EP3542415A1

EP3542415A1 - Device for squinting a beam by displacement of effective dielectric rolls

Info

Publication number: EP3542415A1
Application number: EP17808374.7A
Authority: EP
Inventors: Jean-François Allaeys; Romain Czarny
Original assignee: Thales SA
Current assignee: Thales SA
Priority date: 2016-11-17
Filing date: 2017-11-16
Publication date: 2019-09-25
Also published as: FR3058839A1; FR3058839B1; WO2018091587A1

Abstract

The invention is concerned with a device for squinting an electromagnetic beam (F_inc) comprising at least two superposed dielectric lenses (D₁₁, D₁₂) said device being characterized in that the dielectric lenses are of variable effective thicknesses, and in that at least one of the dielectric lenses can move in at least one direction (y) substantially orthogonal to a plane (xOz) in which the electromagnetic beam is squinted, as well as with an antenna comprising such a device. It is also concerned with a method for squinting an electromagnetic beam.

Description

DEVICE FOR BEAM DEPOINTING BY MOVING EFFECTIVE DIELECTRIC ROLLS

The invention lies in the field of directional antennas, and relates in particular to a device for misalignment of an electromagnetic beam emitted by an active or passive antenna, and the associated misalignment method.

The term "misalignment", associated with an antenna, refers to the fact of orienting in a precise direction the electromagnetic beam emitted by this antenna.

In the following, the word "elevation angle" refers to the angle between the horizontal plane and the line from an antenna to a target point above the horizon. This angle is counted positively when the target point is above the indicated horizontal plane, negatively in the opposite case. The word "azimuth angle" means the horizontal angle between a straight line from the antenna to the target point and a line from the antenna in a reference direction.

We will also talk about the "form factor" of an antenna, defined as the ratio between its length and its width. Thus, a round antenna will have a form factor of one, while an elongated antenna will have a high form factor.

Changing the pointing direction of an antenna is of interest in many areas. For example, the domain of radars, in order to scan a geographical area or to follow a moving target, but also satellite antennas, where a receiver will seek to direct the beam of its antenna towards a moving satellite, or conversely applications in which a mobile carrier will seek to position its antenna towards a fixed point, such as a geostationary satellite. The modification of the pointing direction of antennas is also of interest in a context of territory coverage, when the addition or removal of an antenna requires a repositioning of all other network equipment.

There are many techniques for orienting the beam of an antenna. Among them, the most classic is to mount the antenna on axes to direct it mechanically.

Such a device, however, has a number of disadvantages. Indeed, in order to move the beam of an antenna at both azimuth and elevation, it is necessary to use two mechanical axes. Such a device is generally in the form of a turntable for azimuth orientation, and a device mounted on the rotational turntable of the antenna about an axis to ensure the elevation orientation. In doing so, there is a so-called "singular" point at the zenith: when the antenna reaches the zenith of its trajectory and has to move in a direction perpendicular to the elevation axis, the positioner must make a fast rotation 90 ° along the azimuth axis. This rotation causes a cutoff reception, and can cause rapid wear of the device. This problem is solved by the use of a three-axis device, which has no singular point, but for which the mechanics become complex and expensive. These positioners are more bulky, especially when the antenna has a large form factor and the antenna beam must scan the plane formed by the beam in its initial position and the major axis of the antenna. They also require the use of rotating joints, expensive and subject to wear, and have a significant inertia that requires the use of powerful motors and limits the speed of movement of the assembly.

There are also beam orientation techniques of an antenna called electronic misalignment, which have the advantage of being accurate and fast. The principle of electronic misalignment consists in applying a phase shift having a gradient over the entire wavefront to modify the direction of the emitted beam. These are for example so-called "active" antennas, composed of radiating elements generally spaced a distance less than or equal to λ / 2, λ being the wavelength of the signal. Each of the radiating elements is connected to a phase-shifter, the electromagnetic beam being directed by driving the phase of each of the radiating elements. However, the constraints on the size and spacing of the radiating elements, their number, and the need to connect each of these elements to a controllable phase-shifter make such devices very quickly complex and therefore expensive. In addition, phase shifters may have difficulty withstanding high transmission powers.

The orientation of the electromagnetic beam can also be done by misalignment, changing the direction of the beam after its emission. A device for electronic misalignment of a beam is described in US Pat. No. 4,480,254 to Spencer et al. This device consists of passing the emitted electromagnetic beam through pairs of lenses whose permittivity, and therefore the phase delay, is controllable. The electrical harness can then be pointed in the desired direction. Such a device is also expensive and complex to implement, the lenses being composed of precious metals, and each of the lenses to be powered independently. US Patent 5,557,286 A overcomes precious metals by the use of ferrites. However, the device is also complex to implement and can be limited in its operating range in frequency and / or temperature by the use of magnetically driven dielectrics.

Devices for detaching an electromagnetic beam by mechanical translation of a lens are also known. Such a device is described in the IEEE article: E. Lima et al, "Circular Polarization Wide-Angle Beam Steering at Ka-Band by In-Plane Translation of a Lens Lens Antenna", IEEE Transactions on antennas and propagation, Vol. 63, December 12, 2015. Its defect is that it applies to a cylindrical or spherical wavefront (curvature of the non-zero wavefront along at least one axis), but not to a plane wavefront. In addition, it is necessary to ensure a significant distance between the source and the lens, which impacts congestion of the antennal system. Finally, a displacement of the lens causes a variation of the phase shift applied at the center of the transmitted beam, which can lead to errors when the signal is received if it is too fast, as well as a deformation of the radiation pattern which can be penalizing for with regard to the templates and emission standards to be respected.

Finally, depointing devices are known, such as those described in patent applications US 2010/0039338 A1, WO 2014/128015 A1 or US 2007/0285327 A1, for which two dielectric lenses of variable thickness arranged in the form of disks are positioned above the transmitting antenna, their centers aligned with the center of the beam. The misalignment is done by mechanical rotation of the lenses along the axis of propagation of the incident beam. The rotation of one of the disks relative to the other makes it possible to control the elevation of the beam while the rotation of the two disks makes it possible to control the azimuth. The fact that the disks pivot about an axis centered on the beam makes it possible to keep the phase shift applied at the center of the beam unchanged. This device however has a congestion problem since the emitted wavefront is not rounded. The diameter of the discs being related to the size of the major axis of the antenna, the discs are then oversized, especially when the form factor of the antenna becomes large.

This congestion problem makes the device incompatible with certain uses subject to size constraints, as is the case, for example, for satellite antennas on aircraft. Indeed, the antennal device is then subject to significant dimensioning constraints, particularly with regard to the height of the radome, to minimize its impact on the general aerodynamics of the aircraft. As a result, the satellite antennas used may not be parabolic antennas, but several patch antennas arranged in line and forming a very elongated antenna, to maximize the antennal surface. The use of two dielectric lenses of round shape is not suitable for this type of antenna because too bulky.

As a result, the pointing devices of such satellite antennas generally consist of an associated mechanical misalignment mechanism. to an electronic misalignment mechanism, such as for example a turntable providing an azimuth scan coupled to an electronic misalignment axis allowing an elevation scan. This device makes it possible not to implement a mechanical axis of rotation along the minor axis of the antenna, such a rotation requiring a large volume, and to ensure a displacement of the beam almost instantaneous, but has a singular point at the zenith . Another commonly used device implements two mechanical misalignment axes (in elevation and azimuth) associated with an electronic misalignment axis perpendicular to the elevation axis, making it possible to avoid the presence of a singular point at the zenith. However, such devices combining mechanical and electronic are very expensive.

The object of the invention is therefore to propose a mechanical device allowing the misalignment of an electromagnetic beam along one or two axes which is both inexpensive, compatible with any type of transmitting antenna, and which presents a small footprint. The invention is all the more advantageous in that it makes it possible to detach the beam from the antenna by scanning a plane defined by the initial position of the beam and the major axis of the antenna, by increasing the size of the device. total of an amount that does not depend on this dimension, which is of particular interest since the antenna has a high form factor.

For this purpose, the invention describes a device for detaching an electromagnetic beam comprising at least two superposed dielectric lenses. In the misalignment device according to the invention, the dielectric lenses have variable effective thicknesses, and at least one of the dielectric lenses is movable in at least one direction substantially orthogonal to a plane in which the electromagnetic beam is misaligned.

Each of the dielectric lenses comprises a reference point, the effective thickness of the dielectric lenses varying according to the product between the distance from this reference point in a first direction and distance from this reference point in a second direction perpendicular to the first direction.

The dielectric lenses may be described as having four dials defined from a reference point, the dials opposite from the reference point forming a pair of dials, the effective thickness of each of the dielectric lenses increasing as a function of the distance relative to said intersection point in one of the pairs of dials and decreasing as a function of the distance from said intersection point in the other pair of dials.

Advantageously, the increases and reductions in the effective thickness of the dielectric lenses are done periodically, the period being related to a wavelength of the electromagnetic beam.

According to one embodiment of a misalignment device according to the invention, the variation of the effective thickness of the dielectric lenses comprises a variation of the local thickness.

According to another embodiment of a depointing device according to the invention, the variation of the effective thickness of the dielectric lenses comprises a variation of a refractive index.

According to one embodiment, the dielectric lenses of the depointing device according to the invention each have a reference point. The device then has a position in which the reference points of the dielectric lenses are superimposed on the center of an antenna element emitting said electromagnetic beam, and in which the sum of the effective thicknesses of the dielectric lenses is constant over the entire surface crossed. by said electromagnetic beam.

According to one embodiment, the dielectric lenses of the depointing device according to the invention each have a reference point. The device then has a position in which the reference points of the two dielectric lenses are superimposed on the center of an antenna element emitting said electromagnetic beam, and in which the effective thickness of the two dielectric lenses varies inversely from one another.

According to one embodiment, the depointing device according to the invention comprises two dielectric lenses, the two dielectric lenses being movable and moving in opposite directions.

According to one embodiment, the dielectric lenses are flat. According to another embodiment, they are all or part of rollers.

According to one embodiment of the depointing device according to the invention, the mobility along one axis of the dielectric lens or lenses is ensured by a translation of the dielectric lens or lenses. According to another embodiment, the mobility along one axis of the one or more dielectric lenses is ensured by a rotation of the dielectric lens or lenses around an axis collinear with an axis of the antenna.

Advantageously, the depointing device according to one embodiment of the invention further comprises a first corrective lens configured to modify the shape of a wavefront, said first lens being positioned on one side of the dielectric lenses, and a second corrective lens configured to change the shape of a wavefront opposite the first lens, and positioned on the other side of the dielectric lenses.

According to one embodiment of the invention, the misalignment device further comprises a mechanical pointing axis of the electromagnetic beam.

The invention also describes an antenna comprising at least one misalignment device as presented above. Finally, the invention relates to a method of misalignment of an electromagnetic beam emitted by an antenna element. The method comprises at least a first superposition step of the antennal element by at least two dielectric lenses of variable effective thickness, and a second step of moving at least one of the dielectric lenses in at least one direction substantially orthogonal to a plane in which the electromagnetic beam is misaligned.

The invention will be better understood and other features and advantages will appear better on reading the description which follows, given by way of non-limiting example, and thanks to the appended figures in which:

FIGS. 1a and 1b respectively represent a misalignment device according to one embodiment of the invention, in which the configuration of the dielectric lenses does not cause misalignment of the electromagnetic beam, and a flat view of the component dielectric lenses. these measures ;

FIG. 2 is a three-dimensional representation of a dielectric lens used to implement the invention according to the embodiment described in FIGS. 1a and 1b;

FIGS. 3a and 3b respectively represent a misalignment device according to the embodiment described in FIGS. 1a and 1b, in which the configuration of the dielectric lenses causes the misalignment of the electromagnetic beam, and a flat view of the dielectric lenses composing this device;

FIG. 4 represents a flat view of the dielectric lenses of a misalignment device according to another embodiment of the invention, in which only one of the dielectric lenses is mobile;

FIG. 5 shows a depointing device according to another embodiment of the invention, in which the dielectric lenses are implemented in the form of rollers;

FIGS. 6a and 6b show a sectional view of a misalignment device according to another embodiment of the invention wherein the dielectric lenses are implemented in the form of truncated rolls;

FIGS. 7a and 7b illustrate a depointing device according to another embodiment of the invention, in which there are lenses whose object is to modify the shape of the wavefront;

FIGS. 8a and 8b show two embodiments of an antenna comprising a depointing device according to one embodiment of the invention;

FIG. 9 is a state diagram of a method of misalignment of an electromagnetic beam according to one embodiment of the invention.

In the figures which are presented below, the antenna, also referred to as the antenna element, is represented as an antenna having a rectangular shape factor. This is positioned in an orthonormal coordinate system (xOy), the long side of the antenna along the x axis, the center O of the marker being positioned at the center of the antennal element.

The antenna is represented in a rectangular form, because this form factor poses particular problems of space when associated with a misalignment device according to the state of the art. The invention is however not limited to rectangular antennas, and applies identically, regardless of the antenna aspect ratio, which includes the case of round, spherical and conical antennas, as well as the case antennal element composed of a plurality of radiating elements.

FIG. 1a shows an electromagnetic beam misalignment device according to one embodiment of the invention, in which the configuration of the device does not cause misalignment of the beam. The antenna element Ai emits along the z axis a beam F _inc which passes through the misalignment device. The resulting beam F _e is oriented identically to the initial beam F _inc . The device also comprises two superimposed dielectric lenses Du and D ₂ , whose effective thickness varies proportionally to the product of their coordinates with respect to their respective centers Cn and C- | ₂ along the x-axis and along the y-axis. These dielectric lenses are prisms whose faces are not necessarily flat, can be obtained by diffractive structures, by structuring the dielectric at a scale less than the wavelength of the electromagnetic beam. The gray level of the dielectric lenses shown is a function of their effective thickness, the thickness increasing when the level darkens and vice versa.

The phase shift applied to an electromagnetic wave passing through a lens is a function of the local thickness of the lens traversed, and of its refractive index: it is equal to ^ e, with λ the wavelength of the signal (in

AT

meters), e the local dielectric thickness traversed (in meters) and n the refractive index of the dielectric (in the absence of a lens, in the vacuum n = 1, in the air n ~ 1). Replacing the air with a dielectric of index n for the same thickness e crossing induces a phase retardation ^ (n - 1) e. We

AT

means by effective thickness of a dielectric lens the thickness corresponding to a given phase shift for a given refractive index constant. The object of the variation of the effective thickness of the dielectric lenses is to delay more or less a wavefront as a function of the geographical zone of dielectric crossed, so as to create controlled phase shifts on the wavefront emitted, and thus to direct the beam.

This variation in effective thickness can be obtained by varying the local thickness of the dielectric, that is to say its height along the z axis, in a dielectric whose density, or refractive index, is constant.

Another way to vary the effective thickness is to vary its density, that is to say the refractive index of the substrate. In this way, an electromagnetic wave passing through the dielectric will be more or less delayed depending on its position, which allows to orient the entire beam. The patent application EP 2573872 A1 or the international patent application WO 01/697419 A2 have such a dielectric in which the effective thickness is modified by the variation of an effective index of refraction of the substrate, obtained by changing the density of locally used material (for example by changing the density of dielectric micropiliers per unit area, the pillars not being perceived by the wave as such because small in front of the length of wave, but the average local density of material influencing the phase). Such a dielectric may advantageously be used to implement the misalignment device according to the invention, its local thickness, that is to say its height along the z axis, then can be constant over the entire lens.

It can also be envisaged to combine variation of the refractive index and variation of the local thickness.

In Figure 1a, the centers of the dielectric lenses are located at their intersection with a straight line orthogonal to the plane of the antenna element Ai and which passes through its center O. In the figure, this line corresponds to the axis z. The dielectric lenses are larger than the dimensions of the antennal element in at least one dimension perpendicular to the desired direction of misalignment. The portions of the dielectric lenses facing the antennal element, which are traversed by the electromagnetic beam, are indicated in the figure under the references Ru and R- | ₂ .

The effective thickness of the dielectric lenses follows a very precise law: it varies according to the product of the distance with respect to the centers C-n and C-I2 in one direction and the perpendicular direction, or as a function of the product of x by y. In this way, the phase φ of an electromagnetic wave crossing the dielectric at normal incidence varies according to its coordinates (x, y). The effective thickness is to be considered modulo 2π of the phase shift resulting from the crossing of the dielectric. Thus, the dielectric may have an effective thickness which does not increase (or reduce) linearly over its entire surface, but according to a pattern reproduced periodically.

For one of the dielectric lenses, when x and y are of the same sign, the effective dielectric thickness increases with the distance from the center. When x and y are of different signs, this effective thickness decreases. The effective thickness of the second dielectric lens varies in a manner complementary to that of the first, that is, when x and y are of the same sign, it decreases with distance from the center, and increases with x and y with different signs.

Another way to represent the structure of each of the dielectric lenses is to divide them into four dials. These four dials are for example defined by the x and y axes. They are grouped in pairs of opposite dials, that is to say dials having as common point only the point of intersection of the dials. For one of the dielectric lenses, the effective thickness increases as a function of the product of the distances along the x and y axes in one of the two pairs of dials, and decreases according to the same product in the other. When the centers of the lenses are superimposed on the center of the antenna, the effective thickness of the second dielectric lens varies inversely with that of the first lens: the pair of dials in which the effective thickness increases is opposite of that of the first lens in which the effective thickness decreases, and vice versa.

By the structure of each of the dielectric lenses, the electromagnetic beam emitted by the antenna element A-i is deflected a first time by the first dielectric lens, then a second time by the second dielectric lens. Since the two dielectric lenses are the mirror of each other, this deviation is done first in one direction then in the opposite direction, the two deflections then canceling out. This property is due to the fact that the total effective thickness traversed by an incident wave, sum of the effective thicknesses of the two dielectric lenses, is constant over the whole of the surface traversed by the beam. Thus, the phase shift applied to the electromagnetic beam is identical at all points, and the incident beam pointing direction emitted by the antenna element is not changed.

FIG. 1b is a plan view of the dielectric lenses composing a misalignment device according to the embodiment of the invention shown in FIG. 1a. The first dielectric Du can be decomposed into four dials delimited by the x and y axes: Qn, Q1 ₂ , Q1 ₃ and Q14. In the pair of opposing dials Qn and Q- | ₃ , the effective thickness of the dielectric increases with the product of the distances from the center Ci i, while in the pair of opposite dials Q- | ₂ and Qi ₄ , it decreases in the same way. In the second dielectric D ₂ , the effective thickness increases with the product distances in the opposite dials Q ₂₂ and Q ₂₄ , which are opposite Q-dials | ₂ and Qi ₄ in which the effective thickness decreases. Likewise, the effective thickness decreases in the dials Q21 and C½3, opposite the dials Qn and Q13 in which it increases.

E1 represents the total effective thickness of dielectric traversed by an incident beam emitted when the two dielectric lenses Du and D ₂ have their centers Cn and C- | ₂ superimposed on the center of the antennal element, which represents the so-called "initial" position of the device. The structures of the two dielectric lenses being complementary, when they are in their initial position, the effective thickness traversed is constant both on the x-axis of the abscissa and on the y-axis of the ordinates. An incident beam F _inc crossing the two dielectrics will not be depointed.

Specifically, the thickness of the dielectric varies in mirror images of each other, the total E _total effective thickness traversed by a wave at normal incidence to the point (x, y) can be expressed as:

otaie e _t (x, y) = ^e Dii (x, y) e + _D12 {x, y)

= A + Ae _D11 (x, y) + A - Ae _D12 (x, y)

= 2A + a * x * y- a * x * y = 2A

at any point (x, y), with A the dielectric thickness at the reference points C-11 and C-1 ₂ , e the effective dielectric thickness, Ae the variation of this effective thickness with respect to A, and has the coefficient of variation of the effective thickness of the dielectrics, ie the coefficient of proportionality between the product of the distances at the centers according to x and according to y and the thickness of the dielectric, a * x * y being to be considered at modulo 2π near the introduced phase shift. It can be seen that the effective thicknesses of dielectrics compensate in every respect, the effective thickness being 2A and not varying as a function of the (x, y) coordinates of the position traversed by the electromagnetic wave. There is therefore no beam deflection introduced by the device. It should be noted that the effective thickness A of dielectric was considered equal in the two lenses, but that the result is identical by taking different dielectric thicknesses. The only The stress is based on the coefficient a, which must be identical in both dielectrics.

FIG. 2a is a three-dimensional representation of a dielectric lens D used to implement the invention according to the embodiment described above. Its local thickness varies according to two dimensions according to the product of the coordinates with respect to its center, measured according to each dimension.

FIG. 2b is also a three-dimensional representation of a dielectric lens D used to implement the invention according to the embodiment described above. Its local thickness varies periodically, so that the phase shift brought to an electromagnetic wave passing through it is that referred to, modulo 2π. The repetition period of the pattern is therefore a function of the coefficient a and the wavelength of the electromagnetic beam. The effective thickness of the dielectric lenses therefore increases (or decreases) progressively as a function of the product x ^* y, until the associated phase variation has swept the entire range [0; 2π], then abruptly returns to its initial value before re-increasing (or decreasing). In this way, the local thickness of the lens is maintained within a range, even when it is large. This periodic variation in the thickness of the lens, corresponding to a modulo 2π phase shift of the wave passing through it, is described for example in US patent application 2010/0039338 A1 for one dimension. It must be adapted to the wavelength of the electromagnetic beam, and extended to two dimensions in order to implement the invention. The periodic variation of the effective thickness of the dielectric may also correspond to a periodic variation of the refractive index of the lens.

Figure 3a illustrates the implementation of the misalignment of the electromagnetic beam in the embodiment of the invention shown in Figures 1a and 1b. In order to achieve the misalignment of the beam F _inc emitted by the antenna element A _; it is sufficient to move the dielectric lenses in opposite directions in translation along an axis perpendicular to the axis of desired misalignment. Thus, detaching the beam F _inc emitted in a given direction along the major axis x of the antenna, ie in the plane xOz, requires the displacement of the two dielectrics in translation in opposite directions along the y axis. .

The effective thickness of Ru and R- | ₂ dielectric opposite the antenna element A _; that is traversed by the incident beam F _inc , has a phase gradient along the x-axis, which results in the misalignment of the beam F _e having passed through the two dielectric lenses.

FIG. 3b is an exploded view of the two dielectric lenses Du and

D-12, on which zones Ru and R- are represented | ₂ opposite the antennal element, as well as the total effective thickness E ₃ of dielectric traversed by the emitted beam F _inc , which is the sum of the effective thicknesses of the two dielectric lenses D ₁ and D ₂ .

In this example, the thicknesses of the dielectric lenses no longer compensate. The total effective thickness then has a gradient along the x-axis, but remains constant along the y-axis. The electromagnetic wave passing through this total effective thickness will therefore be out of phase along the x axis only, that is to say in the xOz plane. In the example, the phase shift will be higher on the x negatives than on the x positives, thereby causing a misalignment of the transmitted beam towards the negative x.

To illustrate this deflection, the total E _total effective thickness traversed by a wave at normal incidence to the point (x, y) when moving each of the dielectric lenses of a position, can then be expressed as:

Total ^

= A + Ae _D11 (x, y + 1) + A - Ae _D12 (x, y - 1)

= 2A + * x * y- a * x * y

= 2A + 2ax

The variation of the effective thickness is therefore a function of the position according to x only. Being constant along y, the electromagnetic beam does not lie along the y-axis, that is, in the yOz plane. It will be noted in particular that the phase shift applied at the center of the beam, ie at the point O, does not vary from that applied when the device is in its initial position, as illustrated in Figures 1a and 1b. This property is advantageous, a variation of the phase shift applied to the center of the emitted beam generating an advance or a delay on the signal which can generate errors during the reception of the signal.

Similarly, misalignment along the y-axis can be achieved by varying the position of the dielectric lenses along the x-axis. In general, the misalignment of the electric beam is therefore along an axis perpendicular to the axis of displacement of the dielectric lenses, this displacement being ensured mechanically by translation. The misalignment velocity and its accuracy depend on the chosen coefficient, being the coefficient of proportionality between the product of the distances from the center and the thickness of the lenses. By choosing small, the misalignment angle accuracy will be important, but the size of the dielectric lenses required to achieve a given phase shift will be large and the misalignment speed will be lower, while conversely, by choosing large, the Dielectric lenses required to obtain a given phase shift are small, the speed of misalignment important, but the precision less. A compromise must therefore be made according to the requirements of accuracy, speed and bulk. So that the thickness of the dielectric lenses does not reach too large dimensions on the edges when the antenna element is of large size, the dielectric lenses can be obtained by decreasing locally the thickness of one or more lengths wave to go back to a thickness anywhere between a minimum value and a maximum value close allowing the phase shift generated by the crossing of the lens to scan the interval [0; 2π]. This variation of the effective thickness in steps makes it possible to obtain the desired phase shifts without the local thickness or the refractive index of the lenses reaching too restrictive values.

The embodiment of the invention presented above can be declined in several variants by the skilled person: • The translation of the dielectric lenses is not necessarily limited to one dimension, but can be performed in two dimensions, which causes a deflection of the incident electromagnetic beam in the two orthogonal dimensions;

• The number of dielectric lenses used may be greater than two;

The reference points, from which the effective thicknesses of the dielectric lenses vary and which make it possible to define the initial position in which the beam is not depointed, are in the examples the centers Cn and C- | ₂ dielectric lenses, but these reference points may be chosen elsewhere than at the center;

• The dielectric lenses are not necessarily square or rectangular, and may be of any shape and not necessarily identical as they come opposite the antennary element over their entire translation zone;

• Displacement can be limited to a single lens.

FIG. 4 represents a flat view of the dielectric lenses of a misalignment device according to another embodiment of the invention, in which only one of the dielectric lenses (D ₂ ) is translated, while the other ( Du) remains motionless.

The result is the same as that presented when the two dielectric lenses move, that is to say, by taking the previous notations:

total _. x,) = e _D11 (x, y) + e _D12 (x, y-1)

= A + Ae _D11 (x, y) + A - Ae _D12 (x, y - 1)

= 2A + a * x * y- a * x * (y-1)

= 2A- ax

By displacing only one of the dielectric lenses along the y-axis, the equivalent surface E ₄ traversed by the beam has a gradient along the x-axis only, which causes it to be misaligned along this axis (in the plane χθζ). Since the crossing equivalent surface does not have a gradient along the y-axis, the beam is not misaligned on this axis (in the yOz plane). The phase shift applied at the center of the beam is always the same. The difference with the misalignment obtained by the displacement of the two dielectric lenses, with constant coefficient a, comes from the fact that the misalignment speed is halved but the accuracy is twice as high. To avoid these disadvantages, it is possible to double the value of the coefficient a of variation of the thickness of the dielectric lenses. However, such a modification can have consequences on the lobes of the network of the depointed beam diagram, and on the width of the bandwidth.

This embodiment is nevertheless advantageous because it opens the door to many modes of implementation, for example:

• Stick the dielectric layer closest to the antenna element directly on it, and ensure the mobility of the furthest layer, or

• Glue the furthest dielectric layer to a radome, and ensure mobility of the nearest layer, or integrate the dielectric lens with the radome.

FIG. 5 represents another embodiment of a depointing device according to another embodiment of the invention.

In this embodiment, the dielectric lenses D ₅ and D ₅₂ are no longer flat, but are in the form of rollers positioned around the antenna element A ₅ . The rollers form two nested cylinders. The displacement of the rollers is then no longer ensured by translation of the dielectric lenses, but by rotation. The dielectric lenses are rotated about an axis normal or nearly normal to the direction of propagation of the incident beam, and it is this rotation that causes the deflection of the electromagnetic beam. The axis of rotation of the dielectric lens rollers may advantageously be chosen to be collinear with the largest dimension of the radiating surface. In order to avoid unwanted deflections near the edges of the antenna, it is preferable that the thickness of the dielectric lenses remains small compared to the diameter of the rolls.

The operation of this device is equivalent to that shown for planar dielectric lenses. When the two rolls of dielectric are in initial position, the total effective thickness traversed by a beam arriving at a normal incidence is the same at all points, the pointing direction of the beam is not changed. By rotating one or more rollers about their axis, the displacement of the dielectric lens portions facing the antennal element is comparable to a translation along the y-axis. The total effective thickness of dielectric traversed by the electromagnetic beam then varies, and has a gradient along the x-axis causing a misalignment of the beam on this axis (in the xOz plane).

Similarly, a displacement in translation of the dielectric lenses in the form of rollers D ₅ and D ₅₂ makes it possible to detach the electromagnetic beam in the yOz plane.

Compared with the use of flat dielectric lenses, the use of dielectric lenses arranged in rolls makes it possible to further reduce the size of the device. In addition, it is easier to rotate two rollers on the same axis as to move two planes in translation.

According to another embodiment, the rollers are truncated in a plane parallel to the axis of the cylinder. The device is then in the form of two roll portions superimposed on an antenna element, further reducing the size of the device. The base of the rolls defined by the rollers before truncation is not necessarily in the form of a disc: by choosing cylinders whose base is elliptical and by truncating these cylinders, the radius of curvature of the truncated rollers can be adjusted, from so that it is more or less important in the area facing the electromagnetic beam.

Figures 6a and 6b show a sectional view of such a device implemented from two truncated rolls. In FIG. 6a, the dielectric lenses D ₆ and D ₆₂ , arranged in the form of truncated rolls, are in their initial position: their thicknesses are compensated in every respect.

The incident beam F _inc emitted by the antenna element A ₆ passes through the two dielectric lenses, and the resulting beam F _e is not deflected.

In Fig. 6b, the dielectric lenses D ₆ and D ₆₂ are rotated relative to each other about their axis, collinear with x, and in opposite directions. In the part of the dielectrics facing the emitted electromagnetic beam, this rotation causes a displacement of the dielectric lenses facing the electromagnetic beam comparable to a translation along the y-axis. The resultant beam _E F through the dielectric, thus undergoes a gradient along the x-axis, and is deflected along this axis (ie in the plane xOz).

Embodiments of the invention in which the dielectric lenses are in the form of rollers or truncated rollers are particularly suitable when their radius is large relative to the antennal element, the part of the dielectrics facing this antenna element being able to then be assimilated to a plane, and the displacement of dielectrics seen as a translation in this plane.

They are also suitable, regardless of their radius, in cases where the wavefront emitted by the antenna element is cylindrical, as is the case for example for a line of patch antennas, or a line of slots for which all elements are in phase. In this case, the radius of curvature of the rollers does not impact the dielectric thicknesses traversed. This is not the case when the wavefront is plane, as for example when the antennal element is a parabolic antenna or a patch antenna array distributed in two dimensions in which all the elements are in phase, and that the radius of curvature of the dielectric rolls is not large relative to the antenna element.

FIG. 7a illustrates such a case, in which the incident wavefront F _inc emitted by the antenna A ₇ is plane, while the two dielectric lenses D ₇ and D ₇₂ are of identical local thicknesses. The incident wavefront F _inc can be decomposed into a wave superposition electromagnetic fields that will intersect the dielectric lenses at different positions. Due to the radius of curvature of the rollers, the dielectric thickness traversed varies. In the example, the thickness τι of dielectric traversed by a wave located at the top of the wavefront will be greater than the thickness τ ₂ of dielectric traversed by a wave located in the middle of the front, and which arrives on the dielectric with normal incidence. Over the entire wavefront, the dielectric thickness traversed will therefore be maximum at the ends, and minimum in the middle. The total effective thickness then has an undesired gradient which will cause an unwanted and uncontrolled local misalignment of the beam F _e having passed through the two dielectric lenses, and potentially generate a loss of gain, a degradation of the shape of the radiation, and a pointing error.

To combat this phenomenon, an embodiment of the invention, represented in FIG. 7b, consists in adding a divergent corrective lens L-7-ι between the antenna element and the first dielectric lens D ₇ . This corrective lens is intended to transform the plane incident wavefront into a cylindrical wavefront, and thus to compensate for the radius of curvature of the dielectric lenses D ₇ and D ₇₂ . In this way, the dielectric thickness crossed is identical in every respect. The invention also proposes to add a convergent corrective lens L ₇₂ after the second dielectric lens D ₇₂ , so as to transform the cylindrical wavefront into a wavefront F _e plane.

In this way, it is possible to apply the invention to an antenna element emitting a plane wavefront while limiting the radius of curvature of the dielectric rollers.

The inverse mechanism for adding corrective lenses may also be considered in the opposite case, in the case where the antennal element emits a cylindrical wavefront, and where the dielectric lenses are translational planes.

The device for detaching an electromagnetic beam according to the invention can be used together with any type of antenna, whether it is active or passive, whether it emits a plane, cylindrical or spherical wavefront.

It is based on the use of at least two superimposed dielectric lenses whose effective thickness varies in two dimensions, and having a mirror structure of one another. The use of two or more lenses makes it possible to control the misalignment of the antenna, so that it is done according to one or more specific axes. By using a single dielectric lens, the misalignment could not have been contained on one axis, and the device could hardly have been associated with another mechanical means of misalignment.

In the device according to the invention, the displacement of the dielectric lenses is perpendicular or quasi-perpendicular when the lenses are arranged in the form of rollers, the plane swept by the beam, and not in this plane. This allows the device to provide a device for mechanical misalignment of the beam whose inertia is low and which retains a finite size. In the case of an elongated antenna, an additional elongation of the device requires the elongation of the rollers or dielectric planes of the same amount in the same direction. The other size dimensions of the device do not vary, which is not the case when using known techniques of the state of the art in which the dielectric lenses are in the form of disks. In addition, the device makes it possible to maintain a phase shift applied at the center of the constant beam during the displacement of the lenses.

The invention also relates to an antenna comprising a depointing device as described above. Figures 8a, 8b and 8c describe three embodiments of such an antenna, but other embodiments may be easily developed by those skilled in the art.

In the embodiment described in FIG. 8a, the antenna element A ₈ is rotated about the x-axis by mechanical means M. This rotation makes it possible to detach the beam in the yOz plane. The antenna further comprises two rolls D ₈ and D ₈₂ of dielectric lenses rotating about the x 'axis, collinear with the x axis. These rollers have structures such as those described above, their effective thickness varying in mirror from each other both in length (along the x-axis) and in width (along their circumference). The displacement of one or both lenses makes it possible to adjust the total effective thickness traversed by the beam emitted by the antenna A ₈ , and thus to adjust the misalignment of the beam in the xOz plane.

The antenna as described therefore has a small footprint. Indeed, the use of a mechanical axis to detach the beam along the x-axis would have a significant size that do not present the two nested dielectric rollers according to the invention. The antenna associates a mechanical axis with a misalignment device as described by the invention to provide a possibility of misalignment in two dimensions to the antenna. The device can not scan the yOz axis beyond an angle related to the coefficient a of the dielectric lenses, but does not have singular points in the scanned surface. Note that, for reasons of cost, the misalignment of the beam in the yOz plane is here achieved by a mechanical misalignment of the beam, but it could be obtained in an equivalent manner by an electronic misalignment.

In another embodiment, described in FIG. 8b, the two superposed dielectric lenses D ₈₃ and D ₈₄ are positioned above the antenna element A ₈ and are in the form of roll portions. The assembly is positioned on a turntable P, the rotation of the plate being provided mechanically.

The rotation of one or both dielectric lenses according to the invention allows detaching the elevation of the emitted electromagnetic beam, while the rotation of the plate P to control the azimuth.

The antennal devices described above are provided by way of illustration, the person skilled in the art can easily define new antennal devices from the teachings given above. Embodiments do not limit the scope of the invention, which is defined by the claims. In another embodiment, described in FIG. 8c, the antenna element A ₈ and the two superimposed dielectric lenses D ₈₅ and D ₈₆ are arranged in rotation around a mat M along the z axis.

This embodiment requires the use of only one rotary joint. In the rest position, the antenna points its electromagnetic beam in the horizontal plane. The synchronous rotation of the antennal element and the dielectric rollers makes it possible to vary the pointing azimuth 801 of the antenna, while the rotation of one of the rollers, or both rollers in directions opposite, allows to vary the elevation 802 pointing antenna.

Such a device can advantageously be implemented on a mat or on a vehicle.

The misalignment device according to the invention thus integrates particularly well in a pointing device also comprising one or more mechanical positioners. The misalignment according to the invention does not necessarily require the use of materials sensitive to wear, such as for example the rotary joints necessary to ensure a mechanical rotation about an axis. The fact that the translation of the dielectric planes or the rotation of the dielectric rollers is in a direction perpendicular to the incident beam limits their bulk. The choice of the coefficient a of variation of the effective thickness of the dielectrics makes it possible to regulate the switching speed of the antenna, as well as the size of the device and its precision.

The invention further relates to a method of misalignment of an electromagnetic beam, a state diagram of which is shown in FIG. 9. Said method comprises:

A step 901 of superposition of an antenna element by at least two dielectric lenses, the lenses having an effective thickness varying as described above. The superposition is done in such a way that the beam emitted by the antennal element is directed along the z axis, and the lenses arranged in the xOy plane.

a step 902 of moving at least one of the lenses in at least one direction substantially perpendicular to the desired misalignment axis of the electromagnetic beam. A misalignment of the beam in the xOz plane is thus obtained by a translation of the dielectric lenses along the y axis. When the lenses are arranged in the form of rolls or portions of rollers, this translation along the y-axis is implemented by rotating the dielectric lenses about an axis collinear with the x-axis.

Claims

1. An electromagnetic beam misalignment device (F _inc ) comprising at least two dielectric lenses (Du, D ₂ ) superimposed, said device being characterized in that the dielectric lenses are of variable effective thicknesses, and in that at least one of the dielectric lenses is movable in at least one direction (y) substantially orthogonal to a plane (xOz) in which the electromagnetic beam is misaligned.

A misalignment device according to claim 1, wherein each of the dielectric lenses comprises a reference point (Cn, C- ₂ ), the effective thickness of the dielectric lenses varying according to the product between the distance from this point. reference in a first direction (x) and the distance from said reference point in a second direction (y) perpendicular to the first direction.

3. Device of misalignment according to one of the preceding claims, wherein each of the dielectric lenses comprises four dials (On, Q-I2, Qi3, QH) defined from a reference point, the dials opposite from said point reference unit forming a pair of dials, the effective thickness of each of the dielectric lenses increasing as a function of the distance from said intersection point in one of the pairs of dials (Qn, Q13) and decreasing as a function of distance with respect to said intersection point in the other pair of dials (Q- | ₂ , QH).

4. pointing device according to one of the preceding claims, wherein said increases and reductions in the effective thickness of the dielectric lenses are made periodically, the period being related to a wavelength of the electromagnetic beam.

The misalignment device according to one of claims 1 to 4, wherein the variation of the effective thickness of the dielectric lenses comprises a variation of a local thickness.

6. A misalignment device according to one of claims 1 to 4, wherein the variation of the effective thickness of the dielectric lenses comprises a variation of a refractive index.

7. A misalignment device according to one of the preceding claims wherein the dielectric lenses each have a reference point (Cn, C- | ₂ ), the device having a position in which the reference points of the dielectric lenses are superimposed in the center (O) an antenna element (Ai) emitting said electromagnetic beam (F _inc ), and wherein the sum of the effective thicknesses of the dielectric lenses is constant over the entire surface (Ru, R- ₂ ) traversed by said electromagnetic beam.

8. misalignment device according to one of the preceding claims comprising two dielectric lenses each having a reference point (Cn, C- | ₂ ), the device having a position in which the reference points of the two dielectric lenses are superimposed in the center (O) an antenna element (Ai) emitting said electromagnetic beam (F _inc ), and wherein the effective thickness of the two dielectric lenses varies inversely from each other.

9. misalignment device according to one of the preceding claims comprising two dielectric lenses, wherein the two dielectric lenses are movable and move in opposite directions.

10. Device for misalignment according to one of the preceding claims wherein the dielectric lenses are flat (Du, D ₂ ).

1 1. Depilation device according to one of the preceding claims wherein the dielectric lenses are all or part of rollers (D ₅ , D ₅₂ ).

12. misalignment device according to one of the preceding claims, wherein the mobility along an axis of the dielectric lens or lenses is provided by a translation of the dielectric lens or lenses.

13. A misalignment device according to one of the preceding claims, wherein the mobility along an axis of the one or more dielectric lenses is provided by a rotation of the dielectric lens or lenses around an axis (χ ') collinear with an axis. (x) antenna.

A misalignment device according to one of the preceding claims, further comprising a first corrective lens (L ₇ ) configured to change the shape of a wavefront, said first lens being positioned on one side of the dielectric lenses, and a second corrective lens (L ₇₂ ) configured to change the shape of a wavefront opposite the first lens, and positioned on the other side of the dielectric lenses.

15. Device of misalignment according to one of the preceding claims, said device further comprising a mechanical pointing axis (M) of the electromagnetic beam (F _inc ).

An antenna characterized in that it comprises at least one misalignment device according to one of the preceding claims.

17. A method of misalignment of an electromagnetic beam (F _inc ) emitted by an antenna element (Ai), characterized in that it comprises: A first step (901) of superposition of the antennal element by at least two dielectric lenses (Du, D ₂ ) of variable effective thickness, and

A second step (902) of displacement of at least one of the dielectric lenses in at least one direction (y) substantially orthogonal to a plane (xOz) in which the electromagnetic beam is detuned.