Radome wall for communication applications

Abstract

The invention relates to a radome wall (1) for communication in the frequency band from 17 to 31 GHz for use in aircraft, and also to a radome with a corresponding radome wall (1). The radome wall (1) comprises a multilayer structure with an alternating arrangement of force-absorbing fixed covering layers and shear-resistant core layers, wherein the radome wall (1) has an asymmetrical layer structure with the layer sequence: outer core layer (21) – inner covering layer (12) – inner core layer (22) – outer covering layer (11), wherein the layer thickness of the inner covering layer (12) is at least five times greater than the layer thickness of the outer covering layer (11).

Description

Radome wall for communication applications

[0001] The invention relates to a radome wall for communication in the frequency band from 17 to 31 GHz for use on aircraft, in particular passenger aircraft, as well as a radome with a corresponding radome wall.

[0002] For data transmission via satellite, radio transmission in the frequency range from 17 to 31 GHz is generally used. For transmission from a satellite to a low-earth orbit transceiver, the so-called downlink, the frequency range from 17.7 to 21.2 GHz is generally used, and for transmission from a low-earth orbit transceiver to a satellite (uplink), the frequency range from 27.5 to 31 GHz is regularly used. For example, a corresponding data transmission is used on board passenger aircraft to offer passengers an internet connection during the flight.

[0003] To enable a corresponding data connection, the antennas intended for this purpose must be arranged on the outside of the aircraft fuselage. To protect antennas for emitting and / or receiving electromagnetic radiation from external mechanical or chemical influences, such as wind and rain, they are protected by so-called "radomes". In addition to the structural strength required to protect the antennas, it is essential for radomes that they exhibit suitable transmission characteristics, i.e., that they are sufficiently permeable to electromagnetic radiation in the frequency range relevant to the antenna(s) to be protected - for communications applications, for example, from 17 to 31 GHz.

[0004] In the case of radomes, especially for aircraft, where the spatial arrangement of satellites and antennas arranged on the outside of the aircraft is constantly changing, At the same time, however, the shape of the radome cannot be freely chosen for aerodynamic reasons. For effective data transmission, good transmission behavior of the radome wall over a wide range of angles of incidence, assuming an orthogonal incidence of the radiation, is required. In addition to the actual transmission properties, the lowest possible depolarization of the radio signals is also desirable.

[0005] In the prior art, as disclosed, for example, in EP 2 747 202 A1 or EP 3 533 108 A1, radomes made of symmetrically constructed sandwich structures comprising GRP and foam layers are known. These, on the one hand, exhibit adequate transmission behavior and, on the other hand, offer sufficient structural strength while being lightweight. For this purpose, suitable layer arrangements can be calculated for the desired frequency ranges, particularly with regard to the thickness of the individual layers, whereby the dielectric constants of the individual layer materials must also be taken into account.

[0006] Even though radome walls made of EP 3 533 108 A1, in particular, exhibit very good transmission properties in the frequency range from 17 to 31 GHz and are well suited for use on aircraft, depolarization effects may, under very specific circumstances, require the temporary deactivation of the antennas protected by such a radome. In these rare cases, data communication is interrupted.

[0007] The object of the present invention is to create a radome wall in which the disadvantages of the prior art no longer occur or at least only occur to a reduced extent.

[0008] This object is achieved by a radome wall according to the main claim and by a radome according to the independent claim 11. Advantageous further developments are the subject of the dependent claims.

[0009] Accordingly, the invention relates to a radome wall for satellite communication in the frequency band from 17 to 31 GHz, in particular in the reception band from 17.7 to 21.2 GHz and in the transmission band from 27.5 to 31 GHz, for use on aircraft, comprising a multi-layer structure with an alternating arrangement of force-absorbing solid cover layers and shear-resistant core layers, wherein the radome wall has an asymmetrical layer structure with the layer sequence outer core layer - inner cover layer - inner core layer - outer cover layer, wherein the layer thickness of the inner core layer is at least a factor of five greater than the layer thickness of the outer core layer.

[0010] The invention further relates to a radome for use on aircraft, the wall of which is designed according to the invention.

[0011] First, some terms used in the present invention are explained:

[0012] The "cover layers" are force-absorbing, solid layers of a multi-layer structure, while the "core layers" are only shear-resistant, whereby the specific weight of the cover layer is consequently often higher than the specific weight of the core layers. Adjacent layers of the multi-layer structure are firmly connected to each other, in particular in a shear-resistant manner, e.g. glued together, whereby an intermediate core layer is usually provided between two cover layers in order to keep the cover layers at a distance. The sandwich construction - although regularly with two outer cover layers - is widely used and known in the state of the art, not only in relation to radomes.

[0013] A layer of a multilayer structure is considered to be "internal" if there are further layers of the multilayer structure on either side of the layer in question. A layer of a multilayer structure is therefore considered to be "external" if there is no further layer of the multilayer structure on one side of the layer in question. When assigning a layer as internal or external, only other structural layers of the multilayer structure itself are taken into account, but not layers that do not contribute to the mechanical structure of the multilayer structure, such as paint layers or similar coatings. However, since such coatings can certainly influence the transmission properties of the radome wall, they can be taken into account when determining the thicknesses and / or choosing the dielectric constants of the individual layers of the multilayer structure.

[0014] The wheel shroud according to the invention is particularly designed for use on aircraft and is characterized by an asymmetrical layer sequence of core layer - cover layer - core layer - cover layer, wherein the outer cover layer has a significantly smaller thickness than the inner cover layer. As a result, the basic structural integrity of the radome wall according to the invention, especially under greater mechanical loads, such as those caused by the airflow around the radome wall during a flight, is largely ensured by the inner cover layer. The outer, significantly thinner cover layer primarily serves to protect the adjacent core layer from smaller mechanical loads, such as hail or the impact of smaller particles, such as grains of sand, carried by the airflow around the radome wall. Corresponding protection against mechanical stress on the other side of the radome wall, facing the antennas, is not required and is not provided for in the invention. In the case of larger energetic impact loads, such as those resulting from bird strikes, the basic structural integrity of the radome wall is ensured by the inner cover layer.

[0015] The invention has recognized that with a radome wall designed according to the invention with an asymmetric structure for use on aircraft, in which the inner cover layer has a significantly greater thickness - namely at least by a factor of five - compared to the outer cover layer, not only good transmission properties but also low depolarization can be achieved while at the same time having mechanical properties suitable for the intended use, in particular the necessary structural strength.

[0016] It is preferred if the layer thickness of the inner covering layer is at least a factor of six, preferably at least a factor of seven, greater than the layer thickness of the outer covering layer. It has been shown that the transmission and depolarization properties can be further improved if the thickness ratio of the two covering layers is shifted further in favor of the inner covering layer, whereby, with regard to the intended use on the outside of aircraft, it must at the same time be ensured that the outer covering layer can fulfill its protective function against minor mechanical loads, and the total weight of the radome wall, which is regularly influenced to a not inconsiderable extent by the total thickness of the two covering layers, remains as low as possible.

[0017] With regard to the transmission and depolarization properties, it has also proven advantageous if the layer thickness of the inner nuclear layer is smaller than the layer thickness of the outer nuclear layer.

[0018] Preferably, the layer thickness of the inner cover layer is between 3.5 mm and 3.9 mm, preferably between 3.8 mm and 3.9 mm, more preferably 3.85 mm, the layer thickness of the outer cover layer is between 0.5 mm and 0.6 mm, preferably 0.55 mm, the layer thickness of the inner core layer is between 1.8 mm and 2.0 mm, preferably 1.9 mm, and the layer thickness of the outer core layer is between 2.5 mm and 2.9 mm, preferably 2.7 mm. Alternatively or additionally, a tolerance of ±0.2 mm, preferably ±0.1 mm, more preferably ±0.05 mm can be provided for the layer thicknesses.

[0019] In addition to the thicknesses of the individual layers, the dielectric constants of the individual layers can also influence the transmission and depolarization properties of the radome wall. It has proven advantageous if the dielectric constant of the cover layers is greater than the respective dielectric constant of the core layers. The dielectric constants of the cover layers can be between 2.6 and 2.9, preferably between 2.7 and 2.9, more preferably 2.8, the dielectric constant of the inner core layer can be between 1.7 and 1.9, preferably 1.8, and / or the dielectric constant of the outer core layer can be between 1.1 and 1.4, preferably between 1.15 and 1.35, more preferably 1.25.

[0020] The dielectric constants can be chosen differently for each of the layers of the radome wall. However, the dielectric constants of the two Cover layers are identical to one another. Corresponding identical dielectric constants are usually achieved by using identical materials for the cover layers, which can also simplify production. In particular, the dielectric constants of the two core layers must usually be different. Significant differences in the dielectric constants of the core layers have proven particularly advantageous. Regardless of the specific dielectric constants, it is preferable for the dielectric constant of the inner core layer to be at least 1.3 times, and preferably at least 1.4 times, greater than the dielectric constant of the outer core layer.

[0021] The cover layers can each be formed from one or more layers of prepreg material, preferably quartz glass fiber / epoxy prepreg. The core layers are preferably formed from foam material, preferably rigid polyurethane foam.

[0022] For an explanation of the radome according to the invention, reference is made to the above explanations.

[0023] The invention will now be described by way of example using an advantageous embodiment with reference to the accompanying drawings. They show: Figure 1: a schematic section through a first embodiment of a radome wall according to the invention; and Figure 2a-c: Diagrams of transmission and depolarization properties of the radome wall from Figure 1.

[0024] Figure 1 shows a first exemplary embodiment of a radome wall 1 according to the invention for communication, in particular data transmission, in the frequency band from 17 to 31 GHz for use on aircraft in a sectional view.

[0025] The radome wall 1 comprises two cover layers 11, 12 and two core layers 21, 22. Starting from side 2 of the radome wall 1, which during correct use faces the antenna to be protected from external influences, there is provided - in sequence - an outer core layer 21, an inner cover layer 12, an inner core layer 22 and an outer cover layer 11. On the side 3 of the radome wall 1 which faces away from the antenna to be protected during use, a surface coating 4 can be provided for further protection. However, since this is not an integral structural component of the radome wall 1, it is fundamentally only taken into account with regard to the transmission properties of the radome wall 1. The surface coating 4 may, if necessary,However, expected impairment of the transmission properties of the radome wall 1 can, if necessary, be reduced or avoided by suitable selection of a different surface coating 4 and / or, if necessary, adaptation of the layer thicknesses and / or dielectric constants of the individual cover and core layers 11, 12, 21, 22.

[0026] In the illustrated embodiment, the surface coating 4 comprises a multi-layer material application, comprising the layers:

[0027] The cover layers 11, 12 are made of quartz glass fiber / epoxy resin prepreg, while the core layers 21, 22 are made of a rigid polyurethane foam.

[0028] The thickness of the individual cover 11, 12 and core layers 21, 22, as well as their respective dielectric constants are shown in the table below:

[0029] A tolerance of ±0.2 mm, preferably ±0.1 mm, can be provided for the specified thicknesses.

[0030] As is immediately apparent from the table above, the thickness of the inner cover layer 12 is seven times greater than the thickness of the outer cover layer 11. Furthermore, the thickness of the inner core layer 22 is less than the thickness of the outer core layer 21.

[0031] Figures 2a-c show the transmission and depolarization properties of the radome wall 1 according to Figure 1 as a function of the angle of incidence starting from an orthogonal Impingement of the radiation is shown, ie an angle of 0° means an orthogonal impingement.

[0032] Figure 2a shows the transmission properties of radome wall 1 in the transmission band relevant for satellite communications from 27.5 to 31 GHz as a function of the angle of incidence, specifically as transmission loss in [dB] of both the electrical (dashed line) and the magnetic (solid line) components of the electromagnetic radiation. Up to an angle of incidence of 60°, assuming an orthogonal incidence of the radiation, the transmission loss for both the electrical and magnetic components is less than or barely more than 1 dB (dotted line). Up to an angle of incidence of 70°, the transmission losses are so low that satellite communication—or in this case, transmission—is often still possible even up to this angle of incidence.

[0033] Figure 2b is comparable to Figure 2a, but shows the transmission properties of radome wall 1 in the reception range relevant for satellite communications, from 17.7 to 21.2 GHz, as a function of the angle of incidence. Here, the transmission losses up to an angle of incidence of 60°, assuming an orthogonal incidence of the radiation, are less than or barely more than 1 dB (dotted line) for both the electrical (dashed line) and the magnetic component (solid line). At an angle of incidence of 70°, only the transmission loss for the electrical component of the electromagnetic radiation exceeds 1 dB; nevertheless, satellite communication—or in this case, reception—is usually still possible even at such an angle of incidence.

[0034] Figure 2c shows the depolarization properties of the Radome wall 1 for both the satellite communication relevant transmission band from 27.5 to 31 GHz (solid line) as well as for the corresponding reception band from 17.7 to 21.2 GHz (dashed line) is plotted as a function of the angle of incidence. The depolarization properties are depicted as a cross-polarization discrimination (XPD) value. As can be seen from Figure 2c, the depolarization properties in both the transmit and receive bands are below a critical value of -23 dB (dotted line) up to an angle of incidence of 65° and can therefore be classified as excellent. Even at 70°, the depolarization properties can still be described as very good.

[0035] Taking Figures 2a-c together, it can be seen that the radome wall 1 according to Figure 1 exhibits excellent transmission and depolarization properties up to an angle of incidence of 60°, assuming an orthogonal incidence of the radiation, and still very good transmission and depolarization properties up to an angle of incidence of at least 65° or 70°. At the same time, the radome wall 1 exhibits sufficient structural properties to allow its use on the exterior of aircraft, particularly commercial or passenger aircraft.

Claims

Radome wall (1) for satellite communication in the frequency band from 17 to 31 GHz, in particular in the reception band from 17.7 to 21.2 GHz and in the transmission band from 27.5 to 31 GHz, for use on aircraft, comprising a multi-layer structure with an alternating arrangement of force-absorbing, solid cover layers (11, 12) and shear-resistant core layers (21, 22), characterized in that the radome wall (1) has an asymmetrical layer structure with the layer sequence outer core layer (21) - inner cover layer (12) - inner core layer (22) - outer cover layer (11), wherein the layer thickness of the inner cover layer (12) is at least a factor of five greater than the layer thickness of the outer cover layer (11).Radome wall according to claim 1, characterized in that the layer thickness of the inner cover layer (12) is at least a factor of six, preferably at least a factor of seven, greater than the layer thickness of the outer cover layer (11). Radome wall according to one of the preceding claims, characterized in that the layer thickness of the inner core layer (22) is less than the layer thickness of the outer core layer (21). Radome wall according to one of the preceding claims, characterized in that the layer thickness of the inner cover layer (12) is between 3.5 mm and 3.9 mm, preferably between 3.8 mm and 3.9 mm, more preferably 3.85 mm, the layer thickness of the. outer cover layer (11) is between 0.5 mm and 0.6 mm, preferably 0.55 mm, the layer thickness of the inner core layer (12) is between 1.8 mm and 2.0 mm, preferably 1.9 mm, the layer thickness of the outer core layer (21) is between 2.5 mm and 2.9 mm, preferably 2.7 mm. Radome wall according to one of the preceding claims, characterized in that the dielectric constants of the cover layers (11, 12) are each greater than the respective dielectric constants of the core layers (21, 22). Radome wall according to one of the preceding claims, characterized in that the dielectric constant of the inner core layer (22) is at least a factor of 1.3, preferably at least a factor of 1.4, greater than the dielectric constant of the outer core layer (21).Radome wall according to one of the preceding claims, characterized in that the dielectric constants of the cover layers (11, 12) are each between 2.6 and 2.9, preferably between 2.7 and 2.9, more preferably 2.8, the dielectric constant of the inner core layer (22) is between 1.7 and 1.9, preferably 1.8, and / or the dielectric constant of the outer core layer (21) is between 1.1 and 1.4, preferably between 1.15 and 1.35, more preferably 1.

25. Radome wall according to one of the preceding claims, characterized in that the dielectric constants of the cover layers (11, 12). identical, the dielectric constants of the core layers (21, 22) are different. Radome wall according to one of the preceding claims, characterized in that the cover layers (11, 12) are each separated by one or more Layers of prepreg material, preferably quartz glass fiber / epoxy prepreg, are formed, the thickness of the prepreg preferably being 0.275 mm. Radome wall according to one of the preceding claims, characterized in that the core layers (21, 22) are each formed from foam material, preferably from rigid polyurethane foam. Radome for use on aircraft, characterized in that the wall of the radome is designed according to one of the preceding claims.

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