Flight antenna for high thermal loading

Abstract

An antenna, in particular for a hypersonic flying object, with a baseplate, a cone-shaped forebody and an RF connection, which is arranged beneath an extension of the forebody and has external insulation, wherein the forebody is formed in a cone shape in such a way that its apex angle lies between 25° and 28° and in the rear region it merges into the narrower extension, and wherein the forebody has an elevation angle of 15° to 17° between the baseplate and a lateral surface of the forebody.

Description

[0001] Fluq antenna for high temperature load

[0002] The present invention relates to an antenna or antenna structure, in particular for a hypersonic aircraft. Furthermore, the present invention relates to an aircraft having such an antenna.

[0003] The number of aircraft traveling for extended periods in the hypersonic range at speeds greater than Mach 5 (1715 m / s) over long distances in the atmosphere is constantly increasing. Due to the resulting long duration of atmospheric flow, the antenna systems mounted on the aircraft's outer skin are subject to extreme heat input. Therefore, high-temperature antenna systems are necessary for reliable data transmission. The antenna types used to date allow flight times of up to 55 s.c. under these flight conditions before they overheat.

[0004] Such an antenna is known, for example, from DE 10 2006 024 129, which features a wedge-shaped front body intended to make the antenna aerodynamic and protect the antenna's RF connector behind the front body from incoming airflow. It has been determined that, due to its design, the antenna is unsuitable for incoming airflow lasting several minutes, taking into account its electrical and mechanical properties. Due to its elevated design, the antenna is subject to greater interaction with hot air at very high stagnation point velocities, resulting in increased heat input.

[0005] Existing and known antennas are therefore no longer functional under prolonged thermal stress. Due to costs, delivery times, and approval procedures, corresponding custom designs are impossible or difficult to manufacture. These antennas may also not produce the required antenna pattern. An S-band antenna capable of long-term thermal stress is not currently available.

[0006] The object of the present invention is to provide an antenna which can withstand the thermal stresses during hypersonic flight of a flying object.

[0007] The object is achieved by an antenna according to claim 1 and a flying object according to claim 15.

[0008] The antenna according to the invention, in particular for a hypersonic aircraft, has a base plate and a conical pre-body. Furthermore, the antenna has an extension of the pre-body. An RF connector with external insulation is arranged beneath the extension. The pre-body is conically shaped such that its opening angle is between 25° and 28° and merges into a narrow extension in the rear region, i.e. in a region facing away from the cone apex, in particular at the cone base. The extension is in particular narrower than the conical pre-body. Furthermore, the pre-body has an elevation angle of 15° to 17° between the base plate and a lateral surface of the pre-body.

[0009] Absorbed heat can be transferred via the base plate to the underlying heat-conducting structure of the aircraft.

[0010] Preferably it is an S-band antenna.

[0011] The opening angle is preferably 26.7°.

[0012] Preferably the elevation angle is 16.4°.

[0013] Preferably, the thickness of the base plate is 3 mm. Preferably, the distance between the base plate and the extension is 2 mm to 4 mm, and in particular 3 mm.

[0014] When installed, the surface of the base plate is preferably flush with the surface of the aircraft. The antenna base plate is thus flat and is screwed recessed into the surface of the aircraft. This ensures good heat transfer from the antenna to the aircraft. At the same time, no edges of the base plate are directly exposed to the airflow, thus reducing heat input to the antenna.

[0015] Preferably, an upper edge of the preform and / or an upper edge of the extension, starting from the base plate, has a height of less than 10 mm, and in particular 8 mm or less. When installed, the antenna thus protrudes less than 10 mm, and in particular 8 mm, from the outer surface of the flying object. This creates an antenna with a low installation height, so that the exposure of the antenna structure to the flow is reduced, which simultaneously also allows heat generation at the antenna to be reduced. Thus, interaction with the incoming flow is kept to a minimum by keeping the structure as flat as possible.

[0016] Preferably, the tip of the preform is flush with the surface of the base plate. Thus, the tip of the preform's cone is positioned on the surface of the base plate or flush with it.

[0017] Preferably, the preform is rotationally symmetrical, in particular about the cone axis of the preform.

[0018] Preferably, the antenna has a resonant frequency between 2200 MHz and 2400 MHz. Preferably, the antenna has a return loss of 20 dB or more, and in particular 28 dB.

[0019] Preferably, the antenna has a bandwidth of 100MHz or more.

[0020] Preferably, one or more of the base plate, the preform and the extension are made of a copper-beryllium alloy, in particular CuNi2Be or CuCo2Be.

[0021] Preferably, the base plate, the pre-body and the extension are made of the same material.

[0022] Preferably, the base plate, the pre-body and the extension are formed in one piece.

[0023] For thermal insulation of the RF connector, the outer insulation is preferably made of a temperature-resistant ceramic. The temperature-resistant ceramic is preferably made of glass ceramic.

[0024] Furthermore, the present invention relates to a flying object such as a rocket or a re-entry body of a rocket, wherein the flying object has at least one antenna as described above.

[0025] Preferably, the flying object has at least four antennas, which are arranged in particular along the circumference of the flying object at a distance of substantially 90°.

[0026] The flying object preferably has a recess, the depth of the recess corresponding to the thickness of the base plate, and the antenna is arranged in the recess. The flying object preferably has heat sinks, which are arranged in particular in the recess, with the antenna being arranged on the heat sink. Heat generated at the antenna can be transferred to the heat sinks, thereby reducing the thermal load on the antenna.

[0027] The invention is explained in more detail below using preferred embodiments with reference to the accompanying drawings.

[0028] They show:

[0029] Figure 1 is a schematic sectional view of an antenna according to the present invention,

[0030] Figure 2 is a schematic plan view of an antenna according to the present invention and

[0031] Figure 3 is a perspective, not to scale, view of an antenna according to the present invention.

[0032] The antenna 10 according to the invention has a base plate 12, which can be connected to a flying object 16 (schematically shown in Figure 1) via corresponding bores 14 by means of one or more screws, in particular a countersunk screw. The base plate 12 also has bores 18 for connection to an RF connector. A conical pre-body 20 is integrally connected to the base plate 12. The conical pre-body 20 has an opening angle α of 25° to 28° and in particular 26.7°. Furthermore, the conical pre-body 20 has an elevation angle β of 15° to 17° and in particular 16.4°. The upper edge of the conical pre-body 20 protrudes less than 10 mm and in particular 8 mm above the surface 22 of the base plate 12. At the rear of the conical front body 20 there is a narrow extension 24 which is arranged at a distance from the base plate.This distance is 3 mm to 5 mm, and in particular 3 mm. The length of the extension 24 is 25 mm to 30 mm, and in particular 27.9 mm. An RF connector 26 is arranged below the extension 24, which has an outer insulation made in particular of ceramic, which surrounds the RF connector. The extension 24 is narrower than the conical preform 20, so that the RF connector 26 arranged below the extension 24 is located in the slipstream or dead-water area of ​​the preform, thus minimizing heat input to the RF connector.

[0033] As can be seen from Figure 1, the antenna is arranged in a recess 28 of the flying object 16, so that the surface 22 of the base plate 12 is flush with a surface 30 of the flying object 16. This prevents airflow against the base plate. At the same time, this allows the antenna's installation height to be reduced. Thus, the installation height of the antenna according to the present invention, i.e., the distance between the surface 30 of the flying object 16 and the upper edge of the extension 24 or the conical preform 20, is less than 10 mm and in particular 8 mm or less.

[0034] At the same time, the base plate can be arranged on a (not shown) heat body of the flying object 16, so that heat introduced into the antenna 10 can be passed on to the heat body.

[0035] The conical, axially symmetrical front body ensures minimized shock generation through its elevation angle of 15° to 17° with a cone opening angle of 25° to 27°. This keeps the stagnation point velocity low. Further along, the front body 20 is connected to the core area of ​​the antenna, formed by the extension 24. An RF connector 26 is provided in the first third of the extension 24, which is located in the dead-water area due to the front body 20.

[0036] The combination of recessed mounting, lower height, and modified shape results in an overall reduction in heat input under the same airflow, improved dissipation to the cooler surrounding and underlying structures, and, due to the increased thermal mass in the front area, reduced heat input into the actual radiating body of the antenna's high-frequency range. Comparative wind tunnel tests have shown a potential exposure time approximately 40% longer with the same airflow characteristics. This time can be further extended through active cooling.

[0037] The basic mechanical structure is inherent in the antenna type itself and cannot be changed at will. Any change in the shape has a direct impact on the antenna's function and its frequency range. At the same time, the antenna design affects its interaction with the high-speed flow and the resulting heat input. This influences the change in the antenna's electrical and high-frequency characteristics. Simulations based on the embodiment of the present invention demonstrate an optimization between minimal design and compliance with high-frequency properties. Thus, an antenna is created whose high-frequency properties can be fulfilled with the antenna radiation pattern, antenna matching, and resonant bandwidth behavior.

[0038] The S-band antenna is designed for use on flying objects such as sounding rockets, which are subject to increased temperature stress.

[0039] Its function, for example, is to transmit an S-band radio-frequency signal generated by a telemetry transmitter. The frequency range used here extends from 2200 MHz to 2400 MHz. This range is used for telemetry data transmission from the flying object to the ground. The antenna generates a hemispherical antenna pattern with two different polarizations. Both polarizations together result in the hemispherical radiation pattern. Four such individual S-band antennas generate a spherical antenna pattern, which ensures particularly low dips in field strength in the direction of flight in the rear area of ​​the flying object, which is important for reception of the telemetry ground receiving station regardless of the flight attitude. The conical tip of the front body 20 points in the direction of movement of the flying object.

[0040] Additional frequency ranges of 1.5 GHz and 5.1 GHz are possible with the same mechanical modifications. The basic aerodynamic design remains unchanged, with only changes to the radiator lengths and antenna connection.

[0041] The underlying antenna principle is comparable to a classic lambda / 4 wavelength radiator. For aerodynamic reasons, this radiator is folded over and lies flat over its reflective surface. Its required conductive base surface, formed by the base plate 12, on which it is mounted, has a diameter of at least greater than lambda / 2. The radiator element, formed by the extension 24, is connected to the base surface in the front section via the pre-body 20 to dissipate any electrostatic charges. For loss-free input of the RF S-band signal, a base point impedance of 50 ohms, with few complex components, was determined by simulation. This optimized point on the antenna radiator element is located in the front third. The measured antenna matching (input reflection factor = Sil) in the resonance case is greater than 20 dB, which means that more than one hundredth of the input power is reflected.The resulting antenna pattern contains two polarization patterns with a horizontal and vertical field distribution. These are position-dependent. The entire image of both polarizations covers one hemisphere. The individual antenna body itself is made of a high-temperature copper-beryllium alloy, such as CuNiZBe, whose melting range is between 1030 and 1100°C.

[0042] The axially symmetric antenna preform 20, in a semi-conical shape with a 16° elevation angle, ensures low temperature peaks by displacing the incoming flow at low compression shock intensity. The installation height of only 8 mm reduces interaction with the incoming flow due to the low displaced volume, and the majority of the antenna remains in the slow flow boundary layer. This minimizes the effective stagnation point velocity and thus the heat input. A dead-water zone is created in the rear area, which protects the radiator and the RF connector from the flow. The preform, made of copper-beryllium, dissipates the resulting heat input to the antenna base plate.

[0043] The 3 mm thick base plate, made of the same material, has a flat underside, providing low heat transfer resistance to the mounted base plate of the aircraft. It is flush with the structure of the aircraft, which is made of a material with good thermal conductivity. This structure absorbs the heat input and enlarges the heat sink. This measure significantly extends its thermal resilience. M4 countersunk screws secure the antenna to the rocket structure. The screw directly beneath the front body ensures low heat transfer resistance and directs this warmest point into the heat sink. The base plate secures the RF connector, which is a steel SMA flange socket, with four M2.5 screws.

[0044] Available antenna models are significantly taller in their construction, without good heat dissipation into the structure, or are considerably more expensive to purchase due to the complex construction of a patch antenna.

Claims

Claims: An antenna, in particular for a hypersonic flying object, comprising a base plate, a conical forebody, and an RF connector with external insulation arranged under an extension of the forebody, wherein the forebody is conical such that its opening angle is between 25° and 28° and transitions into the narrower extension in the rear region, and wherein the forebody has an elevation angle of 15° to 17° between the base plate and a lateral surface of the forebody. Antenna according to claim 1, characterized in that it is an S-band antenna. Antenna according to claim 1 or 2, characterized in that the opening angle is 26.7°. Antenna according to any one of claims 1 to 3, characterized in that the elevation angle is 16.4°. Antenna according to any one of claims 1 to 4, characterized in that the base plate has a thickness of 2 mm to 6 mm, and in particular 3 mm. An antenna according to any one of claims 1 to 5, characterized in that, in the installed state, a surface of the base plate is flush with a surface of the aircraft. An antenna according to any one of claims 1 to 6, characterized in that the upper edge of the front section, extending from the base plate, has a height of less than 10 mm, and in particular 8 mm or less. An antenna according to any one of claims 1 to 7, characterized in that the tip of the front section is flush with the surface of the base plate. An antenna according to any one of claims 1 to 8, characterized by a resonant frequency between 2200 MHz and 2400 MHz. An antenna according to any one of claims 1 to 9, characterized by a reflection loss of 20 dB or more, and in particular 28 dB. An antenna according to any one of claims 1 to 10, characterized by a bandwidth of 100 MHz or more.Antenna according to any one of claims 1 to 11, characterized in that the base plate, the front body, and the extension are made of a copper-beryllium alloy, in particular CuNi2Be or CuCo2Be. Antenna according to any one of claims 1 to 12, characterized in that the base plate, the front body, and the extension are formed in one piece. Flying object, in particular a rocket or reentry vehicle of a rocket, with at least one antenna according to any one of claims 1 to 13. Flying object according to claim 14, characterized by at least four antennas, which are arranged in particular along the circumference of the flying object. Flying object according to claim 14 or 15, characterized by a recess, wherein the depth of the recess corresponds to the thickness of the base plate. Flying object according to any one of claims 14 to 16, characterized by heat sinks, in particular arranged in the recesses, wherein the antenna is arranged on the heat sink.

Images