Calculation method of multipath delay in evaporation waveguide and scattering hybrid channel at different distances

Abstract

The present invention discloses a method for calculating the multipath delay of a hybrid evaporation waveguide and scattering channel at different distances. The method comprises: 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; determining the propagation path length in the troposcatter channel based on the positions of the scatterer, the transmitting antenna, and the receiving antenna; determining the multipath delay of the hybrid evaporation waveguide and troposcatter channel at different communication distances based on the propagation path length in the evaporation waveguide channel, the propagation path length in the troposcatter channel, the propagation speed of the radio wave, and the channel delay of the troposcatter channel; and setting the symbol interval of the radio wave communication based on the multipath delay to adapt the radio wave communication to switching of the communication mode. The present invention can quickly calculate the multipath delay of the hybrid evaporation waveguide and troposcatter channel; and 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 embodiments of the present disclosure relate to the field of wireless communication technology, and in particular to a method for calculating multipath delays in an evaporation waveguide and scattering hybrid channel at different distances. Background Art

[0002] Satellites can enable beyond-line-of-sight (BLOS) communications between mobile ships at sea and shore-based infrastructure. However, these communications suffer from low communication rates, 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) communications 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 of the atmospheric refractive index. This causes electromagnetic waves to bend downward along the propagation path of the evaporation duct. When the refractive curvature is greater than the curvature of the sea surface, the electromagnetic waves are trapped in the evaporation duct, creating a unique bent-pipe effect at sea, ultimately enabling transoceanic, beyond-line-of-sight (BLOS) transmission over hundreds of kilometers. Therefore, using evaporation ducting for beyond-line-of-sight (BLOS) communications 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 beyond-horizon (BLOS) propagation of electromagnetic waves 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 of electromagnetic waves in these frequency bands. 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 (e.g., evaporation duct height greater than 12 meters and communication distance less than 200 km), most electromagnetic waves automatically propagate beyond the horizon through the evaporation duct channel. When the evaporation duct is low and the communication distance is long (e.g., evaporation duct height less than 12 meters and communication distance greater than 200 km), most electromagnetic waves automatically propagate beyond the horizon through the tropospheric scatter channel. Therefore, although the formation mechanisms of evaporation ducts and tropospheric scatter are different, electromagnetic waves automatically select a propagation path based on the evaporation duct height.

[0005] While most electromagnetic waves propagate through the evaporative waveguide, a small portion leaks out of the waveguide layer and propagates through the troposcatter channel. Similarly, while most electromagnetic 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 that have traveled through both the evaporative waveguide and the troposcatter channels. Due to the different lengths of the evaporative waveguide and troposcatter channels, the communication signal arrives at the receiver at a different time, resulting in multipath delay. This further causes overlap and interference between adjacent symbols, increases the probability of inter-symbol crosstalk (ISI), degrades the quality of the received signal, and ultimately increases the bit error rate (BER).

[0006] Current methods for calculating multipath delay in maritime beyond-horizon communications only consider the impact of a single channel, either the evaporation duct or the tropospheric scatter. However, extensive data from maritime beyond-horizon communications experiments indicates that the evaporation duct height varies significantly throughout the day, causing the beyond-horizon communication mode to switch between the evaporation duct and the tropospheric scatter channel once or multiple times. During this communication mode switch, the signal strengths reaching the receiver via the evaporation duct and the tropospheric scatter channel are comparable, resulting in significant inter-symbol interference (ISI). This makes multipath delay calculations based solely on the evaporation duct or the tropospheric scatter channel inadequate for waveform design in maritime beyond-horizon communication systems.

[0007] Therefore, it is necessary to improve one or more problems existing in the above-mentioned related technical solutions.

[0008] 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

[0009] The purpose of the embodiments of the present disclosure is to provide a method for calculating the multipath delay of an evaporation waveguide and scattering hybrid channel at different distances, thereby overcoming one or more problems caused by the limitations and defects of related technologies to at least a certain extent.

[0010] The present disclosure provides a method for calculating multipath delay in a hybrid channel of an evaporation waveguide and scattering at different distances, including:

[0011] 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, wherein the center of the circle corresponding to the central angle is the center of the earth;

[0012] When radio wave communication is carried out through a troposcatter channel, the angle between the transmitting antenna and the receiving antenna and the sea level is 0°. The propagation path length of the radio wave in the troposcatter channel is determined based on the positions of the scatterer, the transmitting antenna, and the receiving antenna.

[0013] Obtaining a multipath delay difference between the tropospheric scatter channel and the evaporation waveguide channel based on the propagation path length of the radio wave in the evaporation waveguide channel, the propagation path length of the radio wave in the tropospheric scatter channel, and the propagation speed of the radio wave; and determining the multipath delay of the evaporation waveguide and tropospheric scatter hybrid channel at different communication distances based on the multipath delay difference and the channel delay of the tropospheric scatter channel;

[0014] 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.

[0015] In one embodiment of the present disclosure, the propagation path length of the radio wave in the evaporation waveguide channel is expressed as follows:

[0016]

[0017] 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 in the evaporation waveguide channel, is the radius of the Earth.

[0018] In one embodiment of the present disclosure, the propagation path length of radio waves in the tropospheric scatter channel is expressed as follows:

[0019]

[0020] in, is the propagation path length of radio waves in the tropospheric scatter channel.

[0021] In one embodiment of the present disclosure, the expression for the multipath delay difference between the tropospheric scatter channel and the evaporation waveguide channel is:

[0022]

[0023] in, is the multipath delay difference between the troposcatter channel and the evaporation duct channel, It is the propagation speed of radio waves in the beyond-horizon range at sea.

[0024] In one embodiment of the present disclosure, the channel delay of the tropospheric scatter channel is expressed as:

[0025]

[0026] in, is the radio wave communication distance, is the operating frequency of radio wave scattering communication, D is the antenna aperture diameter, is the equivalent radius of the Earth.

[0027] In one embodiment of the present disclosure, the expression for the multipath delay of the evaporation waveguide and tropospheric scatter hybrid channel at different communication distances is:

[0028]

[0029] in, is the multipath delay of the evaporation duct and tropospheric scatter hybrid channel.

[0030] The technical solutions provided by the embodiments of the present disclosure may have the following beneficial effects:

[0031] In the embodiment of the present disclosure, when the angles between the transmitting and receiving antennas and the sea level are both 0°, the propagation path length of the radio wave is determined based on the propagation speed of the radio wave, the scatterer, and the positions of the transmitting and receiving antennas. This allows for rapid calculation of the multipath delay of the evaporation duct and tropospheric scatter hybrid channel under over-the-horizon conditions at sea. The symbol interval of radio wave communication is set based on the multipath delay, enabling it to fully adapt to the frequent switching between the evaporation duct and tropospheric scatter in over-the-horizon communication modes at sea. This allows the calculated multipath delay to better match the hybrid channel of the evaporation duct and tropospheric scatter, and can be used to guide the waveform design of the over-the-horizon communication system at sea. Furthermore, the system avoids inter-symbol interference, reduces the bit error rate, and improves the performance of the over-the-horizon communication system at sea. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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.

[0033] Figure 1 is a flow chart of a method for calculating multipath delay of an evaporation waveguide and scattering hybrid channel at different distances according to an embodiment of the present invention;

[0034] Figure 2 1 is a scenario diagram of a method for calculating multipath delay of a hybrid channel of evaporation waveguide and scattering at different distances according to an embodiment of the present invention;

[0035] Figure 3 3. This is a comparison diagram of the multipath delay of the evaporation duct and tropospheric scatter hybrid channel and the scattering channel delay at four typical frequencies in the C and X bands when the antenna aperture diameter is 2m according to an embodiment of the present invention;

[0036] Figure 4 3. This is a comparison diagram of the multipath delay of the evaporation duct and tropospheric scatter hybrid channel and the scattering channel delay at four typical frequencies in the C and X bands when the antenna aperture diameter is 4m according to an embodiment of the present invention;

[0037] Figure 5 3. This is a comparison diagram of the multipath delay of the evaporation duct and tropospheric scatter hybrid channel and the scattering channel delay at four typical frequency points in the C and X bands when the antenna aperture diameter is 6m according to an embodiment of the present invention;

[0038] Figure 6 3. This is a schematic diagram of the multipath delay calculation results of the evaporation duct and tropospheric scatter hybrid channel at four typical frequencies in the C and X bands when the antenna aperture diameter is 2 m according to an embodiment of the present invention;

[0039] Figure 7 1 is a schematic diagram of the multipath delay calculation results of the evaporation duct and tropospheric scatter hybrid channel at four typical frequencies in the C and X bands with an antenna aperture diameter of 4m according to an embodiment of the present invention;

[0040] Figure 8 The figure is a schematic diagram of the multipath delay calculation results of the evaporation duct and tropospheric scatter hybrid channel at four typical frequencies of the C and X bands when the antenna aperture diameter is 6m according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] 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.

[0042] 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.

[0043] This example implementation provides a method for calculating the multipath delay of a mixed channel of evaporation waveguide and scattering at different distances. Please refer to Figure 1 The method may include: S101-S104. Specifically as follows:

[0044] S101. When radio wave communication is performed through an evaporation waveguide channel, the length of a propagation path 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 propagation path of the radio wave in the evaporation waveguide channel, wherein the center of the circle corresponding to the central angle is the center of the earth.

[0045] S102, when radio wave communication is performed through a tropospheric scatter channel, the angle between the transmitting antenna and the receiving antenna and the sea level is 0°, and the propagation path length of the radio wave in the tropospheric scatter channel is determined based on the positions of the scatterer, the transmitting antenna, and the receiving antenna.

[0046] S103: Calculate the multipath delay difference between the troposcatter channel and the evaporation waveguide channel based on 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 of the evaporation waveguide and troposcatter hybrid channel at different communication distances based on the multipath delay difference and the channel delay of the troposcatter channel.

[0047] S104: 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.

[0048] In this embodiment, when the angles between the transmitting and receiving antennas and the sea level are both 0°, the propagation path length of the radio wave is determined based on the propagation speed of the radio wave, the scatterer, and the positions of the transmitting and receiving antennas. This allows for rapid calculation of the multipath delay of the evaporation duct and tropospheric scatter hybrid channel under offshore beyond-horizon conditions. The symbol interval of radio wave communication is set based on the multipath delay to fully adapt to the frequent switching between the evaporation duct and tropospheric scatter in offshore beyond-horizon communication. This allows the calculated multipath delay to better match the evaporation duct and tropospheric scatter hybrid channel and can be used to guide the waveform design of the offshore beyond-horizon communication system. This avoids inter-symbol interference, reduces the bit error rate, and improves the performance of the offshore beyond-horizon communication system.

[0049] The details of each step in the above embodiment are described below.

[0050] In S101, when radio waves for communication between a ship at sea and a shore base are propagated through an evaporative waveguide channel, the length of the propagation path of the radio waves 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 propagation path of the radio waves in the evaporative waveguide channel, wherein the center of the circle corresponding to the central angle is the center of the earth.

[0051] Please refer to Figure 2 , Figure 2This is a scenario diagram of the method for calculating multipath delay of a hybrid evaporation waveguide and scattering channel at different distances according to an embodiment of the present invention. 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 scattering 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 evaporation waveguide path length and the scattering path length. If the radio waves for communication between a ship at sea and a shore base are propagated 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 length of arc BD, that is, the arc length , The central angle and the radius of the earth corresponding to the arc length of the propagation path of the communication signal in the evaporation waveguide channel can be used to calculate the The calculation result is as follows:

[0052] (1)

[0053] 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 in the evaporation waveguide channel, is the radius of the Earth, .

[0054] In S102, when radio waves used for communication between a ship at sea and a shore-based system propagate through a tropospheric scatter channel, the transmitting and receiving antennas are both at an angle of 0° to the sea level, i.e., tangent to each other. The intersection of the extended tangent lines is the location of the scatterer. Given the locations of the transmitting and receiving terminals of the maritime BOHIS communication system, the distance between the transmitting terminal (transmitting antenna) of the BOHIS communication system installed on the moving ship at sea and the scatterer, and the distance between the receiving terminal (receiving antenna) of the shore-based BOHIS communication system and the scatterer, can be summed to obtain the propagation path length of the communication signal in the tropospheric scatter channel.

[0055] It should be noted that the distance between the transmitting end of the communication system and the scatterer is equal to the distance between the receiving end of the communication system and the scatterer.

[0056] Please refer to Figure 2 , when the radio waves for communication between ships at sea and shore bases are propagated through the tropospheric scatter channel, that is, Figure 2The propagation path is based on the DA and AB paths in the figure. DA and AB represent the distance between the transmitter of the over-the-horizon communication system installed on the mobile ship at sea and the scatterer, and the distance between the receiver of the shore-based over-the-horizon communication system and the scatterer, respectively. Based on the distance between the transmitter of the over-the-horizon communication system installed on the mobile ship at sea and the scatterer, the distance between the receiver of the shore-based over-the-horizon communication system and the scatterer, and the half-angle of the central angle corresponding to the arc length of the communication signal propagation path in the evaporative waveguide channel, the tropospheric scattering propagation path length within the over-the-horizon range at sea is calculated. The expression is as follows:

[0057] (2)

[0058] in, is the propagation path length of radio waves in the tropospheric scatter channel.

[0059] In S103, based on the propagation path length of the communication signal in the evaporation duct channel, the propagation path length of the communication signal in the troposcatter channel, and the propagation speed of radio waves in the over-the-horizon range at sea, the expression for the multipath delay difference between the troposcatter channel and the evaporation duct channel is obtained as follows:

[0060] (3)

[0061] in, is the multipath delay difference between the troposcatter channel and the evaporation waveguide channel, It is the propagation speed of radio waves in the beyond-horizon range at sea.

[0062] The expression of the channel delay of the tropospheric scatter channel is:

[0063] (4)

[0064] in, is the radio wave communication distance, is the operating frequency of radio wave scattering communication, D is the antenna aperture diameter, is the equivalent radius of the Earth.

[0065] At the same time, the evaporation duct is an excellent channel for beyond-line-of-sight communications at sea, and its delay is on the order of nanoseconds. Therefore, when analyzing the multipath delay of the evaporation duct and tropospheric scatter hybrid channel, the delay of the evaporation duct channel itself is ignored.

[0066] The multipath delay of the hybrid channel of evaporation waveguide and troposcatter at different communication distances is a comprehensive consideration of the multipath delay difference between the troposcatter channel and the evaporation waveguide channel, as well as the channel delay of the troposcatter channel. The maximum value between the two is taken as the hybrid channel multipath delay, and its expression is as follows:

[0067] (5)

[0068] in, is the multipath delay of the evaporation duct and tropospheric scatter hybrid channel.

[0069] In addition, the height of the scatterer from the sea surface can be determined based on the radius of the earth, the central angle corresponding to the arc length of the radio wave propagation path in the evaporation waveguide channel, and the length of the radio wave propagation path in the evaporation waveguide channel. The height calculation process is as follows:

[0070] First, please refer to Figure 2 , the height of the scatterer from the sea surface h for:

[0071] (6)

[0072] Using trigonometric relationships, the distance between the scatterer and the center of the earth is:

[0073] (7)

[0074] Furthermore, the expression of the height of the scatterer from the sea surface is obtained as:

[0075] (8)

[0076] in, is the height of the scatterer from the sea surface, It is the half angle of the central angle of the arc length corresponding to the propagation path of the radio wave in the evaporation waveguide channel.

[0077] The following experiments were conducted using the calculation method of this application, and the experimental results are as follows: Figures 3 to 8 shown.

[0078] When the antenna aperture diameter of the maritime over-the-horizon communication system is 2m, two typical frequencies of 4.7GHz and 6.2GHz in the C band and two typical frequencies of 10GHz and 12GHz in the X band are selected, and the communication distance is set to 100km-300km, the calculation results of formula (5) show that the multipath delay of the evaporation duct and tropospheric scattering mixed channel is the same as the delay of the scattering channel; similarly, the antenna aperture diameter range is set to 2m to 6m with a step size of 2m, Figures 3 to 5 The comparison results of the multipath delay of the evaporation waveguide and tropospheric scattering mixed channel and the scattering channel delay at four typical frequency points in the C and X bands are given under different antenna aperture diameters.

[0079] Figure 3 This is a comparison chart of the multipath delay of the evaporation waveguide and tropospheric scattering hybrid channel and the scattering channel delay at four typical frequencies in the C and X bands when the antenna aperture diameter is 2m according to an embodiment of the present invention. Figure 3 (a) Figure 3 Middle (b), Figure 3 (c) Figure 3 (d) corresponds to the frequencies of C-band 4.7GHz, C-band 6.2GHz, X-band 10GHz, and X-band 12GHz when the antenna aperture diameter is 2m. Figure 3 It can be seen that when the communication distance is 100km-300km, at the four typical frequency points of the C and X bands, the multipath delay of the evaporation waveguide and tropospheric scattering mixed channel is the same as the scattering channel delay.

[0080] Figure 4 This is a comparison chart of the multipath delay of the evaporation duct and tropospheric scatter hybrid channel and the scattering channel delay at four typical frequencies in the C and X bands when the antenna aperture diameter is 4m according to an embodiment of the present invention. Figure 4 (a) Figure 4 (b) Figure 4 (c) Figure 4 (d) corresponds to the frequencies of C-band 4.7GHz, C-band 6.2GHz, X-band 10GHz, and X-band 12GHz when the antenna aperture diameter is 4m. Figure 4 It can be seen that at the two typical C-band frequencies of 4.7 GHz and 6.2 GHz, the multipath delay of the evaporation duct and tropospheric scatter mixed channel is the same as the scattering channel delay. However, at the two typical X-band frequencies of 10 GHz and 12 GHz, when the communication distance is greater than 520 km and 440 km, respectively, the multipath delay of the evaporation duct and tropospheric scatter mixed channel will exceed the scattering channel delay. Therefore, the multipath delay of the evaporation duct and tropospheric scatter mixed channel needs to be comprehensively considered when calculating the multipath delay.

[0081] Figure 5 This is a comparison chart of the multipath delay of the evaporation waveguide and tropospheric scattering hybrid channel and the scattering channel delay at four typical frequencies in the C and X bands when the antenna aperture diameter is 6m according to an embodiment of the present invention. Figure 5 (a) Figure 5 (b) Figure 5 (c) Figure 5 (d) corresponds to the frequencies of C-band 4.7GHz, C-band 6.2GHz, X-band 10GHz, and X-band 12GHz when the antenna aperture diameter is 6m. Figure 5It can be seen that the multipath delay of the evaporation duct and tropospheric scatter mixed channel is the same as the scattering channel delay at the 4.7 GHz frequency. However, at the 6.2 GHz, 10 GHz, and 12 GHz frequencies, when the communication distance is greater than 560 km, 360 km, and 300 km, respectively, the multipath delay of the evaporation duct and tropospheric scatter mixed channel will be greater than the scattering channel delay. Therefore, the multipath delay of the evaporation duct and tropospheric scatter mixed channel needs to be comprehensively considered when calculating the multipath delay.

[0082] When the antenna aperture diameter is 2m, two typical frequencies of 4.7GHz and 6.2GHz in the C band and two typical frequencies of 10GHz and 12GHz in the X band are selected, and the communication distance is set to 100km-300km. The multipath delay of the evaporation waveguide and tropospheric scattering hybrid channel decreases with increasing frequency. Similarly, the antenna aperture diameter range is set to 2m to 6m with a step size of 2m. Figures 6 to 8 A schematic diagram of the multipath delay calculation results of the evaporation waveguide and tropospheric scattering hybrid channel at four typical frequency points in the C and X bands is given for different antenna aperture diameters.

[0083] Figure 6 This is a schematic diagram of the multipath delay calculation results of the evaporation duct and tropospheric scatter hybrid channel at four typical frequency points in the C and X bands when the antenna aperture diameter is 2m according to an embodiment of the present invention. Figure 6 It can be seen that when the communication distance is 100km-300km, at the same frequency, the multipath delay of the evaporation duct and tropospheric scattering mixed channel increases with the increase of communication distance; at the same communication distance, the multipath delay of the evaporation duct and tropospheric scattering mixed channel decreases with the increase of frequency.

[0084] Figure 7 This is a schematic diagram of the multipath delay calculation results of the evaporation waveguide and tropospheric scatter hybrid channel at four typical frequency points of the C and X bands with an antenna aperture diameter of 4m according to an embodiment of the present invention. Figure 7 It can be seen that at the typical X-band frequencies of 10 GHz and 12 GHz, when the communication distance is greater than 520 km, the multipath delays of the two are the same. Therefore, when calculating the multipath delay, it is necessary to comprehensively consider the multipath delay of the evaporation duct and the tropospheric scatter mixed channel.

[0085] Figure 8 This is a schematic diagram of the multipath delay calculation results of the evaporation waveguide and tropospheric scatter hybrid channel at four typical frequency points of the C and X bands with an antenna aperture diameter of 6m according to an embodiment of the present invention. Figure 8It can be seen that at the typical X-band frequencies of 10 GHz and 12 GHz, when the communication distance is greater than 340 km, the multipath delay of the two is the same. When the communication distance is greater than 560 km, at the 6.2 GHz, 10 GHz, and 12 GHz frequencies, the multipath delay at 6.2 GHz is also the same as the multipath delay at 10 GHz and 12 GHz.

[0086] In the present invention, when the angles between the transmitting and receiving antennas and the sea level are both 0°, the multipath delay of the evaporation duct and tropospheric scattering hybrid channel under the conditions of over-the-horizon at sea can be quickly calculated by substituting the communication distance between the ship at sea and the shore base, the operating frequency of the over-the-horizon communication system at sea and the antenna aperture into the derived analytical expression of the multipath delay of the evaporation duct and tropospheric scattering hybrid channel. Therefore, the calculation method of the present invention can fully adapt to the frequent switching between the evaporation duct and tropospheric scattering of the over-the-horizon communication mode at sea, so that the multipath delay calculation results can better match the evaporation duct and tropospheric scattering hybrid channel, and can be used to guide the waveform design of the over-the-horizon communication system at sea. When designing the over-the-horizon communication system at sea, in order to avoid inter-code 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 hybrid channel, reserving enough time for the channel so that the energy of the previous symbol decays to a negligible level, thereby effectively avoiding inter-symbol interference, ultimately reducing the bit error rate and improving the performance of the maritime beyond-horizon communication system.

[0087] The proposed calculation method significantly optimizes the performance of over-the-horizon communications at sea by accurately analyzing the multipath delay differences between evaporation ducts and tropospheric scatter paths. By establishing a path delay calculation model (i.e., Formula (5)) for different communication distances, it effectively reduces inter-symbol interference (ISI) in hybrid channel transmission, improves signal reception quality, and reduces bit error rates. This method avoids the high complexity of traditional numerical simulations, provides efficient theoretical support for communication system waveform design, and enhances the reliability and engineering applicability of evaporation duct and tropospheric scatter communication systems.

[0088] 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 multipath delay of evaporation waveguide and scattering hybrid channel at different distances 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, wherein the center of the circle corresponding to the central angle is the center of the earth; When radio wave communication is carried out through a troposcatter channel, the angle between the transmitting antenna and the receiving antenna and the sea level is 0°. The propagation path length of the radio wave in the troposcatter channel is determined based on the positions of the scatterer, the transmitting antenna, and the receiving antenna. Obtaining a multipath delay difference between the tropospheric scatter channel and the evaporation waveguide channel based on the propagation path length of the radio wave in the evaporation waveguide channel, the propagation path length of the radio wave in the tropospheric scatter channel, and the propagation speed of the radio wave; and determining the multipath delay of the evaporation waveguide and tropospheric scatter hybrid channel at different communication distances 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 a hybrid channel of evaporation waveguide and scattering at different distances according to claim 1 is 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 in the evaporation waveguide channel, is the radius of the Earth.

3. The method for calculating multipath delay of a hybrid channel of evaporation waveguide and scattering at different distances according to claim 2, 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.

4. The method for calculating multipath delay of a hybrid channel of evaporation waveguide and scattering at different distances according to claim 3 is characterized in that: The expression of the multipath delay difference between the troposcatter channel and the evaporation waveguide channel is: in, is the multipath delay difference between the troposcatter channel and the evaporation waveguide channel, It is the propagation speed of radio waves in the beyond-horizon range at sea.

5. The method for calculating multipath delay of a hybrid channel of evaporation waveguide and scattering at different distances according to claim 4, characterized in that: The expression of the channel delay of the tropospheric scatter channel is: in, is the radio wave communication distance, is the operating frequency of radio wave scattering communication, D is the antenna aperture diameter, is the equivalent radius of the Earth.

6. The method for calculating multipath delay of a hybrid channel of evaporation waveguide and scattering at different distances according to claim 5, characterized in that: The expression of multipath delay of the evaporation waveguide and tropospheric scattering hybrid channel at different communication distances is: in, is the multipath delay of the evaporation duct and tropospheric scatter hybrid channel.

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