. The number at position i in the fourth one-dimensional array L4 is used as an auxiliary point for calculating the second feature point P2, and is recorded as P3.

[0087] Step 140, calculating atmospheric refractive index data of the clutter reflection feature point at the sea surface;

[0088] Step 141, according to Calculate the atmospheric refractive index at the first feature point P1 and the second feature point P2 respectively, where n p is the atmospheric refractive index at the sea surface corresponding to the feature point, R_0 is the radius of the earth, H 天线 is the altitude of the transmitting antenna, n 天线 is the atmospheric refractive index at the location of the transmitting antenna, θ t is the signal transmission elevation angle of the beam at the corresponding feature point, θ r is the beam entry angle at the corresponding feature point;

[0089] θ t and θ r The schematic diagram is as follows Figure 4 In the calculation process, the beams at P1 and P2 are considered to be tangent to the earth, that is, θ r =0, then for (Formula 5) it is necessary to 天线 and θ t Solve it.

[0090] The atmospheric refractive index n at the launch equipment 天线 To solve: First, read the atmospheric refractive index at the height of the antenna from the atmospheric refractive index profile measured at the transmitting antenna, which is set as N1, then n 天线 The calculation formula is as follows:

[0091] n 天线 =1+(N1-R_0*H 天线 )×10 -6 (Formula 6)

[0092] θ t Calculate: For the first feature point P1, the corresponding angle θ t1 The calculation formula is as follows:

[0093] θ t1 =[(2×10 -6 )(N1-N min )] 1 / 2 -1×10 -6 (Equation 7)

[0094] For the second feature point P2, the corresponding angle θ t2 The calculation formula is as follows:

[0095] θ t2 =-[(2×10 -6 )(N1-N min )]1 / 2 -1×10 -6 (Equation 8)

[0096] Where Nmin is the minimum value of the atmospheric refractive index in the atmospheric refractive index profile.

[0097] Thus, the atmospheric refractive index n at the first characteristic point P1 can be obtained p1 and the atmospheric refractive index n at the second characteristic point P2 p2 .

[0098] Step 142, according to n p Calculate the sea surface atmospheric refractive index N corresponding to the first feature point P1 and the second feature point P2 respectively p , N p =(n p -1)×10 6 +R_0*H 天线 (Equation 9) to obtain the atmospheric refractive index N at the first characteristic point P1 on the sea surface p1 , and the atmospheric refractive index N at the second characteristic point P2 sea surface p2 .

[0099] Step 150, calculating atmospheric refractive index distribution data of the clutter reflection feature point in the vertical direction;

[0100] First, calculate the angle change θ between the electromagnetic wave signal and the earth's surface caused by the curvature of the earth during its propagation. det .

[0101] like Figure 5 As shown, point t is the launch equipment, H is the altitude of the launch equipment, l is the tangent line of the earth's sphere made by the launch antenna, and the tangent point is Q. det Indicates the change in angle with the earth's surface due to the curvature of the earth during radio wave propagation, θ det The calculation formula is as follows:

[0102]

[0103] Next, the atmospheric refractive index distribution data of the first characteristic point P1 and the atmospheric refractive index distribution data of the second characteristic point P2 in the vertical direction are calculated according to the angle variation.

[0104] First, calculate the atmospheric refractive index distribution in the vertical direction of the first feature point P1. Figure 6As shown in FIG, for calculating the atmospheric refractive index at a certain height in the vertical direction of the first characteristic point P1, the atmospheric refractive index at the same height in the atmospheric refractive index profile data at the transmitting antenna is required as an input parameter. Therefore, the calculation result of the atmospheric refractive index distribution in the vertical direction of the first characteristic point P1 corresponds one-to-one with the atmospheric refractive index data in the vertical direction of the transmitting antenna in terms of height point distribution, and can only be calculated up to the minimum atmospheric refractive index value H in the atmospheric refractive index profile. min The corresponding height.

[0105] Here with Figure 6 As an example, the calculation of point S1 in the vertical direction of the first feature point P1 is as follows:

[0106] H is the altitude of point S1. In the radio wave ray trajectory between the transmitting antenna and the first characteristic point P1, S2 is the point with the same altitude as S1. First, the atmospheric refractive index n at the sea surface of the first characteristic point P1 is calculated according to (Equation 6): p1 , then the atmospheric refractive index n at S2 S2 The calculation method is as follows:

[0107] When H is less than the altitude of the transmitting antenna

[0108] n S2 =(R_0)×n p1 / ((R_0+H)×cos(θ det -(θ p1 +θ det )(H / H min ))) (Formula 11)

[0109] When H is greater than the altitude of the transmitting antenna

[0110] n S2 =(R_0)×n p1 / ((R_0+H)×cos((θ p1 +θ det )(1-H / H min ))) (Formula 12)

[0111] Where θ t1 is the angle calculated using (Equation 7), H min is the height corresponding to the minimum value of the atmospheric refractive index in the atmospheric refractive index profile.

[0112] According to the atmospheric refractive index n at S2 calculated above S2 , use (Equation 9) to calculate the atmospheric refractive index at S2, recorded as N S2 .

[0113] For example Figure 6As shown, the transmitting antenna is at a height H in the vertical direction as point S3. The atmospheric refractive index at point S3 is extracted from the atmospheric refractive index profile and is recorded as N S3 , using N S3 and N S2 Interpolate to obtain the atmospheric refractive index N at S1 S1 , N S1 The calculation formula is as follows:

[0114] N S1 =N S3 +(N S2 -N S3 ) / x S2 *(x p1 -x S2 ) (Formula 13)

[0115] In the formula, x p1 is the horizontal distance between the first feature point P1 and the transmitting antenna, x S2 is the horizontal distance from point S2 to point S3, where x S2 The calculation formula is as follows:

[0116] When H is less than the altitude of the transmitting antenna,

[0117] x S2 =(H 天线 -H) / tan(θ det ×(1-H / H min )) (Formula 14)

[0118] When H is greater than the altitude of the transmitting antenna,

[0119] x S2 =(HH 天线 ) / tan((θ p1 +θ det )-(θ det ×H / H min )) (Formula 15)

[0120] Then, the atmospheric refractive index distribution in the vertical direction at the second feature point P2 is calculated, as shown in FIG. Figure 7 As shown, for the calculation of the atmospheric refractive index at a certain height in the vertical direction of the second characteristic point P2, the atmospheric refractive index at the same height in the atmospheric refractive index profile data at the transmitting antenna is required as an input parameter. Therefore, the calculation result of the atmospheric refractive index distribution in the vertical direction of the second characteristic point P2 corresponds one-to-one with the atmospheric refractive index data in the vertical direction of the transmitting antenna in terms of height point distribution, and can only be calculated up to the minimum atmospheric refractive index H in the atmospheric refractive index profile. min The corresponding height.

[0121] Here with Figure 7 As an example, the calculation of point S4 in the vertical direction of the second feature point P2 is as follows:

[0122] H is the altitude of point S4; in the radio wave ray trajectory between the transmitting antenna and the second characteristic point P2, as shown in Figure 7 The S5 shown is a point at the same height as S4. First, the atmospheric refractive index n at the second characteristic point P2 above the sea surface is calculated according to (Equation 6): p2 , then the atmospheric refractive index n at S5 S5 The calculation method is as follows:

[0123] n S5 =(R_0)×n p2 / ((R_0+H)×cos(θ det (1-H / H min ))) (Formula 16)

[0124] Finally, according to the calculated atmospheric refractive index n at S5 S5 , use (Equation 9) to calculate the atmospheric refractive index at S5, recorded as N S5 .

[0125] The point at the vertical height H of the transmitting antenna is S6. The atmospheric refractive index of point S6 is extracted from the atmospheric refractive index profile and recorded as N S6 , using N S6 and N S5 Interpolate to obtain the atmospheric refractive index N at S4 S4 , N S4 The calculation formula is as follows:

[0126] N S4 =N S6 +(N S6 -N S5 ) / x S5 *(x p2 -x S5 ) (Equation 17)

[0127] In the formula, x p2 is the horizontal distance between the second characteristic point P2 and the transmitting antenna, x S5 is the horizontal distance from point S5 to point S6, where x S5 The calculation formula is as follows:

[0128] x S5 =(x p2 +x p3 ) / 2+(H min -H) / tan(θ det ) (Equation 18)

[0129] In the formula, xp3 is the horizontal distance between the auxiliary point P3 and the antenna.

[0130] Step 160 , interpolating the atmospheric refractive index distribution data in the horizontal space based on the atmospheric refractive index distribution data in the vertical direction of the clutter reflection feature point and the horizontal position data of the clutter reflection feature point, to obtain atmospheric refractive index distribution result data in the spatial section.

[0131] Determine the position of the position to be measured in horizontal space.

[0132] When point S d1 When the corresponding position to be measured d1 is between the position of the transmitting antenna and the horizontal position of the first feature point P1 in the horizontal space, the point S with a height H above the ground d1 The atmospheric refractive index at is: N d1 =N0+(N p1 -N0) / L d1 ×(x d1 -x p0 )(Formula 19); where N d1 Point S d1 The atmospheric refractive index at the position of the transmitting antenna is N0, which is the atmospheric refractive index at the height H corresponding to the transmitting antenna position. p1 is the atmospheric refractive index at the height H corresponding to the first characteristic point P1, L d1 is the horizontal distance between the transmitting antenna and the first feature point P1, x d1 Point S d1 The horizontal position, x p0 is the horizontal position of the transmitting antenna;

[0133] When point S d2 When the corresponding position to be measured d2 is between the horizontal positions of the first feature point P1 and the second feature point P2 in the horizontal space, the point S with a height H from the ground d2 The atmospheric refractive index at is:

[0134] N d2 =N p2 +(N p2 -N p1 ) / L d2 ×(x d2 -x p1 )(Formula 20); where N d2 For S d2 Atmospheric refractive index at N p2 is the atmospheric refractive index at the height H corresponding to the second characteristic point P2, L d2 is the horizontal distance between the first feature point P1 and the second feature point P2, x d2 Point Sd2 The horizontal position, x p1 is the horizontal position of the first feature point P1;

[0135] When point S d3 When the corresponding position to be measured d3 is outside the horizontal position of the second feature point P2 in the horizontal space, the point S with a height H from the ground d3 The atmospheric refractive index at is: N d3 =N p1 +(N p2 -N p1 ) / L d2 ×(x d3 -x p1 )(Formula 21); where N d3 Point S d3 Atmospheric refractive index at x d3 is the horizontal position of point d3.

[0136] Furthermore, the method of the present invention further includes an atmospheric duct diagnosis step: based on the calculation result of the atmospheric refractive index distribution, the atmospheric duct distribution is diagnosed point by point to obtain the atmospheric duct distribution and duct characteristic parameters.

[0137] First, this method diagnoses the atmospheric duct distribution point by point based on the distribution result data of the atmospheric refractive index to determine whether an atmospheric duct exists; then, if an atmospheric duct exists, the duct thickness, duct height and duct strength are determined.

[0138] Atmospheric waveguide diagnosis requires point-by-point analysis in the horizontal direction. Take the waveguide diagnosis of the first characteristic point P1 as an example:

[0139] Step 1: Take out the vertical distribution sequence of atmospheric refractive index at the first characteristic point P1, denoted as M p1 , with M p1 The atmospheric refractive index at the highest point in the middle is taken as the starting point, and a circular judgment is performed. The judgment conditions are as follows:

[0140]

[0141] Where N n and N n-1 M p1 Two atmospheric refractive indices at adjacent heights, where N n is the atmospheric refractive index at a higher altitude, N n-1is the atmospheric refractive index at the lower point, and ΔH is the height difference between the two points. If (Equation 22) is satisfied, an atmospheric duct exists, and the process proceeds to Steps 2 and 3 to calculate the duct thickness, duct height, and duct strength. Otherwise, the loop continues. If no point in the sequence satisfies the equation after all data are evaluated, an atmospheric duct does not exist.

[0142] Step 2: If it is determined that there is an atmospheric duct, directly change N in step S1 to n The heights of the corresponding points are used as the waveguide thickness and waveguide height.

[0143] Step 3: N obtained in step 1 n The value of is recorded as N u , and then use the atmospheric refractive index vertical distribution sequence M at point P1 taken out in step 1 p1 The atmospheric refractive index at the lowest point is taken as the starting point, and a circular judgment is performed. The judgment conditions are as follows:

[0144]

[0145] Where N n+1 and N n M p1 Two atmospheric refractive indices at adjacent heights, where N n+1 is the atmospheric refractive index at a higher altitude, N n is the atmospheric refractive index at the lower altitude point, and ΔH is the height difference between the two points. When (Equation 23) is satisfied, the output N n+1 , denoted as N d .

[0146] The calculation formula of atmospheric waveguide strength is: waveguide strength = N d -N u (Equation 24)

[0147] The present invention discloses an atmospheric refractive index inversion method based on sea surface clutter signal monitoring data. The method uses data monitoring, atmospheric refractive index calculation, and atmospheric duct diagnosis to measure signal echo data. Based on the measured data, the method analyzes the relationship between the distribution of reflection points generated by radio waves in the atmospheric duct on the sea surface and the transmission elevation angle, determines the positions of two characteristic points, and then calculates the atmospheric refractive index distribution in the vertical space between the two characteristic points, combining the parameters of the transmitting antenna and the positions of the reflection points. This calculation also expands the spatial horizontal distribution. Based on the calculated atmospheric refractive index distribution, the atmospheric duct diagnosis analyzes the vertical gradient distribution of the refractive index at each point in the horizontal direction to determine whether an atmospheric duct environment exists, and calculates the waveguide parameters for any waveguide environment that is confirmed to exist.

[0148] The method described in the present invention can analyze and calculate parameters used to characterize the atmospheric duct environment structure in areas where field atmospheric environmental measurements are impossible, effectively expanding the scope of radio wave environment control in different application scenarios. Compared with existing atmospheric duct inversion technologies, the atmospheric duct inversion method proposed in the present invention uses atmospheric refraction effects for analysis. This analysis process better reflects the propagation characteristics of radio waves within the atmospheric duct, and the calculation process is simpler, with higher efficiency and accuracy, and better applicability. Furthermore, the apparatus required for implementing this method is simple, low-cost, and easy to implement.

[0149] Professionals should also be further aware that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0150] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be implemented using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0151] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An atmospheric waveguide inversion method based on sea surface clutter signal monitoring data, characterized in that: The method comprises: Set up and ensure that the signal transmitting and receiving devices are within the waveguide environment; Adjust the signal transmission elevation angle and obtain sea surface clutter reflection signal monitoring data through signal transmission and reception; Analyze the propagation trajectory of radio waves in the atmospheric waveguide based on the sea surface clutter signal monitoring data, determine the reflection point distribution data of the beam, and compile and process the reflection point distribution data to obtain clutter reflection feature points; Calculating atmospheric refractive index data of the clutter reflection feature point at the sea surface; Calculating atmospheric refractive index distribution data of the clutter reflection feature point in the vertical direction; The atmospheric refractive index distribution data in the horizontal space is interpolated according to the atmospheric refractive index distribution data of the clutter reflection feature point and the horizontal position data of the clutter reflection feature point to obtain distribution result data of the atmospheric refractive index in the spatial section.

2. The atmospheric duct inversion method according to claim 1, characterized in that: The method further comprises: Performing atmospheric duct distribution diagnosis point by point based on the atmospheric refractive index distribution result data to determine whether an atmospheric duct exists; In the presence of atmospheric ducting, determine the duct thickness, duct height, and duct strength.

3. The atmospheric duct inversion method according to claim 1, characterized in that: The setting and determining that the signal transmitting and receiving devices are in the waveguide environment specifically includes: The signal transmitting and receiving device is installed on a movable platform on the sea surface; Measuring the temperature, humidity, and atmospheric pressure at different heights where the signal transmitting and receiving devices are located, and calculating the vertical distribution of the atmospheric refractive index based on the measurement results to obtain a calculation result M; wherein the calculation result M includes the atmospheric refractive index N at different heights; T is temperature, P is atmospheric pressure, and e is the water vapor pressure determined by humidity; Calculate the atmospheric refractive index gradient according to the calculation result M. When it satisfies When N n The height of the point is compared with the height of the signal transmitting and receiving device. If the height is greater than the height of the transmitting equipment, it is determined that the signal transmitting and receiving device is in the waveguide environment, otherwise it is not in the waveguide environment; N n and N n-1 are the two atmospheric refractive indices at adjacent heights in the calculation results of the vertical distribution of atmospheric refractive index, where N n is the atmospheric refractive index at a higher altitude, N n-1 is the atmospheric refractive index at a lower altitude point, and ΔH is the height difference between the above adjacent altitudes.

4. The atmospheric duct inversion method according to claim 3, characterized in that: When the signal transmitting and receiving device is not in the waveguide environment, the movable platform is moved to reset and re-determine that the signal transmitting and receiving device is in the waveguide environment.

5. The atmospheric duct inversion method according to claim 1, characterized in that: The adjusting of the signal transmission elevation angle and obtaining sea surface clutter reflection signal monitoring data by signal transmission and reception specifically includes: According to the half-power beam angle θ and the critical refraction angle θ0 of the transmitting antenna in the signal transmitting and receiving device, the transmitting elevation angle is set to θ / 2+θ0, and then the transmitting elevation angle is reduced by a minimum change unit allowed by the adjustment accuracy, an electromagnetic wave signal is transmitted through the signal transmitting and receiving device, and first sea surface clutter reflection signal monitoring data is collected; Then, the transmitting elevation angle is set to -θ / 2-θ0, and then the transmitting elevation angle is increased by a minimum change unit allowed by the adjustment accuracy, an electromagnetic wave signal is transmitted through the signal transmitting and receiving device, and the second sea surface clutter reflection signal monitoring data is collected; The sea surface clutter reflection signal monitoring data includes: azimuth, signal strength and the distance between the reflection point and the emission point.

6. The atmospheric duct inversion method according to claim 5, characterized in that: The analyzing the propagation trajectory of radio waves in the atmospheric waveguide according to the sea surface clutter signal monitoring data, determining the reflection point distribution data of the beam, and compiling and processing the reflection point distribution data to obtain the clutter reflection characteristic points specifically includes: Establishing a coordinate system according to the emission direction of the electromagnetic wave signal so that the emission direction of the electromagnetic wave signal is in the first quadrant of the coordinate system; The first sea surface clutter reflection signal monitoring data is analyzed. When the maximum distance between the reflection point and the emission point is greater than the radio wave propagation line of sight range D limit When the first sea surface clutter reflection signal monitoring data is used, a first one-dimensional array is generated according to the distance between the reflection point and the transmission point, and the data is sorted in ascending order by data size, and a second one-dimensional array representing the position spacing of different reflection points is formed by the data size difference between the latter and the former items of each group; Index each data item that is a preset multiple or greater than the value of the first data item in the second one-dimensional array; if such data item exists, output the first data item obtained by the index as the position of the first feature point P1 on the horizontal coordinate of the coordinate system; if such data item does not exist, output the last data item in the second one-dimensional array as the position of the first feature point P1 on the horizontal coordinate of the coordinate system; Analyzing the second sea surface clutter reflection signal monitoring data, generating a third one-dimensional array based on the distances between reflection points and emission points in the second sea surface clutter reflection signal monitoring data, sorting the data in ascending order by data size, and forming a fourth one-dimensional array representing the positional spacings of different reflection points based on the data size differences between the last item and the first item in each group; Index each data that is a preset multiple or more larger than the value of the first data in the fourth one-dimensional array; output the second data obtained by the index as the position of the second feature point P2 on the horizontal coordinate of the coordinate system; output the first data obtained by the index as the position of the auxiliary point P3 of the second feature point P2 on the horizontal coordinate of the coordinate system.

7. The atmospheric duct inversion method according to claim 6, characterized in that: The preset multiple is 10 times.

8. The atmospheric duct inversion method according to claim 6, characterized in that: The calculating of the atmospheric refractive index data of the clutter reflection feature point at the sea surface specifically includes: according to Calculate the atmospheric refractive index at the first feature point P1 and the second feature point P2 respectively, where n p is the atmospheric refractive index at the sea surface corresponding to the feature point, R_0 is the radius of the earth, H 天线 is the altitude of the transmitting antenna, n 天线 is the atmospheric refractive index at the location of the transmitting antenna, θ t is the signal transmission elevation angle of the beam at the corresponding feature point, θ r is the beam entry angle at the corresponding feature point; According to n p Calculate the sea surface atmospheric refractive index N corresponding to the first feature point P1 and the second feature point P2 respectively p , N p =(n p -1)×10 6 +R_0*H 天线 , get the atmospheric refractive index N at the first characteristic point P1 on the sea surface p1 , and the atmospheric refractive index N at the second characteristic point P2 sea surface p2 .

9. The atmospheric duct inversion method according to claim 8, characterized in that: The calculating of the atmospheric refractive index distribution data of the clutter reflection feature point in the vertical direction specifically includes: Calculate the change in angle between the electromagnetic wave signal and the earth's surface due to the curvature of the earth during its propagation; The atmospheric refractive index distribution data of the first feature point P1 in the vertical direction and the atmospheric refractive index distribution data of the second feature point P2 in the vertical direction are calculated according to the angle variation.

10. The atmospheric duct inversion method according to claim 8, characterized in that: The atmospheric refractive index distribution data in the horizontal space is interpolated based on the atmospheric refractive index distribution data of the clutter reflection feature point and the horizontal position data of the clutter reflection feature point to obtain the distribution result data of the atmospheric refractive index in the spatial section: Determine the position of the position to be measured in horizontal space; When point S d1 When the corresponding position to be measured d1 is between the position of the transmitting antenna and the horizontal position of the first feature point P1 in the horizontal space, the point S with a height H above the ground d1 The atmospheric refractive index at is: N d1 =N0+(N p1 -N0) / L d1 ×(x d1 -x p0 ); where N d1 Point S d1 The atmospheric refractive index at the position of the transmitting antenna is N0, which is the atmospheric refractive index at the height H corresponding to the transmitting antenna position. p1 is the atmospheric refractive index at the height H corresponding to the first characteristic point P1, L d1 is the horizontal distance between the transmitting antenna and the first feature point P1, x d1 Point S d1 The horizontal position, x p0 is the horizontal position of the transmitting antenna; When point S d2 When the corresponding position to be measured d2 is between the horizontal positions of the first feature point P1 and the second feature point P2 in the horizontal space, the point S with a height H from the ground d2 The atmospheric refractive index at is: N d2 =N p2 +(N p2 -N p1 ) / L d2 ×(x d2 -x p1 ); where N d2 For S d2 Atmospheric refractive index at N p2 is the atmospheric refractive index at the height H corresponding to the second characteristic point P2, L d2 is the horizontal distance between the first feature point P1 and the second feature point P2, x d2 Point S d2 The horizontal position, x p1 is the horizontal position of the first feature point P1; When point S d3 When the corresponding position to be measured d3 is outside the horizontal position of the second feature point P2 in the horizontal space, the point S with a height H from the ground d3 The atmospheric refractive index at is: N d3 =N p1 +(N p2 -N p1 ) / L d2 ×(x d3 -x p1 ); where N d3 Point S d3 Atmospheric refractive index at x d3 is the horizontal position of point d3.

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