Space-borne antenna system

Abstract

A space-borne antenna system includes a number of panels being moveable to each other and having a gap in between them when the panels are arranged in an operation condition. The system also includes an RF distribution network for providing transmit signals to the number of panels and combining received signals from the number of panels. The system further includes a set of choke flange assemblies that allow a contactless inter-panel signal transmission across a dedicated gap. A respective choke flange assembly is arranged on the far side of a radiating surface of the dedicated adjacent panels. The system also includes an RF seal assembly for suppressing a signal coupling of signals radiated from the number of panels to the set of choke flange assemblies by sealing the gap.

Claims

1. A space-borne antenna system, comprising: a number of panels in an operational position in which there is a gap between the number of panels; a choke flange assembly configured to transmit inter-panel signals across the gap; and an RF seal assembly configured to suppress a signal coupling of signals radiated from the number of panels to the choke flange assembly by sealing the gap; wherein the RF seal assembly is arranged at a hinge line and comprises a first seal profile and a second seal profile that are affixed as an opposing pair in the gap between the number of panels; wherein the first seal profile and the second seal profile each comprise a first portion which is attached to a respective panel.

2. The antenna system of claim 1, wherein the RF seal assembly is dedicated to the gap between the number of panels.

3. The antenna system of claim 1, wherein the first and the second seal profiles are L-shaped, in a side view in a longitudinal section through the antenna system.

4. The antenna system of claim 3, wherein first portions of the first and the second seal profiles extend when the number of panels are arranged in the operation condition in a plane of the number of panels.

5. The antenna system of claim 1, wherein second portions of the first and the second seal profiles extend in a direction of radiation of signals such that the second portions of the first and second seal profiles are opposing and have a gap in between them.

6. The antenna system of claim 5, wherein the gap between the second portions of the first and the second seal profiles has a constant width in the direction of radiation of signals.

7. The antenna system of claim 5, wherein the gap between the second portions of the first and the second seal profile has a widening or narrowing width in the direction of radiation of signals.

8. The antenna system of claim 1, wherein the number of panels comprise radiation waveguides; and the RF seal assembly and the radiating waveguides of the number of panels are made from a same material.

9. The antenna system of claim 1, wherein the RF seal assembly is mechanically attached to the number of panels via at least one adhesive tape.

10. The antenna system of claim 1, wherein the RF seal assembly is electrically coupled to the number of panels via a metal adhesive tape.

11. The antenna system of claim 1, wherein the number of panels are configured to move between a first position and a second position, wherein the second position is the operational position.

12. A space-borne antenna system, comprising: a number of panels configured to move by means of a hinge between a first position and a second position, wherein the second position is an operational position in which there is a gap between the number of panels; a choke flange assembly configured to transmit inter-panel signals across the gap; and an RF seal assembly configured to suppress a signal coupling of signals radiated from the number of panels to the choke flange assembly, wherein the RF seal assembly is arranged at a hinge line of the hinge.

13. A space-borne antenna system, comprising: a number of panels in an operational position in which there is a gap between the number of panels; a choke flange assembly configured to transmit inter-panel signals across the gap; and an RF seal assembly configured to suppress a signal coupling of signals radiated from the number of panels to the choke flange assembly by sealing the gap, wherein the RF seal assembly comprises a first seal profile and a second seal profile that are affixed as an opposing pair in the gap between the number of panels, wherein the first seal profile and the second seal profile each comprise a first portion which is attached to a respective panel, and wherein the first and the second seal profiles are L-shaped, in a side view in a longitudinal section through the antenna system.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) More details and advantages of the invention will be described by reference to the accompanying figures.

(2) FIG. 1 shows a first embodiment of an RF seal assembly for use in a space-borne antenna system according to the invention.

(3) FIG. 2 shows a second embodiment of an RF seal assembly for use in a space-borne antenna system according to the invention.

(4) FIG. 3 shows a plan view of an RF seal assembly for use in a space-borne antenna system according to the invention.

(5) In the figures, like elements are depicted with like reference numerals. It is to be noted that the embodiments shown in the figures are not drawn to scale and are used to illustrate the basic concept of the invention.

DETAILED DESCRIPTION

(6) An RF seal assembly, as described below, is intended to be used in an antenna system for space-borne applications, for example the Sentinel-1 SAR Antenna Subsystem (SAS) for the Sentinel-1 mission. This antenna system is, as known to a skilled person, a deployable planar active phased array antenna working in C-band (5.405 GHz) with a frequency bandwidth of 100 MHz. The antenna is formed by a central panel mounted on top of the spacecraft and two antenna side wings at the two adjacent sides of the spacecraft. The central panel is equipped with two SAS tiles, whereas the two panels of each side wing carry three SAS tiles each. This leads to an overall number of 14 identical tiles. Each SAS tile possesses all the functions needed to allow for beam shaping and steering.

(7) Each of the number of panels is movable to each other. During transport of the antenna system to space, the panels are folded by means of hinges, due to space reasons. In orbit, they are deployed. As shown in FIG. 3, the connection of two adjacent panels 10, 20 by means of a hinge 70 results in a small gap between the adjacent panels when the panels are arranged in an operation condition, i.e. when all of the panels are arranged in a common plane. A signal transmission coupling between two adjacent panels is realized by means of a choke flange assembly consisting of a first waveguide in one of the panels and a second waveguide in one of the other panels. The first and the second waveguide are affixed in opposing pairs to enable contactless signal transmission over the gap.

(8) The detailed composition of this type of antenna system is known to the person skilled in the art, such as from the above mentioned Sentinel-1 SAR antenna, so that further explanations with respect to details of the antenna system will be omitted.

(9) Referring now to FIG. 1, a part of an antenna system 1 of the type described above is illustrated in the region of two neighboring panels, a first of which is depicted with 10 and a second of which is depicted with 20. As noted above, each of the panels 10, 20 consists of a number of tiles. A tile of the first panel 10 is depicted with 11, a the of the second panel is depicted with 21. The tiles 11, 21 are located adjacent to each other. A gap between the first panel 10 and the second panel 20 and the first tile 11 and the second tile 21, respectively, is depicted with 60. The gap 60 has a length 64 which typically is around 5 mm. In the figure, radiating surfaces 12, 22 of the first and second panel and tile 11, respectively, are directed downwards in the plane of drawing.

(10) To enable contactless inter-panel communication, a choke flange assembly 30 is arranged on the far side of the radiating surfaces of the dedicated adjacent panels 10, 20. The choke flange assembly 30 consists of a first waveguide 31 which is embedded in a (not shown) housing of the first panel 10 and a second waveguide 32 which is embedded in a (not shown) housing of the second panel 20. In between the first and the second waveguides 31, 32, there is a gap 33. Flanges 34, 35 of the first and the second waveguide 31, 32 are located (at least partly) within the gap 60.

(11) To suppress signal coupling of signals radiated from the panels 10, 20 and their tiles 11, 21, respectively, an RF seal assembly 40 is provided within the gap 60. The RF seal assembly 40 consists of a first seal profile 41 attached to the first panel 10 and a second seal profile 51 attached to the second panel 20. The RF seal assembly 40 is provided to seal the gap 60 at least partly.

(12) In a cross-section, i.e. in a side view in a longitudinal section through the antenna system 1, the first and the second seal profile 41, 51 have the shape of an “L”. A respective first portion 45, 55 of the first and second seal profile 41, 51 extends in the plane of the panels 10, 20 (i.e. in a direction perpendicular to the plane of drawing from the left side to the right side) into the gap 60. A respective second portion 46, 56 of the first and second seal profile 41, 51 extends in a direction of radiation of signals radiated from the panels 10, 20 (i.e. in a direction perpendicular to the plane of drawing top down). The length of the second portions 46, 56 is a quarter of the wavelength of the signals radiated from the panels 10, 20.

(13) A respective first portion 45, 55 of the first and second seal profile 41, 51 is attached to the dedicated panel 10, 20 by means of adhesive tape 43, and 53. The attachment of a respective first portion 45, 55 of the first and second seal profile 41, 51 to the dedicated panel 10, 20 may be made by an adhesive tape and/or epoxy glue. Moreover, the seal profiles 41, 51 are electrically coupled to the dedicated panel 10, 20 by means of a conductive foil 42, 52, such as an so-called cho-foil, which is known from prior art as well.

(14) The first and the second seal profile 41, 51 are arranged in opposing pairs in the gap 60 to seal the gap at least partly. In the plane of the first portions 45, 55 of the first and second seal profiles 41, 51, there is a gap 61 having a first length between the seal profiles 41, 51. At the outside ends of the second portions 46, 56, directed to the radiating surfaces 12, 22, there is a gap 62 having a second length between the seal profiles 41, 51. In the first embodiment, shown in FIG. 1, the first length of gap 61 corresponds to the second length of the gap 62. That means the second portions 46, 56 are parallel to each other. The length of the first and the second gap 61, 62 may be around 0.8 mm to 1 mm.

(15) In the second embodiment, shown in FIG. 2, the first length of the gap 61 is smaller than the second length of the gap 62. As a result, the gap between the second portions has a widening width in a direction of radiation of signals, i.e. the angle between the first and the second portions 45, 46; 55, 56 of a respective seal profile 41, 51 is less than 90°. The length of the gap 61 may be around 0.8 mm. The length of the gap 62 may be around 1.2 mm. The remainder of the configuration of the second embodiment, shown in FIG. 2, corresponds to the first embodiment, shown in FIG. 1. However, in an alternative embodiment the angle between the first and the second portion 45, 46; 55, 56 may be greater than 90°.

(16) The first and second seal profiles 41, 51 may be made from the material of the radiating waveguides of the panels 10, 20. This ensures that the RF seal assembly and the waveguides have same coefficients of thermal expansion and minimizes thereto-mechanical stress. Hence, the first and the second seal profiles may be made from CFRP (carbon fiber reinforced plastic), which has a metallization on its surface. For example, the first and the second seal profiles 41, 51 made from CFRP may be copper plated. This allows manufacturing the profiles from left-over waveguides. Alternatively, the seal profiles 41, 51 of the RF seal assembly 40 may be made from a metal, e.g. aluminum.

(17) As shown in FIG. 3, the RF seal assembly may be attached to the panel-to-panel junctions at the hinge line 71.

(18) The effect of the RF seal assembly, i.e. a significant suppression of signal coupling of signals radiated from the panels 10, 20 to the choke flange 30, has been verified with an S-parameter test.

(19) As will be realized by a skilled person, the RF seal assembly 40 is contactless in the sense that the first and the second seal profile 41, 51 do not have any mechanical contact to each other. The configuration of the first and the second seal profile 41, 51 is such that it does not counter-act to the panel latching mechanism, i.e. no excessive additional mechanical force is exerted.

(20) As a further advantage the RF seal assembly does not a mechanical contact between the panels 10, 20.

(21) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

LIST OF REFERENCE SIGNS

(22) 1 antenna system 10 first panel 11 tile of first panel 12 radiating surface of tile 11 20 second panel 21 tile of second panel 22 radiating surface of tile 21 30 choke flange assembly 31 first waveguide 32 second waveguide 33 gap between first and second waveguide 34 flange of the first waveguide 31 35 flange of the second waveguide 32 40 RF seal assembly 41 first seal profile 42 conductive foil 43 adhesive tape 45 first portion of first seal profile extending in a plane of the panel into the gap 60 46 second portion of first seal profile extending in a direction of radiation of signals 51 second seal profile 52 conductive foil 53 adhesive tape 55 first portion of second seal profile extending in a plane of the panel into the gap 60 56 second portion of second seal profile extending in a direction of radiation of signals 60 gap between first and second panel 61 gap between first and second seal profile 62 gap between first and second seal profile at outside ends of portions 45, 55 63 length of portions 45, 55 of first and second profile 64 length of gap 60 between first and second panel