Calculation method of multipath delay in evaporation waveguide and scattering channel at different elevation angles

Abstract

The present invention discloses a method for calculating the multipath delay of an evaporation waveguide and a scattering channel at different elevation angles, comprising: determining the propagation path length in the evaporation waveguide channel based on the radius of the earth and the central angle corresponding to the arc length of the propagation path in the evaporation waveguide channel; obtaining the propagation path length of the radio wave in the tropospheric scattering channel based on the angle between the line connecting the transmitting antenna and the scatterer and the center of the circle, the elevation angles of the transmitting and receiving antennas, and the angle between the line connecting the radio wave receiving antenna and the scatterer and the center of the circle, and the elevation angles of the transmitting and receiving antennas; then calculating the multipath delay of the hybrid channel; setting the symbol interval of the radio wave communication based on the multipath delay to adapt the radio wave communication to the switching of the communication mode. The calculation expression for the multipath delay of the hybrid channel obtained in the present application can quickly calculate the multipath delay of the evaporation waveguide and tropospheric scattering hybrid channel; setting the symbol interval of the radio wave communication based on the multipath delay to avoid inter-symbol interference and reduce the bit error rate.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a method for calculating multipath delays of evaporation waveguides and scattering channels at different elevation angles. Background Art

[0002] Satellites can enable beyond-line-of-sight (BLOS) communication between shore-based systems. However, this approach suffers from disadvantages such as low communication speeds, high costs, and poor anti-interference capabilities. Besides satellite communications, evaporation ducting and tropospheric scattering are two primary methods for achieving high-speed, beyond-line-of-sight (BLOS) communication at sea. The mechanism of evaporation ducting is as follows: as water vapor evaporates and diffuses from the sea surface, the atmospheric humidity above the sea surface decreases sharply with increasing altitude, resulting in a negative gradient in the atmospheric refractive index. This causes radio waves to be refracted downward along the evaporation ducting path. When the refractive curvature is greater than the curvature of the sea surface, the waves are trapped in the evaporation ducting environment, creating a unique bent-pipe effect at sea, ultimately enabling transoceanic, beyond-line-of-sight (BLOS) communication over hundreds of kilometers. Therefore, using evaporation ducting for beyond-line-of-sight (BLOS) communication at sea offers advantages such as long transmission distances, low path loss, high data rates, and strong anti-interference capabilities.

[0003] Tropospheric scattering is another means of propagating radio waves beyond line of sight (BLOS) at sea. The troposphere is home to numerous scatterers, such as vortices, clouds, warm fronts, and cold fronts. These scatterers refract and re-radiate radio waves in frequency bands above very high frequencies, particularly the C-band (4GHz-8GHz), X-band (8GHz-12GHz), and Ku-band (12GHz-18GHz), enabling BLOOS propagation. Tropospheric scatter communications have a range of at least 150 km and up to thousands of kilometers, with high transmission rates. Tropospheric scatter communications are widely used in military and emergency communications due to their numerous advantages, including resistance to nuclear explosions, immunity to solar and geomagnetic storms, and excellent confidentiality and mobility.

[0004] However, offshore evaporation ducts and tropospheric scatter channels are inextricably linked. When the evaporation duct is high and the communication distance is short (for example, the evaporation duct height is greater than 12 meters and the communication distance does not exceed 200 km), most radio waves will automatically propagate through the evaporation duct channel beyond the horizon. When the evaporation duct height is low and the communication distance is long (for example, the evaporation duct height is less than 12 meters and the communication distance exceeds 200 km), most radio waves will automatically propagate through the tropospheric scatter channel beyond the horizon. Therefore, although the formation mechanisms of evaporation ducts and tropospheric scatter are different, radio waves will automatically choose a propagation path based on the evaporation duct height.

[0005] While the majority of radio waves propagate through the evaporative waveguide, a small portion leaks out of the waveguide layer and propagates through the troposcatter channel. Similarly, while the majority of radio waves propagate through the troposcatter channel, a small portion is trapped in the waveguide layer and propagates through the evaporative waveguide. Therefore, during over-the-horizon communication at sea, the signal reaching the receiver is a superposition of signals from both the evaporative waveguide and troposcatter channels. Due to the different lengths of the evaporative waveguide and troposcatter channels, the time it takes for radio waves to reach the receiver differs, resulting in multipath delay. This leads to overlap and interference between adjacent symbols, increasing the probability of inter-symbol crosstalk (ISI), reducing the quality of the received signal, and ultimately increasing the bit error rate (BER).

[0006] Current techniques for calculating multipath delays in maritime BOHI communications only consider a single channel, either the evaporation duct or tropospheric scatter. However, extensive maritime BOHI communication test data demonstrates that the evaporation duct height varies significantly throughout the day, causing BOHI communication to switch between the evaporation duct and tropospheric scatter modes one or more times. When the communication distance is short and the evaporation duct height is high, the maritime BOHI communication system utilizes the evaporation duct. In this case, the transmit antenna elevation angle needs to be set near 0° to trap more radio wave energy in the evaporation duct layer. When the communication distance is long or the evaporation duct height is low, the maritime BOHI communication system utilizes tropospheric scatter. In this case, the transmit antenna elevation angle is generally set between 0° and 5°. Simultaneously, the receive antenna elevation angle also needs to be adjusted to ensure optimal BOHI communication.

[0007] Different transmitting and receiving antenna elevation angles result in different propagation path lengths for radio waves in the troposcatter channel, which in turn leads to different propagation path length differences between the radio waves passing through the evaporation duct and the troposcatter channel. In particular, before and after the communication mode switches between the evaporation duct and the troposcatter, the signal strengths reaching the receiving end after passing through the evaporation duct and the troposcatter channel are comparable, causing severe inter-symbol interference. As a result, the multipath delay calculated by considering only the evaporation duct or the troposcatter channel cannot adapt well to the changes in the offshore evaporation duct environment and cannot further guide the waveform design of the offshore beyond-horizon communication system.

[0008] Therefore, it is necessary to improve one or more problems existing in the above-mentioned related technical solutions.

[0009] It should be noted that this section is intended to provide background or context for the technical solutions of the present disclosure stated in the claims. The description herein is not admitted to be prior art by virtue of being included in this section. Summary of the Invention

[0010] The object of the present invention is to provide a method for calculating the multipath delay of an evaporation waveguide and a scattering channel at different elevation angles, thereby overcoming one or more problems caused by the limitations and defects of related technologies to at least a certain extent.

[0011] The present invention provides a method for calculating multipath delay of an evaporation waveguide and a scattering channel at different elevation angles, the method comprising:

[0012] When radio wave communication is performed through an evaporation waveguide channel, the propagation path length of the radio wave in the evaporation waveguide channel is determined based on the radius of the earth and the central angle corresponding to the arc length of the radio wave propagation path in the evaporation waveguide channel;

[0013] When radio wave communication is performed via a tropospheric scatter channel, the distance between the transmitting antenna and the scatterer is determined based on the angles between the lines connecting the transmitting antenna and the scatterer and the center of the circle, the transmitting antenna elevation angle, and the receiving antenna elevation angle. The distance between the receiving antenna and the scatterer is determined based on the angles between the lines connecting the receiving antenna and the scatterer and the center of the circle, the transmitting antenna elevation angle, and the receiving antenna elevation angle. The center of the circle is the center of the Earth.

[0014] The distance between the transmitting antenna and the scatterer and the distance between the receiving antenna and the scatterer are summed to obtain the propagation path length of the radio wave in the troposcatter channel;

[0015] Determining a multipath delay difference between the tropospheric scatter channel and the evaporation duct channel based on the elevation angle of the transmitting antenna, the elevation angle of the receiving antenna, the propagation path length of the radio wave in the evaporation duct channel, the propagation path length of the radio wave in the tropospheric scatter channel, and the propagation speed of the radio wave; and obtaining the multipath delay of the evaporation duct and tropospheric scatter mixed channel at different elevation angles based on the multipath delay difference and the channel delay of the tropospheric scatter channel;

[0016] The symbol interval of the radio wave communication is set according to the multipath delay, so that the radio wave communication can adapt to the switching of the communication mode.

[0017] In the present invention, the expression for the propagation path length of the radio wave in the evaporation waveguide channel is as follows:

[0018]

[0019] in, is the propagation path length of the radio wave in the evaporation waveguide channel, is the central angle of the arc length corresponding to the propagation path of the radio wave in the evaporation waveguide channel, is the radius of the Earth.

[0020] In the present invention, the distance between the transmitting antenna and the scatterer is expressed as follows:

[0021]

[0022] in, is the distance between the transmitting antenna and the scatterer, is the transmitting antenna elevation angle, is the receiving antenna elevation angle.

[0023] In the present invention, the distance between the receiving antenna and the scatterer is expressed as follows:

[0024]

[0025] in, is the distance between the receiving antenna and the scatterer.

[0026] In the present invention, the expression for the propagation path length of radio waves in the tropospheric scatter channel is as follows:

[0027]

[0028] in, is the propagation path length of radio waves in the tropospheric scatter channel.

[0029] In the present invention, the expression of the multipath delay difference between the tropospheric scatter channel and the evaporation waveguide channel is as follows:

[0030]

[0031] in, is the multipath delay difference between the evaporation duct channel and the tropospheric scatter channel, c is the propagation speed of radio waves.

[0032] In the present invention, the channel delay of the tropospheric scatter channel is , the expression of the multipath delay of the evaporation waveguide and tropospheric scatter hybrid channel is as follows:

[0033]

[0034] in, is the multipath delay of the evaporation waveguide and tropospheric scatter hybrid channel.

[0035] In the present invention, the expression of the channel delay of the tropospheric scatter channel is as follows:

[0036]

[0037] in, is the radio wave communication distance, is the operating frequency of radio wave communication, D is the antenna aperture diameter, is the equivalent radius of the Earth, .

[0038] The technical solution provided by the present invention can have the following beneficial effects:

[0039] The present invention obtains a calculation expression for the multipath delay of a hybrid channel of evaporation duct and tropospheric scatter at different elevation angles based on the elevation angle of a transmitting antenna, the elevation angle of a receiving antenna, the propagation path length of radio waves in an evaporation duct channel and a tropospheric scatter channel, the propagation speed of radio waves, and the channel delay of the tropospheric scatter channel. The multipath delay of the hybrid channel of evaporation duct and tropospheric scatter can be quickly calculated under offshore beyond-horizon conditions. The present invention then sets the symbol interval of radio wave communication according to the multipath delay, so that radio wave transmission can fully adapt to the frequent switching between evaporation duct and tropospheric scatter in offshore beyond-horizon communication mode and the situation where ships or small islands and reefs appear within the line of sight of the transmitting end of the offshore beyond-horizon communication system. The result of the multipath delay calculation can better match the hybrid channel of evaporation duct and tropospheric scatter, and can be used to guide the waveform design of the offshore beyond-horizon communication system. The present invention also avoids inter-symbol interference, reduces the bit error rate, and improves the performance of the offshore beyond-horizon communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification, are used to explain the principles of the present disclosure. Obviously, the drawings described below are only some embodiments of the present disclosure, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0041] Figure 1 This is a flow chart of a method for calculating multipath delays of an evaporation waveguide and a scattering channel at different elevation angles according to an embodiment of the present invention;

[0042] Figure 2 This is a scenario diagram of a method for calculating multipath delays of an evaporation waveguide and a scattering channel at different elevation angles according to an embodiment of the present invention;

[0043] Figure 3 The antenna aperture diameter is 2m, the operating frequency is 4.7GHz, and the transmitting antenna elevation angle is 0. , receiving antenna elevation angle 0 -5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay at ;

[0044] Figure 4 The antenna aperture diameter is 2m, the operating frequency is 4.7GHz, and the transmitting antenna elevation angle is 5 , receiving antenna elevation angle 0 -5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay at ;

[0045] Figure 5 The antenna aperture diameter is 4m, the operating frequency is 4.7GHz, and the transmitting antenna elevation angle is 0 according to the embodiment of the present invention. , receiving antenna elevation angle 0 -5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay at ;

[0046] Figure 6 The antenna aperture diameter is 4m, the operating frequency is 4.7GHz, and the transmitting antenna elevation angle is 5 , receiving antenna elevation angle 0 -5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay at ;

[0047] Figure 7 The antenna aperture diameter is 6m, the operating frequency is 4.7GHz, and the transmitting antenna elevation angle is 0 according to the embodiment of the present invention. , receiving antenna elevation angle 0 -5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay at ;

[0048] Figure 8 The antenna aperture diameter is 6m, the operating frequency is 4.7GHz, and the transmitting antenna elevation angle is 5 , receiving antenna elevation angle 0 -5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay at ;

[0049] Figure 9 The antenna aperture diameter is 2m, the operating frequency is 4.7GHz, 6.2GHz, 10GHz and 12GHz, and the transmitting antenna elevation angle is 2 、Receiving antenna elevation angle 1 , 3 and 5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay at ;

[0050] Figure 10 The antenna aperture diameter is 4m, the operating frequencies are 4.7GHz, 6.2GHz, 10GHz and 12GHz, and the transmitting antenna elevation angle is 2 、Receiving antenna elevation angle 1 , 3 and 5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay at ;

[0051] Figure 11 The antenna aperture diameter is 6m, the operating frequencies are 4.7GHz, 6.2GHz, 10GHz and 12GHz, and the transmit antenna elevation angle is 1 、Receiving antenna elevation angle 1 , 3 and 5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay at ;

[0052] Figure 12 The antenna aperture diameter is 6m, the operating frequencies are 4.7GHz, 6.2GHz, 10GHz and 12GHz, and the transmit antenna elevation angle is 3 、Receiving antenna elevation angle 1 , 3 and 5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay at ;

[0053] Figure 13 The antenna aperture diameter is 6m, the operating frequencies are 4.7GHz, 6.2GHz, 10GHz and 12GHz, and the transmit antenna elevation angle is 5 、Receiving antenna elevation angle 1 , 3 and 5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay. DETAILED DESCRIPTION

[0054] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be embodied in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0055] In addition, the accompanying drawings are merely schematic illustrations of embodiments of the present disclosure and are not necessarily drawn to scale. Like reference numerals in the figures represent like or similar parts, and thus repeated descriptions thereof will be omitted. Some of the blocks shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically separate entities.

[0056] This example implementation provides a method for calculating the multipath delay of the evaporation waveguide and scattering channel at different elevation angles. Please refer to Figure 1 The method may include: S101-S105. Specifically as follows:

[0057] S101 , when performing radio wave communication through an evaporation waveguide channel, determining the propagation path length of the radio wave in the evaporation waveguide channel according to the radius of the earth and the central angle corresponding to the arc length of the radio wave propagation path in the evaporation waveguide channel.

[0058] S102, when conducting radio wave communication through a tropospheric scatter channel, determining the distance between the transmitting antenna and the scatterer based on the angles between the lines connecting the radio wave transmitting antenna and the scatterer and the center of the circle, the transmitting antenna elevation angle, and the receiving antenna elevation angle; determining the distance between the receiving antenna and the scatterer based on the angles between the lines connecting the radio wave receiving antenna and the scatterer and the center of the circle, the transmitting antenna elevation angle, and the receiving antenna elevation angle; wherein the center of the circle refers to the center of the earth.

[0059] S103 , summing the distance between the transmitting antenna and the scatterer and the distance between the receiving antenna and the scatterer to obtain a propagation path length of the radio wave in the troposcatter channel.

[0060] S104: Determine the multipath delay difference between the troposcatter channel and the evaporation waveguide channel based on the elevation angle of the transmitting antenna, the elevation angle of the receiving antenna, the propagation path length of the radio wave in the evaporation waveguide channel, the propagation path length of the radio wave in the troposcatter channel, and the propagation speed of the radio wave. Determine the multipath delay difference between the evaporation waveguide channel and the troposcatter channel based on the multipath delay difference and the channel delay of the troposcatter channel. Obtain the multipath delay of the evaporation waveguide and troposcatter mixed channel at different elevation angles.

[0061] S105 , setting the symbol interval of the radio wave communication according to the multipath delay, so that the radio wave communication adapts to the switching of the communication mode.

[0062] In this embodiment, based on the elevation angle of the transmitting antenna, the elevation angle of the receiving antenna, the propagation path length of the radio wave in the evaporation duct channel and the troposcatter channel, the propagation speed of the radio wave, and the channel delay of the troposcatter channel, a calculation expression for the multipath delay of the evaporation duct and troposcatter mixed channel at different elevation angles is obtained. This allows for rapid calculation of the multipath delay of the evaporation duct and troposcatter mixed channel under maritime beyond-horizon conditions. Setting the symbol interval for radio wave communication based on the multipath delay fully adapts to the frequent switching between the evaporation duct and troposcatter modes in maritime beyond-horizon communication, as well as situations where ships or small islands and reefs block the line of sight of the transmitting end of the maritime beyond-horizon communication system. This allows the calculated multipath delay to better match the evaporation duct and troposcatter mixed channel, and can be used to guide the waveform design of the maritime beyond-horizon communication system. This also avoids inter-symbol interference, reduces the bit error rate, and improves the performance of the maritime beyond-horizon communication system.

[0063] The details of each step in the above embodiment are described below.

[0064] In S101, when shore-to-shore communication is performed through an evaporative waveguide channel, the propagation path length of the radio wave in the evaporative waveguide channel is determined based on the radius of the earth and the central angle corresponding to the arc length of the radio wave propagation path in the evaporative waveguide channel.

[0065] Please refer to Figure 2 , Figure 2 This is a scenario diagram of the multipath delay calculation method for the evaporation waveguide and scattering channel at different elevation angles. Since the evaporation waveguide height varies from a few meters to 20 to 30 meters, and the height of the transmitting and receiving antennas of the shore-based offshore over-the-horizon communication system is much smaller than the radius of the earth, the evaporation waveguide height and the height of the transmitting and receiving antennas are ignored when calculating the propagation path length of the radio wave in the evaporation waveguide channel and the propagation path length of the radio wave in the tropospheric scattering channel. If the shore-to-shore communication is carried out through the evaporation waveguide channel, that is, Figure 2 The distance on the spherical surface with the center of the earth as the center and the radius of the earth as the radius, that is, the arc The length of the arc , in the following, The expression for the propagation path length of the radio wave in the evaporation waveguide channel is as follows:

[0066] (1)

[0067] in, is the propagation path length of the radio wave in the evaporation waveguide channel, is the central angle of the arc length corresponding to the propagation path of the radio wave in the evaporation waveguide channel, is the radius of the Earth.

[0068] In S102, please refer to Figure 2 When shore-to-shore bases communicate via troposcatter channels, that is, according to Figure 2 in 、 The path propagates, and They respectively represent the distance between the transmitting end (transmitting antenna) of the shore-based maritime beyond-horizon communication system and the scatterer, and the distance between the scatterer and the receiving end (receiving antenna) of the shore-based maritime beyond-horizon communication system.

[0069] The distance between the transmitting antenna and the scatterer is determined based on the angles between the lines connecting the radio wave transmitting antenna and the scatterer and the center of the circle, the elevation angle of the transmitting antenna, and the elevation angle of the receiving antenna. Similarly, the distance between the receiving antenna and the scatterer can also be determined.

[0070] The distance between the transmitting antenna and the scatterer is expressed as follows:

[0071] (2)

[0072] in, is the distance between the transmitting antenna and the scatterer, is the transmitting antenna elevation angle, is the receiving antenna elevation angle.

[0073] The distance between the receiving antenna and the scatterer is expressed as follows:

[0074] (3)

[0075] in, is the distance between the receiving antenna and the scatterer.

[0076] In S103, the above two distances are summed to obtain the propagation path length of the radio wave in the tropospheric scatter channel.

[0077] The expression for the propagation path length of radio waves in the tropospheric scatter channel is as follows:

[0078] (4)

[0079] in, is the propagation path length of radio waves in the tropospheric scatter channel, .

[0080] Please refer to Figure 2 , isosceles Pass point C middle The perpendicular line on the edge, intersecting At point E, for The angle bisector of , . According to the sine theorem, we can get Therefore, the distance between the transmitter of the shore-based over-the-horizon communication system and the scatterer is:

[0081] (5)

[0082] Similarly, the distance between the receiving end of the shore-based over-the-horizon communication system and the scatterer can be obtained:

[0083] (6)

[0084] In the quadrilateral In , there is the following relationship:

[0085] (7)

[0086] in, is the angle between the line connecting the transmitting antenna and the center of the earth and the line connecting the transmitting antenna and the scatterer, It is the angle between the line connecting the receiving antenna and the center of the earth and the line connecting the receiving antenna and the scatterer.

[0087] The above relationship can be used to calculate the propagation path length of radio waves in the tropospheric scatter channel: d .

[0088] In S104, the multipath delay difference between the troposcatter channel and the evaporation duct channel is determined based on the elevation angle of the transmitting antenna, the elevation angle of the receiving antenna, the propagation path length of the radio wave in the evaporation duct channel, the propagation path length of the radio wave in the troposcatter channel, and the propagation speed of the radio wave. The expression for the multipath delay difference between the troposcatter channel and the evaporation duct channel is as follows:

[0089] (8)

[0090] in, is the multipath delay difference between the evaporation duct channel and the tropospheric scatter channel, c is the propagation speed of radio waves.

[0091] The delay of the troposcatter channel itself is as follows:

[0092] (9)

[0093] in, is the radio wave communication distance, is the operating frequency of radio wave communication, D is the antenna aperture diameter, is the equivalent radius of the Earth.

[0094] As an excellent channel for over-the-horizon communications at sea, the evaporation duct has a delay on the order of nanoseconds. Therefore, when analyzing the multipath delay of the evaporation duct and troposcatter hybrid channel, the delay of the evaporation duct channel itself is ignored. When analyzing the multipath delay of the hybrid channel, it is necessary to consider both the delay of the troposcatter channel itself and the multipath delay difference between the evaporation duct channel and the troposcatter channel. The maximum of the two is taken as the multipath delay of the evaporation duct and troposcatter hybrid channel, which is expressed as follows:

[0095] (10)

[0096] In addition, the height from the sea surface when the radio waves are scattered can be h Make confirmation.

[0097] The height from the sea surface when the radio waves are scattered is:

[0098] (11)

[0099] The distance between the scatterer and the center of the earth can be obtained from the cosine theorem of trigonometric functions:

[0100] (12)

[0101] Substituting equation (12) into equation (11), we can obtain the height from the sea surface when the radio wave is scattered as equation (13) or equation (14):

[0102] (13)

[0103] (14)

[0104] The following experiment was conducted using the calculation method of this application, and the experimental results are as follows: Figures 3 to 13 shown.

[0105] When the antenna aperture diameter of the shore-based offshore over-the-horizon communication system is 2m, the typical C-band frequency of 4.7GHz is selected, and the elevation angle of the transmitting antenna of the offshore over-the-horizon communication system is set to 0. , while the receiving antenna elevation angle is 0 -5 The calculation results of formula (10) show that when the receiving antenna elevation angle is 0 -5 When the multipath delay of the evaporation waveguide and tropospheric scattering mixed channel is the same as the scattering channel delay. Similarly, when the antenna aperture diameter is changed from 2m, 4m and 6m, and the transmitting antenna elevation angle is set to 0 and 5 . Figures 3 to 8Given different antenna aperture diameters and transmitting antenna elevation angles of 0 and 5 The receiving antenna elevation angle is 0 、1 、2、 3 , 4 and 5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay.

[0106] Figure 3 The antenna aperture diameter is 2m, the operating frequency is 4.7GHz, and the transmitting antenna elevation angle is 0. , receiving antenna elevation angle 0 -5 The comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay. Figure 3 It can be seen that under the above parameter conditions, the multipath delay of the evaporation duct and tropospheric scatter mixed channel is the same as the tropospheric scatter channel delay.

[0107] Figure 4 The antenna aperture diameter is 2m, the operating frequency is 4.7GHz, and the transmitting antenna elevation angle is 5 , receiving antenna elevation angle 0 -5 The comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay. Figure 4 It can be seen that at the same communication distance, the multipath delay of the evaporation waveguide and tropospheric scatter hybrid channel increases with the increase of the receiving antenna elevation angle; at the same receiving antenna elevation angle, the multipath delay of the hybrid channel increases with the increase of the communication distance. In particular, when the receiving antenna elevation angle is 0 When , the multipath delay of the mixed channel of evaporation duct and troposcatter is the same as that of the troposcatter channel. In addition, the multipath delay of the mixed channel is greater than that of the troposcatter channel.

[0108] Figure 5 The antenna aperture diameter is 4m, the operating frequency is 4.7GHz, and the transmitting antenna elevation angle is 0 according to the embodiment of the present invention. , receiving antenna elevation angle 0 -5 The comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay. Figure 5 It can be seen that when the receiving antenna elevation angle is 0 and 1 and the receiving antenna elevation angle is 2 When the communication distance is less than 420 km, the multipath delay of the hybrid channel of evaporation waveguide and troposcatter is the same as that of the troposcatter channel. In addition, the multipath delay of the hybrid channel is greater than that of the troposcatter channel.

[0109] Figure 6 The antenna aperture diameter is 4m, the operating frequency is 4.7GHz, and the transmitting antenna elevation angle is 5 , receiving antenna elevation angle 0 -5 The comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay. Figure 6 It can be seen that when the receiving antenna elevation angle is 0 -5 When , the multipath delay of the hybrid channel is greater than the delay of the tropospheric scatter channel.

[0110] Figure 7 The antenna aperture diameter is 6m, the operating frequency is 4.7GHz, and the transmitting antenna elevation angle is 0 according to the embodiment of the present invention. , receiving antenna elevation angle 0 -5 The comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay. Figure 7 It can be seen that when the receiving antenna elevation angle is 0 and the receiving antenna elevation angle is 1 When the communication distance is less than 400 km, the multipath delay of the hybrid channel of evaporation waveguide and troposcatter is the same as the delay of the troposcatter channel. In addition, the multipath delay of the hybrid channel is greater than the delay of the troposcatter channel.

[0111] Figure 8 The antenna aperture diameter is 6m, the operating frequency is 4.7GHz, and the transmitting antenna elevation angle is 5 , receiving antenna elevation angle 0 -5 The comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay. Figure 8 It can be seen that when the receiving antenna elevation angle is 0 -5 When , the multipath delay of the hybrid channel is greater than the delay of the tropospheric scatter channel.

[0112] Figure 9 The antenna according to the embodiment of the present invention has an aperture diameter of 2m and an operating frequency of 4.7GHz ( Figure 9 (a)), 6.2GHz ( Figure 9 (b)), 10GHz ( Figure 9 (c)) and 12GHz ( Figure 9In (d), the transmitting antenna elevation angle is 2 , receiving antenna elevation angle 1 , 3 and 5 The comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay. Figure 9 It can be seen that when the receiving antenna elevation angle is 1 When the multipath delay of the evaporation waveguide and tropospheric scattering mixed channel is the same as that of the tropospheric scattering channel at 4.7 GHz, the multipath delay of the evaporation waveguide and tropospheric scattering mixed channel is the same as that of the tropospheric scattering channel at 4.7 GHz. However, at 6.2 GHz, 10 GHz and 12 GHz, the receiving antenna elevation angle is 1 , 3 and 5 The multipath delay of the down-mixing channel will be greater than that of the tropospheric scattering channel. Therefore, the multipath delay of the evaporation duct and the tropospheric scattering mixing channel needs to be considered comprehensively when calculating the multipath delay.

[0113] Figure 10 The antenna aperture diameter is 4m and the operating frequency is 4.7GHz according to the embodiment of the present invention. Figure 10 (a)), 6.2GHz ( Figure 10 (b)), 10GHz ( Figure 10 (c)) and 12GHz ( Figure 10 (d)), transmitting antenna elevation angle 2 、Receiving antenna elevation angle 1 , 3 and 5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay.

[0114] Figure 11 The antenna aperture diameter is 6m and the operating frequency is 4.7GHz according to the embodiment of the present invention. Figure 11 (a)), 6.2GHz ( Figure 11 (b)), 10GHz ( Figure 11 (c)) and 12GHz ( Figure 11 (d)), transmitting antenna elevation angle 1 、Receiving antenna elevation angle 1 , 3 and 5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay.

[0115] Figure 12 The antenna aperture diameter is 6m and the operating frequency is 4.7GHz according to the embodiment of the present invention. Figure 12 (a)), 6.2GHz ( Figure 12 (b)), 10GHz ( Figure 12(c)) and 12GHz ( Figure 12 (d)), transmitting antenna elevation angle 3 、Receiving antenna elevation angle 1 , 3 and 5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay.

[0116] Figure 13 The antenna aperture diameter is 6m and the operating frequency is 4.7GHz according to the embodiment of the present invention. Figure 13 (a)), 6.2GHz ( Figure 13 (b)), 10GHz ( Figure 13 (c)) and 12GHz ( Figure 13 (d)), transmitting antenna elevation angle 5 、Receiving antenna elevation angle 1 , 3 and 5 Comparison of the multipath delay of the evaporation waveguide and tropospheric scatter mixed channel and the tropospheric scatter channel delay.

[0117] from Figure 10-13 It can be seen that at the four frequencies of 4.7GHz, 6.2GHz, 10GHz and 12GHz, the receiving antenna elevation angle is 1 , 3 The hybrid channel multipath delay is greater than the tropospheric scatter channel delay at 0 and 5. Therefore, the multipath delay of the evaporation duct and tropospheric scatter hybrid channels must be considered when calculating the multipath delay. In particular, the multipath delay of the evaporation duct and tropospheric scatter hybrid channels increases with increasing antenna aperture diameter and transmit antenna elevation angle.

[0118] In an embodiment of the present invention, when the elevation angles of the transmitting and receiving antennas of the maritime beyond-horizon communication system are changed, the propagation path length of the radio wave in the evaporative waveguide channel remains unchanged, but the propagation path length in the troposcatter channel will change. This is because when the elevation angle of the transmitting antenna is changed, the distance between the transmitting end of the shore-based beyond-horizon communication system and the scatterer changes, causing the receiving end of the shore-based beyond-horizon communication system to also need to adjust the elevation angle of the receiving antenna to ensure that the beyond-horizon communication effect is optimized, thereby causing the path length of the radio wave propagation in the troposcatter channel to change.

[0119] The multipath delay calculation method proposed in this invention can be used to guide the waveform design of the maritime over-the-horizon communication system. When designing the maritime over-the-horizon communication system, in order to avoid inter-symbol interference, the symbol interval Must be greater than the multipath delay of the evaporation duct and tropospheric scatter mixed channel Therefore, the symbol interval is set to 1.5-2 times the multipath delay of the evaporation waveguide and tropospheric scattering mixed channel, reserving enough time for the channel so that the energy of the previous symbol decays to a negligible level, leaving sufficient symbol interval to better adapt to the frequent switching between the evaporation waveguide and tropospheric scattering communication modes and the obstruction of the line of sight of the transmitting end of the maritime beyond-horizon communication system by ships or small islands and reefs, thereby reducing inter-symbol interference and the bit error rate of the maritime beyond-horizon communication system, and ultimately achieving the improvement of the performance of the maritime beyond-horizon communication system.

[0120] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. The method for calculating the multipath delay of the evaporation waveguide and scattering channel at different elevation angles is characterized by: The method comprises: When radio wave communication is performed through an evaporation waveguide channel, the propagation path length of the radio wave in the evaporation waveguide channel is determined based on the radius of the earth and the central angle corresponding to the arc length of the radio wave propagation path in the evaporation waveguide channel; When radio wave communication is performed via a tropospheric scatter channel, the distance between the transmitting antenna and the scatterer is determined based on the angles between the lines connecting the transmitting antenna and the scatterer and the center of the circle, the transmitting antenna elevation angle, and the receiving antenna elevation angle. The distance between the receiving antenna and the scatterer is determined based on the angles between the lines connecting the receiving antenna and the scatterer and the center of the circle, the transmitting antenna elevation angle, and the receiving antenna elevation angle. The center of the circle is the center of the Earth. The distance between the transmitting antenna and the scatterer and the distance between the receiving antenna and the scatterer are summed to obtain the propagation path length of the radio wave in the troposcatter channel; Determining a multipath delay difference between the tropospheric scatter channel and the evaporation duct channel based on the elevation angle of the transmitting antenna, the elevation angle of the receiving antenna, the propagation path length of the radio wave in the evaporation duct channel, the propagation path length of the radio wave in the tropospheric scatter channel, and the propagation speed of the radio wave; and obtaining the multipath delay of the evaporation duct and tropospheric scatter mixed channel at different elevation angles based on the multipath delay difference and the channel delay of the tropospheric scatter channel; The symbol interval of the radio wave communication is set according to the multipath delay, so that the radio wave communication can adapt to the switching of the communication mode.

2. The method for calculating multipath delay of evaporation waveguide and scattering channel at different elevation angles according to claim 1, characterized in that: The expression for the propagation path length of the radio wave in the evaporation waveguide channel is as follows: in, is the propagation path length of the radio wave in the evaporation waveguide channel, is the central angle of the arc length corresponding to the propagation path of the radio wave in the evaporation waveguide channel, is the radius of the Earth.

3. The method for calculating multipath delay of evaporation waveguide and scattering channel at different elevation angles according to claim 2, characterized in that: The distance between the transmitting antenna and the scatterer is expressed as follows: in, is the distance between the transmitting antenna and the scatterer, is the transmitting antenna elevation angle, is the receiving antenna elevation angle.

4. The method for calculating multipath delay of evaporation waveguide and scattering channel at different elevation angles according to claim 3 is characterized in that: The distance between the receiving antenna and the scatterer is expressed as follows: in, is the distance between the receiving antenna and the scatterer.

5. The method for calculating multipath delay of evaporation waveguide and scattering channel at different elevation angles according to claim 4, characterized in that: The expression for the propagation path length of radio waves in the tropospheric scatter channel is as follows: in, is the propagation path length of radio waves in the tropospheric scatter channel.

6. The method for calculating multipath delay of evaporation waveguide and scattering channel at different elevation angles according to claim 5, characterized in that: The expression of the multipath delay difference between the troposcatter channel and the evaporation waveguide channel is as follows: in, is the multipath delay difference between the evaporation duct channel and the tropospheric scatter channel, c is the propagation speed of radio waves.

7. The method for calculating multipath delay of evaporation waveguide and scattering channel at different elevation angles according to claim 6, characterized in that: The channel delay of the troposcatter channel is , the expression of the multipath delay of the evaporation waveguide and tropospheric scatter hybrid channel is as follows: in, is the multipath delay of the evaporation waveguide and tropospheric scatter hybrid channel.

8. The method for calculating multipath delay of evaporation waveguide and scattering channel at different elevation angles according to claim 7, characterized in that: The expression of the channel delay of the tropospheric scatter channel is as follows: in, is the radio wave communication distance, is the operating frequency of radio wave communication, D is the antenna aperture diameter, is the equivalent radius of the Earth, .

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