Lightweight and small full polarization SAR satellite system based on reflector mechanism

Abstract

The application provides a light and small full polarization SAR satellite system based on a reflecting surface mechanism, which comprises a comprehensive electronic cabin, a load cabin, a support cabin, an antenna unfolding mechanism, a multi-polarization phased array feed, and a reflecting surface antenna. The reflecting surface antenna is a double-focus ellipsoidal parabolic reflector, the azimuth focal point and the range focal point do not coincide, and the multi-polarization phased array feed is located at the azimuth focal point. The multi-polarization phased array feed comprises N dual-polarization radiation units arranged in a column in the longitudinal direction, penetrating through the top surface of the feed shell from the inside of the feed shell, and the dual-polarization radiation unit comprises a horn radiation port, a V-polarized radio frequency connection port, and an H-polarized radio frequency connection port; and N double-channel T / R components. The SAR satellite system of the application adopts a double-focus ellipsoidal parabolic surface combined with a multi-polarization phased array feed, has scanning and shaping capabilities along the range direction while realizing full polarization function.

Description

Technical Field

[0001] This application belongs to the field of synthetic aperture radar (SAR) satellite technology, and relates to a lightweight, fully polarimetric SAR satellite system based on a reflector antenna. Background Technology

[0002] Spaceborne synthetic aperture radar (SAR) has the advantages of all-weather and all-time imaging, has a certain penetration capability of the ground surface and forest vegetation, and can provide different polarization information to achieve high-resolution and wide-swath observation capabilities. It is currently a major means of realizing microwave remote sensing observation of the earth.

[0003] Lightweight SAR satellites based on reflector antennas are an important development direction in the field of SAR satellites. Compared with planar phased array SAR satellites, reflector SAR satellites have the advantages of being lightweight and small in size, which reduces the cost of satellite development and also reduces the requirements of the satellite on the rocket envelope size and carrying capacity, thus reducing launch costs.

[0004] Currently, existing SAR satellites with reflector antennas all use a fixed multi-beam feed + parabolic reflector antenna system, which can only achieve single polarization and cannot achieve dual polarization or full polarization. Summary of the Invention

[0005] To address the problems in existing technologies, this invention proposes a lightweight, fully polarimetric SAR satellite system based on a reflector system, which not only achieves full polarization but also has scanning and shaping capabilities along the range direction.

[0006] This application provides a lightweight, compact, fully polarimetric SAR satellite system based on a reflector design. The SAR antenna includes an integrated electronics compartment, a payload compartment, a support compartment, an antenna deployment mechanism, a multi-polarization phased array feed, and a reflector antenna. The reflector antenna and the multi-polarization phased array feed are connected to the support compartment via the antenna deployment mechanism.

[0007] The payload compartment is located on one side of the integrated electronics compartment and is used to carry SAR payloads;

[0008] The support compartment is fixed to one side of the payload compartment and is used to support the antenna deployment mechanism and connect the antenna deployment mechanism to the payload compartment.

[0009] The antenna deployment mechanism is fixed to the support cabin and is used to deploy the reflector antenna and the multi-polarized phased array feed in orbit, while ensuring that the reflector antenna is compact in the retracted state. The reflector antenna is a bifocal ellipsoidal parabolic reflector, which has an azimuth focus in the azimuth direction and a range focus in the range direction. The azimuth focus and the range focus do not coincide. After the reflector antenna is deployed in orbit, the antenna deployment mechanism positions the multi-polarized phased array feed at the azimuth focus.

[0010] The multi-polarization phased array feed is fixedly connected to the antenna deployment mechanism, and the multi-polarization phased array feed includes:

[0011] The feed housing has a top surface and opposing first and second longitudinal sidewalls;

[0012] N dual-polarized radiating elements are arranged in a vertical row, penetrating through the top surface of the feed housing from inside the feed housing. Each dual-polarized radiating element includes a horn radiating port, a V-polarized RF connection port, and an H-polarized RF connection port.

[0013] There are N dual-channel T / R modules, each with a V channel and an H channel. N / 2 of the dual-channel T / R modules are V-polarized dual-channel T / R modules, located on the inner wall of the first longitudinal side wall of the feed housing; the other N / 2 dual-channel T / R modules are H-polarized dual-channel T / R modules, located on the inner wall of the second longitudinal side wall of the feed housing.

[0014] 2N RF connectors are used to connect N dual-channel T / R components to the V-polarized RF connection port and H-polarized RF connection port of the dual-polarized radiating unit, respectively.

[0015] According to at least one embodiment of this application, the distance to the focal point is closer to the bifocal ellipsoidal parabolic reflector.

[0016] According to at least one embodiment of this application, the phased array feed is pushed forward toward the focal point relative to the distance of the bifocal ellipsoidal parabolic reflector.

[0017] According to at least one embodiment of this application, the multi-polarization phased array feed is used to implement multiple polarization modes, including single-polarization mode, dual-polarization mode, and full-polarization mode.

[0018] According to at least one embodiment of this application, the horn radiation port is located outside the feed housing, and the V-polarized RF connection port and the H-polarized RF connection port are located inside the feed housing.

[0019] According to at least one embodiment of this application, N is an integer greater than or equal to 2.

[0020] According to at least one embodiment of this application, the RF connector has a right-angle bend connection structure, a first port and a second port, the first port being used to connect to a dual-channel T / R assembly, and the second port being connected to the V-polarized RF connection port or the H-polarized RF connection port of a dual-polarized radiating unit via an RF cable.

[0021] According to at least one embodiment of this application, the entire interior of the RF connector is filled with a dielectric, eliminating the cavity structure inside the RF connector.

[0022] According to at least one embodiment of this application, the dual-focal ellipsoidal parabolic reflector SAR antenna has an aperture of 9.10m × 3.75m and an azimuth focal length of 4m.

[0023] According to at least one embodiment of this application, the dual-polarized radiating element is implemented by a horn antenna element, and an orthogonal mode coupler is provided at the lower end of the horn radiating port of the dual-polarized radiating element.

[0024] This invention adopts a new imaging system for SAR antennas using a multi-polarization phased array feed and a dual-focus ellipsoidal parabolic reflector, which can realize the full polarization function of SAR satellites, greatly improve the reliability of the system, and at the same time take into account the light weight of the whole satellite, small satellite envelope size, and good overall satellite mechanical properties. Attached Figure Description

[0025] The following description, in conjunction with the accompanying drawings, will further illustrate the above-mentioned features, technical characteristics, advantages, and implementation methods of this application in a clear and understandable manner. The accompanying drawings are for illustrative and explanatory purposes only and do not limit the scope of this application. Wherein:

[0026] Figure 1 This is a schematic diagram of the SAR satellite of the present invention when the reflector and feed source are deployed;

[0027] Figure 2 This is a schematic diagram of the SAR satellite of the present invention when the reflector and feed source are retracted;

[0028] Figure 3 This is a schematic diagram of the SAR antenna system of the present invention;

[0029] Figure 4 This is a schematic diagram of the external structure of the phased array feed of the present invention;

[0030] Figure 5 This is a schematic diagram of the internal structure of the phased array feed of the present invention;

[0031] Figure 6 This is a schematic diagram of the radiation unit structure of the present invention;

[0032] Figure 7This is a schematic diagram of the all-dielectric-filled structure of the high-power connector of the present invention;

[0033] Figure 8 This is a side view of the bifocal ellipsoidal parabolic antenna reflector of the present invention. Detailed Implementation

[0034] To provide a clearer understanding of the technical features, objectives, and effects of this application, specific embodiments of this application will now be described with reference to the accompanying drawings.

[0035] like Figure 1 and Figure 2 As shown, the SAR satellite based on a multi-polarized phased array feed and reflector antenna provided in this application includes: an integrated electronics module 6; a payload module 3; a support module 4; an antenna deployment mechanism 5; and a multi-polarized phased array feed 1, the structure of which is as follows: Figure 4 and Figure 5 As shown; reflector antenna 2 is a double-focal ellipsoidal parabolic reflector, its structure is as follows. Figure 3 and Figure 8 As shown.

[0036] The payload compartment 3 is located on one side of the integrated electronics compartment 6 and is used to carry the SAR payload. The payload compartment 3 has a smaller lateral (i.e., Z-direction in the figure) dimension than the integrated electronics compartment 6, thus forming accommodating spaces on both sides of the payload compartment 3. The payload compartment 3 is asymmetrical (i.e., not centered) relative to the integrated electronics compartment 6, so that the accommodating space on the left (-Z direction) is smaller than the accommodating space on the right (Z direction).

[0037] The support compartment 4 is fixed to one side of the payload compartment 3 and is used to support the antenna deployment mechanism 5 and connect the antenna deployment mechanism 5 to the payload compartment 3. The support compartment 4 is a trapezoidal body with a top surface 41 and an inclined surface 42 that is tilted relative to the payload compartment 3.

[0038] Antenna deployment mechanism 5, fixed to support cabin 4, is used to deploy reflector antenna 2 and multi-polarized phased array feed 1 in orbit, such as... Figure 1 As shown, this design ensures that the reflector antenna 2 has a compact structure when retracted. The antenna deployment mechanism 5 includes multiple support rods connected in an interlaced manner. One end of the antenna deployment mechanism 5 is connected to the top surface 41 and the inclined surface 42 of the support cabin 4, and the other end is connected to the reflector antenna 2 and the multi-polarized phased array feed 1. In the retracted state, the reflector antenna 2 is retracted into the (-Z direction) accommodating space on the left side of the load cabin 3, and the multi-polarized phased array feed 1 is retracted into the (Z direction) accommodating space on the right side of the load cabin 3.

[0039] Among them, the multi-polarization phased array feed 1 can realize multiple polarization modes, including single-polarization mode, dual-polarization mode, and full-polarization mode, such as... Figure 2 and Figure 3As shown, the multi-polarization phased array feed 1 is fixedly connected to the antenna deployment mechanism 5. The multi-polarization phased array feed 1 includes:

[0040] The feed housing 11 has a top surface 111, two opposing longitudinal sidewalls 112 and two opposing transverse sidewalls 113;

[0041] N dual-polarized radiating elements 12 (16 dual-polarized radiating elements in this embodiment) are arranged in a vertical row, penetrating from the inside of the feed housing 11 and passing through the top surface 111 of the feed housing 11. The dual-polarized radiating elements are implemented by horn antenna elements. Figure 4 A single dual-polarized radiating element is shown, featuring a low cross-polarization horn structure. The single dual-polarized radiating element includes a horn radiating port 121, a first polarized RF connection port 12V (V-polarized RF connection port in this embodiment), and a second polarized RF connection port 12H (H-polarized RF connection port in this embodiment). The horn radiating port 121 is located outside the feed housing 11, while the first polarization port V and the second polarization port H are located inside the feed housing 11. An orthogonal mode coupler (not shown) is also provided at the lower end of the horn radiating port. Under the condition of sharing a single dual-polarized radiating element, H-orthogonal polarization and V-orthogonal polarization are implemented independently to achieve dual-polarization functionality.

[0042] There are N dual-channel T / R modules (16 in this embodiment), each with a V-channel and an H-channel. N / 2 (8 in this embodiment) of the dual-channel T / R modules are V-polarized dual-channel T / R modules 13V, and the other N / 2 (8 in this embodiment) are H-polarized dual-channel T / R modules 13H. Eight V-polarized dual-channel T / R modules are located on the inner wall of one longitudinal sidewall 112 of the feed housing 11, and eight H-polarized dual-channel T / R modules are located on the inner wall of the other longitudinal sidewall 112 of the feed housing 11. Figure 3 As shown, it illustrates eight H-polarized dual-channel T / R modules 13H located on the inner wall of the longitudinal sidewall 112. The dual-channel T / R modules are independently configured within the two opposing sidewalls of the feed housing 11 according to H-polarization and V-polarization, allowing the SAR satellite system to flexibly select operating modes as needed: H-single polarization mode, V-single polarization mode, H-dual polarization mode, V-dual polarization mode, and full polarization mode. The dual-channel T / R modules employ S-band gallium nitride (GaN) power devices with an output power exceeding 200W. GaN power devices offer advantages such as high output power, strong radiation resistance, and the ability to operate at high temperatures.

[0043] 2N RF connectors 14 are used to connect the V channel and H channel of the dual-channel T / R assembly 13 to the RF connection ports 12V and 12H of the dual-polarized radiating unit, respectively. For example... Figure 5As shown, the RF connector 14 has a right-angle bend connection structure 143, a first port 141, and a second port 142. Figure 4 As shown, its first port 141 is used to connect to the dual-channel T / R component 13, and the second port 142 is connected to the radio frequency connection ports 12V and 12H of the dual-polarized radiation unit via radio frequency cables.

[0044] In this embodiment, the radio frequency connector 14 has a right-angle bent connection structure 143, and the orientations of the first port 141 and the second port 142 are perpendicular to each other.

[0045] In this embodiment, 16 dual-channel T / R modules with an output power of not less than 200W are directly arranged in the multi-polarized phased array feed. Sixteen dual-polarized radiating units are used, each directly carrying the high-power output of the dual-channel T / R modules. The interior of the high-power RF connector 14 (especially at the right-angle bend connection structure 143 of the RF connector 14) is completely filled with dielectric 144, eliminating the internal cavity structure of the RF connector 14 and enhancing the anti-micro-discharge performance of the high-power RF connector 14.

[0046] like Figure 1 As shown, the SAR satellite system based on a multi-polarization phased array feed and a reflector antenna provided in this application also includes a bifocal ellipsoidal parabolic reflector 2. This bifocal ellipsoidal parabolic reflector 2 is a bifocal ellipsoidal parabola, which, in conjunction with the multi-polarization phased array feed 1, is used to achieve full polarization and range scanning functions.

[0047] Figure 1 A side view of the bifocal ellipsoidal parabolic reflector 2 is shown. Figure 6 A front view of the bifocal ellipsoidal parabolic reflector 2 is shown. (See figure) Figure 1 and Figure 6 As shown, the bifocal ellipsoidal parabolic reflector 2 is a bifocal ellipsoidal parabolic reflector, which has a bifocal ellipsoidal parabolic surface in the azimuth direction ( Figure 6 The focal length in the Y direction is f1, and the focal point in the azimuth direction is p1; its focal length in the range direction is... Figure 6 The focal length in the X direction is f2, and the focal point in the upward direction is p2.

[0048] After the reflector antenna is deployed in orbit, the antenna deployment mechanism 5 positions the phased array feed 1 at the azimuth focus p1 of the dual-focus ellipsoidal parabolic reflector 2, thereby enhancing the antenna beam gain by utilizing the focusing capability of the reflector. The phased array feed 1 is pushed forward relative to the range focus p2 of the dual-focus ellipsoidal parabolic reflector 2 (i.e., closer to the dual-focus ellipsoidal parabolic reflector 2 relative to the range focus p2), increasing the range beam scanning angle, thus enabling flexible shaping of the range beam by utilizing the phase scanning capability of the phased array feed 1.

[0049] Existing SAR satellite systems typically employ standard parabolic antennas; however, this antenna configuration cannot meet the application requirements of forming a beam-scanning SAR antenna with a phased array feed. To address this issue, this invention proposes a dual-focal ellipsoidal parabolic reflector with different focal lengths in the range and azimuth directions, and the azimuth and range focal points do not coincide. This invention achieves full polarization and range scanning capabilities for SAR satellites by employing a novel imaging system combining a multi-polarization phased array feed and a dual-focal ellipsoidal parabolic reflector SAR antenna.

[0050] Existing SAR satellite systems employing fixed multi-beam feeds and parabolic reflector antennas typically utilize a method of centralized high-power amplification within the SAR satellite module, followed by long-distance waveguide transmission to the external fixed multi-beam feed. This approach results in significant insertion loss and low system reliability. To address this issue, the present invention provides a SAR satellite system based on a multi-polarized phased array feed and reflector antenna. In this system, the dual-channel T / R module of the multi-polarized phased array feed is independently configured according to H-polarization and V-polarization. Compared to the centralized high-power amplification method used in existing on-orbit SAR satellites, the present invention employs a redundant design improvement, significantly enhancing system reliability. Furthermore, the present invention utilizes multiple dual-polarized radiating elements, with multiple high-output-power (in this embodiment, output power not less than 200W) dual-channel T / R modules directly arranged on the multi-polarized phased array feed. Compared to the existing method of centralized high-power amplification within the SAR satellite module followed by long-distance waveguide transmission to the external fixed multi-beam feed, this application reduces insertion loss during long-distance transmission of concentrated power.

[0051] Compared with the fixed multi-beam feed in the prior art, the multi-polarized phased array feed used in this application can achieve beam position control by controlling the amplitude and phase of small signals through beam control codes. This can reduce the insertion loss on high-power links in the transmit link and significantly improve the reliability of the system.

[0052] For high-output power dual-channel T / R components, this invention also proposes a high-power connector with a fully dielectric-filled state, whose peak power resistance to micro-discharge can reach over 1000W. This significantly improves the product's ability to withstand micro-discharge, eliminates the internal cavity structure of the connector, and avoids the dielectric micro-discharge mechanism.

[0053] According to a preferred embodiment of this application, the dual-focal ellipsoidal parabolic reflector 2 has an aperture of 9.10m × 3.75m and an azimuth focal length of 4m, ensuring an optimal focal-to-diameter ratio, thereby achieving the highest reflector aperture efficiency and maximum gain. This aperture size of the dual-focal ellipsoidal parabolic reflector antenna is currently the largest among on-orbit SAR satellites. The SAR antenna reflector weight can be as low as 76kg, the phased array feed weight as low as 66kg, and the deployment mechanism weight as low as 46kg. Considering the total weight of the cable and thermal control SAR antenna is 199kg, compared to a planar phased array antenna, the weight is only about one-third of that of a planar phased array antenna.

[0054] To achieve a lightweight satellite with a small satellite envelope, this application employs a rational satellite configuration layout, designs an asymmetrical payload bay and trapezoidal support bay, and designs a phased array feed and reflector antenna deployment mechanism. This meets the on-orbit deployment requirements of the large-aperture reflector antenna while ensuring a compact structure when the large-aperture reflector antenna is folded up, thus guaranteeing good overall satellite mechanical characteristics and adaptability to the mechanical environment during launch.

[0055] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0056] The above description is merely an illustrative embodiment of this application and is not intended to limit the scope of this application. Any equivalent changes, modifications, and combinations made by those skilled in the art without departing from the concept and principles of this application shall fall within the scope of protection of this application.

Claims

1. A lightweight, small-scale, fully polarimetric SAR satellite system based on a reflector design, comprising an integrated electronics compartment, a payload compartment, a support compartment, an antenna deployment mechanism, a multi-polarization phased array feed, and a reflector antenna, wherein the reflector antenna and the multi-polarization phased array feed are connected to the support compartment via the antenna deployment mechanism. in, The payload bay is located on one side of the integrated electronics bay and is used to carry SAR payloads; The support compartment is fixed to one side of the payload compartment and is used to support the antenna deployment mechanism and connect the antenna deployment mechanism to the payload compartment. The antenna deployment mechanism is fixed on the support cabin to enable the reflector antenna and the multi-polarized phased array feed to be deployed on track, while ensuring that the reflector antenna is compact in the retracted state. Among them, the reflector antenna is a dual-focal ellipsoidal parabolic reflector, which is a dual-focal ellipsoidal paraboloid. The dual-focal ellipsoidal parabolic reflector has an azimuth focus in the azimuth direction and a range focus in the range direction. The azimuth focus and the range focus do not coincide. After the reflector antenna is deployed on the track, the antenna deployment mechanism makes the multi-polarized phased array feed located at the azimuth focus. The multi-polarization phased array feed is fixedly connected to the antenna deployment mechanism, and the multi-polarization phased array feed includes: The feed housing has a top surface and opposing first and second longitudinal sidewalls; N dual-polarized radiating elements are arranged in a vertical row, penetrating through the top surface of the feed housing from inside the feed housing. Each dual-polarized radiating element includes a horn radiating port, a V-polarized RF connection port, and an H-polarized RF connection port. There are N dual-channel T / R modules, each with a V channel and an H channel. N / 2 of the dual-channel T / R modules are V-polarized dual-channel T / R modules, located on the inner wall of the first longitudinal side wall of the feed housing; the other N / 2 dual-channel T / R modules are H-polarized dual-channel T / R modules, located on the inner wall of the second longitudinal side wall of the feed housing. 2N RF connectors are used to connect the V-channel and H-channel of N dual-channel T / R components to the V-polarized RF connection port and H-polarized RF connection port of the dual-polarized radiating unit, respectively.

2. The system according to claim 1, wherein, The distance to the focal point is closer to that of a bifocal ellipsoidal parabolic reflector.

3. The system according to claim 1, wherein, The phased array feed is positioned so that the distance between the phased array feed and the bifocal ellipsoidal parabolic reflector is pushed forward toward the focal point.

4. The system according to claim 1, wherein, Multipolar phased array feeds are used to realize multiple polarization modes, including single polarization mode, dual polarization mode, and full polarization mode.

5. The system according to claim 1, wherein, The horn radiating port is located outside the feed housing, while the V-polarized RF connection port and the H-polarized RF connection port are located inside the feed housing.

6. The system according to claim 1, wherein, N is an integer greater than or equal to 2.

7. The system according to claim 1, wherein, The RF connector has a right-angle bend connection structure, a first port and a second port. The first port is used to connect to the dual-channel T / R assembly, and the second port is connected to the V-polarized RF connection port or H-polarized RF connection port of the dual-polarized radiating unit via an RF cable.

8. The system according to claim 7, wherein, The entire interior of the RF connector is filled with dielectric material, eliminating the cavity structure inside the RF connector.

9. The system according to claim 1, wherein, The aperture of the bifocal ellipsoidal parabolic reflector is 9.10m × 3.75m, and the azimuth focal length is 4m.

10. The system according to claim 1, wherein, The dual-polarized radiating element is implemented by a horn antenna element, and an orthogonal mode coupler is provided at the lower end of the horn radiating port of the dual-polarized radiating element.

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