A modeling method for simulating medium and shortwave antennas on a water surface platform

Abstract

This invention discloses a modeling method for simulating medium- and short-wave antennas on a water surface platform, belonging to the fields of medium- and short-wave antenna design and electromagnetic compatibility technology. The method determines the deck height above sea level based on the ship's actual draft under operating conditions. Based on the ship's actual structure and the deck height above sea level, an integrated model of the hull and seawater is created. Seawater is modeled as an infinitely large semi-conductive medium, and the antenna is modeled according to its structure and installation position and attitude on the water surface platform. In this modeling method, the installation carrier and environment are modeled as a single entity. The ship hull, as a metallic body, is in contact with seawater, an infinitely large semi-conductive medium, together forming the installation carrier for the medium- and short-wave antenna. This method can accurately predict the impact of the installation environment, meeting the requirements for antenna radiation patterns in this operating scenario and consistent with actual usage results.

Description

Technical Field

[0001] This invention belongs to the field of medium- and short-wave antenna design and electromagnetic compatibility technology, and more specifically, relates to a modeling method for simulating medium- and short-wave antennas on a water surface platform. Background Technology

[0002] The mounting platform and environment of an antenna can significantly affect its electrical performance, especially when the wavelength corresponding to the antenna's operating frequency is on the same order of magnitude as the size of the mounting platform. This often results in antennas performing well during testing but failing in actual operating environments. To address this, in the early simulation design phase, it's often necessary to integrate the antenna with the mounting platform. This means that given the structure of the mounting platform and the antenna's installation location, the influence of the mounting platform must be considered during antenna design and adjustments.

[0003] For shortwave antennas mounted on satellites, vehicles, etc., the environmental impact is relatively small, and generally only the influence of the mounting platform needs to be considered. However, medium- and shortwave antennas mounted on water surfaces are typically monopole antennas. In the low-end and mid-wave bands of the shortwave band, the wavelengths corresponding to the antenna's operating frequencies reach hundreds of meters. The length of a ship is comparable to or smaller than the wavelength, while the antenna itself is much smaller. Therefore, antenna performance is significantly affected not only by the mounting platform but also by environmental factors such as seawater. When the influence of seawater is not considered in the modeling, or only the reflection effect of seawater is considered, the simulation results show the ship as the main radiator, which does not match the actual test results. How to model accurately predict the impact of the installation environment remains a challenge. Summary of the Invention

[0004] In response to the above-mentioned defects or improvement needs of existing technologies, this invention proposes a modeling method for simulating medium and shortwave antennas on a water surface platform, which takes into account the influence of the carrier and the environment simultaneously and performs integrated modeling.

[0005] To achieve the above objectives, this invention provides a modeling method for simulating medium- and short-wave antennas on a water surface platform, comprising:

[0006] The height of the deck above the sea level is determined based on the actual draft of the ship under its operating conditions.

[0007] Based on the actual structure of the ship and the height of the deck above the sea level, an integrated model of the hull and seawater is created.

[0008] The seawater is modeled as an infinitely large semiconducting medium, and the antenna is modeled according to its structure and installation position and attitude on the water surface platform.

[0009] In some alternative implementations, the relative permittivity of the medium is set to 80.0, and the conductivity is set to 4.0 S / m.

[0010] In some alternative implementations, the integrated modeling of the hull and seawater based on the ship's actual structure and the height of the deck above sea level includes:

[0011] Based on the ship's actual structure and the height of the deck above the sea level, the plane where the hull contacts the sea level is taken as the bottom of the ship. The part of the hull above the sea level is fully modeled, and the part of the hull submerged in the sea is deleted.

[0012] In some alternative implementations, the ship's hull is used as a metallic body to connect with seawater, an infinitely large semiconducting medium, thus serving as the mounting carrier for medium and shortwave antennas.

[0013] In some alternative implementations, the modeling tool is the electromagnetic simulation software FEKO.

[0014] In some alternative implementations, when modeling, the deck surface is the XOY plane, the X-axis is along the length of the ship, the Y-axis is along the width, and the Z-axis is perpendicular to the deck surface and pointing upwards.

[0015] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0016] In the modeling method of this invention, the installation carrier and the environment are modeled as a whole. The hull, as a metal body, is in contact with seawater, an infinitely large semi-conductive medium, and together they become the installation carrier for the medium and short wave antenna. This method can be used to accurately predict the impact of the installation environment, which meets the requirements for the antenna pattern in this working scenario and is consistent with the actual effect in use. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a calculation model provided in an embodiment of the present invention;

[0018] Figure 2 This is a gain pattern provided by an embodiment of the present invention without considering the influence of seawater;

[0019] Figure 3 This is a gain pattern provided by an embodiment of the present invention when the hull is not in contact with seawater;

[0020] Figure 4 This is a gain pattern provided by an embodiment of the present invention when a ship's hull is in contact with seawater. Detailed Implementation

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0022] like Figure 1 As shown, one embodiment of the present invention includes a typical water surface platform calculation model, the modeling tool is the electromagnetic simulation software FEKO, and the operating environment is Windows 10.

[0023] In this embodiment, the medium-wave antenna is located at the outer edge of the deck, operates at a frequency of 400 kHz, and has a height of 14.5 meters. The length of the deck surface is approximately 0.45 wavelengths, the height of the deck surface above the sea surface is approximately 0.025 wavelengths, and the antenna height is only approximately 0.02 wavelengths. The specific parameters of the seawater are: relative permittivity of 80.0 and conductivity of 4.0 S / m. Several different modeling methods were used for simulation to compare the impact of different modeling methods on the calculation results. In the modeling, the deck surface is the XOY plane, the length direction of the ship is the X-axis, the width direction is the Y-axis, and the direction perpendicular to the deck surface upwards is the Z-axis.

[0024] (1) Model A: Ignoring the influence of seawater

[0025] When the antenna and hull are modeled as a single unit, and the influence of seawater is ignored, the calculated far-field radiation gain pattern of the antenna is as follows: Figure 2 As shown.

[0026] The maximum gain of this radiation pattern is approximately 2.15 dBi. Based on the shape of this radiation pattern and the magnitude of the gain, the hull acts as a horizontally polarized radiating antenna, forming a dipole antenna radiation mode together with the vertically polarized monopole antenna. The radiation of the vertically polarized antenna itself is very weak.

[0027] (2) Model B: The hull is not in contact with the seawater.

[0028] By appropriately increasing the distance between the ship's hull and the sea level, positioning the hull at 0.027 wavelengths above the sea surface and the deck at approximately 0.045 wavelengths above the sea level, the seawater is modeled as an infinitely large semiconducting medium. In this model, since the hull is not in contact with the seawater, the seawater's main effect is reflection of electromagnetic waves incident on the sea surface. The calculated far-field radiation gain pattern of the antenna is shown below. Figure 3As shown. The maximum gain of this radiation pattern is approximately 7.8 dBi. Based on the shape of this radiation pattern and the magnitude of the gain value, the main radiation mode at this time is still the horizontal polarization radiation of the ship's hull, with the seawater acting as an infinitely large reflector.

[0029] (3) Model C: The hull is in contact with the seawater

[0030] When modeling the ship based on its actual operational scenario, the deck is approximately 0.025 wavelengths above the sea surface, with the hull just touching the seawater. The seawater is modeled as an infinitely large semiconducting medium. In this model, because the hull is in contact with the seawater, the seawater's influence, besides reflecting electromagnetic waves incident on the sea surface, primarily acts as an infinitely large lossy ground plane surrounding the metal ground plane (i.e., the hull) below the monopole antenna. The calculated far-field radiation gain pattern of the antenna is shown below. Figure 4 As shown. The maximum gain of this radiation pattern is approximately 4.5 dBi. Based on the shape of this radiation pattern and the magnitude of the gain, the main radiation mode at this time is the radiation mode of a vertically polarized monopole antenna standing on an infinitely large floor.

[0031] As can be seen from the gain patterns calculated by the three models above, for a medium-wave antenna located on a water surface platform, the three different modeling methods yielded drastically different results. Model A uses integrated modeling of the antenna and the mounting platform, which is a commonly used modeling method for this type of problem; Model B integrates the antenna and the mounting platform, partially considering the influence of the environment (i.e., seawater); Model C integrates the antenna, platform, and environment into a single model based on the actual operating conditions.

[0032] Model C is modeled according to the actual operating scenario of the antenna, which is located on a ship platform with the hull integrated with the seawater. On the one hand, Model C matches the actual operating scenario. On the other hand, the simulation results obtained from Model C are consistent with the characteristics of radio wave propagation in this frequency band: vertical polarization favors ground wave propagation, and due to its low frequency, it can cover near, medium, and long distances; horizontal polarization favors sky wave propagation, but there is a radiation blind zone at close range, and ionospheric absorption is significant when using sky wave propagation in this frequency band, leading to excessive signal attenuation. Based on feedback, the antenna is currently performing well in this frequency band. Based on the characteristics of radio wave propagation, the actual operating mode of the antenna should be vertical polarization radiation, utilizing the air-seawater interface to operate in ground wave propagation mode. Among the various modeling methods, only Model C can obtain a vertically polarized radiation mode, which meets the requirements for the antenna pattern in actual use.

[0033] When the operating frequency is very low, the ship's metal structure operates at approximately half a wavelength. If the influence of seawater is disregarded, the hull itself will act as an antenna, forming a horizontally polarized radiation pattern. If the hull and seawater are modeled as a single, integrated medium, then the interaction between the hull and seawater becomes an infinitely large semiconducting medium, acting as the ground plane for the antenna. The antenna itself becomes the primary radiating structure, forming a vertically polarized radiation pattern. Since the ground plane is infinitely large, the non-circularity of the antenna's horizontal radiation pattern is 0 dB in the vertically polarized radiation pattern.

[0034] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0035] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A modeling method for simulating medium- and short-wave antennas on a water surface platform, characterized in that, include: The height of the deck above the sea level is determined based on the actual draft of the ship under its operating conditions. Based on the actual structure of the ship and the height of the deck above the sea level, the hull and seawater are modeled as a whole. That is, based on the actual structure of the ship and the height of the deck above the sea level, the plane in contact with the sea level is taken as the bottom of the ship. The part of the hull above the sea level is fully modeled, and the part of the hull submerged in the seawater is deleted. The hull is treated as a metal body and is connected to the infinitely large semi-conductive medium of seawater, which together become the mounting carrier for medium and short wave antennas. The seawater is modeled as an infinitely large semi-conductive medium. The antenna is modeled according to its structure and installation position and attitude on the water surface platform. The deck surface is used as the XOY plane, the length of the ship is the X-axis, the width of the ship is the Y-axis, and the direction perpendicular to the deck surface upwards is the Z-axis.

2. The modeling method according to claim 1, characterized in that, The relative permittivity of the medium was set to 80.0, and the conductivity was set to 4.0 S / m.

3. The modeling method according to claim 1, characterized in that, The modeling tool used was the electromagnetic simulation software FEKO.

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