Dual-frequency circularly polarized antenna based on thermal protection system and artificial reflection surface design method

Abstract

The invention relates to the field of dual-frequency circularly polarized antennas, in particular to a dual-frequency circularly polarized antenna based on a thermal protection system and an artificial reflection surface design method. The dual-frequency circularly polarized antenna based on the thermal protection system comprises the thermal protection system 1 and an artificial reflection surface 7, the thermal protection system 1 is a planar double-layer thermal protection sheet body, the thermal protection system 1 covers the dual-frequency circularly polarized antenna 2 to separate the antenna from an external heat source, and the artificial reflection surface 7 replaces a grounding plate of the antenna. And the grounding plate is placed at the bottom of the antenna substrate, is separated from the antenna by a set distance and is used for repairing the damage of the loading thermal protection system and the grounding plate to the antenna circular polarization performance. The antenna grounding plate is replaced by the artificial reflection surface, the performance of the circularly polarized antenna can be effectively improved under the condition that a thermal protection system is not changed, and good balance between the overall electrical performance and the thermal protection performance of the system is achieved.

Description

Technical Field

[0001] The invention relates to the field of dual-frequency circularly polarized antennas, and in particular to a dual-frequency circularly polarized antenna based on a thermal protection system and an artificial reflection surface design method. Background Art

[0002] In recent years, hypersonic aircraft have attracted great attention from all countries due to their long range, high speed, and high precision. As the front-end part of the aircraft's electronic communication system, the aircraft antenna is a conversion device for the aircraft system to exchange electromagnetic energy with other different electronic systems, and plays a very important role in the communication performance of the aircraft. When working in a hypersonic aircraft, the antenna must not only have good electrical performance characteristics, but also meet the requirements of being able to work in a high temperature environment. Therefore, the antenna usually needs to work under the protection of a thermal protection system. Because the thermal protection system is thick and lossy, it will affect the radiation performance of the antenna, resulting in a narrower bandwidth of the circularly polarized antenna, a lower resonance depth, and a worsening of the circularly polarized axial ratio, affecting the antenna performance.

[0003] Currently, there is a lack of research on the performance restoration of antennas embedded in thermal protection systems. Most of them require a lot of design and simulation. Theoretically, the existing design process is still an engineering method and lacks systematic theoretical design ideas. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a dual-frequency circularly polarized antenna and an artificial reflection surface design method based on a thermal protection system, which can repair the performance damage caused to the embedded circularly polarized antenna by loading a thick and lossy thermal protection system, thereby greatly improving the performance of the antenna.

[0005] The present invention adopts the following technical solutions to achieve the above-mentioned purpose. In a first aspect, the present invention provides a dual-frequency circularly polarized antenna based on a thermal protection system, comprising:

[0006] The invention comprises a thermal protection system 1 and an artificial reflection surface 7. The thermal protection system 1 is a planar double-layer thermal protection sheet. The thermal protection system 1 covers the dual-frequency circularly polarized antenna 2 to separate the antenna from an external heat source. The artificial reflection surface 7 replaces the ground plate of the antenna, is placed at the bottom of the antenna substrate, and is spaced a set distance from the antenna to repair the damage to the circular polarization performance of the antenna caused by loading the thermal protection system and the ground plate.

[0007] Furthermore, the outer layer of the double-layer heat protection plate is a surface ablation layer, whose dielectric constant is 2-9, and the inner layer is a heat insulation layer, whose dielectric constant is 1.2-9.

[0008] Furthermore, the outer layer thickness of the double-layer heat protection plate is 8-12 mm, and the inner layer thickness is 6-15 mm.

[0009] Furthermore, the dual-frequency circularly polarized antenna is a printed antenna having a cross-section smaller than a set value.

[0010] Furthermore, the outer layer 5 of the double-layer heat protection plate is a fiber-reinforced silica composite material with a dielectric constant of 3.2, and the inner layer 6 is a fiber-reinforced silica aerogel composite material with a dielectric constant of 1.2.

[0011] Furthermore, the artificial reflection surface 7 is composed of a dielectric substrate 3 and a metal patch 4 on the surface thereof.

[0012] Furthermore, the dielectric constant of the dielectric substrate 3 material is 1.2-9, and the thickness is 0.25-2 mm.

[0013] In a second aspect, the present invention provides a method for designing an artificial reflective surface, the design method comprising:

[0014] S1. Calculate the termination equivalent network that broadens the axial ratio beam width of the ideal circularly polarized antenna. The equivalent network consists of LC lossless components and transmission lines.

[0015] S2. Design the corresponding artificial reflection surface unit structure according to the obtained equivalent network, the LC element is fitted by the surface metal patch, and the transmission line is fitted by the dielectric substrate;

[0016] S3. Arrange the artificial reflection surface units periodically to obtain an artificial reflection surface.

[0017] The beneficial effects of the present invention are:

[0018] The present invention uses a designed artificial reflection surface to replace the antenna ground plane, which can repair the performance damage caused by the thick and lossy thermal protection system to the embedded circular polarization antenna, such as restoring the resonant frequency, repairing the resonant depth, increasing the axial ratio bandwidth and widening the axial ratio beam width. Without changing the structure of the thermal protection system, a good balance between the overall electrical performance and thermal protection performance of the system is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the placement relationship of the antenna and the thermal protection system according to an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of the structure of an artificial reflective surface according to an embodiment of the present invention;

[0021] Figure 3 In the embodiment of the present invention Figure 2 The schematic diagram of the structure of the artificial reflective surface unit shown, (a) represents the upper surface, (b) represents the lower surface;

[0022] Figure 4A schematic diagram of a structure including an outer layer and an inner layer of a thermal protection system and an artificial reflective surface according to an embodiment of the present invention;

[0023] Figure 5 A schematic diagram of the structural parameters of a dual electric dipole dual-frequency circularly polarized antenna used in an embodiment of the present invention;

[0024] Figure 6 The influence of the thermal protection system and the metal ground on the reflection coefficient of the dual-frequency circularly polarized antenna in the embodiment of the present invention;

[0025] Figure 7 The influence of the thermal protection system and the metal ground on the axial ratio of the dual-frequency circularly polarized antenna in the embodiment of the present invention;

[0026] Figure 8 The reflection coefficient of the dual-frequency circularly polarized antenna of the embodiment of the present invention using an artificial reflective surface instead of the metal ground of the antenna and a rear-loaded thermal protection system;

[0027] Fig. 9 The axial ratio of the dual-frequency circularly polarized antenna of the embodiment of the present invention using an artificial reflective surface instead of the metal ground of the antenna and a rear-loaded thermal protection system;

[0028] Fig.10 The axial ratio beam width of the dual-frequency circularly polarized antenna of the embodiment of the present invention using an artificial reflective surface instead of the metal ground of the antenna and a rear-loaded thermal protection system;

[0029] Fig.11 The dual-frequency circularly polarized antenna of the embodiment of the present invention which uses an artificial reflective surface instead of the metal ground of the antenna and is loaded with a thermal protection system can achieve circularly polarized gain.

[0030] In the accompanying drawings, 1 represents a thermal protection system, 2 represents a dual-frequency circularly polarized antenna, 3 represents a dielectric substrate, 4 represents a metal patch, 5 represents an outer layer of a double-layer thermal protection sheet, 6 represents an inner layer of a double-layer thermal protection sheet, and 7 represents an artificial reflective surface. DETAILED DESCRIPTION

[0031] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0032] Combine the following Figure 1-Figure 11 The present invention is described in detail.

[0033] The present invention provides a dual-frequency circularly polarized antenna based on a thermal protection system, such as Figure 1As shown, it includes a thermal protection system 1 and an artificial reflection surface 7. The thermal protection system 1 is a planar double-layer thermal protection sheet. The thermal protection system 1 covers the dual-frequency circularly polarized antenna 2 to separate the antenna from the external heat source. The artificial reflection surface 7 replaces the ground plate of the antenna, is placed at the bottom of the antenna substrate, and is spaced a set distance from the antenna to repair the damage to the circular polarization performance of the antenna caused by loading the thermal protection system and the ground plate, including -10dB bandwidth narrowing, resonant frequency shift and axial ratio deterioration.

[0034] The double-layer planar heat protection sheet is loaded on the top of the antenna to isolate the antenna from the external heat source. The outer layer 5 of the double-layer planar heat protection sheet is a surface ablation layer with a dielectric constant of 2-9; the inner layer 6 is a heat insulation layer with a dielectric constant of 1.2-9; the outer layer thickness of the double-layer conformal heat protection sheet is 8-12mm; the inner layer thickness is 6-15mm.

[0035] The antenna of the present invention is a dual-frequency circularly polarized antenna, specifically a dual electric dipole patch antenna, comprising a dual electric dipole radiator and a dielectric substrate, the dual electric dipole radiator being printed on both sides of the dielectric substrate, the substrate node constant being 1.2-9, and the thickness being 0.25-2 mm. The antenna of the present invention is placed at the bottom of a thermal protection system, and is protected and isolated from a heat source.

[0036] The present invention also provides a method for designing an artificial reflective surface, the design method comprising:

[0037] S1, calculate the optimal equivalent network for widening the axial ratio beam width of the ideal circularly polarized antenna. The equivalent network consists of L, C lossless components and transmission lines.

[0038] S2, according to the optimal equivalent network obtained in S1, the corresponding artificial reflection surface unit structure is designed, wherein the LC element is fitted by the surface metal patch, and the transmission line is fitted by the dielectric substrate.

[0039] S3, periodically arranging the artificial reflection surface units into an infinite artificial reflection surface.

[0040] S4, place an artificial reflecting surface under the antenna and keep it at a certain distance from the antenna.

[0041] Artificial reflective surfaces designed based on the proposed design method, such as Figure 2 , 3 As shown, the artificial reflection surface is composed of a dielectric substrate and a surface metal patch. The artificial reflection surface replaces the antenna ground plate and is placed at the bottom of the antenna substrate and is spaced a certain distance from the antenna. The dielectric constant of the dielectric substrate material is 1.2-9 and the thickness is 2-5 mm.

[0042] By using the proposed artificial reflective surface instead of the antenna ground plane, the performance damage caused by the thick and lossy thermal protection system to the embedded circularly polarized antenna can be repaired, such as restoring the resonant frequency, repairing the resonant depth, increasing the axial ratio bandwidth and widening the axial ratio beam width. Without changing the structure of the thermal protection system, a good balance between the overall electrical performance and thermal protection performance of the system is achieved.

[0043] like Figure 4 As shown, in this embodiment, the outer layer of the double-layer thermal protection system is a fiber-reinforced silica composite material with a dielectric constant of 3.2, a loss tangent of 0.008, and a thickness of 8 mm; the inner layer is a fiber-reinforced silica aerogel composite material with a dielectric constant of 1.2, a loss tangent of 0.004, and a thickness of 12 mm. The reference antenna is a dual-electric dipole printed antenna with dual-frequency circular polarization characteristics, such as Figure 5 As shown, the dimensions of the antenna's related parameters are set as follows: S1 = 38mm, h = 1.524mm, S2 = 2.76mm, L1 = 2.4mm, L2 = 19mm, L3 = 7mm, L4 = 2mm, W1 = 3.4mm, W2 = 3mm, W3 = 1.5mm, H1 = 6.2mm, H2 = 1mm, R1 = 1.38mm, R2 = 3.1mm, R3 = 3.4mm, R4 = 3.7mm, b1 = 0.8mm, b2 = 0.1mm. The antenna substrate material is RO4003, with a dielectric constant of 3.55, a loss tangent of 0.0027, and a thickness of 1.524mm.

[0044] Artificial reflective surfaces include: dielectric substrates and surface metal patches, such as Figure 2 As shown, the artificial reflection surface is placed at the bottom of the antenna substrate instead of the antenna ground plate, and the distance between the antenna and the antenna is H air =8.9mm. The dimensions of the relevant parameters of the artificial reflective surface are set as follows: a1=a2=0.76mm, b1=0.4mm, b2=0.1mm, g1=0.1mm, g2=0.4mm, D1=5.66mm. Figure 3 shown.

[0045] Loading the thermal protection system will affect the circular polarization performance of the embedded antenna, such as Figure 6 , 7 As shown in the figure, the specific performance is the narrowing of the -10dB bandwidth, the shift of the resonance frequency and the deterioration of the axial ratio. After using the proposed artificial reflection surface to replace the antenna ground plane, the resonance point shift is repaired and the resonance depth is restored, as shown in Figure 8 As shown in Figure 1, the low-frequency bandwidth of the antenna is widened to 2.48-3.6 GHz, and the high-frequency bandwidth is widened to 6.7-7.3 GHz. The 3dB axial ratio bandwidth of the antenna is restored, as shown in Figure 1. Fig. 9As shown in the figure, the 3dB axial ratio bandwidth of the low frequency part is widened to 2.91-3.16GHz, and the 3dB axial ratio bandwidth of the high frequency part is widened to 6.69-7.22GHz. Loading the artificial reflection surface greatly widens the axial ratio beamwidth of the circularly polarized antenna, such as Fig.10 As shown in the figure, its low-frequency axial ratio beam width is widened to an average of 110°, and is above 100°, which is stable in the working frequency band; its high-frequency axial ratio beam width is widened to an average of 65°, and is above 70° in the frequency range of 6.8-7.1GHz. In addition, within the working frequency band of the antenna, the gain is stable at more than 5dB, as shown in the figure. Fig.11 shown.

[0046] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A dual-frequency circularly polarized antenna based on a thermal protection system, characterized in that: The invention comprises a thermal protection system (1) and an artificial reflection surface (7). The thermal protection system (1) is a planar double-layer thermal protection sheet. The thermal protection system (1) covers a dual-frequency circularly polarized antenna (2) to separate the antenna from an external heat source. The artificial reflection surface (7) replaces the antenna's ground plate and is placed at the bottom of the antenna substrate. The artificial reflection surface (7) is spaced a set distance from the antenna and is used to repair damage to the circular polarization performance of the antenna caused by loading the thermal protection system and the ground plate.

2. The dual-frequency circularly polarized antenna based on the thermal protection system according to claim 1, characterized in that: The outer layer of the double-layer heat protection plate is a surface ablation layer, whose dielectric constant is 2-9, and the inner layer is a heat insulation layer, whose dielectric constant is 1.2-9.

3. The dual-frequency circularly polarized antenna based on the thermal protection system according to claim 1, characterized in that: The outer layer thickness of the double-layer heat protection plate is 8-12 mm, and the inner layer thickness is 6-15 mm.

4. The dual-frequency circularly polarized antenna based on the thermal protection system according to claim 1, characterized in that: The dual-frequency circularly polarized antenna is a printed antenna with a cross-section smaller than a set value.

5. The dual-frequency circularly polarized antenna based on the thermal protection system according to claim 1, characterized in that: The outer layer (5) of the double-layer heat protection plate is a fiber-reinforced silica composite material with a dielectric constant of 3.2, and the inner layer (6) is a fiber-reinforced silica aerogel composite material with a dielectric constant of 1.

2.

6. The dual-frequency circularly polarized antenna based on the thermal protection system according to claim 1, characterized in that: The artificial reflection surface (7) is composed of a dielectric substrate (3) and a metal patch (4) on the surface thereof.

7. The dual-frequency circularly polarized antenna based on the thermal protection system according to claim 6, characterized in that: The dielectric substrate (3) material has a dielectric constant of 1.2-9 and a thickness of 0.25-2 mm.

8. A method for designing an artificial reflection surface, applied to the dual-frequency circularly polarized antenna based on a thermal protection system as claimed in claim 6 or 7, characterized in that: The design method comprises: S1. Calculate the termination equivalent network that broadens the axial ratio beam width of the ideal circularly polarized antenna. The equivalent network consists of LC lossless components and transmission lines. S2. Design the corresponding artificial reflection surface unit structure according to the obtained equivalent network, the LC element is fitted by the surface metal patch, and the transmission line is fitted by the dielectric substrate; S3. Arrange the artificial reflection surface units periodically to obtain an artificial reflection surface.

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