EP3155690B1 - Flat antenna for satellite communication - Google Patents

Description

Field of the invention

The present invention relates to the field of flat satellite telecommunication antennas. The invention is particularly suitable for aircraft.

The invention finds a particularly advantageous application for transmitting and receiving data to or from a satellite, particularly for satellite communications of the Satcom type (acronym for satellite communication or " satellite communications" in English terminology).

State of the art

For some telecommunications applications, especially airborne, it is necessary to use flat antennas of very small thickness in order not to change the aerodynamic profile of the carrier, for example when the antenna is positioned on the surface of an aircraft.

These telecommunication antennas comprise a plane surface comprising at least one radiating line capable of transmitting and receiving signals of a frequency determined according to the shape of the radiating line. The signals are transmitted and received in the direction of the satellite which can be detuned with respect to the normal direction of the antenna according to the movements of the carrier. More specifically, these antennas must point a highly directional beam within a cone of at least 60 ° half-angle so that the gain of the antenna remains sufficient to ensure the signal-to-noise ratio necessary for the quality of the link.

avec : i correspondant à l'indice de la ligne, d au pas entre les lignes et λ à la longueur d'onde.A known solution to achieve this pointing is to use a flat antenna 100 as described on the Figure 1 . This flat antenna 100 extends in an xy plane on an outer wall 101 of an aircraft. Radial lines 102 of the flat antenna 100 emit and receive signals in a detented direction 103 at an angle α with respect to the z direction normal to the surface of the flat antenna 100 in the plane perpendicular to the radiating lines 102 (FIG. xoz). This depointage requires adjustment of the phase on each radiating line by means for example of programmable electronic phase shifters. The phase φ _i to be displayed on the line i to obtain a score in the direction a is given by the expression: $${\mathrm{\phi }}_{\mathrm{i}}=2\mathrm{\pi \; id\; sin\; \alpha }/\mathrm{\lambda };$$

with: i corresponding to the index of the line, d to the pitch between the lines and λ to the wavelength.

In order to detach the signals received in a cone, the flat antenna 100 is moreover rotatable β about an orthonormal axis z with the xy axes.

This first solution makes it possible to scan electronically all the pointing directions inside the cone.

However, the direction of the pointing at a is variable with the wavelength λ and does not allow simultaneous operation in two very different frequency bands such as Satcom band Ka for example (20GHz in reception, 30GHz in transmission).

To remedy this problem, it is known to use a ROTMAN lens described, for example, in US Pat. US 3,170,158 . The ROTMAN lens is a known device which usually makes it possible to obtain an antenna radiating several beams in a plane. The lens is provided with N access each giving a beam in a given direction independent of the frequency. The angular sweep is obtained by switching between the N beams available.

The lens is formed by the space between two parallel conductive planes, the input network consists of fixed horns made as a waveguide radiating a polarization perpendicular to the metal planes. The output network may consist of monopole elements perpendicular to the metal planes and to collect the energy radiated by the cornets of the input network. The linear array of the radiating elements is fed via links (coaxial for example) of lengths such that the radiated wave is plane.

According to a similar principle, US Pat. US 8,284,102 , discloses an electronic phase shifter comprising an electronic selector for a linear or curved source array. The focusing of the antenna is performed by internal reflector elements and dielectric or refractive focusing means.

This second solution makes it possible to have a fixed flat antenna on the surface of an aircraft. However, this solution limits the number of directions that can point the antenna according to the number of linear sources. In addition, the implementation of a linear source network and electronic selection means increases the size of the flat antenna.

In addition, the ROTMAN lens is conventionally connected by coaxial cables connected between the ROTMAN lens and the radiating lines of the antenna. The length of the coaxial cables is adapted to introduce a delay necessary for the focusing of the radiated wave by the radiating lines for each horn of the ROTMAN lens. These cables are, of course, equipped with connectors at each end.

Such an antenna poses implementation problems when the antenna is designed to operate in the Ku or Ka high frequency bands. First, the length of the cables must be extremely precise to limit errors on the phase. For example, for an antenna operating at 30 GHz, an error of 0.2 mm in length of a coaxial cable induces a phase error of about 10 °. Secondly, the size of the coaxial cable connectors limits the possibilities of implantation and the number of usable cones. For example, for an antenna operating at 30 GHz, the pitch of the radiating lines and outputs of the Rotman lens is close to 5mm. In addition, a 500mm diameter antenna operating at 30GHz has about 100 different cables, which has a negative impact on specifications and implementation steps. A phase shifter for an antenna array is disclosed in the British application GB 2398172 .

Presentation of the invention

The present invention intends to overcome the disadvantages of the prior art by proposing a fixed flat antenna provided with a mobile horn to sweep a large number of pointing directions of the antenna. The connections between the horn and the radiating plate are made by a multilayer supply circuit.

For this purpose, the present invention relates to a satellite telecommunication flat antenna comprising a radiating plate comprising at least one radiating line, and an adaptation means able to modify the delay of the fields emitted or received by the at least one radiating line. , said adaptation means comprising a rotating horn between the two metal plates, and a multilayer supply circuit having a first layer formed by the at least one metal plate containing a slot-type sensor array and a last layer is provided with at least one coupling slot connected to the at least one radiating line, the first layer and the last layer being connected by at least one transmission line, the length of the at least one transmission line being adapted to introduce a delay necessary for the focusing of the radiated wave by the radiating line.

The invention thus makes it possible to scan a large number of pointing directions by moving the rotating mobile horn associated with the radiating lines of the antenna. The tuning of each radiating line is effected by the length of a transmission line connecting the sensor array of the at least one metal plate and the radiating plate. The invention makes it possible to fix the antenna on a flat surface thus limiting the fragility of the antenna and improving the aerodynamics of the wearer of the antenna. The antenna according to the invention also eliminates the need for coaxial cables and connectors. This antenna structure operates in a very broad band of frequency because the horn allows a pointing independent of the frequency.

According to one embodiment, the horn is able to transmit between the metal plates a wave whose electric field is perpendicular to the metal plates.

According to one embodiment, the length of the at least one transmission line is adapted to introduce an additional delay making it possible to obtain an initial fixed score so that the total score varies from 0 ° to 60 ° for a symmetrical displacement. cornet of ± 30 °. This embodiment, associated with the overall rotation of the antenna 360 ° about its axis z can contain all directions in a 60 ° half-angle cone centered on the direction normal to the antenna.

According to one embodiment, the supply circuit consists of five metal circuit layers separated by four layers of dielectric. This embodiment is particularly suitable for a satellite type antenna (satellite communication acronym or " Sa tellite com munications" in English terminology).

According to one embodiment, the supply circuit is assembled by gluing. This embodiment limits the complexity of assembly operations of the multilayer power supply circuit.

According to one embodiment, two layers of the supply circuit are connected by at least one metallized hole passing through a conductive layer without contact through a non-metallized pellet. This embodiment is particularly suitable for a satellite type antenna (satellite communication acronym or " Sa tellite com munications" in English terminology).

According to one embodiment, the two metal plates containing the slot-type sensor array are fixed on a plane parallel to the plane of said radiating plate.

According to one embodiment, said radiant plate comprises several radiating lines spaced by a half-wavelength. This embodiment makes it possible in particular to avoid problems related to the network lobes.

According to one embodiment, said radiant plate comprises a plurality of radiating lines consisting of an alignment of radiating elements such as dipoles, patches or slots.

According to one embodiment, said radiating plate comprises a plurality of radiating lines each comprising a splitter with an input and a plurality of outputs corresponding to the number of radiating elements of the radiating line.

Brief description of the drawings

• la Figure 1 illustre une antenne de télécommunications par satellite plate et mobile selon l'état de la technique ;
• la Figure 2 illustre une antenne de télécommunications par satellite plate partiellement représentée selon un mode de réalisation de l'invention ;
• la Figure 3 illustre le cornet mobile de l'antenne de la Figure 2 ;
• la Figure 4 illustre le circuit d'alimentation multicouches de l'antenne de la Figure 2 ;
• la Figure 5 illustre une voie du circuit d'alimentation multicouches selon un mode de réalisation dans une vue en perspective ;
• la Figure 6 illustre la voie de la Figure 5 dans une vue en coupe ;
• la Figure 7 illustre la première couche de lignes de transmission du circuit d'alimentation multicouches pour un exemple d'antenne comportant 49 lignes rayonnantes ;
• la Figure 8 illustre la deuxième couche de lignes de transmission du circuit d'alimentation multicouches pour l'exemple de la Figure 7 ; et
• la Figure 9 illustre la première et la deuxième couche de lignes de transmission du circuit d'alimentation multicouche pour l'exemple de la Figure 7 ;

The invention will be better understood by means of the description, given below purely for explanatory purposes, of the embodiments of the invention, with reference to the figures in which:

• the Figure 1 illustrates a flat and mobile satellite telecommunications antenna according to the state of the art;
• the Figure 2 illustrates a flat satellite telecommunications antenna partially shown according to one embodiment of the invention;
• the Figure 3 illustrates the mobile horn of the antenna of the Figure 2 ;
• the Figure 4 illustrates the multi-layer feed circuit of the antenna of the Figure 2 ;
• the Figure 5 illustrates a multilayer power supply circuit path according to an embodiment in a perspective view;
• the Figure 6 illustrates the path of Figure 5 in a sectional view;
• the Figure 7 illustrates the first layer of transmission lines of the multilayer power supply circuit for an exemplary antenna having 49 radiating lines;
• the Figure 8 illustrates the second layer of transmission lines of the multilayer power supply circuit for the example of the Figure 7 ; and
• the Figure 9 illustrates the first and second transmission line layers of the multilayer power supply circuit for the example of the Figure 7 ;

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

The Figure 2 discloses a satellite dish antenna 10 consisting of a radiating plate 16 connected to an adaptation means 11 adapted to modify the delays of the fields transmitted or received by the radiating plate 16.

The radiating plate 16 extends in a plane xy and has a plurality of radiating lines 17 disposed along the y-axis at a step close to half a wavelength along the x-axis. Each radiating line 17 consists of an alignment of N radiating elements (not shown), for example dipoles, patches or slots arranged at a pitch less than a wavelength along the y-axis and fed by a splitter having an input and N outputs.

The adaptation means 11 consists of a horn 12 movable in rotation between two metal plates 13a and 13b parallel to the radiating plate 16. The horn 12, shown in FIG. Figure 3 is rotatable about the axis z '(parallel to or coincident with the z axis) extending in a direction normal to the xy plane. The mobility of the horn 12 is provided by a digitally controlled guide 20.

The horn 12 radiates between the two metal plates 13a, 13b a TEM wave (for electrical-magnetic transverse) whose electric field is perpendicular to the metal plates 13a, 13b. The adaptation means 11 also comprises a multilayer supply circuit 14, shown in FIG. Figure 4 , connecting the horn 12 to the radiating plate 16. This supply circuit 14 consists of five copper circuit layers 13a, 20-23 separated by four layers of dielectric. The whole is assembled by gluing. The first layer 13a is formed by the upper metal plate 13a. A coupling slot 27 formed in this layer 13a gives one of the sensors of the sensor network.

The layers 13a, 20 and 21 form a triplate type transmission line whose conductive line is located on the layer 20 and the ground planes on the layers 13a and 21.

The layers 21, 22 and 23 form a second transmission line of the triplate type, the conductive line of which is located on the layer 22 and the ground planes on the layers 21 and 23. A bushing 28 for connecting the lines 25 of the layers 20 and 22 is made by means of a metallized hole through the conductive layer 21 without contact through a non-metallized chip or pellet. The layer 23 is provided with a coupling slot 26 for feeding a line 17 of the radiating plate 16.

This structure makes it possible to obtain a transmission coefficient between the coupling slot 27 and the radiating plate 16 of module substantially equal to one and of easily controllable delay by adjusting the length of the lines 25 of the layers 20 and 22. These lines also induce an additional delay making it possible to obtain an initial fixed score so that the total score varies from 0 ° to 60 ° for a symmetrical movement of the horn 12 by approximately ± 30 °.

The Figures 5 and 6 represent an embodiment of the adaptation means 11 for a channel. The adaptation means 11 consists of the metal plates 13a, 13b arranged around the horn 12 (not shown). The propagation of the waves emitted and received by the horn 12 are transmitted to the multilayer supply circuit 14 by a coupling slot 27. The propagation is closed between the metal plates 13a and 13b at the rear of the slot 27 by a metal part 30 whose profile allows the adaptation of the transmission.

The supply circuit 14 consists of four layers of printed circuit assembled by gluing. The material used can be for example Rogers RT / duroid 5880 thickness 0.508mm.

The layers 13a and 21 are connected in the vicinity of the slot 27 by metallized holes to prevent the propagation of undesirable modes in the circuit. The energy taken by the slot 27 flows in the line 25a and then in the line 25b after changing the layer produced by means of the passage 28. The layers 13a, 21 and 23 are connected in the vicinity of the crossing by metallized holes allowing avoid the spread of undesirable modes in the circuit. The crossing is made by a metallized hole connecting the layers 20 and 22. It passes through the layer 21 without contact through a non-metallized pellet.

The coupling at the input of a line of the radiating plate 16 is formed by the slot 26. The layers 21 and 23 are connected in the vicinity of the slot 26 by metallized holes to prevent the propagation of undesirable modes in the circuit.

The input of the line of the radiating plate 16 is also made in triplate technology between the radiating line 17 and the ground planes 36 and 37. It is embedded in a metal part 40 ensuring precise positioning and low impedances between the different metal layers 23, 36 and 37. The coupling between the radiating line 17 and the line 25b is obtained thanks to the slot 26 and the connection of the radiating line 17 to the ground plane 37 through the metallized hole 41. The layers 36 and 37 are connected by metallized holes 42 to prevent the propagation of undesirable modes in the circuit.

The Figures 7, 8 and 9 give the appearance of the complete circuit for an example of an antenna comprising 49 radiating lines. The coupling slots with the radiating lines 26 are aligned at a step close to half a wavelength (5 mm at 30 GHz). The slots 27 in connection with the horn 12 are arranged on the output curve (close to an arc) at a step also close to half a wavelength. The length of the lines 25a, 25b adjusted by means of the position of the bushings 28 gives the delay necessary for the focusing and the initial pointing of the beam to 30 ° (centrally located horn).

This embodiment makes it possible to limit the bulk of the supply circuit 14 to connect the horn 12 to the radiating lines 17.

The invention also makes it possible to point all the directions contained in the 60 ° half-angle cone centered on the z axis by means of a rotation of the horn 12 of ± 30 ° approximately around the z 'axis and a rotation of the antenna assembly 360 ° about the z axis. This antenna structure operates in a very wide band of frequencies because the mobile horn 12 provides a score independent of the frequency.

Claims (10)

1. Flat antenna (10) for satellite communications comprising :

   - a radiating plate (16) comprising at least one radiating line (17); and

   - an adaptation means (11) capable of modifying delays in fields transmitted or received by the said at least one radiating line (17) on the radiating plate (16);

   characterised by the fact that the said adaptation means (11) comprises:

   - a moveable horn (12) rotating between two metallic plates (13a, 13b); and

   - a multilayer (13a, 20-23) feeding circuit (14) with a first layer (13a) formed by at least one of the metallic plates (13a, 13b) housing a network of slit-like sensors, and a last layer (23) equipped with at least a coupling slit connected to the said at least one radiating line (17) of the radiating plate (16);

   - the first layer (13a) and the last layer (23) connected by at least one transmission line (25);

   - the length of the said at least one transmission line (25) connecting the first layer (13a) to the last layer (23) designed to introduce a delay needed to focus the wave radiated by the radiating line (17).
2. Flat antenna according to claim 1, characterised by the fact that the horn (12) is capable of transmitting through the metallic plates (13a, 13b) a wave with an electric field that is perpendicular to the metallic plates (13a, 13b).
3. Flat antenna according to claim 1 or 2, characterised by the fact that the length of the said at least one transmission line (25) is designed to introduce an additional delay that allows for an initial fixed pointing to be obtained, such that the total pointing varies between 0° and 60° for a symmetrical movement of the horn (12) of approximately ±30°.
4. Flat antenna according to one of claims 1 to 3, characterised by the fact that the feeding circuit (14) is made up of five layers (13a, 20-23) of metallic circuits separated by four dielectric layers.
5. Flat antenna according to one of claims 1 to 4, characterised by the fact that two layers (20, 22) of the feeding circuit (14) are connected by at least one metal hole running through a non-contact conductive layer through a non-metallic pad.
6. Flat antenna according to one of claims 1 to 5, characterised by the fact that the feeding circuit (14) is assembled by adhesive bonding.
7. Flat antenna according to one of claims 1 to 6, characterised by the fact that the two metallic plates (13a, 13b) containing the network of slit-like sensors are secured on a plane parallel to the plane of the said radiating plate (16).
8. Flat antenna according to one of claims 1 to 7, characterised by the fact that the said radiating plate (16) has several radiating lines (17) spaced out by a half-wavelength.
9. Flat antenna according to one of claims 1 to 8, characterised by the fact that the said radiating plate (16) comprises several radiating lines (17) composed of aligned radiating elements, including dipoles, patches or slits.
10. Flat antenna according to one of claims 1 to 9, characterised by the fact that the said radiating plate (16) comprises several radiating lines (17), each comprising a splitter with one input and several outputs in alignment with the number of radiating elements of the radiating line.

Images