ES2834448T3 - Aiming and deflection system for a microwave beam - Google Patents

Abstract

Controllable deflection system of an incident microwave beam with a wavelength between 1 mm and 1 m, comprising: - a forming device arranged along an optical axis and configured to collimate said beam in emission mode or focusing said beam in reception mode, - a first device for deflecting an incident microwave beam comprising a first diffractive dielectric component (C1) with sub-wavelength microstructures arranged so as to form an artificial material exhibiting a periodic variation of the index of effective refraction, called the first diffractive dielectric component, this first diffractive dielectric component being associated with a first rotation mechanism (R1) on a first controllable axis (Ω1), characterized in that it comprises upstream of the first deflection device in the emission mode or downstream of the first diverter device in the reception mode: - a second diverter device viation configured to deflect an incident microwave beam from the forming device to the first deflection device in emission mode, or to deflect an incident microwave beam from the first deflection device to the forming device in receive mode, being this second deviation device associated with a second rotation mechanism (R2) about a second controllable axis (Ω2) that coincides with the optical axis of the forming device, because the angle (Ω1, Ω2) formed by the first and second axis of rotation is greater than 0 ° and less than or equal to 90 °, and because the first rotation mechanism (R1) is integral with the second rotation mechanism (R2) in such a way that a rotation of the second rotation mechanism about its controllable axis (Ω2) causes a rotation of the first rotation mechanism on this same axis.

Description

DESCRIPTION

Aiming and deflection system for a microwave beam

The field of the invention is that of the deflection and pointing systems of a microwave beam.

The invention applies to the treatment of a microwave beam, corresponding to frequencies between 300 MHz and 300 GHz, with a typical wavelength of 1 mm to 1 m. Such frequencies are used in particular in the field of:

• satellite telecommunications from mobile platforms,

• reconfigurable data links for high-speed communications, or

• low cost millimeter or centimeter wave radar.

Many systems require the ability to control the direction in which the beam is emitted or received. This property is called pointing. Examples of such systems include airborne radars, missile guidance systems, "detection and avoidance" systems, communication systems, jammers, and periscope radar systems.

To aim, the antenna must be configured to emit and receive a wave in a given direction in space. For example, in today's telecommunications field, it is increasingly likely that an antenna will have to be redirected, after updating the coverage of the territory. It is important to have smart and remotely controlled antennas, smart for their ability to orient themselves to cover different areas in space and remotely controlled for their ability to be remotely controlled from a central office.

For "tracking", or chasing, the antenna must be configured to follow a target such as a satellite or an airplane.

In addition, there is growing interest in the development of compact, low-mass, space-saving steerable beam antennas that are easy to use and integrate into a platform, and at low cost.

There are several known techniques for creating a steerable beam antenna, but they have some drawbacks.

The Cassegrain-type parabolic antenna is adversely affected by shading effects due to the position of the source (more specifically by the secondary reflector) in front of the reflector. Also to preserve good efficiency, a large diameter-to-wavelength ratio is required. At low frequencies, this antenna cannot be integrated in a small volume.

In addition, traditional mechanical solutions to orient the antenna use a fragile 2-axis gimbal mechanism. This pointing system requires a large mechanical path since the volume occupied by the antenna varies according to its orientation. In addition, to avoid moving parts with active RF radiation, the transmit and receive signals must pass through microwave rotary joints which degrade performance and can be expensive and bulky when high power levels (several tens of watts) are required.

This type of antenna also suffers from its offset range, which is generally limited to 60 °.

A known solution to getting rid of moving parts is the use of an active electronically scanned antenna, which avoids the need to resort to pointing mechanics: its profile remains flat regardless of the direction of orientation, which is a great advantage. when integrated into a fairing. Orientation is electrically controlled. However, this antenna has disadvantages in terms of price, power consumption, complexity, management of the heating temperature, power maintenance and also an accessible angular range that remains limited to less than 60 °.

One solution to making an RF deflection system is to use two diffractive components that can rotate around the same axis, combined with a lens and an RF source. Such a system is described in patent FR 3 002697. The diffractive components and the lens each have a plurality of periodic sub-wavelength MS microstructures formed in a dielectric material in a Risley scan pattern; said microstructures are arranged to form an artificial material that has a periodic variation in the effective refractive index, this arrangement allows the diffractive function to be performed. As shown in Fig. 15 of patent FR 3 002 697, the structure of the diffractive component C1 can be manufactured on one face of the component, while the structure of the lens L is manufactured on the other face of the component. The aiming of the beam emitted by the source S is ensured by the independent rotations (symbolized by the arrows) of the double lens-diffractive grating component L + C1 and of the diffractive component C2 around an axis O as shown in Figure 1; the components L + C1 and C2 are arranged in a plane normal to the axis of rotation O and the axis of symmetry of the beam emitted by the source S and passing through its center coincides with this axis O. The advantage of such a deflection system is which is compact, with a fixed S power supply and mechanical orientation capabilities, while ensuring high efficiency. For example, for an application at 30 GHz (Ka band), using a dielectric material with a refractive index of 1.5 (dielectric constant 2.25), the thickness of the diffractive component is about 30 mm. The total thickness of the deflection system is therefore about 100 mm. For a source located in the focal plane object of the L lens, that is, about 200mm from the lens, the total thickness of the agile antenna is about 300mm. However, this thickness may still be too great for some applications embedded in mobile platforms.

Furthermore, certain areas, especially around and in the direction of the axis of rotation O, of the components are difficult to target dynamically, especially quickly. Indeed, regarding azimuth and elevation controlled gimbal pointing systems, in this direction, the antenna pointing system presents a singular zone ("keyhole" in English) that requires the use of very high rotational speeds. (or even infinite) of the prisms when a pointed object passes near the axis of rotation O.

The following documents can also be cited. Patent FR 2570886 presents a rotating prism scanning microwave antenna. US patent 3242496 describes a scanning antenna. Patent EP 2584650 describes a steerable beam antenna with hemispherical coverage.

Consequently, there is still a need for a steerable beam deflection system that simultaneously meets all of the above requirements, particularly in terms of mass and volume reduction, displacement, ease of use and integration into a platform, and cost reduction.

The deflection system according to the invention uses two deflection devices, at least one of which comprises a diffractive dielectric component structured on a scale less than wavelength. Combined with a simple mechanics based on rotations, this approach allows to obtain angular deviations of up to 120 ° with one or more microwave sources at a lower cost, that is, a solid angle coverage of 3n sr, that is, three times that of it is accessible with an electronically scanned antenna, without a singular control point and without an active mobile microwave part.

More specifically, the object of the invention is a controllable deflection system for a microwave beam with a wavelength between 1 mm and 1 m, comprising:

• a forming device configured to collimate said beam in emission mode or focus said beam in receive mode,

• a first device for deflecting an incident microwave beam comprising a first diffractive dielectric component with sub-wavelength microstructures arranged so as to form an artificial material exhibiting a periodic variation of the effective refractive index, called the first diffractive component, being this first diffractive dielectric component associated with a first rotation mechanism about a first controllable axis.

It is mainly characterized in that it comprises, upstream of the first diverter device in the transmission mode or, downstream of the first diverter device in the reception mode:

• a second deflection device configured to deflect an incident microwave beam from the forming device to the first deflection device in emission mode, or to deflect an incident microwave beam from the first deflection device to the forming device in the reception mode, this second deflection device being associated with a second rotation mechanism about a second controllable axis that coincides with the optical axis of the forming device,

because the angle formed by the first and second axis of rotation is greater than 0 ° and less than or equal to 90 °, and because the first rotation mechanism is integral with the second rotation mechanism in such a way that a rotation of the second rotation mechanism Rotation about its controllable axis results in a rotation of the first rotation mechanism about the same axis.

According to a characteristic of the invention, the first deflection device comprises another diffractive dielectric component with sub-wavelength microstructures, arranged in parallel to the first diffractive dielectric component (referred to as the third diffractive dielectric component), this third dielectric component diffractive is associated with a third mechanism of rotation about the first controllable axis, independent of the first mechanism of rotation but integral with the second mechanism of rotation.

The second deflection device may incorporate a second diffractive dielectric component with sub-wavelength microstructures (called a second diffractive dielectric component) and the device for forming the beam emitted by the emitting medium or received by the receiving medium may incorporate a lens. Optionally it comprises a fourth diffractive dielectric component with sub-wavelength microstructures (designated fourth diffractive dielectric component) arranged in parallel to the first diffractive dielectric component.

Each diffractive dielectric component can typically be a prism or grating.

The lens of the beamforming device and the second diffractive dielectric component are advantageously combined to form a two-sided non-resonant holographic component, with sub-wavelength microstructures formed on a single side in a non-periodic arrangement determined by a calculation of interference on said face between an incident beam and a predetermined exit beam; the holographic component is associated with the second rotation mechanism.

The microstructures of the holographic component can be formed on a predetermined 3D surface. Alternatively, they are formed in a predetermined volume resting on said face of the holographic component, and implanted in a non-periodic three-dimensional arrangement.

According to another feature of the invention, the beam-forming device and the second deflection device are combined to form a Cassegrain-type mirror system.

Preferably, the second deflector is configured to deflect the beam in the first deflector at normal incidence.

The first deflecting device deflects the beam by a first deflection angle from the first axis, the second deflection device deflects the beam by a second deflection angle from the second axis. The first deflection angle is advantageously greater than or equal to the second deflection angle.

Another object of the invention is a steerable beam antenna comprising means for transmitting / receiving a microwave beam with a wavelength between 1 mm and 1 m and a system for deflecting the beam as described.

The transmitting / receiving means, the shaping device and the second deflection device can be combined to form an assembly capable of forming an incident beam in the first deflection device in emission mode or of receiving a beam from the first deflection device in reception mode; this set is associated with the second rotation mechanism. This set is in this case a network antenna.

Other characteristics and advantages of the invention will be apparent from the following detailed description, given by way of non-limiting example and with reference to the attached drawings in which:

Figure 1 shows a schematic representation of a steerable antenna according to the state of the art,

Figures 2 schematically represent, seen in section, a steerable antenna equipped with a first example of embodiment of a deflection system according to the invention, with two prisms and with a lens for shaping the beam emitted by the source (fig. 2a), with a prism and with a holographic component that combines the second prism and the shaping lens (fig. 2b),

Figure 3 shows schematically, seen in section, a steerable antenna equipped with a second embodiment of a deflection system according to the invention, with three prisms,

Figure 4 shows schematically, seen in section, a steerable antenna equipped with a third embodiment of a deflection system according to the invention, with four prisms,

Figure 5a schematically represents, seen from above, a first example of implementation of sub-wavelength microstructures of a holographic component, with constant sections on its height according to a square Cartesian mesh detailed on a larger scale in figure 5b, and perspective view (fig. 5c),

Figure 6a shows schematically, viewed from above, another example of implementation of sub-wavelength microstructures of a holographic component, according to a mesh with isophasic lines and phase gradient lines, detailed on a larger scale in Figure 6b,

Fig. 7 shows schematically, seen in section, a steerable antenna equipped with a fourth example of embodiment of a deflection system according to the invention, the second deflection device of which has a Cassegrain-type configuration with two mirrors, with a concave primary mirror ( fig. 7a) and a primary mirror with reflectors (fig. 7b),

Fig. 8 shows schematically, in sectional view, a steerable antenna comprising a patchwork antenna (Fig. 8a) and a powered network antenna (Fig. 8b).

From one figure to another, the same elements are marked by the same references.

In the remainder of the description, the terms "front", "back" are used to refer to the orientation of the figures described. Similarly, the "upstream / downstream" directions are those of the beam; in the figures the direction of the beam indicated by the arrows is that of the emission mode. Insofar as the device can be placed in other orientations, directional terminology is given for illustration and is not limiting.

Insofar as the deflection system according to the invention is intended to be used in collaboration with a source capable of emitting (and / or with a receiver capable of receiving) a microwave beam, a source is shown in the figures to illustrate beam deviations. The description is made considering that the antenna is in issue; but of course the invention applies to the reception mode. We will take dielectric prisms as an example of diffractive dielectric components; but we could also consider dielectric networks. The expression "diffractive component" is used, of course, with the same meaning as that indicated in the preamble with reference to patent FR 3002697, that is, a component with sub-wavelength microstructures arranged in such a way as to form an artificial material which has a periodic variation of the effective refractive index to thus carry out the diffractive function.

An example of a diverter system according to the invention is described in connection with Figure 2a.

The system for deflecting a microwave beam with a wavelength between 1 mm and 1 m intended to be associated with -means of emission S - reception, comprises:

• An incident beam shaper (or shaper), configured to collimate in emission mode (the wavefront emitted by the source, which is quasi-spherical in the case of a point source S, has the shape of a wave flat), or to focus in receive mode.

• A first device for deflecting the microwave beam comprising a first dielectric prism C1 with sub-wavelength microstructures. This prism C1 is associated with a first rotation mechanism R1 (indicated by the arrow) around a first axis 01 normal to the plane of the prism C1. Thus, this first deflection device is configured to deflect the incident beam by a first non-zero fixed angle 01 with respect to the axis of rotation 01. The rotation of C1 around the axis 01 ensured by the first controllable rotation mechanism R1 allows the have a circle described around 01. By construction, this angle 01 can be set between 0 and 60 °.

• Between the transmission-reception means and the first deflection device there is a second deflection device associated with a second rotation mechanism R2 about a second axis 02 (indicated by the arrow) that can be controlled. It is configured to, in emission mode, deflect towards the deflection device by a fixed angle 02 other than zero with respect to the axis of rotation 02, the incident microwave beam from the source, and in reception mode, to deflect towards the device for forming by a fixed angle 02 other than zero with respect to the axis of rotation 02, the incident microwave beam from the deflection device. The angle (01, 02) formed by the first and second axis of rotation is greater than 0 ° and less than or equal to 90 °: 0 ° <(01,02) <90 °; in other words, the prism C1 of the first deflector is inclined with respect to 02.

• The first rotation mechanism R1 is mounted on the second rotation mechanism R2. Therefore, the first rotation mechanism R1 is integral with the second rotation mechanism R2: the rotation of the second diverter device around the axis 02 causes the first diverter device to rotate around 02. But the rotation of the first diverter device Deflection around axis 01 is independent of rotation around axis 02: it does not cause the second deflection device to rotate.

To ensure complete angular coverage, the prism C1 and the second deflector must then deflect the beam with 01> 02. The rotation of C1 around the axis 01 ensured by the first rotation mechanism R1, allows the beam to describe a circle around 01, which combined with the rotation of the second deflection device around the roll axis 02 ensured by the second mechanism of R2 rotation, allows the beam to be placed in a solid angle cone with a value of 2n (1-cos (201)).

The second deflection device may comprise one or more dielectric prisms with sub-wavelength microstructures, as shown in Figures 2a, 2b, 3 and 4.

According to a first embodiment described in relation to Fig. 2a, the second deflection device has a single dielectric prism C2 with sub-wavelength microstructures, referred to as the second prism, as does the first deviation device. deviation has a single prism C1. This makes it possible to improve the compactness of the antenna.

This second prism allows the beam to be pre-deflected upstream of the first deflection device in emission mode, by a fixed angle 02 not zero with respect to the axis 02 normal to the plane of the prism C2. The angle between axes 01 and 02 can also be equal to 02 as shown in the figures; in this case the beam deflected by this second prism C2 advantageously has a normal incidence on the prism C1 in emission mode. By construction, this angle 02 can be set between 0 and 60 °. Combined with the first prism C1, this makes it possible to achieve a maximum deviation 01 + 02 of 120 °. For full angular coverage (that is, including the 02 direction), the 01 angle needs to be greater than or equal to the 02 angle. The addition of a rotational mechanics that rotates around the 02 axis leads to a pointing domain of solid angle 3n mr.

According to a second embodiment described in relation to Fig. 3, the second deflection device has a single prism designated as second prism C2, and the first deflection device has, in addition to the first prism C1, another prism designated as third prism C3.

This C3 dielectric prism with sub-wavelength microstructures is arranged in parallel and above the first prism C1 (therefore it is normal to axis 01); it is capable of deflecting the incident beam by a fixed non-zero angle 03 with respect to the axis 01. By construction, this angle 03 can be set between 0 and 60 °. It is associated with a third rotation mechanism R3 for rotation about the axis 01 (indicated by the arrow) that can be controlled, independently of the first rotation mechanism R1 associated with C1. Like the first rotation mechanism R1, this third rotation mechanism R3 is mounted on the second rotation mechanism R2. Thus, the first and third rotation mechanism R1 and R3 are integral with the second rotation mechanism R2. This first deflection device with two structured dielectric prisms C1 and C3 in independent rotations around axis 01, allows the beam to be dynamically displaced in a solid angle cone with a variable deflection angle (with respect to 01) 013 = 03 01, which it can reach 013max angle. Depending on the configuration of C1 and C3, by construction, 013max can go from 60 ° to 70 ° depending on the level of performance required. The directions of rotation of the first and third rotation mechanisms R1, R3 can optionally be opposite; in this case we speak of counter-rotating prisms C1 and C3.

The combination of these two deflection devices makes it possible to achieve a maximum deviation 013max + 02 of 120 °. For full angular coverage, the angle 013max needs to be greater than or equal to angle 02. Combined with the rotation mechanism that rotates around the axis 02, a solid angle pointing domain 3n sr is obtained.

The rotation mechanisms R1, R2 and R3 can be controlled, for example, manually or preferably by a motor controlled by a servo-mechanism.

According to a third embodiment described in relation to Fig. 4, the second deflection device has, in addition to the prism C2, a second prism with sub-wavelength microstructures, known as the fourth prism C4. This fourth prism C4 is arranged in parallel to the prism C1 of the first deflection device and just before (= upstream) in emission mode as shown in the figure, and therefore it is normal to axis 01; consequently, it is inclined with respect to prism C2 by an angle formed by axes 01 and 02. It is configured to deflect the incident beam (coming from prism C2 and therefore already deflected by an angle 02) by a different fixed angle 04 zero. This prism is associated with the rotation mechanism R2 of the second deflection device, around the axis 02. By construction, this angle 04 can be set between 0 and 60 °. The angle of deviation of the second deviation device is then equal to 02 04 with respect to axis 02. In the figure the angle formed by axes 01 and 02 is also equal to 02 04: therefore the beam of C4 has an incidence normal in C1.

For all these embodiments, the source beam-forming device has a lens in the focus of which the emission means S. are located. This lens makes it possible to shape the quasi-spherical wavefront emitted by a point source S. The shaping can be fixed and independent of the second prism C2 and its rotation mechanism as shown in Figures 2a, 3, 4. In this case, the assembly of the source S and the shaping lens L is fixed with respect to the rotations around 01 and 02 and allows easy interconnection with emission and / or reception microwave circuits.

This conformal lens L can be a dielectric lens:

• massive diffractive with a hyperbolic profile, or

• with microstructures as described in patents FR 2980648 or FR 3002697, and can be diffractive or refractive.

According to a variant that is applied to the construction modes described above, the lens L for shaping the beam emitted by the emitting means S (or to the receiving means) is combined with the second prism C2 in a holographic component CH, to obtain a single component that performs a double function of shaping and deflecting the beam emitted by the source S, as shown in figure 2b. In this case, the sub-wavelength microstructures are implanted on a single face of the CH component according to a non-periodic arrangement determined by an interference calculation on said face, between the beam emitted by the source that falls on this face and the beam desired output output (of this CH component), in this case a plane wave deviated with an angle 02. It should be remembered that microstructures are qualified as sub-wavelengths when the following condition is met for cells (or meshes) in which are implanted:

(Distance between adjacent cell centers) <A / n

where A is the chosen target wavelength from the range of wavelengths corresponding to microwaves, that is, a wavelength typically comprised between 1mm and 1m, and n the refractive index of the dielectric material in which the microstructures are formed.

In the case that this holographic component has a flat face (2D surface) as shown in figure 2b, it is a calculation of interference on this flat face between the incident beam emitted by the source and the output beam that, in the case of a steerable beam antenna, it is a plane wave with an exit angle (in emission mode) corresponding to the angle of orientation of the beam. The height and size of each MS microstructure of CH (which can also be seen in figure 5c) are determined experimentally or calculated to equal the phase delay of modulus 2n introduced locally by each microstructure, with in the conjugate of the phase of the hologram at that same point.

The implementation of sub-wavelengths of the MS microstructures is carried out from a geometric mesh M generally of Cartesian base, that is, rectangular or even square, as shown in Figures 5a, 5b and 5c. A hexagonal or even circular mesh can also be provided. Within this mesh, the base of a microstructure cannot, of course, exceed a mesh (or cell) of the mesh, but can only partially occupy it. Some meshes may be empty, others fully occupied by the microstructure base, and for others, the microstructure base only partially occupies the corresponding mesh, depending on the given implementation.

However, this simple implementation causes a phase error due to the resolution of the sampling and therefore a reduction in the efficiency of the antenna aperture. To solve this problem, a mesh base is chosen in a suitable coordinate system to adjust the phase in the best possible way. A sub-wavelength geometric structure is made from an M mesh that coincides with the isophasic lines in one direction and with the phase gradient lines in directions respectively perpendicular to the isophasic lines, as shown in Figs. 6a and 6b.

To improve the efficiency of orientation at low elevation angles (high angle 0), the microstructures of the holographic component can be formed on a non-planar surface, that is, on a predetermined three-dimensional surface, such as a surface with symmetry of revolution such as a cone. , a sphere or any arbitrary three-dimensional surface.

The microstructures are all made up of dielectric material in predefined shapes, either sticking out in the form of pillars or hollow in the form of holes. A combination of holes and pillars is also possible. The microstructures have any shape, preferably with axes of symmetry. They have a square, hexagonal or circular section, or a combination of different geometries, or a section that conforms to the isophase and phase gradient lines. They can be constant in their section throughout their height or variable as in the case of a pyramidal or conical structure, etc. The height of the MS microstructures is generally the same (as shown in Figure 5c), but not necessarily. They can be perpendicular to the component surface or inclined, for example 30 °. It is also possible to have a variable slope on the same component. The inclination is determined experimentally, typically as a function of the direction of the inflection or incidence of the beam.

According to a generalization of the previous embodiment, and even to perform the collimation or focus function (depending on the emission or reception mode) and the beam deflection function, the holographic component CH comprises superimposed layers of MS microstructures of sub-length waveforms formed in their volume and implanted according to a non-periodic three-dimensional arrangement determined by a calculation of interferences on said volume, between the beam emitted by the incident source in this volume and the desired output beam. This volume rests, of course, on the face of the CH component in which the microstructures are formed; this volume is delimited in particular by this face. The calculation of the volume interference can be carried out experimentally by successive adjustments or by calculation, for example by transforming the volume of CH into a stack of K parallel 2D or 3D surfaces (with K being an integer typically between 2 and 100) in each one of which a surface interference pattern is calculated. The stacking of microstructure layers is obtained, for example, by matching, for each volume calculation point, a microstructure whose height is reduced by a factor K and whose section makes it possible to generate a local phase delay corresponding to the conjugate of the phase of the hologram at this same point reduced by a factor K.

Another way of obtaining the distribution of the 3D microstructures consists, from the interference calculation obtained on the face of the CH component between the incident beam emitted by the source and the output beam, in projecting the section of each of the microstructures in the volume of the component following the curves resulting from the intersection between the isophasic planes of the volume hologram and the planes containing the phase gradients.

In other words, you can perform this interference calculation on that volume:

• discretely for different values of z (dimension of the stack); it is a kind of reiteration for several implementation surfaces considered at different values of z, of the 2D interference calculation described above for a single implementation surface. The height and section of the microstructures will then be determined on each of these surfaces as indicated above, or

• continuously in z, the height and section of the microstructures being then determined by the calculation itself.

This CH component is housed in the second deflection device and is therefore subject to rotation around axis 02 by the second rotation mechanism. This holographic CH component allows for increased weight and efficiency.

An example of a configuration with a holographic component CH is shown in Figure 2b: a single prism C1 that deflects the beam at a fixed angle 01 with respect to its axis of rotation 01, is used in the aperture of the antenna. As already indicated, to ensure complete angular coverage, it is necessary that the prism C1 and the holographic component CH deflect the beam with 01> 02. The rotation of C1 around the axis 01 provided by the first rotation mechanism, allows the beam to describe a circle around 01, which combined with a rotation of the set C1 and CH around the axis of rotation 02 provided by the second rotation mechanism , allows the beam to be placed in a solid angle cone with a value of 2n (1-cos (201)).

It is also possible to add to the previous configurations, a mechanism for translating the transmission means S // reception along the vertical axis (parallel to axis 02) to control the opening of the emitted and received beam.

To help the two deviation devices and / or compensate for the variation of the deviation of C2 when the frequency of the wave emitted by the source S is modified, it is also possible to add to the previous configurations a translation mechanism of the emission means. S / reception in the plane normal to axis 02. This is particularly useful for generating small deflection angles and avoids the need to perform a complete turn (= one complete turn of the second rotation mechanism) especially around singular points such as those shown. found at the address of 02 for example. This allows easy and total control of the beam (position and aperture).

In the examples above, the second deflection device had one or more prisms, but may not have a prism. This space-saving alternative to the previously described embodiments is based on a combination of the source beam shaping device and the second deflection device, using reflector antenna type configurations; this combination remains associated with the second rotation mechanism R2 around axis 02. The beam emitted by the source is, for example, deflected and distributed in the first deflection device by:

• an off-axis Cassegrain configuration with a parabolic primary mirror M1 and a concave secondary mirror M2, as shown in figure 7a,

• a Cassegrain-type configuration in which mirror M1 is a reflectarray mirror, as shown in Figure 7b.

For these two reflector variants, the M2 concave secondary mirror can be replaced by any other type of reflector to achieve Gregorian configurations, ADE (acronym for the Anglo-Saxon expression "Axially Displaced Ellipse") or Dielguide (also known by the Anglo-Saxon name "Splashplate ”).

The invention also has as its object a steerable antenna comprising a deflection system as described, and the microwave transmission / reception means S arranged at the focus of the shaping device as shown in the figures already described.

In all the configurations described, the source S can be monopulse, connected or not to a "magic T" that allows the direct extraction of monopulse signals (sum and differences along the two axes of the cone). These signals make it possible to know the angle difference between the target and the sum of the beam's pointing angle, which is known by adding encoders on the three axes of rotation of the device. This makes it possible to measure the deviation of a target in the main radiation lobe from the source radiation pattern.

Alternatives to all these embodiments of a steerable antenna can also be made by combining a non-point source (or more generally non-point emission-reception means), its shaping device and the second deflection device to form a set configured to emit a plane wave in the first deflector in transmit mode or to receive a plane wave from the first deflector in receive mode. This assembly is, for example, itself an antenna of network A (with plates (“patchs antenna” in English), as shown in Fig. 8a, with slot, Vivaldi, ...), without phase changers or with fixed phase changers. In fact, this network antenna does not have to be equipped with phase changers, since the offset of the angle 02 + 013 is carried out by the deflection system. On the other hand, you can have multiple channels to do advanced radar processing. The network antenna can be positioned perpendicular to axis 02 as shown in Figures 8a and 8b, but this is not necessary. It can also be placed directly against the C1 prism. Whatever its configuration, this network antenna A is associated with the second rotation mechanism R2 around the axis 02.

It is possible to turn on the antenna of network A as shown in figure 8b. The 02 firing angle ensures that the performance of the patches in the fixed pointing direction of the antenna is not lost.

This assembly, configured to emit a plane wave deflected towards the first deflector in emission mode (or to receive a plane wave deflected by the first deflector in receive mode), can also be a reflecting antenna, a cone of high gain, or other.

These alternatives described in relation to Figures 7a, 7b, 8a, 8b, also apply to a first deflection device with a single prism C1.

For these embodiments, each prism (C1 and optionally C3) of the first deflection device is associated with a rotation mechanism around 01 (R1 and optionally R3), while a single rotation mechanism around 02 (R2) is associated with the second deflection device comprising one or more prisms (C2 or CH and optionally C4), or a Cassegrain type configuration, or a network antenna. And we have: 0 ° <(01, 02) <90 °.

A fairing is advantageously used to encompass the source and optionally the shaping device or even the first diverter device. This fairing is covered on the outside or lined on the inside with absorbent material that makes it possible to absorb the waves emitted by the source S but not intercepted by the lens L, as well as the parasitic reflections of the device. This helps to improve the radiation pattern of the antenna and reduce its radar equivalent area. This absorber can be made of dielectric and / or magnetic material (or composite), structured on a sub-wavelength scale to reduce the level of reflections at the air / absorber interfaces.

This structuring can be done in two ways:

• Or by using a layer composed of microstructures of sub-wavelengths so that the structure adapts locally in height and thickness to present the equivalent effective index (as presented in patent FR 2 980 648) that allows to produce an adapted antireflection layer locally to the incidence and frequency of the incident wave.

• Either using a three-dimensional pyramidal structure, for example (see the article by W. H.

Southwell "Pyramid-array surface-relief structures producing antireflection index matching on optical surfaces", J. Opt. Soc. A., Vol 8, No 3, March 1991) at the interface by orienting, for example, the sub-wavelength microstructures according to the incidence of the beam. This orientation is not essential, an orientation normal to the fairing surface can be maintained.

Depending on the operating wavelength of the device, the size of the microstructures is therefore different. These structured surfaces can be produced by machining, additive manufacturing, or chemical etching.

The advantages of the invention are as follows:

❖ The mechanics that must be established for this type of deviation system is more reliable than connecting rods (ring motors). The rotating mass is low because the use of plastic dielectric materials allows the use of additive manufacturing techniques, and ensures a reasonable weight for fast and light mechanics. The dimensioning of the actuators and the servo control of the rotation mechanisms do not depend on the distribution of the mass in the emitting part, which facilitates modularity.

❖ The angular range accessible by the system in transmission / reception is 3n sr (maximum deviation 120 °) compared to less than n sr (maximum deviation 60 °) for other systems.

❖ The use of dielectric prisms ensures the bandwidth and makes this system accessible at the highest frequencies.

❖ The use of a central emitter reduces costs by using a centralized power emitter (for example, -progressive wave tube - TOP) for high frequencies; no need to use rotating unions to pass the microwave signal.

❖ Controlling the position of the source in relation to the lens along the perpendicular axis allows control of the beam aperture.

Claims (20)

1. Controllable deflection system of an incident microwave beam with a wavelength between 1 mm and 1 m, comprising: - a forming device arranged along an optical axis and configured to collimate said beam in emission mode or focus said beam in receive mode, - a first device for deflecting an incident microwave beam comprising a first diffractive dielectric component (C1) with sub-wavelength microstructures arranged so as to form an artificial material exhibiting a periodic variation of the effective refractive index, called the first dielectric component diffractive, this first diffractive dielectric component being associated with a first rotation mechanism (R1) on a first controllable axis (01), characterized in that it comprises upstream of the first deflection device in the emission mode or downstream of the first deflection device in receive mode: - a second deflection device configured to deflect an incident microwave beam from the forming device towards the first deflection device in emission mode, or to deflect an incident microwave beam from the first deflection device towards the forming device in reception mode, this second deflection device being associated with a second rotation mechanism (R2) on a second controllable axis (02) that coincides with the optical axis of the forming device, because the angle (01, 02) formed by the first and second axis of rotation is greater than 0 ° and less than or equal to 90 °, and because the first rotation mechanism (R1) is integral with the second rotation mechanism (R2 ) in such a way that a rotation of the second rotation mechanism about its controllable axis (02) causes a rotation of the first rotation mechanism about this same axis. 2. Controllable deflection system according to the preceding claim, characterized in that the first deflection device comprises another diffractive dielectric component (C3) with sub-wavelength microstructures arranged in parallel to the first diffractive dielectric component (C1), called the third diffractive dielectric component, this third diffractive dielectric component being associated with a third rotation mechanism (R3) on the first controllable axis (01), independent of the first rotation mechanism (R1) and integral with the second rotation mechanism (R2). 3. System controllable bypass according to one of preceding claims, wherein the deflection device comprises second diffractive dielectric component (C2) with microstructures subwavelength called second dielectric diffractive component, and the device for forming the beam emitted by the emitting means or received by the receiving means comprises a lens (L). 4. System controllable bypass according to the preceding claim, characterized in that the second deflecting means comprises a further diffractive dielectric component (C4) with microstructures subwavelength arranged parallel to the first diffractive dielectric component (C1), called the fourth diffractive dielectric component. 5. System controllable bypass according to one of claims 3 to 4, characterized in that the lens (L) of the forming beam device is a diffractive lens dielectric microstructures. 6. System controllable bypass according to one of claims 3 to 4, characterized in that the lens (L) of the forming beam device is a refractive lens dielectric microstructures. 7. System controllable bypass according to one of claims 3 to 4, characterized in that the lens (L) of the forming beam device is a solid dielectric refractive lens. 8. System controllable bypass according to one of claims 3 to 4, characterized in that the lens (L) of the forming beam device and the second dielectric component diffractive (C2) are combined to form a nonresonant holographic component (CH) with two faces, with sub-wavelength microstructures formed on a single face according to a non-periodic arrangement determined by a calculation of the interference on that face between an incident beam and a predetermined exit beam, and because the holographic component (CH) is associated with the second rotation mechanism (R2). 9. System according controllable bypass the preceding claim, characterized in that the microstructures (MS) of the holographic component (CH) are formed in a predetermined three - dimensional surface. 10. System controllable bypass according to claim 9, characterized in that the microstructures of the holographic component (CH) are formed in a predetermined volume resting on said face of the holographic component, and implanted as a non - periodic three - dimensional arrangement. 11. System controllable bypass according to one of claims 1 to 2, wherein the beam forming device and the second deflecting means are combined to form a Cassegrain mirror system. 12. System according controllable deflection of the preceding claims, wherein each dielectric diffractive component is a prism or a network. 13. System according controllable deflection of the preceding claims, wherein the second deflecting means configured to deflect the beam in the first deflection device at normal incidence. 14. System controllable bypass according to one of the preceding claims, wherein the first deflecting means deflects the beam with a first deflection angle (01, 013) with respect to the first axis (01), the second deflecting means deflects the beam with a second angle of deviation (02, 02 + 04) with respect to the second axis (02), and because the first angle of deviation is greater than or equal to the second angle of deviation. 15. steerable beam antenna comprising means for transmitting / receiving a microwave beam with a wavelength of from 1 mm to 1 m and a system to deflect the beam according to one of the preceding claims. 16. steerable beam antenna according to claim, characterized in that the emission means (S) are configured to be monopulse. 17. Antenna steerable beam according to one of claims 15 or 16, comprising a translation mechanism of the means of emission / reception along the second axis (02) and / or in a plane normal to the second axis (02 ). 18. Steerable beam antenna comprising - means of emission / reception of a microwave beam with a wavelength between 1 mm and 1 m comprising an antenna of the array (A) arranged perpendicularly or not with respect to an optical axis, and - a system for deflecting the beam, comprising a first device for deflecting an incident microwave beam comprising a first diffractive dielectric component (C1) with sub-wavelength microstructures arranged so as to form an artificial material exhibiting a periodic variation of the effective refractive index , called the first diffractive dielectric component, this first diffractive dielectric component being associated with a first rotation mechanism (R1) about a first controllable axis (01), in which the transmission / reception means are associated with a second rotation mechanism (R2) on a second controllable axis (02) that coincides with the optical axis of the antenna of the network (A), the angle (01, 02) formed by the first and second axis of rotation is greater than 0 ° and less than or equal to 90 °, the first rotation mechanism (R1) is integrated in the second rotation mechanism (R2) of such that a rotation of the second rotation mechanism about its controllable axis (02) causes a rotation of the first rotation mechanism about this same axis the transmitting / receiving means are configured to collimate said beam in the emission mode or to focus said beam in the receive mode and form an incident beam at the first deflector in the emission mode or to receive a beam from the first Bypass device in receive mode. 19. steerable beam antenna according to claim, wherein the network antenna (A) is disposed perpendicularly with respect to the optical axis. 20. steerable beam antenna according to claim 18 or 19, wherein the network antenna is on.