Dual Polarization Antenna

Abstract

A dual-polarization (RHCP, LHCP) antenna (1), comprising: a plurality of antenna elements arranged in cell units (8), each cell unit (5) including four antenna elements (3) and two 1-to-4 junctions (5), a first of the two junctions (5) being associated with a first polarization and a second of these two junctions being associated with a second polarization, an array of dividers / combiners (4, 6), the four antenna elements (3) of each cell unit (8) being superimposed, a plurality of cell units (8) being juxtaposed, each cell unit (8) comprising two antenna elements (3) and two other offset antenna elements (3).

Description

Dual polarization antenna technical field

[0001] The present invention relates to a radio frequency (RF) module, intended to form the passive part of a direct radiating array (DRA). State of the art

[0002] Antennas are devices 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 offer higher directivity but are bulky and heavy, making them unsuitable for applications such as satellites, where weight and size must be minimized.

[0003] We also know of DRA antenna arrays that combine several radiating elements (antenna elements) with different phases to improve gain and directivity. The signals received on the different radiating elements, or emitted by these elements, are amplified and phase-shifted relative to each other in order to control the shape of the receive and transmit lobes of the array.

[0004] At high frequencies, for example at microwave frequencies, the different radiating elements are all connected via a waveguide network to a port allowing the antenna to be connected to an electronic circuit including, for example, an RF electronic circuit and an amplifier.

[0005] We also know of dual-polarization antennas capable of simultaneously transmitting and receiving signals with two polarizations. In this case, the signals transmitted or received by each antenna element are combined, or separated respectively, according to their polarization by means of a polarizer. The polarizer can also be integrated into the antenna element. A dual-polarization antenna has two ports to connect each of the two polarizations separately to the electronic circuit.

[0006] Antennas designed to transmit high frequencies, particularly microwave frequencies, are difficult to design. It is often desirable to place the individual antennas in the array as close together as possible to reduce the amplitude of secondary transmission or reception lobes in directions other than the preferred transmission or reception direction. However, reducing the spacing between the individual antennas in the array is incompatible with the size of the waveguide array required to combine the signals received by the individual antennas, or to divide the signals to be transmitted.

[0007] It is also often necessary to reduce the size of the antenna, and especially its width and height in the plane perpendicular to the direction of signal transmission, in order to be able to fit it in the small volume available in a satellite or aircraft.

[0008] Another goal when designing such an antenna is also to reduce its weight, particularly in applications for space or aeronautics.

[0009] Examples of known antennas are described in particular in WO2019 / 226201 A2, US2011 / 267250 A1, WO2017 / 053417 A1 and US2017 / 117637 A1.

[0010] One goal is to provide an antenna adapted to the Ka frequency band, particularly for LHCP and RHCP polarized satellite communications.

[0011] Finally, it is also desirable to develop antennas with a new modular design that allows the number of elementary antennas to be varied according to needs, without having to redesign the entire antenna. A design is considered modular when different types of antennas can easily be created by adding or removing standardized antenna elements during the design phase, without requiring a complete redesign of the antenna or waveguide array. In particular, it is desirable to be able to design an antenna modularly by adding units with multiple antennas while ensuring spatial filtering.

[0012] The antenna must also, of course, have very high efficiency, gain, and radiation pattern characteristics that are compatible with the application's specifications.

[0013] Finally, the antenna must be able to be manufactured industrially and without falling within the scope of existing patent protection. Brief summary of the invention

[0014] According to one aspect, a dual-polarization antenna (RHCP, LHCP) comprises: at least one first port for connecting the antenna to an active circuit to transmit or receive a signal with a first polarization (LHCP); at least one second port for connecting the antenna to an active circuit to transmit or receive a signal with a second polarization (RHCP); several dual-polarization antenna elements, the antenna elements being arranged in cell units, each cell unit including four antenna elements and two 1-to-4 junctions, one of the two junctions being associated with a first polarization and the other of these two junctions being associated with a second polarization, each said junction comprising four branches to connect it to one of the polarizations of each antenna element of the corresponding unit and a common trunk, a network of dividers / combiners to connect the trunk of each said 1-to-4 junction of a cell unit associated with the first polarization with the first port and to connect the trunk of each said 1-to-4 junction associated with the second polarization with the second port, the four antenna elements of each cell unit being superimposed, several cell units being juxtaposed,each cell unit comprising two antenna elements in a foreground and two further antenna elements in a second plane parallel to the foreground, said planes being offset from each other in a direction perpendicular to said planes by a distance less than the width of one antenna element.

[0015] This structure allows for the creation of an elementary antenna network, hereafter simply called an antenna, in a modular manner by juxtaposing antenna units, each consisting of four superimposed elementary antennas.

[0016] Each antenna unit has two 1-to-4 junctions and thus allows it to receive and transmit signals according to two distinct polarizations.

[0017] Each antenna unit thus comprises four superimposed antenna elements, but offset two by two.

[0018] The arrangement of the antenna elements of each unit in two planes offset from each other in a perpendicular direction A beamforming effect at the plane of the blade, less than the width of an antenna element, allows for beamforming, or spatial filtering, of the signals received or transmitted within a cell unit. This ensures that in certain directions, the signals interfere constructively, while in other directions, the interference is destructive. This beamforming at the elementary level of each unit allows for greater freedom when combining antenna units, since each antenna unit already contains pairs of out-of-phase antennas. It also facilitates the connection of the different antennas using the waveguide network that links them together.

[0019] The terms "superposition," "juxtaposition," or "stacking" describe the situation of an antenna oriented in a particular way with cell units formed from four antenna elements stacked one above the other. However, it is understood that the antenna can transmit and receive independently of its orientation in space, and that the invention relates to any antenna that can be rotated so that, in at least one possible orientation, the antenna elements / components are superimposed, juxtaposed, or stacked according to the arrangement described and claimed.

[0020] The number of antenna elements is preferably exactly equal to four.

[0021] The divider / combiner network that connects the antenna units to the ports preferably includes a first sub-array of dividers / combiners with a stack of adjacent blades. This makes it easy to create an antenna with a larger number of elemental antennas by adding more blades and / or increasing the number of cell units per blade.

[0022] In each blade, the first subnetwork of dividers / combiners is arranged to connect together the trunks of each 1-to-4 junction of that blade.

[0023] Some blades are associated with a first polarization and other blades are associated with the second polarization.

[0024] The first sub-array of dividers / combiners in the plates associated with the first polarization is arranged to connect the 1-4 junction trunks associated with this first polarization. Similarly, the first sub-array of dividers / combiners in the plates associated with the second polarization is arranged to connect the 1-4 junction trunks associated with this second polarization.

[0025] The first sub-array of dividers / combiners advantageously features an alternation of first blades associated with the first polarization and second blades associated with the second polarization. Thus, each blade is dedicated to a single polarization.

[0026] The antenna advantageously includes a second sub-array of dividers / combiners arranged to connect said first blades together and with the first port, and to connect said second blades together and with the second port.

[0027] Each blade preferably extends in a first direction substantially perpendicular to the direction of signal transmission, and between the two planes defined by the extreme lateral edges of the antenna elements associated with this blade.

[0028] A first blade and a second blade preferably extend between the two planes defined by the extreme lateral edges of the antenna elements associated with these two blades. Thus, the width of the array of dividers / combiners is less than or equal to the maximum width of the associated antenna elements; the total antenna width is therefore given by the width of the elemental antenna array, and it is possible to add new antenna elements and connect them without the divider / combiner array determining the total width.

[0029] The second sub-network of dividers / combiners is advantageously provided between said blades and said ports.

[0030] The second sub-array of dividers / combiners preferably includes portions of waveguide extending in a second direction substantially perpendicular to the direction of signal transmission.

[0031] In one embodiment, each blade is associated with four cell units.

[0032] Each antenna element can be connected to two adjacent blades.

[0033] In one embodiment, the antenna comprises 32 blades, of which 16 are associated with a first polarization and 16 with a second polarization.

[0034] The first sub-network of dividers / combiners of each blade has at least one bifurcation in the H plane.

[0035] Each antenna element preferably includes a septum to combine in transmission or separate in reception the two polarizations of a radio frequency signal.

[0036] Each antenna element preferably has a square cross-section perpendicular to the direction of signal propagation.

[0037] The antenna can be made monolithically.

[0038] The antenna can be made by 3D printing a core and depositing at least a surface layer on the inner face of this core. Brief description of the figures

[0039] Examples of implementation of the invention are given in the description illustrated by the attached figures in which: · Figure 1 illustrates a perspective view of an antenna comprising four cell units according to the invention. • Figure 2 illustrates an example of a blade designed to connect the first polarizations of four superimposed cell units. • Figure 2 illustrates an example of two blades placed side by side to connect the first and second polarizations of four superimposed cell units. • Figure 4 illustrates a first divider / combiner network made up of 32 juxtaposed plates. • Figure 5 illustrates a 1-to-4 junction with four branches intended to be connected to the first bias of the elementary antennas of a cell unit, and a trunk for the common signal. • Figure 6 illustrates a perspective view of a power combiner / divider in the H plane. • Figure 7 illustrates a side view of a power combiner / divider in the H plane. • Figure 9 illustrates a second divider / combiner network in the E plane. • Figure 10 schematically illustrates how one of the polarities of the superimposed elementary antennas are connected via the associated blade. • Figure 11 schematically illustrates the connections within the second network of combiners / dividers. Example(s) of an embodiment of the invention

[0040] The present invention relates generally to an antenna array, hereafter simply called an antenna, comprising several elementary antennas 3 (radiating elements) arranged in a matrix such that the apertures of these elementary antennas are all in the same plane. The direction d of signal transmission, within the antenna and at the antenna output, is perpendicular to this plane.

[0041] Figure 1 illustrates an antenna 1 comprising four juxtaposed cell units 8, each cell unit comprising four superimposed elementary antennas 3. The antenna 1 in this example thus comprises 16 elementary antennas, numbered by row and column of 3. ; up to 3B ; B and forming a matrix with four rows and four columns, each column being formed in this example from a single cell unit. As we will see later, the number of columns can be increased by juxtaposing additional cell units, and the number of rows can be increased by superimposing additional cell units within each column.

[0042] The spacing between two adjacent antenna elements and the spacing between two lines is advantageously less than the nominal wavelength of the signal to be transmitted; this reduces undesirable side lobes in transmission or in reception sensitivity.

[0043] The successive lines of the antenna are out of phase; in the illustrated example, the even lines are out of phase with the odd lines by a step corresponding to half the width of a basic antenna. This phase shift allows beamforming, or spatial filtering, of the signals received or transmitted by the antenna elements of the cell unit 8, such that in certain directions, the signals interfere constructively while in other directions the interference is destructive.

[0044] The antenna elements 3 each include an aperture forming a radiating element oriented towards the ether, and two ports for connection to the junction 5 described later. One of the two ports is for a first polarization and the other for a second polarization. The antenna includes a polarizer, preferably in the form of a septum 32, allowing the two polarizations LHCP and RHCP of a signal to be separated during reception and the two polarizations to be combined during transmission. In another embodiment, the antenna elements 3 may include a different type of polarizer, or be connected to a separate polarizer.

[0045] Antenna 1 further comprises a series of junctions 1-to-45. Two junctions 5 are associated with each cell unit, in order to respectively divide and combine the LHCP first polarization signals of the four elementary antennas of the cell unit, and to to divide and respectively combine the RHCP second polarization signals from the four elementary antennas of the cell unit. In this example, the number of junctions 1-to-45 is therefore equal to 8.

[0046] In the case of an antenna with several superimposed cell units 8, and therefore more than 4 lines, the signals at the output of the junctions 5 are combined using a first power divider / combiner in the H-plane, separately for each polarization. A port 7 (Figure 8) allows each polarization to be connected to an active electronic circuit.

[0047] Figures 2 to 4 illustrate an example of a first divider-combiner 4 with the 1-to-4 junctions of the associated cell units, in the case of a dual-polarization antenna comprising 16x16 antenna elements 3. The first divider / combiner consists of several juxtaposed blades 2, each blade being dedicated to one of the two polarizations LHCP or RHCP. Since each antenna element provides two polarizations, the number of blades is therefore equal to twice the number of antenna elements per line, i.e., 32 blades in this example.

[0048] Each blade 2 is designed to be connected to all the antenna elements 3 in a column, that is, to four superimposed cell units 8 in this example. It therefore comprises branches 500 to 50015, each of these branches being directly connected to one of the two output ports of one of the antennas. Two levels of 1-to-2 junctions in the H plane form a 1-to-4 junction (reference 5) allowing the signals within each cell unit 8 to be combined / split; the signal common to the trunk 501 of the blade 2 junctions is combined using two additional levels of 1-to-2 junctions in the H plane, the resulting signal from the summation of the signals in all the branches 500 of a blade 2 thus being found at the trunk 23 of that blade.

[0049] Figure 2 illustrates a single blade 2. Figure 3 shows two juxtaposed blades, one dedicated to a first LHCP polarization of several superimposed cell units and the other to the second polarization RHCP of the same cell units. Figure 4 illustrates the juxtaposition of 32 blades 2 constituting the first divider / combiner array of the antenna.

[0050] Figure 5 illustrates a 1-to-4-junction 5 present in each cell unit. The junction thus comprises four branches 500 intended to be connected to four ports of the antenna elements 3 of a cell unit 8. The first level includes two 1-to-2 junctions 51 to combine / split the signals of the same polarization from two superimposed antenna elements. Since the two antennas of each pair are out of phase, the junction is made in the H plane. A second 1-to-2 junction 50 then combines the trunks of the two junctions 51 into a common trunk 501.

[0051] Figures 6 and 7 illustrate in more detail an example of a 1-to-2 junction. This example relates to the first power divider / combiner 21 in the first network 4; however, the implementation of the 1-to-2 junctions 50 and 51 in the cell units, and of the second power divider / combiner 22 in the first network 4, can be identical or similar, with only the direction of the junction branches differing. As can be seen in particular in Figure 7, the height bi of the trunk 201 is less than the height b2 of the portion of the junction in which the signals combine or divide, this height b2 being itself less than the total height b3 of the two branches 200.

[0052] Figure 8 illustrates the rear of antenna 1, that is, the side opposite the front face from which the antenna elements 3 point. This figure shows, in particular, a second divider / combiner array 6 in plane E, designed to combine / divide the signals from the different plates 2, independently for each polarization. This array 6 comprises a first half-array 6LHCP for the first polarization LHCP, whose branches form a first comb intended to be connected to the plates 2 of the first polarization. A second half-array 6RHCP for the second polarization RHCP comprises branches forming a second comb interposed between the first comb and intended to be connected to the plates 2 of second polarization. The trunk of the first half-array forms the first port 7LHCP of antenna 1 and the trunk of the first half-array forms the first port 7RHCP.

[0053] Figure 9 illustrates one of the half-arrays, for example, the first half-array 6LHCP. In the example shown, it has 16 branches 60o to 60i5 forming the comb intended to connect to the stem / port of the various blades 2. The number of branches 60 depends, of course, on the number of blades 2. Four levels of junctions 1-to-261,62,63,64 in plane E successively combine / divide the signals from these different branches, which are joined into a common stem 7 forming one of the two ports of the antenna. The output of this stem 7 is bent at 90° to facilitate connection to a waveguide or directly to the electronic circuit.

[0054] Figure 10 schematically illustrates the junction tree within each blade 2, the blade grouping both the first divider / combiner network 4 and the junctions 1-to-45 of the cell units 8 associated with this blade.

[0055] Figure 11 schematically illustrates the junction tree within the second divider / combiner network 6.

[0056] The antenna is advantageously made monolithically, preferably by 3D printing a metal or polymer core, then deposition of at least one conductive layer on the inner faces of the antenna's waveguides.

[0057] The example above relates to an antenna with 16x16 antenna elements. This number is not limiting, and the number of antenna elements can be any number. However, the number of lines is preferably a multiple of 4 so that the antenna can be designed by stacking cell units, each containing four antenna elements. This number is also advantageously a power of two so that a first network of 4 dividers / combiners can be implemented. with an equal number of junctions between each branch of this network and the blade trunk, thus more easily ensuring paths of isophase length to the different branches.

[0058] The number of antenna elements per branch, and therefore of blades 2, can be arbitrary. However, this number is advantageously a power of two, so as to be able to create a second divider / combiner network 6 with an equal number of junctions between each branch of this network and the ports 7 of the antenna, thus more easily guaranteeing paths of isophase length to the different branches.

[0059] The antenna may have a mounting hole passing through the divider array in a direction perpendicular to the signal transmission direction, allowing it to be mounted by threading it around a cylindrical mounting bar. This solution allows for easy adjustment of the antenna's orientation by rotating it around the bar. Reference numbers used in the figures Antenna Blade First power divider / combiner in the blade (H-plane) Second power divider / combiner in the blade (H-plane) Branch of a power divider / combiner in the blade Trunk of a power divider / combiner in the blade Main trunk of the blade Antenna element Septum First divider / combiner network (H-plane) Junction 1-4 of a cell unit First power divider / combiner in the junction Second power divider / combiner in the junction Branch of a 1-4 junction in the cell unit Trunk of a 1-4 junction in the cell unit Second divider / combiner network (plane E) Connecting branch between the second divider network and a blade First power divider / combiner in the E-plane Second power divider / combiner in the E-plane Third power divider / combiner in the E-plane Fourth power divider / combiner in the E-plane Port Cell unit Index for left-hand polarized components Index for right-hand polarized components

Claims

Demands 1. Dual polarization antenna (1) (RHCP, LHCP), comprising: at least one first port (7) for connecting the antenna to an active circuit for transmitting or emitting a signal with a first polarization (LHCP); at least one second port (7) for connecting the antenna to an active circuit for transmitting or emitting a signal with a second polarization (RHCP); several dual-polarized antenna elements (3), the antenna elements being arranged in cell units (8), each cell unit (5) including four antenna elements (3) and two 1-to-4 junctions (5), one of the two junctions (5) being associated with a first polarization and the other of these two junctions being associated with a second polarization, each said junction (5) comprising four branches (500) for connecting it to one of the polarizations of each antenna element (3) of the corresponding unit and a common trunk (501), a divider / combiner array (4,6) to connect the trunk (501) of each said 1-to-4 junction (5) of a cell unit (8) associated with the first polarization with the first port (7) and to connect the trunk (501) of each said 1-to-4 junction (5) associated with the second polarization with the second port (7), the four antenna elements (3) of each cell unit (8) being superimposed, several cell units (8) being juxtaposed, characterized in that each cell unit (8) comprises two antenna elements (3) in a first plane and two other antenna elements (3) in a second plane parallel to the first plane, said planes being offset from each other in a direction perpendicular to said planes by a distance less than the width of an antenna element.

2. Antenna according to claim 1, said divider / combiner array (4, 6) comprising a first divider / combiner sub-array (4) formed of a stack of juxtaposed blades (2) and arranged to connect together the trunks (501) of each said junction 1 to 4 (5) of several units of superimposed cells (8) associated with the first polarization and to connect together the trunks (501) of each said junction 1 to 4 (5) of several units of superimposed cells (8) associated with the second polarization.

3. Antenna according to claim 2, said first sub-array of dividers / combiners (4) comprising an alternation of first blades (2LHCP) associated with the first polarization and second blades (2RHCP) associated with the second polarization.

4. Antenna according to claim 3, comprising a second sub-array of dividers / combiners (6) arranged to connect said first blades (2LHCP) to each other and with the first port (7LHCP), and to connect said second blades (2RHCP) to each other and with the second port (7RHCP).

5. Antenna according to any one of claims 2 to 4, each blade (2) extending in a first direction substantially perpendicular to the direction of signal transmission, and between the two planes defined by the extreme lateral edges of the antenna elements associated with this blade.

6. Antenna according to any one of claims 3 to 5, a said first blade (2LHCP) and a said second blade (2RHCP) extending between the two planes defined by the extreme lateral edges of the antenna elements associated with these two blades.

7. Antenna according to any one of claims 4 to 6, the second sub-array (6) being provided between said blades (2) and said ports and comprising portions of waveguide extending in a second direction substantially perpendicular to the direction of signal transmission.

8. Antenna according to any one of claims 1 to 7, each blade (2) is associated with four cell units (8).

9. Antenna according to any one of claims 3 to 8, comprising 32 said blades.

10. Antenna according to any one of claims 1 to 9, each antenna element (3) comprising a septum (32) for combining in transmission or separating in reception the two polarizations of a radio frequency signal.

11. Antenna according to claim 10, each antenna element (3) being connected to two adjacent blades (2LHCP, 2RHCP).

12. Antenna according to any one of claims 1 to 11, each antenna element (3) having a cross-section perpendicular to the direction of signal propagation of square shape.

13. An antenna according to any one of claims 1 to 12, comprising at least one cylindrical opening in a direction perpendicular to the signal transmission direction, and intended for mounting the antenna on a rod for holding and orienting it.

14. An antenna according to any one of claims 1 to 13, comprising a core produced by 3D printing and at least one surface layer on the inner face of this core.

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