Method for constructing a network antenna whose radiating elements are mounted on a curved support surface
The process of mounting radiant elements on a curved support surface allows for the creation of network antennas that can efficiently scan and cover a wider area than traditional flat antennas, addressing the limitations of existing technologies.
Patent Information
- Application Number
- FR2022005733
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-06-14
- Publication Date
- 2025-03-28
- Estimated Expiration
- 2042-06-14
AI Technical Summary
Existing network antennas are flat and limited in their ability to efficiently scan and cover a wide area around an aircraft, as their radiant elements are arranged in a regular pattern on a flat surface, which restricts their capacity to adapt to non-flat surfaces.
A process for creating a network antenna with radiant elements mounted on a support surface with non-zero curvature, involving a dimensioning phase where equivalent flat antennas are defined, and real radiant elements are positioned and oriented on the curved surface with calculated geometric phase shifts to maintain antenna functionality.
This process allows for the creation of network antennas that can efficiently scan and cover a wider area than traditional flat antennas, adapting to various curved surfaces such as aircraft fuselages, while maintaining radiation power and polarization consistency.
Smart Images
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Abstract
Description
Title of the invention: Method for producing an array antenna whose radiating elements are mounted on a curved support surface
[0001] The present invention relates to electronically scanned array antennas, in particular array antennas for aeronautics or telecommunications.
[0002] Today, network antennas are flat, the radiating elements of which they are made up being arranged in a regular pattern in a plane.
[0003] For example, the front radar of a fighter aircraft transmits and receives on a front antenna consisting of a plate of radiating elements, which is arranged transversely to the longitudinal axis of the aircraft. This front antenna allows observation of an area located in front of the aircraft.
[0004] This front antenna is topped with a radome of substantially conical or ogival shape for aerodynamic reasons, the axis of the radome being substantially aligned with the longitudinal axis of the aircraft.
[0005] To increase the exploration of the space around the aircraft, it is known to carry additional antennas on board the aircraft, the plates of which are arranged perpendicular to the front antenna.
[0006] It would be desirable to increase the capacities of an array antenna by using the external surfaces of the carrying platform, such as the fuselage of an aircraft, whatever their shapes to carry the radiating elements of the array antenna. The radiating elements would therefore no longer be arranged in a plane.
[0007] There is therefore a need for a production method making it possible to size and then manufacture an array antenna whose radiating elements are carried by a support surface having at least one non-zero curvature.
[0008] The aim of the present invention is to meet this need.
[0009] For this purpose, the invention relates to a method for manufacturing an electronically scanned array antenna comprising a plurality of real radiating elements, each real radiating element being mounted on a support surface, characterized in that, the support surface having a non-zero curvature and a real radiating element being positioned at an implantation point of the support surface so as to rest in an inclined plane, said inclined plane being inclined relative to a plane locally tangent to the support surface at the implantation point, the method comprises, in a dimensioning phase, the steps of: defining a reference direction around which the pointing direction of the array antenna can be modified by electronic phase shift; defining a reference plane normal to the reference direction; definition of an equivalent array antenna in the reference plane, the equivalent array antenna being a planar antenna comprising a plurality of equivalent radiating elements forming a regular pattern in the reference plane; for each equivalent radiating element: projection of a center of the equivalent radiating element, in the reference direction, onto the support surface, so as to obtain an implantation point of a center of a corresponding real radiating element; definition of an inclined plane at the implantation point on the support surface; projection of a contour of the equivalent radiating element, in the reference direction, into the inclined plane, to obtain a contour of the corresponding real radiating element;evaluation of a distance between the point of implantation of the real radiating element and the center of the equivalent radiating element and calculation, as a function of said distance, of a geometric phase shift to be applied to the signals emitted or received by the real radiating element during operation of the network antenna, and in that the method comprises, in a manufacturing phase, the steps of producing the network antenna in accordance with the results of the dimensioning phase.;
[0010] According to particular embodiments, this method comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations:
[0011] - the evaluation step consists of determining a gain of each real radiating element in order to adjust a radiation power, evaluated in the reference plane, that this real radiating element produces.
[0012] - the evaluation step consists of determining an adjustment of a polarization of each actual radiating element as a function of its installation position and / or its inclination on the support surface relative to the reference plane.
[0013] - the inclined plane is chosen parallel to the reference plane.
[0014] - the method begins with a step of delimiting at least one support surface elementary on the support surface, the elementary support surface grouping the real radiating elements to be activated to allow the network antenna to observe a domain around the reference direction.
[0015] - the support surface is a cone, an ogive, or a surface generated by rotation of a curve around an axis.
[0016] The invention also relates to a computer program product comprising software instructions which, when executed by a computer, implement the steps of the dimensioning phase of the manufacturing process.
[0017] The invention also relates to a network antenna resulting from the implementation of the preceding manufacturing method.
[0018] The invention and its advantages will be better understood upon reading the description detailed description which will follow of a particular embodiment, given solely as a non-limiting example, this description being made with reference to the appended drawings in which:
[0019] [Fig.l] [Fig.l] is a schematic representation of an embodiment of the production method according to the invention;
[0020] [Fig.2] [Fig.2] is a schematic representation in an axial plane of a first embodiment of an array antenna resulting from the implementation of the method of [Fig.l] for a conical support surface;
[0021] [Fig.3] [Fig.3] is a schematic representation in a transverse plane of the antenna of [Fig.2]; and,
[0022] [Fig.4] [Fig.4] is a schematic representation in a transverse plane of a second embodiment of an array antenna resulting from the implementation of the method of [Fig.l] for a conical support surface. General presentation of the method
[0023] From a general point of view, the method according to the invention relates to the placement of radiating elements on a support surface of any curvature in order to produce a functional electronically scanned array antenna.
[0024] A preferred embodiment of the method will be presented in relation to the block diagram of [Fig.l] and for the case of the production of an array antenna carried by a conical support surface S, this antenna being illustrated in Figures 2 and 3.
[0025] The support surface S is a cone with axis A, vertex S0, and half-angle at the vertex o.
[0026] The production method 100 comprises a first dimensioning phase 105, followed by a manufacturing phase 205.
[0027] The first step 110 of the dimensioning phase 105 consists of delimiting one or more elementary support surfaces Sk on the support surface S of the carrier. A two-dimensional surface immersed in a three-dimensional space is locally characterized by two curvatures, respectively evaluated along two directions tangent to the surface and orthogonal to each other. The elementary support surface carries the radiating elements activated simultaneously for the observation of a domain located on one side of the axis A. In the embodiment of FIGS. 2 and 3, the support surface S is subdivided into four elementary support surfaces, S1, S2, S3 and S4 by axial planes P1 and P2 at right angles to each other. Alternatively, the support surface could be subdivided into a different number of elementary support surfaces, possibly so that two neighboring elementary surfaces partially overlap.
[0028] In the following, we are more particularly interested in the first elementary support surface SL
[0029] Then, in a step 120, a reference direction VI is defined for the elementary support surface SI. The reference direction VI makes an angle α with the axis A. The reference direction corresponds to the axis of the antenna beam “at rest”, that is to say without introducing an electronic phase shift between the signals emitted or received by the active radiating elements of the antenna to depoint the beam in a depointing direction D (making an angle with respect to the reference direction VI).
[0030] In a step 130, a reference plane PRefl is defined as the plane normal to the reference direction VL.
[0031] In a step 140, an equivalent array antenna is defined in the reference plane PRefl. This virtual antenna is a planar antenna. It is composed of a plurality of equivalent radiating elements EEij. The equivalent radiating elements are arranged in the reference plane PRefl according to a regular pattern.
[0032] For example and preferably, this regular pattern is a rectangular matrix composed of rows and columns of equivalent radiating elements.
[0033] The equivalent radiating elements EEij are indexed by the integers i and j, respectively between 1 and Ni and 1 and Nj, Ni being the maximum number of equivalent radiating elements along a first direction of the reference plane and Nj being the maximum number of radiating elements along the other direction of the reference plane.
[0034] The equivalent radiating elements are identical to each other. Each equivalent radiating element preferably has a square shape, with side a. Alternatively, the radiating element may have another shape, for example that of a disc.
[0035] The edge of an equivalent radiating element is separated from the opposite edge of the neighboring equivalent radiating element by an interval e. Thus, the pitch between equivalent radiating elements according to the rows or columns of the regular pattern is equal to the sum of a and e.
[0036] The method 100 continues by carrying out the following steps to match each equivalent radiating element EEij with a real radiating element ERij constituting the network antenna to be manufactured.
[0037] In step 150, the center, CEij, of the current equivalent radiating element is projected, along the reference direction VI, onto the support surface, in order to determine the location, on this support surface, of the implantation point CRij of the corresponding real radiating element ERij.
[0038] Step 160 consists of defining an inclined plane Pij passing through the implantation point CRij of the real radiating element ERij. A priori, the inclination of the inclined plane Pij is quantified by two angles, for example evaluated from the main directions of the elementary support surface SI in the vicinity of the implantation point CRij of the real radiating element ERij.
[0039] Step 170 consists of projecting, along the reference direction VI, the outer contour of the current equivalent radiating element EEij onto the inclined plane Pij to obtain the outer contour of the corresponding real radiating element ERij.
[0040] Finally, step 180 consists of evaluating a path difference dij between the implantation point CRij of the real radiating element ERij and the center CEij of the equivalent radiating element EEij of the reference plane PRefl.
[0041] The introduction of a “geometric” phase shift <pij, proportionnel à la différence de marche dij, aux signaux émis ou reçu par l’élément rayonnant réel ERij, a pour effet que le comportement de l’antenne réseau, évalué dans le plan de référence PRefl, correspond à celui de l’antenne réseau équivalente plane.
[0042] Optionally, an adjustment of the gain Gij of the real radiating element ERij is calculated so that the power that it radiates, evaluated in the reference plane, corresponds to the power that the equivalent radiating element EEij would radiate. This gain makes it possible to take into account the difference in surface area between the real element and the equivalent element, but also the distortion of the radiation pattern in the event of a strong inclination of the inclined plane Pij of implantation of the real element ERij relative to the reference plane.
[0043] Steps 150 to 180 are iterated for each equivalent radiating element EEij.
[0044] Finally, in step 210 of phase 205, the actual network antenna is produced in accordance with the dimensioning obtained at the end of phase 105. Remarks and variant embodiments
[0045] When the support surface considered has strong curvatures, as is the case for the fuselage of an aircraft, it must first be subdivided to define a plurality of elementary support surfaces. The method then applies to each elementary support surface successively. For example, as shown in Figures 2 and 3, when the support surface is a cone and the reference direction makes an angle of inclination with the axis of the cone, the maximum elementary support surface that can be considered is a half-cone resulting from the section of the cone by an axial plane, which includes the axis A and the vector product of the directions A and V.
[0046] The inclination of each inclined plane Pij can be chosen so that all the inclined planes are parallel to each other. For example, according to a first approach, each inclined plane is defined so as to be parallel to the reference plane as illustrated in Figures 2 and 3. This then involves compensating for the curvatures of the support surface by mounting each real radiating element so that it is arranged parallel to the reference plane. In operation, a geometric phase shift is then introduced for each radiating element, which depends on the distance between the real radiating element considered and the reference plane. In this way, the signals evaluated in the reference plane are in phase for all real radiating elements arranged on the support surface. From there, an electronic phase shift can be added to depoint the array antenna beam away from the reference direction, so that it points in the depointing direction D.
[0047] But, more generally, the inclination of an inclined plane is independent of that of the other inclined planes and depends only on the position of implantation on the support surface considered. For example, according to a second approach, each inclined plane is tangent to the support surface. The dimensions of each real radiating element and the gaps between two neighboring real radiating elements are adapted during the step 170 of projection of the contours of the equivalent radiating elements of the equivalent array antenna. In operation, a geometric phase shift is introduced which depends on the distance between the point of implantation of the real radiating element and the center of the equivalent radiating element, so that the signals evaluated in the reference plane are in phase for all the real radiating elements.
[0048] Advantageously, the gain Gij of the real radiating element ERij is adjusted so that the intensity of the radiation that it produces, evaluated in the reference plane, is equal to the intensity of the radiation of the equivalent radiating element EEij.
[0049] Advantageously, it is necessary to ensure that all the real radiating elements emit with an identical polarization relative to a trihedron associated with the reference plane. For this, it is necessary to adjust the polarizations of each real radiating element according to their position and their orientation on the support surface.
[0050] Theoretically, a radiating element can be mounted on the support surface so as to be inclined by 90° relative to the reference plane. However, the radiation pattern would then be impacted by the tilt angle of the actual radiating element, especially since the beam misalignment angle must be added to this tilt angle. Indeed, the radiated surface area decreases, resulting in a loss of gain and a larger beam opening. The central frequency for which the antenna is calculated shifts upwards since the projections of the actual radiating elements and their spacings are smaller. This has the effect, in particular, of increasing the levels of the secondary and diffuse lobes. There is therefore a limit on the tilt angle to keep radiation patterns within acceptable operating limits. For example, the tilt angle must not lead to an angle relative to the reference plane greater than + / -60°..
[0051] Example of application for a conical support surface
[0052] The method of [Fig.l] will now be illustrated by an implementation on a conical surface with reference to Figures 2 and 3.
[0053] The method 100 begins with a phase 105 of dimensioning the antenna to be manufactured.
[0054] Step 110: the support surface S is here the surface of a conical radome. Such a radome is conventionally fitted to the nose of a fighter aircraft. A cone is a simple shape for which it is easier to explain the invention in detail, possibly by carrying out explicit calculations. A cone is characterized by zero curvature along a generatrix of the cone and constant curvature in a plane transverse to the X axis.
[0055] On this surface, several elementary support surfaces are delimited. For example, four elementary support surfaces are delimited, each elementary support surface extending between axial planes P1 and P2. For reasons of symmetry in this embodiment, the planes P1 and P2 are at right angles.
[0056] In the following, we consider the first elementary support surface SI.
[0057] Step 120: we define the reference direction VI for the support surface SI. The reference direction must allow, by electronic phase shift, observation within an extended domain covering not only the front of the cone (i.e. in the direction of the axis A of the cone), but also on the side of the cone.
[0058] Knowing that the electronically controlled depointing of a beam is limited due to the degradations impacting the radiation pattern, this “electronic” depointing is arbitrarily limited to a maximum value ^max, for example approximately + / -60°.
[0059] Thus, in the plane of figure 2, if we still want to be able to observe along the axis A of the cone, the reference direction VI must make an angle of inclination a less than or equal to (Pmax with the axis A of the cone, a is for example chosen equal to 60°.
[0060] In the axial plane containing the reference direction VI, the electronic depointing then allows observation in a range between 0 and 120° relative to the axis A of the cone.
[0061] In the plane of [Fig.3], the reference direction V1 is taken according to the bisector of the angle between the planes PI and P2 (|3=45°).
[0062] The angle [3 being less than ^max and considering the four reference directions VI, V2, V3 and V4 around the axis A, the antenna according to the invention allows observation in a range extended between 0° and +120 over 360° around the axis A. This is to be compared to an antenna according to the state of the art (plate arranged perpendicular to the axis A) which allows observation in a range between 0° and +60° over 360° around the axis A.
[0063] Step 130: we define a reference plane PRefl as the plane normal to the reference direction VL
[0064] Step 140: the equivalent array antenna is composed of a plurality of equivalent radiating elements EEij. The equivalent array antenna is advantageously oriented in the reference plane so that the columns indexed by the index i of the pattern formed by the equivalent radiating elements are arranged parallel to the plane defined by direction A and direction V ([Fig.2]) and that the lines, indexed by the index j, are arranged in a plane transverse to direction A ([Fig.3]).
[0065] The method continues by carrying out steps 150 to 180 for each equivalent radiating element EEij.
[0066] Step 150: the center CEij of the equivalent radiating element EEij is projected onto the support surface along the reference direction VI in order to determine the location of the implantation point CRij of the real radiating element ERij.
[0067] Step 160: in the present embodiment, we choose to place each real radiating element ERij in an inclined plane Pij which is parallel to the reference plane whatever i and j.
[0068] Step 170: the external shape of the equivalent radiating element EEij is projected along the reference direction VI onto the inclined plane Pij to obtain the external shape of the corresponding real radiating element ERij. Since the projection is orthogonal here, there is no deformation of the contour of the radiating element.
[0069] Step 180: This step makes it possible to define the electrical path difference between each radiating element and the reference plane.
[0070] The path difference (or "geometric" phase shift 00) for the real radiating element ERij is a function of the distance dij between the implantation point CRij of the real radiating element ERij and the center CEij of the equivalent radiating element EEij is evaluated.
[0071] The geometric phase shift to be introduced is then given by:
[0072] =
[0073] with X the wavelength of the electromagnetic signal emitted or received.
[0074] The preceding steps are repeated for another support surface delimited on the cone, for example the other half-cone.
[0075] In this embodiment, the actual radiating elements being positioned in inclined planes parallel to the reference plane, there is no radiation power compensation to be calculated.
[0076] The method 100 continues with a phase 205 of manufacturing the antenna as such according to the dimensioning determined at the end of the implementation of the steps of phase 105. Each real radiating element ERij is consequently produced, by implanting it at the point CRij of the elementary support surface, and by suitably tilting it relative to this support surface to obtain the antenna 100.
[0077] Second embodiment
[0078] [Fig.4] illustrates a second embodiment of an antenna 200 obtained by implementing the method according to the invention.
[0079] In an axial plane, this second embodiment is identical to the first embodiment shown in [Fig.2], the real radiating elements ERij being arranged along inclined planes Pij parallel to each other and to the reference plane.
[0080] But, in a transverse plane, the real radiating elements ERij are now arranged according to inclined planes Pij tangent to the support surface S, i.e. to the circle of radius R resulting from the intersection of the support surface with the transverse plane considered.
[0081] This second embodiment has the advantage of rotational symmetry around the axis A, so that the reference direction V can be chosen, at a given instant of operation of the network antenna, in any direction around the axis A. Once the reference direction V has been chosen, the radiating elements to be activated are those located between the axial planes PI and P2.
[0082] The implementation of the method according to the invention however leads to a strong geometric deformation between equivalent radiating elements on the reference plane and real radiating elements on the support surface.
[0083] This deformation cannot be compensated by an adjustment of the radiated power (or by an adjustment of the shape of the equivalent radiating elements and / or the pattern that they form), especially since the radiating elements located near the planes PI and P2, which are strongly inclined with respect to the reference plane, risk degrading the radiation pattern in the reference direction V. Under these conditions, the planes PI and P2 are chosen so that they make an angle [3 with respect to the reference direction V less than or equal to ^max- Thus, only the radiating elements located on the support surface between the planes PI and P2 are activated for transmission (respectively reception) according to the associated reference direction V. Benefits
[0084] Alternatively, instead of considering radiating elements of the radiating plane type, other technologies are conceivable such as a Vivaldi antenna, a dipole antenna, etc.
[0085] The method according to the invention applies to any support surface, regardless of its curvature. For a complex surface, computer tools can be used to define an optimal reference direction, simulate the geometry of the antenna, and calculate the geometric phase shifts to be introduced and possibly the gain adjustments to obtain the desired behavior.
[0086] By geometry of the antenna is meant the curvatures of the support surface at each point thereof, the chosen reference direction, and, for each radiating element, its point of implantation, the inclination of the radiating element relative to the support surface and the shape of its contour.
[0087] In particular, the method can be iterated by modifying the values of the parameters (extension of the support surface, reference direction, pattern of the equivalent network antenna, or even inclination of the real radiating elements) to optimize the network antenna produced.
[0088] Preferably, the support surface is a cone, an ogive, or more generally any surface generated by the rotation of a curve around an axis.
Claims
Claims
1. Method for producing (100) an electronically scanned array antenna comprising a plurality of real radiating elements (ERij), each real radiating element being mounted on a support surface (S), characterized in that, the support surface having a non-zero curvature and a real radiating element being positioned at an implantation point (CRij) of the support surface so as to rest in an inclined plane (Pij), said inclined plane being inclined relative to a plane locally tangent to the support surface at the implantation point, the method comprises, in a dimensioning phase (105), the steps of: - definition (120) of a reference direction (VI) around which the pointing direction (D) of the network antenna can be modified by electronic phase shift; - definition (130) of a reference plane (PRefl) normal to the reference direction; - definition (140) of an equivalent array antenna in the reference plane, the equivalent array antenna being a planar antenna comprising a plurality of equivalent radiating elements (EEij) forming a regular pattern in the reference plane; - for each equivalent radiating element, - projection (150) of a center (CEij) of the equivalent radiating element, according to the reference direction, onto the support surface, so as to obtain an implantation point of a center (CRij) of a corresponding real radiating element; - definition (160) of an inclined plane (Pij) at the point of implantation on the support surface; - projection (170) of a contour of the equivalent radiating element, according to the reference direction, in the inclined plane, to obtain a contour of the corresponding real radiating element; - evaluation (180) of a distance (dij) between the point of implantation of the real radiating element and the center of the equivalent radiating element and calculation, as a function of said distance, of a geometric phase shift to be applied to the signals emitted or received by the real radiating element during operation of the network antenna, and in that the method comprises, in a manufacturing phase (205), the steps of producing the network antenna in accordance with the results of the sizing phase.
2. A method of production (100) according to claim 1, wherein the evaluation step (180) consists of determining a gain (Gij) of each real radiating element in order to adjust a radiation power, evaluated in the reference plane, that this real radiating element produces.
3. A method of production (100) according to claim 1 or claim 2, wherein the evaluation step (180) consists of determining an adjustment of a polarization of each actual radiating element as a function of its implantation position and / or its inclination on the support surface relative to the reference plane.
4. Production method (100) according to any one of claims 1 to 3, in which the inclined plane is chosen to be parallel to the reference plane.
5. Production method (100) according to any one of claims 1 to 4, in which the method begins with a step (110) of delimiting at least one elementary support surface on the support surface, the elementary support surface grouping the actual radiating elements to be activated to allow the network antenna to observe a domain around the reference direction.
6. A manufacturing method (100) according to any one of claims 1 to 5, wherein the support surface is a cone, an ogive, or a surface generated by rotation of a curve around an axis.
7. Computer program product comprising software instructions which, when executed by a computer, implement the steps of the dimensioning phase of the production method according to any one of the preceding claims.
8. Array antenna resulting from the implementation of a production method according to any one of the preceding claims.