A hybrid radio wave propagation model of evaporation ducting and tropospheric scattering under over-the-horizon conditions

Abstract

The present invention discloses a radio wave propagation model for a hybrid mode of evaporation duct and tropospheric scattering under over-the-horizon conditions. The model comprises: comparing a formula for calculating radio wave propagation loss in an evaporation duct environment using an improved advanced propagation model with a formula for calculating radio wave propagation loss in a tropospheric scattering environment using a tropospheric scattering model, to obtain a target intersection point, wherein the target intersection point is composed of a boundary propagation value and a boundary propagation loss value. The present invention solves the technical problem that, when given a radio wave propagation distance, the existing advanced propagation model cannot determine whether the current radio wave propagation mode is evaporation duct or tropospheric scattering based on the radio wave frequency and the height of the transmitting and receiving antennas, thereby resulting in a certain deviation between the calculated result and the measured path loss.

Description

Technical Field

[0001] The present invention relates to the technical field of marine radio wave propagation, and in particular to a radio wave propagation model of a hybrid mode of evaporation duct and tropospheric scattering under over-the-horizon conditions. Background Art

[0002] Free space refers to the unobstructed space in which radio waves propagate. The primary spatial influences on radio wave propagation are the first and minimum Fresnel zones. In engineering calculations, as long as these zones are unobstructed, radio waves can be considered to propagate in free space. Line-of-sight propagation occurs when radio waves travel from the transmitter to the receiver within the visible range of the transmitting and receiving antennas, unobstructed by obstacles but subject to possible reflections from the sea surface. Line-of-sight propagation occurs when the distance between the transmitter and receiver does not exceed the limit for line-of-sight propagation. Therefore, within line-of-sight at sea, radio wave propagation can be approximated as free-space propagation.

[0003] Evaporation ducting and tropospheric scattering are the two primary modes of beyond-horizon (BLOS) radio wave propagation over the ocean. The mechanism of evaporation ducting is that as water vapor evaporates and diffuses from the sea surface, the atmospheric humidity above the sea surface decreases with increasing altitude. This causes the atmospheric refractive index to decrease with increasing altitude, exhibiting a negative gradient. This causes radio waves to refract downward. When the curvature of the downward refraction is greater than the curvature of the sea surface, the radio waves are trapped in the evaporation ducting layer, significantly reducing propagation path loss and ultimately enabling beyond-horizon (BLOS) propagation (typically up to hundreds of kilometers). Therefore, evaporation ducting can enable high-speed beyond-horizon communications at sea.

[0004] The mechanism of tropospheric scatter is that numerous scatterers in the troposphere (primarily vortexes, clouds, warm and cold fronts, and horizontal stratification) cause refraction and re-radiation of frequencies above very high frequencies, particularly microwaves and millimeter waves. This allows radio waves to propagate beyond line of sight, with transmission distances reaching up to 600 to 700 kilometers. Using this tropospheric scatter mode for communication offers numerous advantages, including resistance to nuclear explosions, immunity to solar storms, security, confidentiality, and maneuverability. Therefore, tropospheric scatter communications are also important means of military and emergency communications.

[0005] Currently, the Advanced Propagation Model (APM) is a commonly used model for calculating radio wave propagation path loss in an evaporation duct environment. However, at a given propagation distance, this model cannot distinguish whether the current radio wave propagation mode is evaporation duct or tropospheric scatter based on the operating frequency, the height of the transmitting and receiving antennas, and the height of the evaporation duct, resulting in a certain deviation between the calculated results and the measured path loss. At the same time, the ITU-related model is commonly used to calculate radio wave propagation path loss in a tropospheric scatter environment. However, under beyond-horizon conditions at sea, when the evaporation duct height is high, the radio wave propagation mode is the evaporation duct mode, and there is a certain deviation between the calculated results of the above model and the measured path loss. Affected by complex meteorological conditions at sea, the radio wave propagation mode in beyond-horizon conditions constantly switches between evaporation duct and tropospheric scatter, making it difficult to accurately predict radio wave attenuation using a single radio wave propagation model.

[0006] Therefore, the present invention fully considers the respective characteristics of the two maritime beyond-horizon propagation modes, evaporation duct and tropospheric scatter, and establishes a radio wave propagation model of a mixed mode of evaporation duct and tropospheric scatter under beyond-horizon. The model can adaptively identify the current radio wave propagation mode according to the radio wave frequency, the height of the transmitting and receiving antennas, and the evaporation duct height, and then accurately predict the radio wave propagation path loss on the maritime beyond-horizon communication link, so that the communication rate and maximum communication distance of the maritime beyond-horizon communication system have future predictability, thereby guiding the setting of its parameters such as its transmission power. Summary of the Invention

[0007] An embodiment of the present invention provides a radio wave propagation model for a mixed mode of evaporation ducting and tropospheric scattering under beyond-horizon conditions, so as to at least solve the technical problem that, when a radio wave propagation distance is given, the existing advanced propagation model cannot determine whether the current radio wave propagation mode is evaporation ducting or tropospheric scattering based on the radio wave frequency and the heights of the transmitting and receiving antennas, thereby resulting in a certain deviation between the calculated results and the measured path loss.

[0008] According to one aspect of an embodiment of the present invention, a radio wave propagation model for a hybrid mode of evaporation ducting and tropospheric scattering under over-the-horizon conditions is provided. The model may include: when radio waves propagate under line-of-sight conditions at sea, determining the limit distance of radio wave propagation under line-of-sight conditions at sea based on the height of the transmitting antenna and the height of the receiving antenna; when the radio wave propagation distance at sea is less than or equal to the limit distance of radio wave propagation under line-of-sight conditions at sea, the expression of the model for radio wave propagation at sea is:

[0009]

[0010] in, is the frequency when radio waves propagate under line-of-sight conditions at sea, is the distance when radio waves propagate under line-of-sight conditions at sea, The propagation distance of radio waves on the sea is The radio wave propagation loss is It is the maximum distance of radio wave propagation under line-of-sight conditions at sea;

[0011] When the propagation distance of radio waves at sea is greater than the limit distance of radio wave propagation under the line-of-sight condition at sea, the expression of the model when radio waves propagate in a tropospheric scattering environment or in an evaporative duct environment is:

[0012]

[0013] in, When the propagation distance of radio waves on the sea is The radio wave propagation loss determined by the improved advanced propagation model when , or when the radio wave propagation distance at sea is The radio wave propagation loss is determined using the tropospheric scatter model. In order to calculate the radio wave propagation loss in an evaporative duct environment using an advanced propagation model, is the difference in radio wave propagation attenuation, In order to calculate the radio wave propagation loss in the tropospheric scattering environment using the tropospheric scattering model, is the boundary propagation length, is the distance that radio waves propagate in an evaporation waveguide environment, is the distance the radio wave propagates in a tropospheric scattering environment, and the boundary propagation length is the length the radio wave propagates when switching between an evaporative waveguide and a tropospheric scattering environment;

[0014] When the propagation distance of radio waves on the sea is The process of determining the radio wave propagation loss using the improved advanced propagation model is as follows: based on the radio wave propagation frequency and radio wave propagation distance at the radio wave propagation limit distance, the maximum free space propagation loss at the radio wave propagation limit distance is obtained; the radio wave propagation limit distance is substituted into the advanced propagation model to obtain the minimum evaporation waveguide propagation attenuation at the radio wave propagation limit distance; based on the maximum free space propagation loss and the minimum evaporation waveguide propagation attenuation, the radio wave propagation attenuation difference is obtained; based on the radio wave propagation attenuation difference, the advanced propagation model is translated to obtain the improved advanced propagation model; and the radio wave propagation loss of the radio wave in the evaporation waveguide environment is calculated using the improved advanced propagation model;

[0015] The process of determining the boundary propagation length is as follows: when the radio wave propagation loss determined by the improved advanced propagation model in the evaporation duct environment is equal to the radio wave propagation loss determined by the tropospheric scattering model in the evaporation duct environment, the boundary propagation length is determined.

[0016] Optionally, based on the height of the transmitting antenna and the height of the receiving antenna, the expression for determining the limit distance of radio wave propagation under line-of-sight conditions at sea is:

[0017]

[0018] in, is the maximum distance of radio wave propagation under line-of-sight conditions at sea, is the height of the transmitting antenna, is the height of the receiving antenna.

[0019] Optionally, the expression of the advanced propagation model is:

[0020]

[0021] in, is the frequency of radio waves when they propagate in an evaporation waveguide environment. It is the spatial field quantity of the wave field when the radio wave propagates in the evaporation waveguide environment.

[0022] Optionally, the process of determining the spatial field quantity of the wave field when the radio wave propagates in the evaporation waveguide environment is as follows:

[0023] The narrow-angle parabolic equation is selected as part of the spatial field quantity, where the expression of the narrow-angle parabolic equation is:

[0024]

[0025] in, is the complex amplitude of the wave field when the radio wave propagates in the evaporation waveguide environment, is the free space wave number of radio waves when they propagate in an evaporation waveguide environment, is the refractive index of the medium, and They represent the horizontal distance from the ground and the height from the ground respectively.

[0026] Alternatively, the expression for calculating the radio wave propagation loss in the tropospheric scattering environment using the tropospheric scattering model is:

[0027]

[0028] in, is the meteorological factor, is the frequency of radio waves when they propagate in a tropospheric scattering environment, is the minimum scattering angle, is the path length, is the height from the lowest scattering point to the line connecting the receiving and transmitting points, is the height of the lowest scattering point above the ground, is the exponential decay coefficient of tropospheric inhomogeneity intensity with height, is the interface dielectric coupling loss, and The transmit and receive antenna gains are

[0029] Optionally, based on the maximum free space propagation loss and the minimum evaporation wave propagation attenuation, the expression for the difference in electric wave propagation attenuation is obtained as follows:

[0030]

[0031] in, is the difference in radio wave propagation attenuation, The minimum evaporation wave conductive wave propagation attenuation is is the maximum free space propagation loss.

[0032] Beneficial effects of the present invention:

[0033] The present invention proposes a radio wave propagation model for a hybrid mode of evaporation duct and tropospheric scattering under over-the-horizon conditions. The model can adaptively identify the current radio wave propagation mode based on the radio wave frequency, the heights of the transmitting and receiving antennas, and the evaporation duct height, and predict the radio wave propagation attenuation. Affected by complex weather conditions at sea, the radio wave propagation mode under over-the-horizon conditions continuously switches between the evaporation duct and tropospheric scattering. Therefore, compared with the pure waveguide mode of the APM model, the absolute error between the radio wave propagation path loss in the C and X bands calculated by the proposed model is smaller than the measured path loss. The model can be used to predict the radio wave propagation attenuation in the hybrid mode of evaporation duct and tropospheric scattering under over-the-horizon conditions at sea. The prediction results can be further combined with parameters such as the transmitting and receiving antenna gain, transmitting power, and receiving sensitivity of the marine over-the-horizon communication system to accurately predict its maximum communication range. In addition, the prediction results can be used to guide the adjustment of the transmitting power and the transmitting and receiving antenna heights of the marine over-the-horizon communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0035] Figure 1 This is a flow chart of a radio wave propagation model of a hybrid mode of evaporation duct and tropospheric scatter under over-the-horizon conditions according to an embodiment of the present invention;

[0036] Figure 22 is a comparison chart of calculation results under the model proposed in an embodiment of the present invention and the APM model (pure waveguide);

[0037] Figure 3 Schematic diagram of the predicted path loss of pure waveguide mode on links of different lengths in the X-band and C-band according to the model proposed in an embodiment of the present invention and the APM model;

[0038] Figure 4 3 is a distribution diagram of the absolute errors between the model proposed in the embodiment of the present invention and the APM model in pure waveguide mode and the measured path loss. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0040] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way are interchangeable where appropriate so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0041] Example 1

[0042] According to an embodiment of the present invention, a radio wave propagation model for a hybrid mode of evaporation ducting and tropospheric scattering under over-the-horizon conditions is provided. It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system comprising at least one set of computer-executable instructions, and although a logical order is shown in the flowcharts, in some cases, the steps shown or described may be executed in an order different from that shown.

[0043] Figure 1 FIG. 1 is a flow chart of a radio wave propagation model of a hybrid mode of evaporation duct and tropospheric scattering under over-the-horizon conditions according to an embodiment of the present invention. Figure 1 As shown, the model can include the following steps:

[0044] Step S101 : When radio waves propagate in the line-of-sight condition at sea, the radio wave propagation limit distance in the line-of-sight condition at sea is determined based on the height of the transmitting antenna and the height of the receiving antenna.

[0045] In the technical solution provided in the above step S101 of the present invention, the height of the transmitting antenna and the height of the receiving antenna are calculated to obtain the maximum distance of radio wave propagation under the line-of-sight condition at sea.

[0046] Step S102: When the propagation distance of radio waves at sea is less than or equal to the limit distance of radio wave propagation under the line-of-sight condition at sea, the expression of the model for radio wave propagation at sea is:

[0047]

[0048] in, is the frequency when radio waves propagate under line-of-sight conditions at sea, is the distance when radio waves propagate under line-of-sight conditions at sea, The propagation distance of radio waves on the sea is The radio wave propagation loss is It is the maximum distance of radio wave propagation under line-of-sight conditions at sea.

[0049] In the technical solution provided in the above step S102 of the present invention, the frequency when the radio wave propagates under the condition of line of sight at sea and the distance when the radio wave propagates under the condition of line of sight at sea are substituted into the above formula to obtain the loss of the radio wave when propagating at sea when the propagation distance of the radio wave at sea is less than or equal to the limit distance of the radio wave propagation under the condition of line of sight at sea.

[0050] Step S103: When the propagation distance of radio waves at sea is greater than the limit distance of radio wave propagation under the line-of-sight condition at sea, the expression of the model when radio waves propagate in a tropospheric scattering environment or in an evaporative duct environment is:

[0051]

[0052] in, When the propagation distance of radio waves on the sea is The radio wave propagation loss determined by the improved advanced propagation model when , or when the radio wave propagation distance at sea is The radio wave propagation loss is determined using the tropospheric scatter model. In order to calculate the radio wave propagation loss in an evaporative duct environment using an advanced propagation model, is the difference in radio wave propagation attenuation, In order to calculate the radio wave propagation loss in the tropospheric scattering environment using the tropospheric scattering model, is the boundary propagation length, is the distance that radio waves propagate in an evaporation waveguide environment, is the distance the radio wave propagates in a tropospheric scattering environment, and the boundary propagation length is the length the radio wave propagates when switching between an evaporative waveguide and a tropospheric scattering environment;

[0053] When the propagation distance of radio waves on the sea is The process of determining the radio wave propagation loss using the improved advanced propagation model is as follows: based on the radio wave propagation frequency and radio wave propagation distance at the radio wave propagation limit distance, the maximum free space propagation loss at the radio wave propagation limit distance is obtained; the radio wave propagation limit distance is substituted into the advanced propagation model to obtain the minimum evaporation waveguide propagation attenuation at the radio wave propagation limit distance; based on the maximum free space propagation loss and the minimum evaporation waveguide propagation attenuation, the radio wave propagation attenuation difference is obtained; based on the radio wave propagation attenuation difference, the advanced propagation model is translated to obtain the improved advanced propagation model; and the radio wave propagation loss of the radio wave in the evaporation waveguide environment is calculated using the improved advanced propagation model;

[0054] The process of determining the boundary propagation length is as follows: when the radio wave propagation loss determined by the improved advanced propagation model in the evaporation duct environment is equal to the radio wave propagation loss determined by the tropospheric scattering model in the evaporation duct environment, the boundary propagation length is determined.

[0055] In the technical solution provided in the above step S103 of the present invention, when the propagation distance of radio waves at sea is greater than the limit distance of radio wave propagation under the line-of-sight condition at sea, the radio wave propagation loss in the tropospheric scattering environment is calculated using the tropospheric scattering model, wherein the evaporation duct environment and the tropospheric scattering environment are both at the evaporation duct height. The process of solving the evaporation duct height is as follows: log in to the climate system of the weather forecast center in area A, download the meteorological data at the required time and then analyze the meteorological data, and extract the meteorological data at the point closest to the link by setting the longitude and latitude of the sea area where the offshore test link is located, including relative humidity, sea surface atmospheric pressure, sea surface Temperature, air temperature 2m above the sea surface and wind speed component 10m above the sea surface; the meteorological data extracted at the point closest to the offshore test link are input into the evaporation duct height prediction model, and the atmospheric corrected refractive index profile within the range of 0-50 meters at the point closest to the offshore test link is calculated, where the calculation step is 0.1 meter; the height corresponding to the minimum corrected refractive index in the corrected refractive index profile is the evaporation duct height, and the radio wave propagation frequency and radio wave propagation distance at the extreme distance of radio wave propagation are substituted into the formula for calculating the free space propagation loss to obtain the maximum free space propagation loss at the extreme distance of radio wave propagation. , the formula for free space propagation loss is: ,in, The free space propagation loss at the extreme distance of radio wave propagation is calculated. The advanced propagation model is translated by the radio wave propagation attenuation difference to obtain an improved advanced propagation model. The radio wave propagation distance is substituted into the translated advanced propagation model to obtain the radio wave propagation loss in the evaporation duct environment. The radio wave propagation distance is substituted into the translated advanced propagation model to obtain the formula for the radio wave propagation loss in the evaporation duct environment: Will and Perform joint solution, that is = , and obtain the boundary propagation length. According to the boundary propagation length, it is determined whether the radio wave propagates in the evaporation waveguide environment or the radio wave propagates in the tropospheric scattering environment. Figure 2 This is a comparison chart of the calculation results of the model proposed in the embodiment of the present invention and the APM model (pure waveguide) mode, according to the distance the radio wave propagates at sea and and The relationship between them is used to obtain models of different ranges of radio waves propagating at sea.

[0056] The above method of this embodiment is further introduced below.

[0057] As an optional embodiment, in step S101, based on the height of the transmitting antenna and the height of the receiving antenna, the expression for determining the limit distance of radio wave propagation under the line-of-sight condition at sea is:

[0058]

[0059] in, is the maximum distance of radio wave propagation under line-of-sight conditions at sea, is the height of the transmitting antenna, is the height of the receiving antenna.

[0060] In this embodiment, the height of the transmitting antenna and the height of the receiving antenna are calculated to obtain the maximum distance of radio wave propagation under line-of-sight conditions at sea.

[0061] As an optional embodiment, in step S103, the expression of the high-level propagation model is:

[0062]

[0063] in, is the frequency of radio waves when they propagate in an evaporation waveguide environment. It is the spatial field quantity of the wave field when the radio wave propagates in the evaporation waveguide environment.

[0064] As an optional embodiment, in step S103, the process of determining the spatial field quantity of the wave field when the radio wave propagates in the evaporation waveguide environment is as follows:

[0065] The narrow-angle parabolic equation is selected as part of the spatial field quantity, where the expression of the narrow-angle parabolic equation is:

[0066]

[0067] in, is the complex amplitude of the wave field when the radio wave propagates in the evaporation waveguide environment, is the free space wave number of radio waves when they propagate in an evaporation waveguide environment, is the refractive index of the medium, and They represent the horizontal distance from the ground and the height from the ground respectively.

[0068] The narrow-angle parabolic equation is solved based on the discrete matching Fourier method, and the spatial field quantity in the environment of the evaporation waveguide is obtained.

[0069] In this embodiment, since the electromagnetic wave propagates in the atmospheric waveguide, the trapping angle is usually no more than Therefore, the narrow-angle parabolic equation is selected as the propagation model of radio waves in the evaporation waveguide.

[0070] The narrow-angle parabolic equation is solved using the discrete matching Fourier method, and the complex amplitude of the wave field is obtained recursively. .

[0071] As an optional embodiment, in step S103, the expression for calculating the radio wave propagation loss in the tropospheric scattering environment using the tropospheric scattering model is:

[0072]

[0073] in, is the meteorological factor, is the frequency of radio waves when they propagate in a tropospheric scattering environment, is the minimum scattering angle, is the path length, is the height from the lowest scattering point to the line connecting the transmitting and receiving points, is the height of the lowest scattering point above the ground, is the exponential decay coefficient of tropospheric inhomogeneity intensity with height, is the interface dielectric coupling loss, and The transmit and receive antenna gains are

[0074] As an optional embodiment, in step S103, the expression for obtaining the difference in electric wave propagation attenuation based on the maximum free space propagation loss and the minimum evaporation wave electric wave propagation attenuation is:

[0075]

[0076] in, is the difference in radio wave propagation attenuation, The minimum evaporation wave conductive wave propagation attenuation is is the maximum free space propagation loss.

[0077] Experimental part:

[0078] The measured path loss data on three cross-sea test links, namely, A-B Yangjiang, Guangdong-Wenchang, Hainan, C-B Yangxi, Guangdong-Wenchang, Hainan, and D-B Jizhao Bay, Zhanjiang, Guangdong-Wenchang, Hainan, were selected. The obtained evaporation duct height values ​​and radio wave propagation parameters (including radio wave frequency, transmitting antenna height and receiving antenna height) were input into the established radio wave propagation model of the evaporation duct and tropospheric scattering mixed mode under beyond-the-horizon conditions. The calculated radio wave propagation path loss was compared with the radio wave propagation path loss calculated by the APM model considering only the evaporation duct mode to verify the accuracy of the model proposed in the present invention.

[0079] The accuracy of the proposed model was verified using X-band path loss data measured over a two-week period on three cross-sea test links: A-B, C-B, and D-B. This data was combined with C-band path loss data measured on a link between E and F on day P. The link lengths for A-B, C-B, and D-B were 248 km, 188 km, and 150 km, respectively, while the link length for E-F was 146.7 km. The obtained evaporation duct height and radio wave propagation parameters were input into the proposed model and the pure duct model of the APM model for comparison. Figure 3 Schematic diagram of the predicted path loss of pure waveguide mode in X-band and C-band at different link lengths according to the model proposed in the embodiment of the present invention and the APM model. Figure 3 (d) It can be seen that in the C band, the calculation results of the model proposed in this invention are closer to the measured path loss than the pure waveguide mode of the APM model. This is because the evaporation waveguide height is low during the period of 16:00-18:00, and the radio waves propagate beyond the horizon through the tropospheric scattering mode. Figure 3 As can be seen from (a)-(c), the calculation results of the model proposed in the present invention are also closer to the measured path loss than the pure waveguide mode of the APM model in the X-band.

[0080] The absolute error between the path loss of the proposed model and the APM model in pure waveguide mode and the measured path loss is calculated. The path loss data collected on the 188 km test link from site A to site B on R day is selected as the measured path loss.

[0081] Figure 4 This is a distribution diagram of the absolute errors between the model proposed in the embodiment of the present invention and the APM model in pure waveguide mode and the measured path loss. The number of measured path loss samples is 56,543. The results show that the absolute errors between the model proposed in the present invention and the measured path loss do not exceed 5dB and 10dB in 61.21% and 91.92% of the cases, respectively, while the absolute errors between the APM model in pure waveguide mode and the measured path loss do not exceed 5dB and 10dB in only 18.55% and 47.18% of the cases. Therefore, the absolute error of the path loss predicted by the model proposed in the present invention is smaller than that predicted by the APM model in pure waveguide mode.

[0082] In an embodiment of the present invention, when radio waves propagate under line-of-sight conditions at sea, the limit distance of radio wave propagation under line-of-sight conditions at sea is determined based on the height of the transmitting antenna and the height of the receiving antenna. When the propagation distance of radio waves at sea is less than or equal to the limit distance of radio wave propagation under line-of-sight conditions at sea, the expression of the model for radio wave propagation at sea is:

[0083]

[0084] in, is the frequency when radio waves propagate under line-of-sight conditions at sea, is the distance when radio waves propagate under line-of-sight conditions at sea, The propagation distance of radio waves on the sea is The radio wave propagation loss is It is the maximum distance of radio wave propagation under line-of-sight conditions at sea.

[0085] When the propagation distance of radio waves at sea is greater than the limit distance of radio wave propagation under the line-of-sight condition at sea, the expression of the model when radio waves propagate in a tropospheric scattering environment or in an evaporative duct environment is:

[0086]

[0087] in, When the propagation distance of radio waves on the sea is The radio wave propagation loss determined by the improved advanced propagation model when , or when the radio wave propagation distance at sea is The radio wave propagation loss is determined using the tropospheric scatter model. In order to calculate the radio wave propagation loss in an evaporative duct environment using an advanced propagation model, is the difference in radio wave propagation attenuation, In order to calculate the radio wave propagation loss in the tropospheric scattering environment using the tropospheric scattering model, is the boundary propagation length, is the distance that radio waves propagate in an evaporation waveguide environment, is the distance that radio waves propagate in a tropospheric scattering environment, and the boundary propagation length is the length that radio waves propagate when switching between an evaporation duct and a tropospheric scattering environment. The process of determining the radio wave propagation loss determined by the improved advanced propagation model is as follows: based on the radio wave propagation frequency and radio wave propagation distance at the radio wave propagation limit distance, the maximum free space propagation loss at the radio wave propagation limit distance is obtained; the radio wave propagation limit distance is substituted into the advanced propagation model to obtain the minimum evaporation waveguide propagation attenuation at the radio wave propagation limit distance; based on the maximum free space propagation loss and the minimum evaporation waveguide propagation attenuation, the radio wave propagation attenuation difference is obtained; based on the radio wave propagation attenuation difference, the advanced propagation model is translated to obtain the improved advanced propagation model; the radio wave propagation loss of the radio wave in the evaporation waveguide environment is calculated using the improved advanced propagation model; the process of determining the boundary propagation length is as follows: when the radio wave propagation limit distance is 0, the radio wave propagation loss in the evaporation waveguide environment is 1, and the boundary propagation length is 2. When the radio wave propagation loss determined by the improved advanced propagation model in an evaporation duct environment is equal to the radio wave propagation loss determined by the tropospheric scattering model in the evaporation duct environment, the boundary propagation length is determined. This solves the technical problem that the existing advanced propagation model cannot determine whether the current radio wave propagation mode is evaporation duct or tropospheric scattering according to the radio wave frequency and the heights of the transmitting and receiving antennas when the radio wave propagation distance is given, thereby resulting in a certain deviation between the calculated result and the measured path loss. The technical effect of automatically identifying the current radio wave propagation mode as evaporation duct or tropospheric scattering according to the radio wave frequency, the heights of the transmitting and receiving antennas and the evaporation duct height and accurately predicting the radio wave propagation attenuation is achieved.

[0088] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages or disadvantages of the embodiments.

[0089] In the above embodiments of the present invention, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0090] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only exemplary. For example, the division of units can be a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0091] Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple units. Some or all of the units may be selected to achieve the purpose of the present embodiment according to actual needs.

Claims

1. A radio wave propagation model of hybrid evaporation duct and tropospheric scattering mode under over-the-horizon conditions, characterized in that: include: When radio waves propagate under line-of-sight conditions at sea, the maximum propagation distance of radio waves under line-of-sight conditions at sea is determined based on the height of the transmitting antenna and the height of the receiving antenna; When the propagation distance of radio waves at sea is less than or equal to the limit distance of radio wave propagation under the condition of line of sight at sea, the expression of the model for radio wave propagation at sea is: in, is the frequency when radio waves propagate under line-of-sight conditions at sea, is the distance when radio waves propagate under line-of-sight conditions at sea, The propagation distance of radio waves on the sea is The radio wave propagation loss is It is the maximum distance of radio wave propagation under line-of-sight conditions at sea; When the propagation distance of radio waves at sea is greater than the limit distance of radio wave propagation under the line-of-sight condition at sea, the expression of the model when radio waves propagate in a tropospheric scattering environment or in an evaporative duct environment is: in, When the propagation distance of radio waves on the sea is The radio wave propagation loss determined by the improved advanced propagation model when , or when the radio wave propagation distance at sea is The radio wave propagation loss is determined using the tropospheric scatter model. In order to calculate the radio wave propagation loss in an evaporative duct environment using an advanced propagation model, is the difference in radio wave propagation attenuation, In order to calculate the radio wave propagation loss in the tropospheric scattering environment using the tropospheric scattering model, is the boundary propagation length, is the distance that radio waves propagate in an evaporation waveguide environment, is the distance the radio wave propagates in a tropospheric scattering environment, and the boundary propagation length is the length the radio wave propagates when switching between an evaporative waveguide and a tropospheric scattering environment; The expression for calculating the radio wave propagation loss in the tropospheric scattering environment using the tropospheric scattering model is: in, is the meteorological factor, is the frequency of radio waves when they propagate in a tropospheric scattering environment, is the minimum scattering angle, is the path length of radio wave transmission in the stratosphere scattering model, is the height from the lowest scattering point to the line connecting the receiving and transmitting points, is the height of the lowest scattering point above the ground, is the exponential decay coefficient of tropospheric inhomogeneity intensity with height, is the interface dielectric coupling loss, and are the transmitting and receiving antenna gains respectively; When the propagation distance of radio waves on the sea is The process of determining the radio wave propagation loss using the improved advanced propagation model is as follows: based on the radio wave propagation frequency and radio wave propagation distance at the radio wave propagation limit distance, the maximum free space propagation loss at the radio wave propagation limit distance is obtained; the radio wave propagation limit distance is substituted into the advanced propagation model to obtain the minimum evaporation waveguide propagation attenuation at the radio wave propagation limit distance; based on the maximum free space propagation loss and the minimum evaporation waveguide propagation attenuation, the radio wave propagation attenuation difference is obtained; based on the radio wave propagation attenuation difference, the advanced propagation model is translated to obtain the improved advanced propagation model; and the radio wave propagation loss of the radio wave in the evaporation waveguide environment is calculated using the improved advanced propagation model; The process of determining the boundary propagation length is as follows: when the radio wave propagation loss determined by the improved advanced propagation model in the evaporation duct environment is equal to the radio wave propagation loss determined by the tropospheric scattering model in the evaporation duct environment, the boundary propagation length is determined.

2. The model according to claim 1, characterized in that The expression for determining the limit distance of radio wave propagation under the condition of line of sight at sea based on the height of the transmitting antenna and the height of the receiving antenna is: in, is the maximum distance of radio wave propagation under line-of-sight conditions at sea, is the height of the transmitting antenna, is the height of the receiving antenna.

3. The model according to claim 1, characterized in that The expression of the advanced propagation model is: in, is the frequency of radio waves when they propagate in an evaporation waveguide environment. It is the spatial field quantity of the wave field when the radio wave propagates in the evaporation waveguide environment.

4. The model according to claim 1 or 3, characterized in that The process of determining the spatial field quantity of the wave field when the radio wave propagates in the evaporation waveguide environment is as follows: The narrow-angle parabolic equation is selected as part of the spatial field quantity, where the expression of the narrow-angle parabolic equation is: in, is the complex amplitude of the wave field when the radio wave propagates in the evaporation waveguide environment, is the free space wave number of radio waves when they propagate in an evaporation waveguide environment, is the refractive index of the medium, and They represent the horizontal distance from the ground and the height from the ground respectively. The narrow-angle parabolic equation is solved based on the discrete matching Fourier method, and the spatial field quantity in the environment of the evaporation waveguide is obtained.

5. The model according to claim 1, characterized in that The expression for the difference in electric wave propagation attenuation based on the maximum free space propagation loss and the minimum evaporation wave electric wave propagation attenuation is: in, is the difference in radio wave propagation attenuation, The minimum evaporation wave conductive wave propagation attenuation is is the maximum free space propagation loss.

6. A computer system, characterized in that include: One or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors are caused to implement the model of claim 1.

7. A computer-readable storage medium, characterized in that Computer-executable instructions are stored, and when the instructions are executed, they are used to implement the model of claim 1.

8. A computer program product, characterized in that The invention comprises computer executable instructions for implementing the model of claim 1 when the instructions are executed.

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