PERFECTED DEVICE FOR ELECTRONIC DEVIATION OF A MICROFREQUENCY BEAM.

Abstract

This electronic deflection device for a microwave beam is characterized in that the body is integrated into a waveguide and in that the means (3) for generating the elastic wave are arranged opposite the face of the body (2) of the entry of the microwave beam into it, so that the elastic wave and the incident beam propagate in opposite directions in the body, to deflect this beam in a direction transverse to the body.

Description

The present invention relates to a certificate of addition to the electronic deflection device of a microwave beam described in the main patent. The main patent describes an electronic deflection device for a microwave beam emitted by a radiating source, characterized in that it comprises a magnetostrictive ferrite body disposed in the path of the beam and subjected to magnetic polarization and means for generating at least one elastic wave in the body to create in it a network of stresses generating a phase network, in order to deflect the beam. In this main patent, the means for generating elastic waves in the body are arranged on a lateral face of the body relative to the entry face of the microwave beam into it. It was explained that this elastic wave allows the outgoing beam to be deflected by the face opposite to the face on which the beam entered the body. This arrangement has a number of disadvantages, particularly in terms of longitudinal bulk in the direction of radiation, this bulk being at least equal to the length L of ferrite traversed. Furthermore, this arrangement is poorly suited to performing a scan in two planes, often necessary for example for applications in three-dimensional radars. The purpose of this certificate of addition is to propose a different arrangement of these means, allowing the problems mentioned above to be resolved. To this end, the invention relates to an electronic deflection device for a microwave beam, according to any one of claims 1, 2, 3, 5, 6, 7, 8, 9, 10, 11 or 14 and 15 of the main patent, characterized in that the body is integrated into a waveguide and in that the means for generating the elastic wave are arranged opposite the face of the body at the entry of the microwave beam into it, so that the elastic wave and the incident beam propagate in opposite directions in the body, to deflect this beam in a direction transverse to the body. According to one embodiment, the frequency of the elastic wave is varied to vary the direction of the deflected beam in a plane defined by said transverse direction and by the direction of the incident beam. According to another embodiment, the body is in the form of a plate forming part of a planar waveguide and the direction of the elastic wave is varied relative to the direction of the incident beam and its frequency to achieve a sweep of the deflected beam in a cone around said transverse direction. The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings, in which - Fig. 1 represents a perspective view of one embodiment of a device according to the invention, - Fig. 2 shows a cross-sectional view of the device shown in Fig. 1, - Fig. 3 illustrates the operating mode of the device according to the invention shown in Figs. 1 and 2, - Fig. 4 illustrates another operating mode of a device according to the invention, and - Fig.5 represents another embodiment of a device according to the invention operating in accordance with Fig.4. As can be seen in Figs. 1 and 2, an electronic deflection device for a microwave beam emitted by a radiating source 1 comprises a magnetostrictive ferrite body 2 placed in the beam path and subjected to magnetic polarization. This device also includes means 3 for generating at least one elastic wave in the body to create a stress network within it, generating a phase lattice, in order to deflect the beam. This ferrite body 2 is integrated into a waveguide, and the elastic wave generation means 3 are arranged opposite the face of the body at the entry point of the microwave beam into it, such that the elastic wave and the incident beam propagate in opposite directions within the body, deflecting the beam in a direction transverse to the body. In one embodiment, the frequency of the elastic wave is varied to vary the direction of the deflected beam in a plane defined by this transverse direction and by the direction of the incident beam. Indeed, in the case of a scan in a plane, illustrated in Fig. 3, the directions of the vectors ki and K, representing respectively the wave vectors of the incident beam and the elastic wave, are opposite to each other and collinear with the axis of the waveguide OZ. The elastic mode propagating in the magnetostrictive ferrite creates a step size perturbation A for the incident mode. This incident mode is a leaky mode that attenuates exponentially, the energy loss being due to radiation of the mode deflected outwards from the waveguide by the exit face. The deflection angle e can be written as follows: Proj. / kd = ki + K the axis of the waveguide where kd represents the wave vector of the beam deflected ki the wave vector of the incident beam, and K is the elastic wave vector. that's to say cos e = i - I Ao Ai A where Ao represents the microwave wavelength in a vacuum, I have the microwave wavelength of the incident mode, and At the elastic wavelength. In particular, we have for the elastic center frequency Fo, Ai = A and e = n / 2 and we obtain a sweep around this direction by varying the elastic frequency F in a band AF around Fo. Of course, this variation in the direction of the deflected beam is located in a plane defined by said transverse direction and by the direction of the incident beam. The embodiment shown on the Fig. 1 and 2 show an operating frequency of f = 15 GHz. The waveguide is an image guide with a metal plate 4 positioned opposite the face of the body from which the deflected beam exits, this plate having a thickness of 1 mm. A ceramic layer 5 in Al2O3, Er = 10 and 1.5 mm thick, is arranged between the body 2 and the plate 4. The magnetostrictive ferrite body can be made of NixZn1~x Fe2O4 with x = 0.36, 2.8 mm thick. For this composition x = 0.36, we have xgyropoMs = 0.66 w where xgyro represents the gyromagnetic ratio, po the permeability of a vacuum, Ms the saturation magnetization of the ferrite, and w the microwave pulse. Therefore, magnetic losses are low. Given the width of the image guide (4 cm), the modes are very similar to those of the unlimited planar guide and will be noted in the same way. the incident mode is the quasi-TE1 mode the diffracted mode is the quasi-TE mode and the elastic mode and the quasi-mode SHo whose center frequency is Fo = 500 kHz This elastic mode is produced by transducers arranged on the face of the body opposite the face of the incident beam entry into it, this face having a flare 6 facilitating their attachment, a spacer 7 made of Ni0.5Zn0.5FeO ferrite satisfying the relation egyropO Ms / w~1 being interposed between these means of generation and the body to absorb the remaining energy of the incident mode. On the side of the entrance face of the incident beam in the guide, a layer of ceramic-filled silicone resin 8 with Er = 10 is glued, to absorb elastic waves without disturbing the incident mode. The microwave power supply of the device is achieved by a standard rectangular guide 9, the radiating source 10 being a sector horn in the plane E and the adaptation to the image guide being made by a ceramic piece 11 of constitution Al2O3 with = =10. The ferrite body is magnetically polarized along the z-axis and advantageously includes a bridge 12 parallel to this magnetization to maintain the magnetization at a constant value Mo ~ 0.7 Ms. This magnetization is achieved, for example, by inserting a permanent magnet 13 into this bridge. Under these conditions, by varying F in a band AF / F = 1 / 3 around Fo, we obtain a sweep of 30 on each side of the OY normal, with a control power of 3 watts, a switching time of 110 ijs. and insertion losses of 3dB. We have just described a method for scanning in a single plane, but scanning in two planes is also possible, and in this case, the waveguide is necessarily a planar waveguide. In the following description, a planar waveguide is defined as a waveguide consisting of a stack of homogeneous layers all parallel to the same plane P. A detailed description of these planar waveguides can be found in "Theory of Electromagnetic Waveguides," Chapter III, by C. Vassallo, Edition EYROLLES, for microwave modes and "Acoustic fields and waves in solids" chap. X by BA AULD, J. WILEZ AND SONS edition, for elastic modes. In this case, the ferrite body is in the form of a plate that forms part of the construction of this waveguide. For this embodiment, the elastic wave is produced by a network of transducers fed with variable frequency and phase so as to perform an electronic scan of the direction of the elastic wave vector t in the plane P in an angular range av around the propagation direction ki of the incident beam. In this configuration, the operation of which is illustrated in Fig. 4, it was found that the diffracted mode is radiated outwards by a face of the body in the direction of spherical coordinates e and ç around the normal to the plane P, these coordinates being given by the following relation: Proj. / p kd = ki + K p that is to say Sin Y 2 n - = ----- Sin e cos # HAS 1 cos Y sin e sin ç Ai A Ao where Y is the angle made by the wave vector K with the direction of the wave vector ki. Thus, by varying the frequency of the elastic wave in the AF bandwidth around Given that Fo corresponds to A = Ai and the angle Y is within the range ##, a scan is performed in two planes with a single deflected microwave beam across the entire cone with a half-angle at the apex #max. A calculator solving the preceding equations for each direction e and cet allows the corresponding frequency and phase shift to be applied to the transducers mentioned previously. The other provisions of this device are the same as those provided for in the case of a scan in a plane described previously, except that the elastic absorber is glued to the three lateral faces of the ferrite plate other than the one on which the transducers are fixed. An embodiment of this device is shown in Fig. 5, which is a top view of the device along the OZ axis of Fig. 4. The planar waveguide is formed of two Al2O3 ceramic plates and Ni 0 36 Zn o 64 Fe2O4 of the same thickness and composition 0.36 0.64 than those described previously and generally referenced by 14 on this figure, arranged on a metal plate 15. The incident and diffracted modes are the TE1 and TE modes. The elastic mode is the SHo mode produced by an array of transducers 16 composed of bars polarized in a direction parallel to the electrodes and excited according to the d15 mode. These transducers, welded to the ferrite body, are fed via variable phase shifters 17a from a source 17b. On the three other sides of this ferrite body, an elastic absorption element 18 made of charged silicone resin, with a dielectric constant Er = 10, is arranged. The matching of the incident mode at the entrance face of the body is made between a sectoral horn 19 in the plane E, corrected by a lens 20, and the planar waveguide by the corresponding portion of absorber 18 described previously. Furthermore, a magnetic bridge constructed in the same way as described previously is also arranged under this body and maintains the magnetic polarization along the OY axis at a value Mo = 0.7Ms as will be described in more detail later. Under these conditions, with a bandwidth AF / F = 1 / 3 and a sweep of 10. of the direction of the wave vector K on each side of the OY axis we obtain a sweep in two planes throughout the cone with half-angle at the apex emax = 30, with a control power of 20 watts. This device, whose cost can be significantly reduced by using interdigitated transducers produced by photogravure, has numerous potential applications in addition to those already mentioned in the main patent. For example, it can be mounted on any mobile device to maintain communication with a fixed point, such as a satellite, despite the rapid and erratic movement of that device, which could be, for instance, a land vehicle. In this case, and insofar as this device is flat, it can be placed on the roof of the vehicle without difficulty. It was mentioned previously that the magnetic polarization must have certain characteristics. Indeed, this magnetic polarization Mo must satisfy the relation 0.3 Ms S Mo S 0.9Ms where Ms represents the saturation magnetization of the ferrite satisfying the relation Ms < 0.8 w / ygyro.po where w represents the angular frequency of the microwave wave, ygyro the gyromagnetic ratio, and po the permeability of free space.

Claims

DEMANDS 1. Electronic deflection device for a microwave beam according to any one of claims 1, 2, 3, 5, 6, 7, 8, 9, 10, 11 or 14 and 15 of the main patent, characterized in that the body is integrated into a waveguide and in that the means (3;16) for generating the elastic wave are arranged opposite the face of the body from which the microwave beam enters it, so that the elastic wave and the incident beam propagate in opposite directions in the body, to deflect this beam in a direction transverse to the body.

2. Device according to claim 1, characterized in that the frequency (F) of the acoustic wave is varied to vary the direction of the deflected beam in a plane defined by said transverse direction and by the direction of the incident beam.

3. Device according to claim 1, characterized in that the body (14) is in the form of a plate forming part of a planar waveguide and in that the direction of the elastic wave is varied relative to the direction of the incident beam and its frequency (F) to achieve a plane sweep of the deflected beam in a cone around said transverse direction.

4. A device according to any one of the preceding claims, characterized in that the magnetic polarization Mo satisfies the relation 0.3 Ms ( Mo S 0.9 Ms, where Ms represents the saturation magnetization of the ferrite satisfying the relation Ms < 0.8 w / ygyro po where w is the angular frequency of the microwave wave, xgyro is the gyromagnetic ratio, and po the permeability of a vacuum.

5. Device according to any one of the preceding claims, characterized in that a magnetic bridge (12) parallel to the direction of the magnetization is formed between the corresponding faces of the body to close the magnetic circuit.

6. Device according to claim 5, characterized in that a permanent magnet (13) is integrated into the bridge (12).

7. Device according to any one of the preceding claims, characterized in that an element for absorbing the remainder of the incident energy is interposed between the transducers (3; 16) and the ferrite body (2; 14).

8. Device according to any one of the preceding claims, characterized in that an elastic absorption element (8;18) is interposed between the microwave source and the ferrite body.