Thermal control apparatus and method for a flexible membrane antenna for space

Abstract

The application discloses a heat control device and method for a flexible thin film antenna in space, which is mainly used for providing heat control for large flexible antennas such as phased array radars in space. A solar shield with high infrared emissivity, low solar absorptivity and microwave permeability is arranged on the front surface of the antenna, and when the back surface of the antenna is irradiated by the sun, the solar shield can quickly dissipate heat by using the high infrared emissivity, and when the front surface of the antenna is irradiated by the sun, the solar shield can prevent the antenna from absorbing too much heat and making the temperature of the antenna too high by using the low solar absorptivity; an insulating layer and a low solar absorptivity coating are arranged on the back surface of the antenna, and when the back surface is irradiated by the sun, the low solar absorptivity coating can reflect most of the solar heat, and when the back surface is in a shadow area, the insulating layer can prevent the temperature of the antenna from being too low. Therefore, the antenna can always be in a relatively suitable temperature range in the complex and changeable space orbit thermal environment. The application has the characteristics of strong adaptability and wide applicability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of space-based phased array radar flexible antenna, and particularly relates to a heat control device and method for a space flexible thin film antenna. BACKGROUND

[0002] Space-based synthetic aperture radar (SAR) can provide timely strategic missile target identification and interception, multi-missile sub-guide automatic guidance at all times and in all weather. Meanwhile, it also has the ability of penetration detection, which can detect targets at a certain depth below the ground, search enemy underground missile launchers, accurately detect enemy missile launches, assist in reading missile trajectories, and track the flight process of missiles in real time, thereby providing strong support for effective missile early warning and interception.

[0003] In order to achieve long-distance, large-range and high-precision early warning observation, a space-based SAR early warning radar needs a large-aperture antenna with high gain. However, for space-based applications, due to the constraints of launch capacity, cost, and deployment reliability, the antenna needs to meet the requirements of large aperture while having a relatively light weight and a highly reliable deployment method. Therefore, large and lightweight antenna technology is a key technology that must be solved for the development of space-based SAR early warning radars.

[0004] Although rigid solid surface antennas are mature in technology and have high gain, they are too heavy and bulky, with a single antenna weight exceeding the current satellite weight. Obviously, it is difficult to meet the application requirements of space-based early warning radars. Flexible thin film antennas have the advantages of light weight, small storage volume, low cost, and unique advantages in reliability and cost, and are currently the preferred design scheme for space-based SAR antennas. However, a flexible SAR antenna without special thermal control measures will experience temperature alternation from +56℃ to -181℃, with a temperature difference of up to 237℃. Such a wide range of temperature changes will cause significant thermal deformation of the antenna array, thereby seriously affecting the resolution of the radar. Patent CN200820180207.1 proposes a thermal control method for solid surface antennas. However, due to the characteristics of high structural stiffness, wide material temperature range, and small restrictions on thermal control measures, the thermal control measures used in the patent cannot be directly applied to flexible thin film antennas.

[0005] Therefore, to realize space applications, appropriate thermal control technology must be adopted to keep the antenna within an appropriate temperature range at all times, thereby reducing thermal deformation caused by temperature changes and ensuring that the antenna array accuracy meets the use requirements. SUMMARY

[0006] Therefore, the application provides a heat control device and method for a space flexible thin film antenna, which is a heat control method combining fast heat dissipation, heat preservation layer and light and heat performance control surface, provides a suitable temperature environment for the antenna, and solves the problem of large array surface deformation caused by sharp temperature change.

[0007] To achieve the above object, the technical scheme of the application is as follows: a heat control device for a space flexible thin film antenna, which is composed of an antenna base film and a circuit layer made on the front surface of the antenna base film.

[0008] The heat control device comprises a sun shield germanium coating, a sun shield base film, an infrared reflective film of a heat preservation layer and a heat insulation net of the heat preservation layer.

[0009] The infrared reflective film of the heat preservation layer and the heat insulation net of the heat preservation layer are arranged in intervals to form a heat control structure on the back surface of the antenna.

[0010] The sun shield germanium coating is prepared on the sun shield base film to serve as a heat control structure on the front surface of the antenna.

[0011] Further, the heat control structure on the back surface of the antenna is composed of 3-50 layers of the infrared reflective film (4) of the heat preservation layer and 2-49 layers of the heat insulation net of the heat preservation layer arranged in intervals, and the number of layers of the heat insulation net is less than that of the infrared reflective film by one layer.

[0012] Further, the sun shield base film is a 5-100 micron thick polyimide film.

[0013] Further, the infrared reflective film of the heat preservation layer is prepared by punching a 5-20 micron thick polyimide or polyester film to form a circular hole array with a diameter of 100-500 microns, and then preparing a 1 nm-5 micron thick metal film coating by using a film deposition technique; and the heat insulation net of the heat preservation layer is an aromatic nylon fiber net.

[0014] Another embodiment of the application provides a heat control method for a space flexible thin film antenna, which is composed of an antenna base film (3) and a circuit layer (6) made on the front surface of the antenna base film; and the heat control is performed by using the following steps:

[0015] Step 1. The antenna base film (3) is prepared by using a flexible copper-clad plate, and a 5-100 micron thick polyimide film is adhered to the front surface of the space flexible thin film antenna as a sun shield base film by using a space silicon-based rubber.

[0016] Step 2. A 1 nm-5 micron thick sun shield germanium coating (1) is prepared on the surface of the sun shield base film (2) prepared in Step 1 by using a film deposition technique.

[0017] Step 3. A 5-20 micron thick polyimide or polyester film is punched by a puncher to form a 100-500 micron diameter circular hole array on the film, and then a 1 nm-5 micron thick metal film coating is prepared on the film by a film deposition technique as a heat insulation layer infrared reflective film.

[0018] Step 4. After the space flexible film antenna is adhered to the back of the space silicon-based rubber adhesive heat insulation layer infrared reflective film, an aromatic nylon fiber mesh is adhered to the back of the space flexible film antenna as a heat insulation mesh; 3-50 layers of infrared reflective film and 2-49 layers of heat insulation mesh are sequentially adhered, and the number of heat insulation mesh layers is less than the number of infrared reflective film layers by one layer.

[0019] Further, the film deposition conditions of Step 2 are as follows: the substrate temperature is room temperature, the purity of the germanium target material is 99.99%, the base vacuum degree is better than 3.5×10-3 Pa, the argon partial pressure is 0.1-0.4 Pa, the sputtering voltage is 200-800 V, the sputtering current is 0.1-2.5 A, the sputtering power is 60-200 W, and the target / substrate distance is 50-300 mm.

[0020] Further, the film deposition conditions of Step 3 are as follows: the substrate temperature is room temperature, the purity of the gold, silver, and aluminum target materials is 99.99%, the base vacuum degree is better than 3.5×10-3 Pa, the argon partial pressure is 0.2-0.5 Pa, the sputtering voltage is 300-750 V, the sputtering current is 0.1-2.2 A, the sputtering power is 50-200 W, and the target / substrate distance is 50-200 mm.

[0021] Beneficial effects:

[0022] 1. The antenna front surface of the present application adopts a heat dissipation layer with high infrared emissivity, low solar absorptivity, and microwave permeability. When the sun irradiates the back surface of the antenna, the heat is quickly dissipated by the high infrared emissivity. When the sun irradiates the front surface of the antenna, the low solar absorptivity prevents the antenna from absorbing too much heat and causing the temperature of the antenna to be too high. The back surface of the antenna adopts an insulating heat preservation layer and a low solar absorptivity coating. When the sun irradiates the back surface, the low solar absorptivity coating reflects most of the solar heat. When in the shadow area, the insulating heat preservation layer prevents the temperature of the antenna from being too low. Thus, the antenna is always in a relatively suitable temperature range in the complex and variable space orbital thermal environment. The problem of the antenna array surface being deformed due to the severe periodic temperature changes during the in-orbit period of the antenna, thereby affecting the key performance of the radar resolution, is solved. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The figure is a schematic diagram of the designed antenna thermal control structure. In the figure, 1 is a germanium coating on the surface of a solar shield; 2 is a base film of the solar shield; 3 is a base film of the antenna; 4 is an infrared reflective film of a heat preservation layer; 5 is a heat insulation mesh of the heat preservation layer; and 6 is a circuit layer made on a copper film of the antenna. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] The solution of this invention is to employ a heat dissipation layer with high infrared emissivity, low solar absorptivity, and microwave transmittance on the front of the antenna. When the sun shines on the back of the antenna, its high infrared emissivity allows for rapid heat dissipation, while its low solar absorptivity prevents the antenna from absorbing excessive heat and overheating when the sun shines on the front. The back of the antenna employs a heat insulation layer and a low solar absorptivity coating. When the sun shines on the back, the low absorptivity coating reflects most of the solar heat, and in the shaded area, the heat insulation layer prevents the antenna from cooling too drastically. This ensures that the antenna remains within a suitable temperature range even in the complex and variable thermal environment of space orbit. This solves the problem of significant deformation of the antenna array caused by drastic periodic temperature changes experienced by the antenna during its time in orbit, which affects key performance characteristics such as radar resolution.

[0026] According to calculations, without effective thermal control measures, when the thin-film antenna uses only the most basic structural and circuit functional layers, the highest temperature the geostationary orbit antenna will experience in orbit will be +57.5℃, and the lowest temperature will be -180.6℃, a temperature difference of 238.1℃. Such drastic temperature changes will cause significant thermal deformation of the antenna, severely impacting the accuracy of the antenna array. Effective thermal control measures must be implemented to reduce the maximum temperature while minimizing the temperature gradient.

[0027] The initial thermal control solution involved designing and fabricating a high-emissivity, low-absorbency thermal control coating on the front of the antenna (facing the ground). This coating's high absorptivity-to-emissivity ratio effectively dissipates solar radiation absorbed from the back of the antenna into the cold, black background of space, thus significantly reducing the overall maximum temperature of the antenna. Analysis showed that the front thermal control layer required a coating material with a surface emissivity of at least 0.8 and an absorptivity of at least 0.2. In addition to these surface performance requirements, the thermal control layer, being on the front of the antenna, also needed good wave transmission performance. Based on these requirements, we selected a 5-100 micrometer thick polyimide film as the substrate for the front thermal control coating. Then, using thin-film deposition techniques such as magnetron sputtering, we fabricated a 1-5 micrometer thick germanium coating with low microwave insertion loss, low solar absorptivity, and antistatic properties as the front thermal control coating for the antenna.

[0028] After adding a heat dissipation coating to the front of the antenna, calculations showed that the highest temperature the antenna would experience on orbit decreased from +57.5℃ to +16.2℃, and the lowest temperature was -182.2℃. The temperature difference decreased from 231.8℃ to 198.4℃.

[0029] In order to further reduce the influence of the external environment on the antenna temperature change, a high reflectivity light blocking layer is designed and prepared on the back of the antenna to reflect the radiant heat from the sun, further prevent the external heat flow from heating the antenna, and effectively reduce the maximum temperature of the antenna. The antenna back thermal control layer requires a surface with high infrared reflectivity, and in order to prevent the absorbed heat from heating the antenna, the thermal insulation performance is good. Since heat transfer in space is mainly in the form of heat conduction and heat radiation, in order to obtain good thermal insulation performance, it is necessary to increase the contact thermal resistance and reduce the infrared absorption, therefore, through design analysis, the double-sided aluminum or gold-coated polyimide or polyester film is used as the infrared reflective film, which can obtain very high infrared reflectivity, and the nylon net between the two infrared reflective films can obtain very small thermal resistance. With a layer of nylon net and two infrared reflective films adhered to each other, in order to obtain very high thermal insulation performance, at least 3 layers or more are required. In order to prevent the infrared reflective film from bulging after being adhered in a vacuum, holes are punched on the film to ensure that the gas is not enclosed between the two films.

[0030] After the above scheme is adopted, the antenna surface temperature change range is -32.7℃ to -64.1℃, and the temperature gradient can be reduced from the original 172.8℃ to 31.4℃. The temperature change range can basically meet the requirements of the space-based SAR flexible antenna on the temperature change range. At this time, the overall temperature change range of the antenna is between +79.7℃ and -128.8℃, which is within the range that the selected structure and the material of the electrical performance layer can withstand.

[0031] The method of the application is as follows:

[0032] 1. A layer of 5-100 microns thick polyimide film is adhered to the front surface (circuit surface) of the flexible copper-clad plate as a solar screen substrate by using space-based silicone rubber;

[0033] 2. A 1 nanometer-5 microns thick germanium coating layer with low microwave insertion loss, low solar absorption rate and anti-static property is prepared on the surface of the polyimide film completed in step 1 by using a thin film deposition technology such as magnetron sputtering, as a solar screen surface thermal control coating;

[0034] 3. A 5-20 microns thick polyimide or polyester film is prepared with a 100-500 microns diameter circular hole array on the film by using a hole puncher, and then a 1 nanometer-5 microns thick coating layer with low solar absorption rate, low infrared emissivity and anti-static property is prepared by using a thin film deposition technology such as magnetron sputtering, and the coating layer material can be selected from gold, silver, aluminum and other metal thin films, as an infrared reflective film of the heat preservation layer;

[0035] 4. After the infrared reflective film is adhered to the antenna back surface by the space silicone rubber, a layer of aromatic nylon fiber net is adhered to the antenna back surface as a heat insulation net; 3-50 layers of infrared reflective film and 2-49 layers of heat insulation net are adhered in sequence, and the number of the heat insulation net layers is less than that of the infrared reflective film layers by one layer;

[0036] The film deposition conditions of step 2 are as follows: the substrate temperature is room temperature, the purity of the germanium target material is 99.99%, the base vacuum is better than 3.5*10 -3 Pa, the argon partial pressure is 0.1-0.4 Pa, the sputtering voltage is 200-800 V, the sputtering current is 0.1-2.5 A, the sputtering power is 60-200 W, and the target / base distance is 50-300 mm.

[0037] The film deposition conditions of step 3 are as follows: the substrate temperature is room temperature, the purity of the gold, silver and aluminum target materials is 99.99%, the base vacuum is better than 3.5*10 -3 Pa, the argon partial pressure is 0.2-0.5 Pa, the sputtering voltage is 300-750 V, the sputtering current is 0.1-2.2 A, the sputtering power is 50-200 W, and the target / base distance is 50-200 mm.

[0038] Example 1

[0039] 1. A 13-micron-thick polyimide film is adhered to the front surface (the surface with the circuit) of the flexible copper-clad plate by the space silicone rubber as a solar shield base;

[0040] 2. A 1-micron-thick germanium coating layer with low microwave insertion loss, low solar absorptance and anti-static is prepared on the surface of the polyimide film completed in step 1 of the example by the magnetron sputtering film deposition technology as a solar shield surface thermal control coating; the film deposition conditions are as follows: the substrate temperature is room temperature, the purity of the germanium target material is 99.99%, the base vacuum is better than 3.5*10 -3 Pa, the argon partial pressure is 0.3 Pa, the sputtering voltage is 3500 V, the sputtering current is 0.25 A, the sputtering power is 150 W, and the target / base distance is 90 mm;

[0041] 3. A 25-micron-thick polyimide or polyester film is punched by a puncher to form an array of circular holes with a diameter of 100 microns, and then a 100-nanometer-thick gold film is prepared as a heat insulation infrared reflective film with low solar absorptance, low infrared emissivity and anti-static by the magnetron sputtering film deposition technology; the film deposition conditions are as follows: the substrate temperature is room temperature, the purity of the gold target material is 99.99%, the base vacuum is better than 3.5*10 -3Pa, argon partial pressure is 0.4 Pa, sputtering voltage is 400 V, sputtering current is 0.2 A, sputtering power is 80 W, aluminum film deposition rate is 35.7 nm / min, target / base distance is 70 mm;

[0042] 4. After the antenna back surface prepared in step 2 of the embodiment is bonded with the infrared reflective film of the heat preservation layer by using the space-based silicone rubber, a layer of aromatic nylon fiber net is bonded thereon as a heat insulation net; 10 layers of infrared reflective film and 9 layers of heat insulation net are sequentially bonded.

[0043] Example Two:

[0044] 1. The front surface (with circuit surface) of the antenna prepared from the flexible copper-clad plate is bonded with a 25-micron-thick polyimide film as a solar shield substrate by using the space-based silicone rubber;

[0045] 2. A 300-nanometer-thick germanium coating layer with low microwave insertion loss, low solar absorptivity and anti-static is prepared on the polyimide film surface prepared in step 1 of the embodiment by using the magnetron sputtering thin film deposition technology as a solar shield surface thermal control coating; the thin film deposition conditions are as follows: the substrate temperature is room temperature, the purity of the germanium target material is 99.99%, the base vacuum degree is better than 3.5*10 -3 Pa, argon partial pressure is 0.3 Pa, sputtering voltage is 3500 V, sputtering current is 0.25 A, sputtering power is 150 W, target / base distance is 90 mm;

[0046] 3. The 25-micron-thick polyimide, polyester and other films are punched by a puncher to prepare a circular hole array with a diameter of 300 microns on the film, and then a 200-nanometer-thick gold film is prepared as a heat preservation layer infrared reflective film with low solar absorptivity, low infrared emissivity and anti-static by using the magnetron sputtering thin film deposition technology; the thin film deposition conditions are as follows: the substrate temperature is room temperature, the purity of the gold target material is 99.99%, the base vacuum degree is better than 3.5*10 -3 Pa, argon partial pressure is 0.4 Pa, sputtering voltage is 400 V, sputtering current is 0.2 A, sputtering power is 80 W, aluminum film deposition rate is 35.7 nm / min, target / base distance is 70 mm;

[0047] 4. After the antenna back surface prepared in step 2 of the embodiment is bonded with the infrared reflective film of the heat preservation layer by using the space-based silicone rubber, a layer of aromatic nylon fiber net is bonded thereon as a heat insulation net; 10 layers of infrared reflective film and 9 layers of heat insulation net are sequentially bonded.

[0048] Example Three:

[0049] Step 1. The front surface (with circuit surface) of the antenna prepared from the flexible copper-clad plate is bonded with a 25-micron-thick polyimide film as a solar shield substrate by using the space-based silicone rubber;

[0050] Step 2. A 500-nm-thick low-microwave-insertion-loss, low-solar-absorption, anti-static germanium coating is prepared on the surface of the polyimide film prepared in step 1 of the embodiment by using a magnetron sputtering thin film deposition technique, as a solar shield surface thermal control coating; the thin film deposition conditions are as follows: the substrate temperature is room temperature, the purity of the germanium target material is 99.99%, the base vacuum is better than 3.5x10 -3 Pa, the argon partial pressure is 0.3 Pa, the sputtering voltage is 3500 V, the sputtering current is 0.25 A, the sputtering power is 150 W, and the target / base distance is 90 mm;

[0051] Step 3. A 25-μm-thick polyimide or polyester film is punched by a puncher to prepare an array of 800-μm-diameter circular holes on the film, and then a 200-nm-thick gold film is prepared as a low-solar-absorption, low-infrared-emissivity, anti-static thermal insulation layer infrared reflective film by using a magnetron sputtering thin film deposition technique; the thin film deposition conditions are as follows: the substrate temperature is room temperature, the purity of the gold target material is 99.99%, the base vacuum is better than 3.5x10 -3 Pa, the argon partial pressure is 0.4 Pa, the sputtering voltage is 400 V, the sputtering current is 0.2 A, the sputtering power is 80 W, the aluminum film deposition rate is 35.7 nm / min, and the target / base distance is 70 mm;

[0052] Step 4. After the thermal insulation layer infrared reflective film is bonded to the back of the antenna prepared in step 2 of the embodiment by using a space silicone rubber, an aromatic nylon fiber mesh is bonded to the film as a heat insulation mesh; 25 layers of infrared reflective films and 24 layers of heat insulation meshes are sequentially bonded.

[0053] In conclusion, the above is only a preferred embodiment of the present application, and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A thermal control device for a flexible membrane antenna for space use, characterized in that, The space flexible thin film antenna is composed of an antenna base film (3) and a circuit layer (6) made on the front side of the antenna base film (3); The thermal control device comprises a solar shield germanium coating (1), a solar shield base film (2), an infrared reflective film (4) of a thermal insulation layer and a thermal insulation net (5) of the thermal insulation layer; The infrared reflective film (4) of the thermal insulation layer and the thermal insulation net (5) of the thermal insulation layer are arranged in intervals to form a thermal control structure on the back side of the antenna; The solar shield base film (2) is prepared with the solar shield germanium coating (1) on the solar shield base film (2) as the thermal control structure on the front side of the antenna; The thermal control structure on the back side of the antenna is composed of 3-50 layers of the infrared reflective film (4) of the thermal insulation layer and 2-49 layers of the thermal insulation net (5) of the thermal insulation layer arranged in intervals, and the number of layers of the thermal insulation net is less than that of the infrared reflective film by one layer; The solar shield base film (2) is a 5-100 micron thick polyimide film; The infrared reflective film (4) of the thermal insulation layer is prepared by punching a 5-20 micron thick polyimide or polyester film to form a circular hole array with a diameter of 100-500 microns on the film, and then depositing a 1-5 micron thick metal film coating on the film by a film deposition technique; The thermal insulation net (5) of the thermal insulation layer is an aromatic nylon fiber net; After adding the heat dissipation coating on the front side of the antenna, the highest temperature experienced by the antenna as a whole in orbit is reduced from +57.5℃ to +16.2℃, the lowest temperature is -182.2℃, and the temperature difference is reduced from 231.8℃ to 198.4℃; The temperature change range of the antenna surface is -32.7℃ to -64.1℃, and the temperature gradient is reduced from 172.8℃ to 31.4℃; the temperature change range meets the requirements of the space-based SAR flexible antenna on the temperature change range, and the temperature change range of the antenna as a whole is between +79.7℃ and -128.8℃, which is within the range that the selected structure and the material of the electrical performance layer can withstand.

2. A method for thermal control of a flexible membrane antenna for space applications, characterized in that, The space flexible thin film antenna is composed of an antenna base film (3) and a circuit layer (6) made on the front side of the antenna base film (3); the thermal control is performed by the following steps: Step 1. The antenna base film (3) is prepared by using a flexible copper-clad plate, and a 5-100 micron thick polyimide film is adhered to the front side of the space flexible thin film antenna as a solar shield base film (2) by using a space silicone rubber; Step 2. A 1-5 micron thick solar shield germanium coating (1) is prepared on the surface of the solar shield base film (2) completed in step 1 by a film deposition technique; Step 3. A 5-20 micron thick polyimide or polyester film is punched by a puncher to form a circular hole array with a diameter of 100-500 microns on the film, and then a 1-5 micron thick metal film coating is prepared on the film by a film deposition technique as an infrared reflective film of a thermal insulation layer; Step 4. After the back side of the space flexible thin film antenna completed in step 2 is adhered to the infrared reflective film of the thermal insulation layer by using a space silicone rubber, an aromatic nylon fiber net is adhered to the infrared reflective film of the thermal insulation layer as a thermal insulation net; 3-50 layers of the infrared reflective film and 2-49 layers of the thermal insulation net are sequentially adhered, and the number of layers of the thermal insulation net is less than that of the infrared reflective film by one layer.

3. A method for thermal control of a flexible membrane antenna for space use according to claim 2, characterized in that, The film deposition conditions of step 2 are as follows: the substrate temperature is room temperature, the purity of the germanium target is 99.99%, the base vacuum is better than 3.5×10-3 Pa, the argon partial pressure is 0.1-0.4 Pa, the sputtering voltage is 200-800 V, the sputtering current is 0.1-2.5 A, the sputtering power is 60-200 W, and the target / substrate distance is 50-300 mm.

4. A method of thermal control of a flexible membrane antenna for space use according to claim 3, characterized in that, The film deposition conditions of step 3 are as follows: the substrate temperature is room temperature, the purity of the gold, silver or aluminum target is 99.99%, the base vacuum is better than 3.5×10-3 Pa, the argon partial pressure is 0.2-0.5 Pa, the sputtering voltage is 300-750 V, the sputtering current is 0.1-2.2 A, the sputtering power is 50-200 W, and the target / substrate distance is 50-200 mm.

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