Design Method of Dual-Frequency Circularly Polarized Antenna and Artificial Reflector Based on Thermal Protection System

Abstract

This invention relates to the field of dual-band circularly polarized antennas, specifically to a dual-band circularly polarized antenna based on a thermal protection system and a method for designing an artificial reflective surface. The dual-band circularly polarized antenna based on a thermal protection system of this invention includes a thermal protection system 1 and an artificial reflective surface 7. The thermal protection system 1 is a planar double-layer thermal protection sheet, which covers the dual-band circularly polarized antenna 2, isolating the antenna from external heat sources. The artificial reflective surface 7 replaces the antenna's ground plane, is placed at the bottom of the antenna substrate, and is spaced a predetermined distance from the antenna. It is used to repair the damage to the antenna's circular polarization performance caused by the thermal protection system and ground plane. By using an artificial reflective surface instead of the antenna ground plane, this invention can effectively improve the performance of the circularly polarized antenna without changing the thermal protection system, achieving a good balance between the overall electrical performance and thermal protection performance of the system.

Description

Technical Field

[0001] This invention relates to the field of dual-frequency circularly polarized antennas, and more specifically to a dual-frequency circularly polarized antenna based on a thermal protection system and a method for designing an artificial reflective surface. Background Technology

[0002] In recent years, hypersonic aircraft have attracted significant attention from various countries due to their long range, high speed, and high precision. As the front-end component of an aircraft's electronic communication system, the aircraft antenna is a conversion device for electromagnetic energy exchange between the aircraft system and other electronic systems, playing a crucial role in the aircraft's communication performance. When operating in hypersonic aircraft, antennas must not only possess excellent electrical performance characteristics but also meet the requirement of operating in high-temperature environments. Therefore, antennas typically need to operate under the protection of a thermal protection system. Because the thermal protection system is thick and lossy, it can affect the antenna's radiation performance, leading to a narrower bandwidth, reduced resonance depth, and deteriorated circular polarization axial ratio in circularly polarized antennas, thus impacting antenna performance.

[0003] Currently, there is a lack of research on the performance repair of antennas embedded in thermal protection systems. Most of them require a lot of design and simulation. From a theoretical point of view, the existing design process is still an engineering method and lacks a systematic theoretical design approach. Summary of the Invention

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

[0005] The present invention achieves the above-mentioned objectives by adopting the following technical solution: Firstly, the present invention provides a dual-frequency circularly polarized antenna based on a thermal protection system, comprising:

[0006] It includes a thermal protection system 1 and an artificial reflective 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 isolate the antenna from external heat sources. The artificial reflective surface 7 replaces the ground plane of the antenna and is placed at the bottom of the antenna substrate, with a set distance between it and the antenna. It is used to repair the damage to the circular polarization performance of the antenna caused by the thermal protection system and the ground plane.

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

[0008] Furthermore, the outer layer of the double-layer heat protection sheet has a thickness of 8–12 mm, and the inner layer has a thickness of 6–15 mm.

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

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

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

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

[0013] Secondly, the present invention provides a method for designing an artificial reflective surface, the method comprising:

[0014] S1. Calculate the termination equivalent network for widening the axial ratio beamwidth of an ideal circularly polarized antenna. The equivalent network consists of LC lossless components and transmission lines.

[0015] S2. Design the corresponding artificial reflective surface unit structure based on the obtained equivalent network. The LC element is fitted by a surface metal patch, and the transmission line is fitted by a dielectric substrate.

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

[0017] The beneficial effects of this invention are as follows:

[0018] This invention uses a designed artificial reflective surface to replace the antenna ground plane, which can repair the performance damage caused to embedded circularly polarized antennas by a thick, lossy thermal protection system. This includes restoring the resonant frequency, repairing the resonant depth, increasing the axial ratio bandwidth, and widening the axial ratio beamwidth. A good balance between the overall electrical performance and thermal protection performance of the system is achieved without changing the structure of the thermal protection system. Attached Figure Description

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

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

[0021] Figure 3 As described in the embodiments of the present invention Figure 2 The schematic diagram of the artificial reflective surface unit structure shown is as follows: (a) represents the upper surface, and (b) represents the lower surface.

[0022] Figure 4This is a schematic diagram of an embodiment of the present invention, including an outer layer, an inner layer, and an artificial reflective surface of a thermal protection system;

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

[0024] Figure 6 This illustrates the influence of the thermal protection system and the metal ground plane on the reflection coefficient of the dual-frequency circularly polarized antenna in this embodiment of the invention.

[0025] Figure 7 This illustrates the influence of the thermal protection system and the metal ground plane on the axial ratio of the dual-frequency circularly polarized antenna in this embodiment of the invention.

[0026] Figure 8 The reflection coefficient of the dual-frequency circularly polarized antenna in the thermal protection system is obtained by using an artificial reflective surface to replace the antenna's metal ground in this embodiment of the invention.

[0027] Figure 9 The axial ratio of the dual-frequency circularly polarized antenna in the thermal protection system is adjusted by using an artificial reflective surface instead of the antenna's metallic ground in this embodiment of the invention.

[0028] Figure 10 The axial ratio beamwidth of the dual-frequency circularly polarized antenna in this embodiment of the invention is achieved by using an artificial reflective surface instead of the antenna's metallic ground and then applying a thermal protection system.

[0029] Figure 11 The dual-frequency circularly polarized antenna of the embodiment of the present invention, which uses an artificial reflective surface to replace the antenna metal ground and then loads a thermal protection system, can achieve circular polarization gain.

[0030] In the attached diagram, 1 represents the thermal protection system, 2 represents the dual-frequency circularly polarized antenna, 3 represents the dielectric substrate, 4 represents the metal patch, 5 represents the outer layer of the double-layer thermal protection sheet, 6 represents the inner layer of the double-layer thermal protection sheet, and 7 represents the artificial reflective surface. Detailed Implementation

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

[0032] The following is combined with Figures 1-11 The present invention will be described in detail below.

[0033] This 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 reflective 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 isolate the antenna from external heat sources. The artificial reflective surface 7 replaces the ground plane of the antenna and is placed at the bottom of the antenna substrate, with a set distance between it and the antenna. It is used to repair the damage to the circular polarization performance of the antenna caused by the thermal protection system and the ground plane, including -10dB bandwidth narrowing, resonant frequency shift and axial ratio deterioration.

[0034] A double-layer planar thermal protection sheet is loaded on top of the antenna to isolate the antenna from external heat sources. The outer layer 5 of the double-layer planar thermal 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 thickness of the outer layer of the double-layer conformal thermal protection sheet is 8-12 mm; the thickness of the inner layer is 6-15 mm.

[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 is printed on both sides of the dielectric substrate. The substrate node constant is 1.2-9 and the thickness is 0.25-2mm. The antenna of the present invention is placed at the bottom of the thermal protection system, which protects it from heat sources.

[0036] This invention also provides a method for designing artificial reflective surfaces, the method comprising:

[0037] S1 calculates the optimal equivalent termination network for widening the axial ratio beamwidth of an ideal circularly polarized antenna. The equivalent network consists of lossless L and C components and a transmission line.

[0038] S2. Based on the optimal equivalent network obtained in S1, design the corresponding artificial reflective surface unit structure. The LC element is fitted with a surface metal patch, and the transmission line is fitted with a dielectric substrate.

[0039] S3 arranges the artificial reflective surface units periodically into an infinitely large artificial reflective surface.

[0040] S4. Place the artificial reflective surface below the antenna and 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 reflective surface consists of a dielectric substrate and a surface metal patch. The artificial reflective surface replaces the antenna ground plane and is placed at the bottom of the antenna substrate, with a certain distance between it and the antenna. The dielectric substrate material has a dielectric constant of 1.2-9 and a thickness of 2-5 mm.

[0042] By using the proposed method of replacing the antenna ground plane with an artificial reflective surface, the performance degradation caused to embedded circularly polarized antennas by a thick, lossy thermal protection system can be repaired. This includes restoring the resonant frequency, repairing the resonant depth, increasing the axial ratio bandwidth, and widening the axial ratio beamwidth. A good balance between the overall electrical performance and thermal protection performance of the system is achieved without altering the structure of the thermal protection system.

[0043] like Figure 4 As shown, in this embodiment, the outer layer of the dual-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 various 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: a dielectric substrate and a surface metal patch, such as Figure 2 As shown, the artificial reflective surface replaces the antenna ground plane and is placed at the bottom of the antenna substrate, with a distance of H between it and the antenna. air = 8.9mm. The exemplary dimensional settings for the relevant parameters of this artificial reflective surface are as follows: a1 = a2 = 0.76mm, b1 = 0.4mm, b2 = 0.1mm, g1 = 0.1mm, g2 = 0.4mm, D1 = 5.66mm, as shown below. Figure 3 As shown.

[0045] Adding a thermal protection system can affect the circular polarization performance of an embedded antenna, such as... Figure 6 , 7 As shown, this manifests as a narrowing of the -10dB bandwidth, a shift in the resonant frequency, and a deterioration in the axial ratio. Replacing the antenna ground plane with the proposed artificial reflective surface corrected the resonant shift and restored the resonance depth, as shown below. Figure 8 As shown, this widens the antenna's bandwidth to 2.48-3.6 GHz at low frequencies and to 6.7-7.3 GHz at high frequencies. The antenna's 3 dB axial ratio bandwidth is restored, as shown... Figure 9As shown, the 3dB axial ratio bandwidth in the low-frequency range is broadened to 2.91-3.16 GHz, and the 3dB axial ratio bandwidth in the high-frequency range is broadened to 6.69-7.22 GHz. Adding an artificial reflective surface significantly broadens the axial ratio beamwidth of the circularly polarized antenna, as shown... Figure 10 As shown, its low-frequency axial-ratio beamwidth is widened to an average of 110°, and all are above 100°, remaining stable within the operating frequency band; its high-frequency axial-ratio beamwidth is widened to an average of 65°, with axial-ratio beamwidths exceeding 70° in the 6.8-7.1GHz frequency range. Furthermore, within the antenna's operating frequency band, the gain remains stable above 5dB, such as... Figure 11 As shown.

[0046] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A dual-frequency circularly polarized antenna based on a thermal protection system, characterized in that, It includes a thermal protection system (1) and an artificial reflective 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 isolate the antenna from external heat sources. The artificial reflective surface (7) replaces the ground plane of the antenna and is placed at the bottom of the antenna substrate, with a set distance between it and the antenna. It is used to repair the damage to the circular polarization performance of the antenna caused by the thermal protection system and the ground plane. The artificial reflective surface is obtained as follows: Calculate the termination equivalent network to broaden the axial ratio beamwidth of an ideal circularly polarized antenna. The equivalent network consists of LC lossless components and transmission lines. Based on the obtained equivalent network, design the corresponding artificial reflective surface unit structure. The LC components are fitted with surface metal patches, and the transmission lines are fitted with dielectric substrates. The artificial reflective surface is obtained by periodically arranging the artificial reflective surface units. The outer layer of the double-layer thermal protection sheet is a surface ablation layer with a dielectric constant of 2-9, and the inner layer is a thermal insulation layer with a dielectric constant of 1.2-9. The outer layer of the double-layer thermal protection sheet has a thickness of 8~12 mm, and the inner layer has a thickness of 6~15 mm. The dual-frequency circularly polarized antenna is a printed antenna with a cross-section smaller than the set value; The outer layer (5) of the double-layer thermal protection sheet 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. The artificial reflective surface (7) is composed of a dielectric substrate (3) and a metal patch (4) on its surface; The dielectric substrate (3) has a dielectric constant of 1.2-9 and a thickness of 0.25-2 mm.

2. A method for designing an artificial reflective surface, applied to a dual-frequency circularly polarized antenna based on a thermal protection system as described in claim 1, characterized in that, The design method includes: S1. Calculate the termination equivalent network for widening the axial ratio beamwidth of an ideal circularly polarized antenna. The equivalent network consists of LC lossless components and transmission lines. S2. Design the corresponding artificial reflective surface unit structure based on the obtained equivalent network. The LC element is fitted by a surface metal patch, and the transmission line is fitted by a dielectric substrate. S3. Arrange the artificial reflective surface units periodically to obtain the artificial reflective surface.

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