Radio wave propagation model of evaporation waveguide and troposphere scattering mixed mode under beyond visual range

Abstract

The invention discloses an evaporation waveguide and troposphere scattering mixed mode radio wave propagation model beyond visual range. According to the model, a formula for calculating radio wave propagation loss of radio waves in an evaporation waveguide environment by using an improved advanced propagation model is compared with a formula for calculating radio wave propagation loss of radio waves in a troposphere scattering environment by using a troposphere scattering model, and a target intersection point is obtained, the target intersection point is composed of a demarcation propagation value and a demarcation propagation loss value. The technical problem that a certain deviation exists between a calculation result and actually measured path loss due to the fact that an existing advanced propagation model cannot judge that a current radio wave propagation mode is an evaporation waveguide or troposphere scattering according to radio wave frequency and transmitting and receiving antenna height under the condition of a radio wave propagation distance is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of offshore 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 a space without any obstruction when radio waves propagate. During the process of radio wave propagation, the main spaces that affect radio wave propagation are the first Fresnel zone and the minimum Fresnel zone. In engineering calculations, as long as these areas are not blocked, it can be approximately considered that radio waves propagate in free space. Line-of-sight propagation refers to a propagation mode in which radio waves propagate from the transmitting end to the receiving end within the distance range where the transmitting antenna and the receiving antenna can "see" each other, without any obstacles, but there may be waves reflected from the sea surface. When the distance between the transmitting end and the receiving end does not exceed the limit distance of line-of-sight propagation, it belongs to line-of-sight propagation. Therefore, within the line-of-sight range at sea, radio wave propagation can be approximated as free space propagation.

[0003] Evaporative waveguides and tropospheric scattering are the two main modes of over-the-horizon propagation of radio waves at sea. The mechanism of evaporative waveguide generation is: with the evaporation and diffusion of water vapor on the sea surface, the atmospheric humidity above the sea surface decreases with increasing altitude, causing the corresponding atmospheric refractive index to decrease with increasing altitude, showing a negative gradient change trend, which will cause the radio waves to refract downward and propagate. When the curvature of the downward refraction is greater than the curvature of the sea surface, the radio waves will be trapped in the evaporative waveguide layer, greatly reducing the loss of the radio wave propagation path, and ultimately achieving over-the-horizon propagation (usually up to hundreds of kilometers). Therefore, the use of evaporative waveguides can achieve high-speed over-the-horizon communication at sea.

[0004] The mechanism of tropospheric scattering is: a large number of scatterers in the troposphere (mainly various vortex air masses, clouds, warm fronts, cold fronts, horizontal stratification, etc.) will cause refraction and re-radiation of the frequency bands above the very high frequency, especially microwaves and millimeter waves, so that radio waves can be transmitted beyond the line of sight. The transmission distance can be up to 600 to 700 kilometers. Using the tropospheric scattering propagation mode of radio waves for communication has many advantages such as resistance to nuclear explosions, unaffected by solar storms, good security, confidentiality and mobility. Therefore, tropospheric scattering communication is also an important means of military communication and emergency communication.

[0005] At present, the commonly used model for calculating the path loss of radio wave propagation in the evaporation duct environment is the Advanced Propagation Model (APM). However, under a given propagation distance, the model cannot determine whether the current radio wave propagation mode is evaporation duct or tropospheric scattering 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 commonly used model for calculating the path loss of radio wave propagation in the tropospheric scattering environment is the ITU-related model. However, under the condition of beyond-horizon at sea, when the height of the evaporation duct 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 the complex meteorological conditions at sea, the radio wave propagation mode under beyond-horizon conditions constantly switches between evaporation duct and tropospheric scattering, making it difficult for a single radio wave propagation mode to accurately predict radio wave attenuation.

[0006] Therefore, the present invention fully considers the respective characteristics of the two over-the-horizon propagation modes of evaporation duct and tropospheric scattering at sea, and establishes a radio wave propagation model of a mixed mode of evaporation duct and tropospheric scattering under over-the-horizon. The current radio wave propagation mode can be adaptively determined according to the radio wave frequency, the heights of the transmitting and receiving antennas, and the height of the evaporation duct, and then the radio wave propagation path loss on the over-the-horizon communication link at sea can be accurately predicted, so that the performance of the over-the-horizon communication system at sea, such as the communication rate and the maximum communication distance, has future predictability, thereby guiding the setting of its parameters such as the transmission power. Summary of the invention

[0007] An embodiment of the present invention provides a radio wave propagation model of a mixed mode of evaporation duct and tropospheric scattering under beyond-horizon conditions, so as to at least solve 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 height 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.

[0008] According to one aspect of an embodiment of the present invention, a radio wave propagation model of a hybrid mode of evaporation duct 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, based on the height of the transmitting antenna and the height of the receiving antenna, determining the limit distance of radio wave propagation under line-of-sight conditions at sea; 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 when radio waves propagate at sea is:

[0009] in, is the frequency when the radio wave propagates 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 limit 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 condition of line of sight at sea, the expression of the model when radio waves propagate in the tropospheric scattering environment or in the evaporative duct environment is:

[0010] 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 the propagation distance of the radio wave at sea is The radio wave propagation loss determined using the tropospheric scatter model is 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 evaporative 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 evaporative waveguide or a tropospheric scattering environment; When the propagation distance of radio waves on the sea is The process of determining the radio wave propagation loss determined by using the improved advanced propagation model is as follows: based on the radio wave propagation frequency and the 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 wave propagation loss determined by the improved advanced propagation model in the evaporation duct environment is equal to the wave propagation loss determined by the tropospheric scattering model in the evaporation duct environment, the boundary propagation length is determined.

[0011] 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 the condition of line of sight at sea is:

[0012] in, is the limit 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.

[0013] Optionally, the expression of the advanced propagation model is:

[0014] in, is the frequency of radio waves when they propagate in an evaporative waveguide environment, It is the spatial field quantity of the wave field when the radio wave propagates in the evaporation waveguide environment.

[0015] 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: The narrow-angle parabolic equation is selected as part of the space field quantity, where the expression of the narrow-angle parabolic equation is:

[0016] 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 evaporative 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.

[0017] Optionally, the expression for calculating the radio wave propagation loss in the tropospheric scattering environment using the tropospheric scattering model is:

[0018] 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

[0019] Optionally, based on the maximum free space propagation loss and the minimum evaporation wave electric wave propagation attenuation, the expression of the electric wave propagation attenuation difference is obtained as follows:

[0020] in, is the difference in radio wave propagation attenuation, is the minimum evaporation wave conductive wave propagation attenuation, is the maximum free space propagation loss.

[0021] Beneficial effects of the present invention: The present invention proposes a radio wave propagation model of 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 according to the radio wave frequency, the heights of transmitting and receiving antennas and the height of the evaporation duct, and predict the radio wave propagation attenuation. Affected by the complex weather at sea, the radio wave propagation mode under over-the-horizon conditions is constantly switched between the evaporation duct and the 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 model proposed in the present invention and the measured path loss is smaller, and the model can be used to predict the radio wave propagation attenuation of the hybrid mode of evaporation duct and tropospheric scattering under over-the-horizon conditions at sea. The prediction result can be further combined with the parameters such as the transmitting and receiving antenna gain, the transmitting power and the receiving sensitivity of the over-the-horizon communication system at sea to make an accurate prediction of its maximum communication distance. In addition, the prediction result can be used to guide the adjustment of the transmitting power and the transmitting and receiving antenna heights of the over-the-horizon communication system at sea. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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: Figure 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 2 is a comparison diagram of calculation results under the model proposed in the embodiment of the present invention and the APM model (pure waveguide); Figure 3 It is a schematic diagram of the path loss predicted for the pure waveguide mode of the APM model on links of different lengths in the X-band and C-band according to the model proposed in the embodiment of the present invention; Figure 4 It is a distribution diagram of 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

[0023] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only embodiments of a part of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0024] It should be noted that the terms "first", "second", etc. in the specification 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 can be 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 that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0025] Example 1 According to an embodiment of the present invention, a radio wave propagation model of a hybrid mode of evaporation waveguide and tropospheric scattering under over-the-horizon conditions is provided. It should be noted that the steps shown in the flowchart 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 flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0026] Figure 1 is a flow chart of a radio wave propagation model of a hybrid mode of evaporation waveguide and tropospheric scattering under over-the-horizon conditions according to an embodiment of the present invention. Figure 1 As shown, the model may include the following steps: Step S101, 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.

[0027] 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 limit distance of radio wave propagation under the line-of-sight condition at sea.

[0028] 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 condition of line of sight at sea, the expression of the model when radio waves propagate at sea is:

[0029] in, is the frequency when the radio wave propagates 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.

[0030] 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 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.

[0031] Step S103, when the propagation distance of radio waves at sea is greater than the limit distance of radio wave propagation under the condition of line of sight at sea, the expression of the model when radio waves propagate in a tropospheric scattering environment or in an evaporative waveguide environment is:

[0032] 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 the propagation distance of the radio wave at sea is The radio wave propagation loss determined using the tropospheric scatter model is 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 evaporative 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 evaporative waveguide or a tropospheric scattering environment; When the propagation distance of radio waves on the sea is The process of determining the radio wave propagation loss determined by using the improved advanced propagation model is as follows: based on the radio wave propagation frequency and the 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 wave propagation loss determined by the improved advanced propagation model in the evaporation duct environment is equal to the wave propagation loss determined by the tropospheric scattering model in the evaporation duct environment, the boundary propagation length is determined.

[0033] 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 condition of line of sight at sea, the tropospheric scattering model is used to calculate the radio wave propagation loss in the tropospheric scattering environment, wherein the evaporation duct environment and the tropospheric scattering environment are both at the evaporation duct height, and the evaporation duct height is solved by logging into the climate system of the weather forecast center in area A, downloading the meteorological data at the required time and then analyzing the meteorological data, and extracting 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 at 2m above the sea surface and wind speed component at 10m above the sea surface; input the extracted meteorological data at the point closest to the offshore test link into the evaporation duct height prediction model, and calculate the atmospheric corrected refractive index profile within the range of 0-50 meters at the point closest to the offshore test link, 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 substitute the radio wave propagation frequency and radio wave propagation distance at the extreme distance of radio wave propagation 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, is the free space propagation loss at the extreme distance of radio wave propagation. The advanced propagation model is translated by the radio wave propagation attenuation difference to obtain an improved advanced propagation model. The distance of radio wave propagation is substituted into the translated advanced propagation model to obtain the radio wave propagation loss in the evaporative waveguide environment. The distance of radio wave propagation is substituted into the translated advanced propagation model to obtain the formula of radio wave propagation loss in the evaporative waveguide environment: Will and Solve the problem jointly, that is = , and obtain the boundary propagation length. According to the boundary propagation length, it is determined whether the radio wave propagates in the evaporative waveguide environment or the radio wave propagates in the tropospheric scattering environment. Figure 2 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 of the radio wave propagation at sea and and The relationship between them is used to obtain models of different ranges of radio waves propagating at sea.

[0034] The above method of this embodiment is further introduced below.

[0035] As an optional implementation manner, in step S101, based on the height of the transmitting antenna and the height of the receiving antenna, an expression for determining the limit distance of radio wave propagation under the line-of-sight condition at sea is:

[0036] in, is the limit 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.

[0037] In this embodiment, the height of the transmitting antenna and the height of the receiving antenna are calculated to obtain the limit distance of radio wave propagation under the line-of-sight condition at sea.

[0038] As an optional implementation manner, in step S103, the expression of the high-level propagation model is:

[0039] in, is the frequency of radio waves when they propagate in an evaporative waveguide environment, It is the spatial field quantity of the wave field when the radio wave propagates in the evaporation waveguide environment.

[0040] As an optional implementation manner, 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: The narrow-angle parabolic equation is selected as part of the space field quantity, where the expression of the narrow-angle parabolic equation is:

[0041] 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 evaporative 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.

[0042] 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.

[0043] 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. The narrow-angle parabolic equation is solved by discrete matching Fourier method, and the complex amplitude of the wave field is obtained recursively. .

[0044] As an optional implementation manner, in step S103, the expression for calculating the radio wave propagation loss of the radio wave in the tropospheric scattering environment using the tropospheric scattering model is:

[0045] 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

[0046] As an optional implementation manner, 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:

[0047] in, is the difference in radio wave propagation attenuation, is the minimum evaporation wave conductive wave propagation attenuation, is the maximum free space propagation loss.

[0048] Experimental part: 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 over-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.

[0049] The X-band measured path loss data obtained on three cross-sea test links from A to B, C to B, and D to B in a time period (half a month) and the C-band measured path loss data obtained on the E to F link on P day were used to verify the accuracy of the model proposed in the present invention. Among them, the link lengths of A to B, C to B, and D to B are 248km, 188km, and 150km respectively, and the link length of E to F is 146.7km. The obtained evaporation duct height value and radio wave propagation parameters are input into the model proposed in the present invention and the pure duct mode 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 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 the present 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 It can be seen from (a) to (c) that the calculation results of the model proposed in the present invention are closer to the measured path loss than the pure waveguide mode of the APM model in the X-band.

[0050] The absolute error between the model proposed in the present invention and the APM model in pure waveguide mode and the measured path loss is calculated. The path loss data collected on the 188km test link from A to B on R day is selected as the measured path loss.

[0051] Figure 4It 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. Among them, the number of measured path loss samples is 56543. 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, accounting for 61.21% and 91.92% respectively, while the absolute errors between the APM model in pure waveguide mode and the measured path loss do not exceed 5dB and 10dB, accounting for only 18.55% and 47.18%. Therefore, the absolute error of the path loss predicted by the model proposed in the present invention is smaller than that of the APM model in pure waveguide mode.

[0052] In the embodiment of the present invention, when the radio wave propagates under the line-of-sight condition at sea, the limit distance of radio wave propagation under the line-of-sight condition at sea is determined based on the height of the transmitting antenna and the height of the receiving antenna; when the propagation distance of the radio wave 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 when the radio wave propagates at sea is:

[0053] in, is the frequency when the radio wave propagates 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.

[0054] When the propagation distance of radio waves at sea is greater than the limit distance of radio wave propagation under the condition of line of sight at sea, the expression of the model when radio waves propagate in the tropospheric scattering environment or in the evaporative duct environment is:

[0055] 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 the propagation distance of the radio wave at sea is The radio wave propagation loss determined using the tropospheric scatter model is 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 evaporative 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 evaporative waveguide or 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 the 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 by 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 When the wave propagation loss determined by the improved advanced propagation model in the evaporation duct environment is equal to the wave propagation loss determined by the tropospheric scattering model in the evaporation duct environment, the boundary propagation length is determined, which solves the technical problem that the existing advanced propagation model cannot determine whether the current wave propagation mode is evaporation duct or tropospheric scattering according to the wave frequency and the height of the transmitting and receiving antennas when the wave propagation distance is given, thereby causing a certain deviation between the calculated result and the measured path loss. The technical effect of automatically identifying the current wave propagation mode as evaporation duct or tropospheric scattering according to the wave frequency, the height of the transmitting and receiving antennas and the evaporation duct height and accurately predicting the wave propagation attenuation is achieved.

[0056] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0057] In the above embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0058] 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 schematic. For example, the division of units can be a logical function division. There may be other division methods in actual implementation. For example, 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.

[0059] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed over multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

Claims

1. A radio wave propagation model of mixed mode of evaporative waveguide and tropospheric scattering under over-the-horizon conditions, characterized in that: include: 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 the condition of line of sight at sea, the expression of the model when radio waves propagate at sea is: in, is the frequency when the radio wave propagates 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 limit 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 condition of line of sight at sea, the expression of the model when radio waves propagate in the tropospheric scattering environment or in the 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 the propagation distance of the radio wave at sea is The radio wave propagation loss determined using the tropospheric scatter model is 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 evaporative 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 evaporative waveguide or a tropospheric scattering environment; When the propagation distance of radio waves on the sea is The process of determining the radio wave propagation loss determined by using the improved advanced propagation model is as follows: based on the radio wave propagation frequency and the 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 wave propagation loss determined by the improved advanced propagation model in the evaporation duct environment is equal to the 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 limit 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 evaporative 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 space 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 evaporative 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 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.

6. The model according to claim 1, characterized in that The expression for the difference in radio 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, is the minimum evaporation wave conductive wave propagation attenuation, is the maximum free space propagation loss.

7. 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.

8. 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.

9. A computer program product, characterized in that The invention comprises computer executable instructions, which are used to implement the model of claim 1 when being executed.

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