Dual-polarization ridged antenna

Abstract

The present invention relates to a dual-polarization (P1, P2) antenna (1) obtained by additive manufacturing, comprising: a polarizer (10) comprising: a first port (101) intended for a first signal with a first polarization (P1); a second port (102) intended for a second signal with a second polarization (P2); an output port intended for a signal with dual polarization; a septum (103) for combining the first signal on the first port (101) with the second signal on the second port (102); a radiating element (20) that preserves the polarizations, comprising a waveguide a first end of which is connected to the output port of the polarizer (10) and a second end (201) of which is coupled to free space, the waveguide comprising an internal channel provided with three ridges (202) parallel to a direction of propagation of a signal through the internal channel, characterized in that an external portion (203) of each ridge (202) extends out of the waveguide via the second end (201), a height of the external portion (203) of each ridge, measured radially with respect to the direction of propagation, decreasing with distance from the second end (201). The present invention also relates to an array of antennas as described above and to a satellite comprising at least one such antenna.

Description

Dual-polarized ridged antenna Technical field

[0001] The present invention relates to a dual-polarization antenna of the Vivaldi type, an array of such antennas and a satellite supporting such antennas. State of the art

[0002] Antennas are elements used to transmit or receive electromagnetic signals into free space. 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 such as satellites, for example, where weight and volume must be reduced.

[0003] Antenna arrays are also known that combine several radiating elements (antenna elements) out of phase to improve gain and directivity. The signals received on the different radiating elements, or emitted by these elements, are amplified and phase-shifted with each other so as to control the shape of the receiving and transmitting lobes of the array.

[0004] Dual-polarized antennas are also known that can transmit or receive signals with two polarizations simultaneously. In this case, the signals transmitted or received by each antenna element are combined or separated according to their polarization by means of a polarizer. The polarizer can also be integrated into the antenna element. A dual-polarized antenna has two ports for connecting each of the two polarizations separately to or from an electronic circuit or waveguides.

[0005] It is also often necessary to reduce the size of the antenna, and in particular its width and height in the plane perpendicular to the direction of signal transmission, in order to be able to accommodate it in the reduced volume available in a satellite or aircraft.

[0006] Such antennas intended to transmit high frequencies, particularly for microwave frequencies, are difficult to design. In particular, it is often desired to bring the various elementary antennas of the array as close together as possible in order to reduce the overall size and to attenuate the amplitude of the secondary transmission or reception lobes, in directions other than the transmission or reception direction which must be favored. This reduction in the size of the elementary antennas and their spacing, however, creates problems of reflection of a portion of the transmission signal which returns to the antenna or to another port. This results in a loss of efficiency in the transfer of transmitted energy, and disturbances of each port by the signals transmitted on the other ports.

[0007] One goal when designing such an antenna is also to reduce its weight, particularly in space or aeronautical applications.

[0008] A goal is also to provide an antenna suitable for LHCP and RHCP polarization satellite communications.

[0009] One goal is also to provide an antenna whose geometry facilitates its additive printing, for example by making it possible to limit the supports required during printing.

[0010] Finally, it is also desirable to produce antennas with a modular design that allows the number of elementary antennas to be varied according to needs, without having to review the entire antenna design. The design is said to be modular when different types of antennas can easily be designed by adding or removing standardized antenna elements during antenna design, without having to redesign the entire antenna or waveguide array.

[0011] The antenna must also of course have very high efficiency, gain and radiation pattern characteristics compatible with the application specifications.

[0012] Finally, the antenna must be able to be manufactured industrially and without falling within the scope of protection of existing patents. Brief summary of the invention

[0013] According to the invention, these aims are achieved in particular by means of a dual-polarization antenna obtained by additive manufacturing comprising: a polarizer comprising: a first port intended for a first signal with a first polarization; a second port intended for a second signal with a second polarization; an output port intended for a signal with dual polarization; a septum making it possible to combine the first signal on the first port with the second signal on the second port;a polarization preserving radiating element, comprising a waveguide having a first end connected to the output port of the polarizer and a second end coupled to free space, the waveguide comprising an internal channel provided with three grooves parallel to a direction of propagation of a signal in the internal channel, characterized in that an external portion of each groove extends out of the waveguide by the second end, a height of the external portion; of each streak measured radially relative to the direction of propagation decreasing away from the second end.

[0014] The outer portions of the ridges allow for an increase in the bandwidth over which the antenna impedance is matched to the impedance of free space.

[0015] Since the height of these outer portions decreases away from the second end of the radiating element, the appearance of an outer portion resembles that of a Vivaldi-type antenna horn plate. However, the feeding of the radiating element of the present antenna differs radically from the feeding of a conventional Vivaldi antenna since it is carried out via a septum polarizer. In addition, the three outer portions of the ridges are not coplanar, unlike a conventional Vivaldi-type antenna.

[0016] The grooves inside the inner channel can serve as support for the outer portions of the grooves, especially when the antenna printing direction coincides with the wave propagation axis in the channel.

[0017] In one embodiment, a section of the radiating element perpendicular to the propagation direction may be invariant by rotation of 120° around the propagation direction. This 120° symmetry notably implies a spacing of 120° between each of the streaks. Surprisingly, this streak configuration makes it possible to increase the discrimination of higher order modes compared to the fundamental mode.

[0018] In order to preserve the invariance by rotation of 120°, the section of the radiating element can be circular, triangular, hexagonal. In general, this section can be polygonal with a number of sides multiple of 3.

[0019] In one embodiment, one of the three ridges is formed by extending the septum along a wall of the inner channel. The septum can then also serve as a support for the ridge and the outer portion of the ridge during additive printing.

[0020] The striations may be inclined relative to the inner wall of the inner channel. In a preferred embodiment, the striations have a height extending radially relative to the propagation axis, but inclinations relative to the radial direction are possible.

[0021] The diameter of the waveguide may be 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.

[0022] The antenna can be monobloc.

[0023] The height of each outer portion of at least one streak may decrease linearly, exponentially, and / or stepwise.

[0024] Each external groove portion may comprise at least one lateral impedance matching step arranged in the extension of a lateral wall of the internal channel.

[0025] At least one sidewall of the inner channel may include an impedance matching slot extending from the second end of the radiating element waveguide.

[0026] According to the invention, these aims are also achieved by means of an antenna network comprising a plurality of antennas as described above.

[0027] The plurality of antennas may be arranged in an array in one or two directions.

[0028] According to the invention, these aims are also achieved by means of a satellite comprising at least one antenna or antenna network as described above. Brief description of the figures

[0029] Examples of implementation of the invention are indicated in the description illustrated by the appended figures in which:

[0030] Figure 1 schematically illustrates a cross-sectional view of a dual-polarized antenna.

[0031] Figure 2 illustrates a dual-polarized antenna with a circular cross-section.

[0032] Figure 3 illustrates a dual-polarized antenna with a triangular cross-section whose angles are truncated.

[0033] Figure 4 illustrates a dual-polarized antenna with a hexagonal cross-section.

[0034] Figure 5a illustrates a top view of a dual-polarized antenna with a hexagonal cross-section.

[0035] Figure 5b illustrates a sectional view of the same antenna shown in Figure 5a.

[0036] Figure 6 illustrates a dual-polarized antenna including impedance matching elements.

[0037] Figure 7 illustrates an array of dual-polarized antennas arranged in a two-dimensional matrix. Example(s) of embodiment of the invention

[0038] The present invention relates to a dual polarization antenna 1 comprising a septum polarizer 10 and a radiating element 20 provided with three ridges 202 within the internal channel of the radiating element waveguide. The three ridges project outward from the channel at the end of the radiating element waveguide intended to be coupled to free space.

[0039] The term "free space" is used in the context of the present application to designate the space outside the antenna, and in which the signals emitted by the antenna propagate. This means in particular that no device is intended to be coupled to the end of the antenna on the "free space" side. Thus, the free space can correspond, for example, to the space itself when the antenna is equipped on a satellite in orbit, but more generally, the free space designates any volume of space outside the antenna. The free space has its own impedance depending on the characteristics of the space surrounding the antenna.

[0040] As schematically illustrated in Figure 1, the antenna 1 comprises two main parts, a septum polarizer 10 and a radiating element 20.

[0041] The polarizer 10 comprises an orthomode transducer in the form of a waveguide, one end of which comprises a first port 101 and a second port 102 with single polarization, and the other end of which comprises an output port intended for a signal with dual polarization. The two ports are separated by a septum 103 whose height extends along a diameter of the waveguide. In transmission, these two ports are each capable of propagating a signal with linear polarization (P1, P2). These two signals are then combined into a signal with dual polarization via the septum 103 which is propagated towards the radiating element 20. The septum 103 makes it possible to control the phase between the two orthogonal modes so as to create, for example, circular polarization, 45° inclined polarization or vertical / horizontal polarization. In reception, the septum 103 separates two polarizations of a dual-polarization signal received via the radiating element.

[0042] The septum 103 also extends longitudinally with respect to the polarizer waveguide (i.e., with respect to the direction of propagation of the waves in the polarizer) and its height decreases until it disappears completely or until it forms a longitudinal groove on an internal wall of the antenna. The decrease in height is typically done in steps (i.e., in successive stages) along the longitudinal direction but it can also be linear, exponential, or according to another decreasing profile according to the particular needs.

[0043] The radiating element 20 is intended to be coupled on the one hand to the output port of the polarizer 10 and on the other hand to free space. It therefore forms the extension of the polarizer in the emission direction of the antenna.

[0044] As used herein, the term "coupling" does not exclude the two coupled elements from being formed and / or manufactured as a single piece. It may be a theoretical coupling of two elements having a different function, but forming an object not resulting from the mechanical assembly of these two elements.

[0045] As schematically illustrated in Figure 1, the radiating element 20 comprises a waveguide, a first end of which is coupled to the output port of the polarizer 10 and a second end 201 of which is coupled to the free space. This waveguide comprises an internal channel, the walls of which are provided with three grooves 202 extending parallel to the direction of propagation of the waves in the internal channel. Each of the three grooves comprises an external portion 203 extending out of the waveguide by its second end 201 so as to form fins projecting in the longitudinal direction.

[0046] The 202 grooves make it possible in particular to lower the cut-off frequency of the waveguide and thus to allow the miniaturization of the antenna. In addition, the grooves also make it possible to adapt the impedance of the antenna to the impedance of the free space in order to reduce the phenomenon of reflection of the signals at the radiating element - free space interface.

[0047] The height of the ridges may be constant or variable along the longitudinal direction. Figure 5b illustrates an embodiment in which the height of the ridges is variable longitudinally in the waveguide.

[0048] As illustrated in Figures 1 to 4, the external portion 203 of each groove 202 has a height, measured in the radial direction relative to the direction of propagation, which decreases as it moves away from the second end 201 of the waveguide of the radiating element. This decreasing profile of the external portions 203 makes it possible in particular to significantly increase the bandwidth of the antenna in the manner of a traditional Vivaldi antenna. They are also particularly suitable for questions of adaptation of the impedance of the antenna to the impedance of free space.

[0049] Surprisingly, the combination of the ridges 202 inside the waveguide and the external portions 203 makes it easier to additively print the antenna 1, particularly the printing of the external portions. Indeed, the ridges 202 can serve as support for the external portions 203 during their printing. This makes it possible to reduce the quantity of additional supports required which must be manually removed after printing. This results in a saving in weight and cost since the manufacturing time is reduced.

[0050] In a preferred embodiment, the polarizer waveguide and the radiating element 10 have a rotational invariance of 120° around the propagation direction. In other words, a section of these waveguides perpendicular to the propagation direction in the antenna is rotationally invariant by 120° relative to the propagation direction. This implies in particular that the grooves 202 are distributed in the internal channel of the waveguides so as to be spaced 120° apart from each other.

[0051] Surprisingly, this distribution of the 120° streaks makes it possible to increase the discrimination between the fundamental mode and the higher order modes, thus limiting the risk of superposition of these higher modes.

[0052] Preferably, the section of the waveguide of the polarizer 10 and of the radiating element 20 is circular, triangular or hexagonal so as to respect the invariance by rotation of 120° around the direction of propagation. More generally, polygonal sections with 3n sides, where n is a positive integer, make it possible to respect the symmetry at 120°. The waveguides can thus form cylinders if the section is circular, or prisms with a triangular, hexagonal base, etc. The angles of the prisms can be truncated.

[0053] The grooves 202 may be arranged on the internal walls of the internal channel of the waveguides corresponding to the faces or angles of the prisms.

[0054] Figure 2 illustrates an antenna 1 whose section of the radiating element and the polarizer is circular. The grooves 202, and therefore the external portions 203, are spaced 120° apart on the internal wall of the waveguides.

[0055] Figure 3 illustrates an antenna 1 whose section of the radiating element and the polarizer is triangular. The angles of the triangular-based prism formed by the waveguides of the polarizer and the element radiant can be truncated. The ridges 202 can be arranged on the internal walls of the waveguides corresponding to the truncated parts of the prism or corresponding to the faces of the prism. The triangles forming the section of the waveguides can be equilateral, which implies an invariance by rotation of 120° around the direction of propagation, or isosceles.

[0056] Figures 4 and 6 illustrate antennas 1 whose sections of the radiating element and the polarizer are hexagonal. In Figure 4, the grooves 202 are arranged on the internal walls of the waveguides corresponding to the angles of the hexagonal-based prism formed by the waveguides. In Figure 6, however, the grooves 202 are arranged on the internal walls of the waveguides corresponding to the faces of the prism.

[0057] Advantageously, one of the grooves may be formed by extending the septum 103 in the longitudinal direction of the antenna. Thus, the septum 103, a groove 202 and the corresponding external portion 203 of the groove are aligned longitudinally.

[0058] In one embodiment, one or more grooves are inclined relative to the radial direction. This means that the height direction of the grooves is not aligned with the radial direction relative to the propagation direction. In particular, the angle between the height direction of the groove and the wall of the waveguide supporting the groove may be other than 90°.

[0059] 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.

[0060] The antenna 1 comprises a core which is preferably manufactured by an additive manufacturing process. The polarizer 10 and the radiating element 20 are preferably produced monolithically, their core being manufactured in a single additive printing step. In this application, the expression “additive manufacturing” designates any process for manufacturing the core by adding material, according to the computer data stored on the computer medium and defining the geometric shape of the core.

[0061] The core may for example be manufactured by an additive manufacturing process of the SLM (Selective Laser Melting) type. The core may also be manufactured by other additive manufacturing methods, for example by hardening or coagulation of liquid or powder in particular, including without limitation methods based on stereolithography, inkjets (binder jetting), DED (Direct Energy Deposition), EBFF (Electron Beam Freedom Fabrication), FDM (Fused Deposition Modeling) PFF (Plastic Free Forming), by aerosols, BPM (Ballistic Particle Manufacturing), SLS (Selective Laser Sintering), ALM (Additive Layer Manufacturing), polyjet, EBM (Electron Beam Melting, photopolymerization, etc.

[0062] The core can, for example, be made of photopolymer made by several surface layers of liquid polymer hardened by ultraviolet radiation during an additive manufacturing process.

[0063] The core can also be formed from a conductive material, for example a metallic material, by an additive manufacturing process of the SLM type in which a laser or an electron beam melts or sinters several thin layers of a powdery material.

[0064] According to one embodiment, the metal layer is deposited in the form of a film by electrodeposition or electroplating on the internal faces of the core. Metallization makes it possible to cover the internal faces of the core with a conductive layer.

[0065] The application of the metal layer may be preceded by a surface treatment step on the internal faces of the core in order to promote adhesion of the metal layer. The surface treatment may include an increase in surface roughness, and / or the deposition of an intermediate bonding layer.

[0066] The reduction in height of each outer portion 203 of groove 202 may decrease linearly, exponentially and / or in steps depending on the applications.

[0067] In order to match the antenna impedance to the free space impedance, the radiating element may include impedance matching elements.

[0068] In an embodiment illustrated in FIG. 6, the external portions 203 of the ridges 202 may comprise at least one lateral impedance matching step 204. These steps are typically arranged in the extension of the wall of the waveguide of the radiating element 20 and extend laterally on one or both sides of the external portions 203.

[0069] In one embodiment illustrated in Figure 6, one or more walls of the waveguide of the radiating element 20 include impedance matching slots 204.

[0070] Multiple impedance matching elements may be combined on the same antenna. These impedance matching elements may also include protrusions disposed on one or more internal walls of the radiating element waveguide in addition to the ridges 202.

[0071] As illustrated in Figure 7, several dual-polarized antennas as described above may be grouped together to form an antenna array 30.

[0072] The antennas in such an array are typically arranged in a one- or two-dimensional matrix, i.e., the antennas may be arranged contiguously along one or two axes. Figure 7 illustrates a two-dimensional matrix arrangement. However, the arrangement of the antenna array, i.e., the configuration of adjacent antennas, may also differ from that of a matrix and may, for example, be triangular.

[0073] The antenna array is preferably miniaturized in that the periodicity of the antenna array is less than or equal to 80% of the nominal wavelength of the signals transmitted / received by each antenna.

[0074] The present invention also relates to a satellite comprising at least one antenna as described above or an antenna array as described above. Reference numbers used in the figures Dual polarization antenna 1 Polarizer 10 First port 101 Second port 102 Septum 103 Radiant element 20 Second end 201 Streak 202 External portion 203 Side step 204 Slot 205 30 antenna network

Claims

Claims 1. Antenna (1) with dual polarization (P1, P2) obtained by additive manufacturing comprising: a polarizer (10) comprising: a first port (101) intended for a first signal with a first polarization (P1); a second port (102) intended for a second signal with a second polarization (P2); an output port intended for a signal with dual polarization; a septum (103) for combining the first signal on the first port (101) with the second signal on the second port (102);a polarization-preserving radiating element (20) comprising a waveguide having a first end connected to the output port of the polarizer (10) and a second end (201) coupled to free space, the waveguide comprising an internal channel provided with three grooves (202) parallel to a direction of propagation of a signal in the internal channel, characterized in that an outer portion (203) of each groove (202) extends out of the waveguide via the second end (201), a height of the outer portion (203) of each groove measured radially relative to the direction of propagation decreasing away from the second end (201).; 2. Antenna (1) according to claim 1, in which a section of the waveguide perpendicular to the direction of propagation is invariant by rotation of 120° around the direction of propagation.

3. Antenna (1) according to one of the preceding claims, in which a section of the waveguide perpendicular to the direction of propagation is circular, triangular or hexagonal.

4. Antenna (1) according to one of the preceding claims, in which one of the three grooves (202) is formed by the extension of the septum (103).

5. Antenna (1) according to one of the preceding claims, in which at least one of the three grooves (202) forms an angle with an internal wall of the internal channel of less than 90°.

6. Antenna (1) according to one of the preceding claims, wherein a diameter of the waveguide 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.

7. Antenna (1) according to one of the preceding claims being monobloc.

8. Antenna (1) according to one of the preceding claims, in which the height of each external portion (203) of at least one groove (202) decreases linearly, exponentially and / or in steps.

9. Antenna (1) according to one of the preceding claims, in which each external portion (203) of groove (202) comprises at least one lateral impedance matching step (204) arranged in the extension of a lateral wall of the internal channel.

10. Antenna (1) according to one of the preceding claims, wherein at least one side wall of the internal channel comprises an impedance matching slot (205) extending from the second end (201) of the waveguide of the radiating element (20).

11. Antenna array (30) comprising a plurality of antennas (1) according to one of the preceding claims.

12. Antenna array (30) according to the preceding claim, the plurality of antennas being arranged in a matrix in one or two directions.

13. Satellite comprising at least one antenna according to one of claims 1 to 10.

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