Dual polarized antenna with ridges

Abstract

The aim is to make the dual-polarized antenna lighter and smaller. The invention relates to an antenna (1) with dual polarization (P1, P2) obtained by additive manufacturing, comprising a polarization part (10), which polarization part (10) has: a first port (101) for a first signal having a first polarization (P1); a second port (102) for a second signal having a second polarization (P2); an output port for signals with dual polarization; a septum (103) that couples a first signal on the first port (101) and a second signal on the second port (102); 1. An antenna comprising: a radiating element (20) maintaining dual polarization, the radiating element (20) comprising a waveguide having a first end connected to an output port of the polarizing section (10) and a second end (201) coupled to free space, the waveguide comprising an inner channel with three ridges (202) parallel to the direction of propagation of the signal in the inner channel, An outer portion (203) of each ridge (202) extends outward from the waveguide through the second end (201), and the height of the outer portion (203) of each ridge, measured in a direction extending relative to the direction of propagation, decreases with increasing distance from the second end (201).

Description

[Technical Field]

[0001] The present invention relates to a Vivaldi type dual polarized antenna, an array of such antennas and a satellite supporting such antennas. [Background technology]

[0002] Antennas are elements used to transmit electromagnetic signals into free space and to receive such signals. Simple antennas, such as dipoles, have limited performance in terms of gain and directivity. Parabolic antennas allow for higher directivity, but are bulky and heavy, making them unsuitable for applications where weight and volume must be reduced, such as satellite applications.

[0003] Antenna arrays are also known that combine multiple phase-shifted radiating elements (antenna elements) to improve gain and directivity. The signals received by or radiated from different radiating elements are amplified and phase-shifted, thereby controlling the shape of the transmit and receive lobes of the network.

[0004] Dual-polarized antennas are also known, capable of simultaneously transmitting and receiving signals in two polarized waves. In this case, the signals transmitted and received by each antenna element are combined and separated according to their polarization by a polarization unit. The polarization unit may be integrated into the antenna element. Dual-polarized antennas have two ports that connect the two polarized waves to electronic circuits or waveguides, respectively.

[0005] To accommodate antennas within satellites or aircraft with reduced available volume, it is often necessary to reduce the size of the antenna, particularly its width and height in the plane perpendicular to the direction of signal transmission.

[0006] Such antennas intended for transmission at high frequencies, especially microwave frequencies, are difficult to design. In particular, it is often desirable to place the various element antennas of the array as close together as possible, in order to reduce the overall space required and to attenuate the amplitude of secondary radiation or reception lobes in directions other than the preferred radiation or reception direction. However, this reduction in element antennas and their spacing creates the problem of reflection of a portion of the transmitted signal back to the antenna or to another port. This results in reduced transfer efficiency of the radiated energy and interference with each port due to signals radiated from other ports.

[0007] Patent Document 1 discloses an antenna horn that includes a polarizing section and four protruding sections that protrude outward in the longitudinal direction of the horn.

[0008] Patent Document 2 discloses a hexagonal waveguide including a section with a polarizing portion and a section with a ridge in the inner channel of the waveguide.

[0009] US Patent No. 5,949,999 discloses an antenna array in which each antenna has a septum polarizing section and three longitudinal ridges extending along its internal channel, one of the ridges extending longitudinally to form a septum. Summary of the Invention [Problem to be solved by the invention]

[0010] One objective when designing such antennas is also to reduce their weight, especially in space or aeronautical applications.

[0011] Another object is to provide an antenna suitable for LHCP (left-handed circularly polarized wave) and RHCP (right-handed circularly polarized wave) satellite communications.

[0012] Also, one of the objectives is to provide an antenna with a shape that facilitates additive printing, for example by allowing for limiting the number of supports required during printing.

[0013] Finally, it is also desirable to produce antennas with a modular design in which the number of element antennas can be changed as needed without the need to redesign the entire antenna. A design is said to be modular if it is possible to easily design different types of antennas by adding or removing standardized antenna elements during the antenna design, without the entire antenna or waveguide array having to be redesigned for this purpose.

[0014] Of course, the antenna must have very high performance, gain and radiation pattern characteristics to meet the application specifications.

[0015] Finally, the antenna must be manufacturable industrially and without falling within the scope of existing patent protection. [Means for solving the problem]

[0016] According to the present invention, these objects are achieved by a dual polarized antenna, obtained by additive manufacturing, comprising a polarization section, said polarization section comprising: a first port for a first signal having a first polarization; a second port for a second signal having a second polarization; an output port for signals with dual polarization; a septum coupling the first signal on the first port and the second signal on the second port; wherein the antenna comprises a radiating element that maintains the dual polarization, the radiating element comprising a waveguide having a first end connected to the output port of the polarization section and a second end coupled to free space, the waveguide comprising the inner channel with three ridges parallel to the direction of propagation of the signal in the inner channel, An outer portion of each ridge extends out from the waveguide through the second termination, and a height of the outer portion of each ridge, measured in a direction extending relative to the direction of propagation, decreases with distance from the second termination.

[0017] The outer portion of the ridge increases the bandwidth over which the impedance of the antenna is matched to the impedance of free space.

[0018] The height of these outer sections decreases with distance from the second end of the radiating element, giving the outer sections a similar appearance to the horn plates of a Vivaldi antenna. However, the feeding of the radiating elements of this antenna is via a septum polarization section, which is fundamentally different from the feeding of conventional Vivaldi antennas. In addition, the three outer sections of the ridge are not coplanar, as is the case with classical Vivaldi antennas.

[0019] The ridges within the internal channel can serve as support for the outer portions of the ridges (when printed), especially if the direction of the printing of the antenna coincides with the axis of wave propagation within the channel.

[0020] In one embodiment, the section (cross section) of the radiating element perpendicular to the propagation direction remains unchanged when rotated 120° relative to the propagation direction. This 120° symmetry means, in particular, that the ridges are spaced 120° apart. Surprisingly, this ridge configuration improves the discrimination of higher order modes compared to the fundamental mode.

[0021] To maintain invariance under 120° rotation, the section (cross section) of the radiating element may be circular, triangular, hexagonal, etc. In general, this cross section may be a polygon with a number of sides that is a multiple of three.

[0022] In one embodiment, one of the three ridges is formed by an extension of a septum along the wall of the interior channel, which also serves as support for the ridge and the outer portion of the ridge during additive printing.

[0023] The ridges may be inclined relative to the inner wall of the internal channel. In one preferred embodiment, the ridges have a height extending radially relative to the axis of propagation, although they may also be inclined relative to the radial direction.

[0024] The diameter of the waveguide may be less than the wavelength at the highest operating frequency of the antenna, and preferably less than half the wavelength at the highest operating frequency of the antenna.

[0025] The antenna may be integral.

[0026] The height of each outer portion of the at least one ridge may decrease linearly, exponentially and / or stepwise.

[0027] Each outer ridge may include at least one lateral impedance matching step located on an extension of a sidewall of the inner channel.

[0028] At least one sidewall of the internal channel may include an impedance matching slot extending from the second end of the radiating element waveguide.

[0029] In accordance with the present invention, these objects are also achieved by an antenna array comprising a plurality of the above-described antennas.

[0030] Multiple antennas may be arranged in rows and columns along one or two directions.

[0031] According to the invention, these objects are also achieved by a satellite equipped with at least one antenna or antenna array as described above.

[0032] Several embodiments of the present invention are illustrated in the accompanying description and illustrated by the accompanying figures. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 shows a schematic cross-sectional view of a dual polarized antenna. [Figure 2] Figure 2 shows a dual polarized antenna with a circular cross section. [Figure 3] Figure 3 shows a dual polarized antenna with a truncated triangular cross section. [Figure 4]Figure 4 shows a dual polarized antenna with a hexagonal cross section. [Figure 5a] FIG. 5a shows a top view of a dual polarized antenna with a hexagonal cross section. [Figure 5b] FIG. 5b is a cross-sectional view of the antenna shown in FIG. 5a. [Figure 6] FIG. 6 shows a dual polarized antenna with an impedance matching element. [Figure 7] FIG. 7 shows an array of dual polarized antennas arranged in a two-dimensional matrix. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention relates to a dual polarized antenna 1 comprising a septum polarized section 10 and a radiating element 20 comprising three ridges 202 within the internal channel of the radiating element waveguide, the three ridges protruding outward from the channel at the end of the radiating element waveguide intended to be coupled into free space.

[0035] The term "free space" is used in this application to mean the space outside the antenna through which the signal emitted from the antenna propagates. This means in particular that no devices coupled to the end of the antenna on the "free space" side are intended. Free space can correspond to outer space itself, for example, if the antenna is mounted on a satellite in orbit, but more generally, free space refers to any amount of space outside the antenna. Free space has a natural impedance that depends on the characteristics of the space surrounding the antenna.

[0036] As shown schematically in FIG. 1, the antenna 1 comprises two main parts: a septum polarisation section 10 and a radiating element 20 .

[0037] The polarization section 10 comprises an orthogonal mode converter in the form of a waveguide, one end of which has a first port 101 and a second port 102 with a single polarization, and the other end of which has an output port intended for signals with dual polarization. The two ports are separated by a septum 103 of a height extending along the diameter of the waveguide. In transmission, the two ports can each carry a linearly polarized signal (P1, P2). These two signals are combined via the septum 103 into a dual-polarized signal, which is propagated towards the radiating element 20. The septum 103 allows the phase between the two orthogonal modes to be controlled, for example, to produce circular polarization, 45° tilt polarization, or vertical / horizontal polarization. In reception, the septum 103 separates the two polarization parts of the dual-polarized signal received via the radiating element.

[0038] The septum 103 also extends longitudinally with respect to the polarization waveguide (i.e., relative to the direction of wave propagation within the polarization waveguide) and its height decreases until it disappears completely or until it forms a longitudinal ridge on the inner wall of the antenna. The decrease in height is typically stepped (i.e., continuous) along the length, but may follow a linear, exponential, or other decreasing profile depending on specific needs.

[0039] The radiating element 20 is intended to be coupled on the one hand to the output port of the polarizing section 10 and on the other hand to free space, so that it forms an extension of the polarizing section in the radiation direction of the antenna.

[0040] As used herein, the term "coupled" does not exclude two elements that are coupled from being formed and / or manufactured as a single piece, which may be a theoretical coupling of two elements with different functions, but which forms an object that does not result from the mechanical assembly of these two elements.

[0041] As shown schematically in Figure 1, the radiating element 20 comprises a waveguide section, the first end of which is coupled to the output port of the polarization section 10 and the second end 201 of which is coupled to free space. The waveguide section comprises an internal channel whose walls comprise three ridges 202 extending parallel to the direction of wave propagation within the internal channel. Each of the three ridges comprises an outer portion 203 extending out from the waveguide section by its second end 201 so as to form a longitudinal ridge.

[0042] The ridge 202 allows in particular to lower the cut-off frequency of the waveguide and thus to miniaturize the antenna, and in addition, it also allows to match the impedance of the antenna to the impedance of free space, since it reduces the signal reflection phenomenon at the interface between the radiating element and free space.

[0043] The height of the ridges may be constant or variable along the length. Figure 5b shows an embodiment in which the height of the ridges is varied along the length of the waveguide.

[0044] 1 to 4, the outer portion 203 of each ridge 202 has a height, measured in a direction extending relative to the direction of propagation, that decreases with increasing distance from the second end 201 of the waveguide of the radiating element. This decreasing profile of the outer portion 203 allows the antenna to significantly increase its bandwidth, particularly as in a conventional Vivaldi antenna. It is also particularly well suited to the problem of matching the antenna's impedance to that of free space.

[0045] Surprisingly, the combination of the ridges 202 within the waveguide and the outer portion 203 facilitates additional printing of the antenna 1, especially the printing of the outer portion. In fact, the ridges 202 can act as a support for the outer portion 203 during its printing. This reduces the amount of auxiliary support that must be manually removed after printing. This results in a shorter manufacturing time, and therefore an increased gain in weight and cost.

[0046] In a preferred embodiment, the polarization waveguides and radiating elements 10 are rotationally invariant through 120° relative to the propagation direction. In other words, the sections of these waveguides perpendicular to the propagation direction of the antenna are invariant under a rotation of 120° relative to the propagation direction. This means, in particular, that the ridges 202 are distributed in the inner channel of the waveguide at intervals of 120° from one another.

[0047] Surprisingly, this 120° ridge distribution allows for enhanced discrimination between the fundamental and higher order modes, thus limiting the risk of superposition of these higher order modes.

[0048] Preferably, the sections of the waveguides of the polarization section 10 and the radiating element 20 are circular, triangular or hexagonal, with emphasis on invariance under 120° rotations around the propagation direction. More generally, polygonal sections with 3n sides, where n is a positive integer, allow for emphasis on 120° symmetry. Thus, the waveguides may form cylinders if the sections are circular, or prisms with triangular, hexagonal, etc. bases. The angle of the prisms can be truncated.

[0049] The ridges 202 may be disposed on the inner walls of the waveguide's internal channel corresponding to the faces or angles of the prisms.

[0050] 2 shows an antenna 1 in which the radiating elements and polarizing sections are circular in section. The ridges 202, and therefore the outer sections 203, are arranged at 120° intervals on the inner wall of the waveguide.

[0051] FIG. 3 shows an antenna 1 in which the sections of the radiating elements and polarizers are triangular. The angles of the triangular-based (mainly triangular) prisms formed by the polarizers and the radiating element waveguides may be truncated. The ridges 202 may be located on the inner walls of the waveguides corresponding to the truncated parts of the prisms or the faces of the prisms. The triangles forming the waveguide sections may be equilateral. An equilateral triangle means invariance when rotated 120° relative to the direction of propagation. The triangles may also be isosceles.

[0052] Figures 4 and 6 show an antenna 1 in which the sections of the radiating elements and polarizers are hexagonal. In Figure 4, the ridges 202 are located on the inner wall of the waveguide corresponding to the angles of the hexagonal-based prism formed by the waveguide, while in Figure 6, the ridges 202 are located on the inner wall of the waveguide corresponding to the faces of the prism.

[0053] Advantageously, one of the ridges may be formed by an extension of the septum 103 in the longitudinal direction of the antenna, so that the septum 103, the ridge 202 and the corresponding outer portion 203 of the ridge are aligned in the longitudinal direction.

[0054] In one embodiment, one or more ridges are inclined with respect to the radial direction, meaning that the direction of the height of the ridge is not aligned radially with respect to the propagation direction. In particular, the angle between the direction of the height of the ridge and the wall of the waveguide supporting the ridge may be other than 90°.

[0055] In one embodiment, the diameter of the waveguide of the radiating element is less than the wavelength at the highest operating frequency of the antenna, preferably less than half the wavelength at the highest operating frequency of the antenna.

[0056] The antenna 1 comprises a core that is preferably manufactured by an additive manufacturing process. The polarizing portion 10 and the radiating element 20 are preferably manufactured monolithically, and the core is manufactured in a single additive printing step. As used herein, the term "additive manufacturing" refers to any process of manufacturing a core by adding material, defining the geometry of the core according to computer data stored on a computer medium.

[0057] The core may be manufactured using an additive manufacturing process such as, for example, SLM (Selective Laser Melting). The core can additionally be manufactured by other additive manufacturing methods, for example, especially by hardening or solidifying a liquid or powder, including, without limitation, stereolithography, inkjet (binder jetting), DED (Direct Energy Deposition), EBFF (Electron Beam Free Forming), FDM (Fused Deposition Modeling), PFF (Plastic Free Forming), aerosol, BPM (Ballistic Particle Manufacturing), SLS (Selective Laser Sintering), ALM (Additive Layer Manufacturing), Polyjet, EBM (Electron Beam Melting), photopolymerization, etc.

[0058] The core may be made from, for example, a photopolymer made by multiple surface layers of liquid polymer that are cured by ultraviolet radiation during an additive manufacturing process.

[0059] The core may also be formed from a conductive material, such as a metallic material, by an additive manufacturing process of the SLM type, in which a laser or electron beam melts or sinters multiple thin layers of powdered material.

[0060] According to one embodiment, the metal layer is deposited in the form of a film on the inner surface of the core by electrodeposition or electroplating. By metallization, the inner surface of the core is covered with a conductive layer.

[0061] The application of the metal layer may be preceded by a surface treatment step of the inner surface of the core to promote adhesion of the metal layer. The surface treatment may comprise one or both of increasing the surface roughness and depositing an intermediate tie layer.

[0062] The decrease in height of each outer portion 203 of ridge 202 may be linear, exponential, and / or stepwise, depending on the application.

[0063] An impedance matching element may be included in the radiating element to match the antenna impedance to the free space impedance.

[0064] 6, the outer portion 203 of the ridge 202 may comprise at least one side impedance matching step 204. These steps are typically located in the extension of the wall of the waveguide of the radiating element 20 and extend laterally on one or two sides of the outer portion 203.

[0065] In one embodiment shown in FIG. 6, one or more walls of the waveguide section of the radiating element 20 are provided with impedance matching slots 204 .

[0066] Multiple impedance matching elements can be combined on the same antenna and may comprise, in addition to the ridge 202, protrusions located on one or more inner walls of the waveguide of the radiating element.

[0067] As shown in FIG. 7, multiple dual polarized antennas such as those described above may be grouped together to form an antenna array 30.

[0068] The antennas in such an array are typically grouped in a one- or two-dimensional matrix, i.e., the antennas may be arranged consecutively along one or two axes. Figure 7 shows a two-dimensional matrix arrangement. However, the arrangement of the antenna array, i.e., the configuration of adjacent antennas, may be different from that of the array, e.g., triangular.

[0069] The antenna array is preferably miniaturized so that the periodicity of the antenna array is limited to no more than 80% of the nominal wavelength of the signal transmitted and received by each antenna.

[0070] The invention also relates to a satellite comprising at least one antenna as described above or an antenna array as described above. [Point 1] The antenna (1) for dual polarization (P1, P2) obtained by additive manufacturing comprises a polarization part (10), the polarization part (10) comprising: a first port (101) for a first signal having a first polarization (P1); a second port (102) for a second signal having a second polarization (P2); an output port for signals with dual polarization; a septum (103) that couples the first signal on the first port (101) and the second signal on the second port (102); The antenna comprises a radiating element (20) that maintains the dual polarization, the radiating element (20) comprising a waveguide having a first end connected to the output port of the polarizing section (10) and a second end (201) coupled to free space, the waveguide comprising the inner channel with three ridges (202) parallel to the direction of propagation of the signal in the inner channel, An antenna (1), characterized in that an outer portion (203) of each ridge (202) extends out from the waveguide through the second end (201), and the height of the outer portion (203) of each ridge, measured in a direction extending relative to the direction of propagation, decreases with increasing distance from the second end (201). [Point 2] The antenna (1) according to aspect 1, wherein the section of the waveguide perpendicular to the propagation direction remains unchanged even when rotated 120° around the propagation direction. [Point 3] 3. Antenna (1) according to aspect 1 or 2, wherein the section of the waveguide perpendicular to the propagation direction is circular, triangular or hexagonal. [Point 4] 4. The antenna (1) according to any one of aspects 1 to 3, wherein one of the three ridges (202) is formed by an extension of the septum (103). [Point 5] 5. The antenna (1) according to any one of aspects 1 to 4, wherein at least one of the three ridges (202) forms an angle of less than 90° with the inner wall of the internal channel. [Point 6] 6. An antenna (1) according to any one of aspects 1 to 5, wherein the diameter of the waveguide is smaller than the wavelength at the highest operating frequency of the antenna, preferably smaller than half the wavelength at the highest operating frequency of the antenna. [Point 7] 7. The antenna (1) according to any one of aspects 1 to 6, which is integrated. [Point 8] 8. The antenna (1) of any one of aspects 1 to 7, wherein the height of each outer portion (203) of at least one ridge (202) decreases linearly, exponentially, and / or stepwise. [Point 9] 9. An antenna (1) according to any one of aspects 1 to 8, wherein each of the outer portions (203) of the raised portions (202) comprises at least one side impedance matching step (204) arranged on an extension of a side wall of the internal channel. [Point 10] 10. An antenna (1) according to any one of aspects 1 to 9, wherein at least one sidewall of the internal channel is provided with an impedance matching slot (205) extending from the second end (201) of the waveguide portion of the radiating element (20). [Point 11] An antenna array (30) comprising a plurality of antennas (1) according to any one of aspects 1 to 10. [Point 12] 12. The array (30) of antennas according to aspect 11, wherein a plurality of the antennas are arranged in rows and columns in one or two directions. [Point 13] A satellite comprising at least one antenna according to any one of aspects 1 to 10. [Explanation of symbols]

[0071] Dual polarized antenna 1 Polarization section 10 First port 101 Second port 102 Septum 103 Radiating element 20 2nd End 201 Ridge 202 External part 203 Horizontal step 204 Antenna Array 30

Claims

1. The antenna (1) for dual polarization (P1, P2) obtained by additive manufacturing comprises a polarization part (10), said polarization part (10) comprising: a first port (101) for a first signal having a first polarization (P1); a second port (102) for a second signal having a second polarization (P2); an output port for signals with dual polarization; a septum (103) that couples the first signal on the first port (101) and the second signal on the second port (102); The antenna comprises a radiating element (20) that maintains the dual polarization, the radiating element (20) comprising a waveguide having a first end connected to the output port of the polarizing section (10) and a second end (201) coupled to free space, the waveguide comprising the inner channel with three ridges (202) parallel to the direction of propagation of the signal in the inner channel, An antenna (1), characterized in that an outer portion (203) of each ridge (202) extends out from the waveguide through the second end (201), and the height of the outer portion (203) of each ridge, measured in a direction extending relative to the propagation direction, decreases with increasing distance from the second end (201).

2. 2. An antenna (1) according to claim 1, wherein the section of the waveguide perpendicular to the propagation direction is invariant to a rotation of 120° about the propagation direction.

3. 3. Antenna (1) according to claim 1 or 2, wherein the section of the waveguide perpendicular to the propagation direction is circular, triangular or hexagonal.

4. 4. An antenna (1) according to any one of claims 1 to 3, wherein one of the three ridges (202) is formed by an extension of the septum (103).

5. 5. The antenna (1) according to any one of claims 1 to 4, wherein at least one of the three ridges (202) forms an angle of less than 90° with the inner wall of the internal channel.

6. 6. Antenna (1) according to any one of claims 1 to 5, wherein the diameter of the waveguide is smaller than the wavelength at the highest operating frequency of the antenna, preferably smaller than half the wavelength at the highest operating frequency of the antenna.

7. Antenna (1) according to any one of claims 1 to 6, which is integral.

8. 8. An antenna (1) according to any one of claims 1 to 7, wherein the height of each outer portion (203) of the at least one ridge (202) decreases linearly, exponentially and / or stepwise.

9. 9. The antenna (1) according to claim 1, wherein each of the outer portions (203) of the ridges (202) comprises at least one side impedance matching step (204) arranged on an extension of a side wall of the internal channel.

10. 10. The antenna (1) of claim 1, wherein at least one sidewall of the internal channel comprises an impedance matching slot (205) extending from the second end (201) of the waveguide portion of the radiating element (20).

11. An array (30) of antennas comprising a plurality of antennas (1) according to any one of claims 1 to 10.

12. 12. The array of antennas (30) of claim 11, wherein a plurality of said antennas are arranged in rows and columns in one or two directions.

13. A satellite equipped with at least one antenna according to any one of claims 1 to 10.

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