EP0623970A1 - Circular or elliptical sectionned antenna, fixed or rotating, fed by single or multiple microwave generators producing multipolarized waves - Google Patents

Abstract

The invention relates to an antenna allowing application or irradiation by microwaves. - The subject of the invention is an antenna for microwaves characterised in that it is multipolarising, closed at each of its ends by an isotropic or anisotropic reflection short circuit, (causing the polarisation plane of the waves to turn), fed directly by one or more generators in TE11 mode and the central, fixed or rotating part (B) of which is equipped over almost its whole length with one or more non-resonant elongate slot or slots, matched at their extremities (7, 8) inclined with respect to the generatrices of the cylinder. - Application to devices for application of microwaves. <IMAGE>

Description

The present invention relates to devices allowing irradiation by microwaves (electromagnetic waves of frequencies between 200 MHz and 140 GHz) called antennas or applicators.

The object of the invention is to better control and improve the radiation characteristics of microwaves, coming from one or more generators; in particular to improve the efficiency as well as the spatial distribution of the radiated energy towards the outside, in one or more portions of space, even in all space, and this with multiple polarizations which allow a better penetration waves in the materials, better efficiency and better decoupling.

To make it easier to understand, the antenna can be considered as a closed conductive enclosure, made up of a pipe made of a good conductive material (waveguide) of circular or oval section closed at each of its ends by a reflection short-circuit. isotropic (metal plate) or anisotropic, in which one or more generators emit, and the central part of which is provided with one or more slots, not parallel to the generators (nor a fortiori to the axis of the cylinder) emitting waves at multiple polarizations. To complete this very brief description, to facilitate the presentation and to highlight the various characteristics, we will divide the description of the device into three parts A, B, C.

1 °) The first part of the antenna, which we will call A, is a waveguide (hollow cylinder) made of a good conductive material (copper, silver, gold, aluminum, stainless steel, etc ...), preferably non-magnetic, filled with an insulating material with little absorption (air, vacuum, "Teflon", ceramic, etc.) with dielectric constant ε _A and permeability µ _A , bringing or rather guiding the waves coming from one or more generators, directly or indirectly, in the central part B of the antenna; it is this part B which radiates microwave energy, under multiple polarizations, towards the outside.

According to a characteristic of the invention, part A is a waveguide of circular, oval or elliptical section in which one or more generators emit waves which propagate according to TE₁₁ mode and whose end not connected to B is closed by an isotropic reflection short circuit (made of good metal conductor for example) or anisotropic which, upon reflection, rotates the plane of polarization of the waves (various examples will be given).

< λ < 3,41 $\text{R}\sqrt{\text{εµ}}$

où ε et µ sont la permittivité (constante diélectrique) et la perméabilité du milieu et A la longueur d'onde du générateur en espace libre, ce qui conditionne soit les limites des dimensions radiales partant de la (ou des) longueur(s) d'ondes du (ou des) générateur(s) ou inversement les longueurs d'ondes partant des dimensions radiales, ceci sera illustré par des exemples. Dans le cas d'un guide elliptique, R est remplacé par les demi-axes de l'ellipse a et b, auxquels correspondent deux polarisations et deux longueurs d'ondes guidées λ_ga et λ_gb, différentes pour des émetteurs de même fréquence ; réciproquement, si deux générateurs émettent dans un guide circulaire en mode TE₁₁ avec des fréquences différentes, leurs longueurs d'ondes guidées sont différentes.According to a characteristic of the invention, so that only the TE₁₁ mode propagates, the value of the radius R or of the semi-axes a and b of the ellipse must satisfy the conventional relation: 2.61 $\text{R}\sqrt{\text{εµ}}$

<λ <3.41 $\text{R}\sqrt{\text{εµ}}$

where ε and µ are the permittivity (dielectric constant) and the permeability of the medium and At the wavelength of the generator in free space, which conditions either the limits of the radial dimensions starting from the length (s) d waves of the generator (s) or vice versa the wavelengths starting from the radial dimensions, this will be illustrated by examples. In the case of an elliptical guide, R is replaced by the half-axes of the ellipse a and b , to which correspond two polarizations and two wavelengths guided λ _ga and λ _gb , different for transmitters of the same frequency; conversely, if two generators transmit in a circular guide in TE₁₁ mode with different frequencies, their guided wavelengths are different.

According to one of the characteristics of the invention, the generators can have different frequencies, whether the guide is circular or elliptical but the propagation conditions of the TE₁₁ mode must be satisfied.

According to another characteristic of the invention, if the guide is circular and if several generators emit simultaneously in part A, they are arranged so as to emit, in TE₁₁ mode, waves polarized orthogonally to each other because the waves TE₁₁ orthogonally polarized are fully decoupled and can therefore neither interact nor interfere.

According to a characteristic of the invention, if the guide is elliptical, the generators emit, in TE₁₁ mode, with polarizations directed along the axes a and b of the ellipse, therefore orthogonal, which ensures total decoupling and this with generally different wavelengths λ _ga and λ _gb because they can only be equal in a very specific case of generator frequencies.

According to a characteristic of the invention, the generator (s) is (or are) placed (s) so as to obtain optimum efficiency, which implies a distance from each transmitter (antenna) to the neighboring short circuit quarter of the guided wavelength of TE₁₁ mode corresponding to or to (2n + 1) λ _g / 4 (n = whole number) and, optionally, an adaptation system using stubs or screws for example .

According to another characteristic of the invention, several generators which do not transmit simultaneously (for example magnetrons supplied by each of the phases of the network) can transmit according to the same polarization without interacting or interfering if their antennas are separated by a suitable distance.

According to another characteristic of the invention, the open end of part A is generally connected, to facilitate disassembly and adjustments, by flanges to part B, but in the case where it is desired to rotate the part B so that the waves sweep over a large portion or all of the space, a rotating joint is inserted between the flanges of A and B, which does not disturb the propagation of the TE₁₁ mode but which makes it possible to rotate the part B without move part A, the generators remaining stationary.

According to another characteristic of the invention, when the insulator of part A is different from that of part B, characterized by ε _B and µ _B , an adaptation device is necessary to avoid reflections and therefore increase the yield ; it will be, for example, a conical part or a change of guide section by steps or steps of the Tchebycheff type, that is to say a quarter wave plate [(2 n + 1) λ _g / 4] such that the constants of this blade ε _AB and µ _AB verify the classical relation ${\text{ε}}_{\text{AB}}{\text{µ}}_{\text{AB}}\text{=}\sqrt{{\text{ε}}_{\text{AT}}{\text{ε}}_{\text{B}}{\text{µ}}_{\text{AT}}{\text{µ}}_{\text{B}}}\text{.}$

• a) par le fait que la (ou les) fente(s) n'est pas (ou ne sont pas) généralement parallèle(s) aux génératrices du cylindre ni, a fortiori, à l'axe,
• b) par le fait qu'elles peuvent être concourantes ou parallèles entre elles,
• c) par le fait qu'elle(s) s'étend(ent) sur presque toute la longueur de la partie centrale B de l'antenne,
• d) par le fait qu'elles sont non résonnantes et généralement munies à leurs extrémités de dispositifs servant à éviter les reflets, ce qui améliore le rendement; par exemple: une partie en pointe à chaque extrémité qui donne une variation progressive d'impédance ou bien une ou plusieurs parties plus étroites de longueurs voisines de λ_g/4 et calculables à l'aide du polynome de Tchébycheff,
• e) par le fait que sa (ou leurs) largeur(s) et son (ou leurs) inclinaison(s) sont telles que l'énergie rayonnée vers l'extérieur suit une loi choisie et bien définie: par exemple uniforme en fonction de la distance à la partie A,
• f) par le fait que, s'il y a plusieurs fentes, leurs extrémités, tant au début qu'à la fin, ne sont généralement pas dans le même plan de section droite mais décalées les unes par rapport aux autres pour limiter au maximum les réflexions et améliorer le rendement.

2) The antenna also includes a central part which we will call B, essentially consisting of a hollow cylinder (waveguide) made of a good conductive material, preferably non-magnetic (copper, brass, silver, gold, aluminum, etc.). ...) of circular, oval or elliptical cross section; filled with a poorly absorbent insulator (air, vacuum, "Teflon", ceramic, etc.) with permittivity ε _B and permeability µ _B ; propagating the TE₁₁ mode; cylinder provided with one or more openings in the form of wave diffusing slots of generally constant widths characterized:

• a) by the fact that the slot (s) is not (or are not) generally parallel (s) to the generatrices of the cylinder nor, a fortiori, to the axis,
• b) by the fact that they may be concurrent or parallel to each other,
• c) by the fact that it (they) extend (s) over almost the entire length of the central part B of the antenna,
• d) by the fact that they are non-resonant and generally provided at their ends with devices serving to avoid reflections, which improves the yield; for example: a point part at each end which gives a progressive variation of impedance or one or more narrower parts of lengths close to λ _g / 4 and calculable using the Tchebycheff polynomial,
• e) by the fact that its (or their) width (s) and its (or their) inclination (s) are such that the energy radiated outwards follows a chosen and well defined law: for example uniform as a function of the distance to part A,
• f) by the fact that, if there are several slots, their ends, both at the beginning and at the end, are generally not in the same plane of cross section but offset from one another to limit as much as possible reflections and improve performance.

According to another characteristic of the invention, one can obtain not only all kinds of distribution of the radiated energy but also all kinds of polarizations of the radiated waves by the use of more or less wide or more or less inclined slits, on a same antenna, with respect to the generators of the cyclinder, or even sinuous as a function of the distance to part A because in the case of circular or elliptical guides - for values of ε _B , µ _B and given generators - the polarizations of the waves emitted , in a given cross section plane are functions of the width of the slit and the angle at the center between the central electric vector E of the TE₁₁ mode and the radius passing through the axis of the slit while the intensity is a function of the width and number of streamlines cut by the slit.

According to another characteristic of the invention, the central part B is generally connected to the parts A and C by means of flanges, between which it is possible to place rotary joints to give B an alternating or continuous movement of rotation to radiate omnipolarized waves in a given spatial angle or in all of space, A and C remaining fixed.

According to another characteristic of the invention, the antenna can be made watertight by covering the slots with an insulating material which is not very absorbent (for example "Teflon", ceramic, etc.) which, by a suitable shape, can improve the characteristics and better adapt them to needs.

According to another characteristic of the invention, the antenna can be made watertight by placing B in a tube made of insulating material which is not very absorbent, to allow part B to rotate, the choice of material depends on the aggressiveness of the medium to irradiate.

According to a characteristic of the invention, when the insulator of part B is different from that of part C, an adaptation device is necessary to avoid reflections and increase the yield. The problem and the solution are identical to those existing between A and B and described in 1 °).

3 °) The third part C of the antenna consists of a waveguide, made of material. good conductor, preferably non-magnetic, of circular or elliptical cross-section containing a poorly absorbent insulator with permittivity ε _C and permeability µ _C in which waves propagate in TE suivant mode; one of its ends is connected, generally by flanges directly, or indirectly via a rotating joint to part B, the other end is terminated by a short circuit is isotropic (the classic metal plate) or anisotropic which, upon reflection, changes the plane of polarization of the waves.

According to a characteristic of the invention, part C generally comprises one or more generators, real or fictitious (virtual) - this will be explained by continued- depending on the conditions of use, the desired power, the space available, etc.

According to a characteristic of the invention, if there are in part C several generators emitting simultaneously in a circular guide, in TE₁₁ mode, they are arranged so as to emit waves orthogonally polarized with respect to each other and cannot interact.

According to a characteristic of the invention, if the generators emit in an elliptical guide, the waves are polarized along the axes of the ellipse therefore orthogonally, which ensures total decoupling.

According to a characteristic of the invention to obtain maximum efficiency, the generators (antennas) are at a distance from the short circuit equal to (2 n + 1) λ _g / 4 and are possibly adapted (as in part A), for example using stubs.

According to a characteristic of the invention, the generators can have different frequencies but compatible with the propagation of the TE₁₁ mode.

According to another characteristic of the invention, if ε _C and µ _C are different from ε _B and µ _B , an adaptation is made according to the same laws and with the same methods as between A and B.

If there is no real generator in part C, we can consider that there are one or more fictitious or virtual generators: in the case of an isotropic short circuit, the waves arriving from B, coming from A, are reflected on the metal shutter plate C which constitutes, as in optics, a "simple mirror" with isotropic reflection and the reflected wave, of the same polarization and the same frequency, seems to come from a fictitious generator (virtual ) located beyond the mirror; because microwaves are electromagnetic waves identical to waves in the optical domain and differ only in wavelength. It is well known in optics (G. BRUHAT, Optique, MASSON and CIE Editeurs) that there are mirrors which not only reflect light but rotate its plane of polarization during reflection. It is an anisotropic reflection due to a circular or rectilinear birefringence (this will be for example a nickel mirror subjected to a magnetic field or a layer of silver or aluminum deposited on a birefringent glass, etc ... ); these very common phenomena are observed daily by the wearers of "Polaroid" glasses.

In microwaves, there are also mirrors which change the polarization of the waves during reflection, these are short circuits a little more complex than the simple metal plate, we will call them anisotropic or active short circuits (implied on the plane of polarization of the waves, in optics one speaks of "active media" and "active mirrors") to differentiate them and we will describe some examples.

According to a characteristic of the invention, if there is no (real) generator in part C, an anisotropic or active short circuit will generally be used which rotates the plane of polarization of the waves during reflection.

According to one of the characteristics of the invention, an anisotropic or active short circuit will be chosen which will generally rotate the plane of polarization of the waves by 90 ° so that the reflected wave is orthogonal to the incident wave and cannot disturb, in possibly returning to A (when it is not completely radiated), the generator that emitted it.

According to one of the characteristics of the invention, the anisotropic or active short-circuit, which rotates the polarization angle by 90 ° during reflection, can consist, for example, of either a ferrite or a cold magnetized plasma attached to a metal blade, or a quarter-wave birefringent element whose neutral lines are 45 ° from the direction of polarization of the incident wave coming from B (direction A to C) attached to a metal blade, etc. ...

The invention naturally applies to all sources and to all frequencies of microwave radiation as well as to all dimensions of antennas.

• Figure 1 est représentée une vue schématique perspective d'une antenne selon l'invention ;
• Figure 2 sont représentées les sections droites aux deux extrémités de la fente de l'antenne de la figure 1 ;
• Figure 3 est représentée une antenne elliptique alimentée par un seul générateur réel et terminée partie C par un court-circuit actif ou anisotrope ;
• Figure 4 est représenté en perspective l'élément biréfringent quart d'onde du court-circuit anisotrope de l'antenne de la figure 3 ;
• Figure 5 est représentée une vue perspective d'une antenne de section circulaire étanche et tournante ;
• Figure 6 est représentée une vue perspective d'une antenne à fentes croisées ;
• Figure 7 est représentée une vue perspective d'une antenne tournante étanche, de section réduite alimentée par une seule extrémité ;
• Figure 8 est représentée la coupe suivant l'axe de l'antenne de la figure 7 pour en montrer l'adaptation lors de la réduction de la section.

Other advantages and characteristics will emerge on reading the descriptions given below by way of indication but not limiting of the embodiments of the device of the invention as well as the appended drawings in which:

• Figure 1 shows a schematic perspective view of an antenna according to the invention;
• Figure 2 shows the cross sections at both ends of the antenna slot of Figure 1;
• FIG. 3 shows an elliptical antenna supplied by a single real generator and terminated in part C by an active or anisotropic short circuit;
• Figure 4 is shown in perspective the quarter wave birefringent element of the anisotropic short circuit of the antenna of Figure 3;
• Figure 5 is shown a perspective view of an antenna of circular and sealed circular section;
• Figure 6 is shown a perspective view of an antenna with crossed slits;
• Figure 7 is shown a perspective view of a sealed rotating antenna, of reduced section supplied by one end;
• Figure 8 is shown the section along the axis of the antenna of Figure 7 to show the adaptation when reducing the section.

There is shown in Figure 1 a microwave antenna 1 of elliptical cross section consisting of a waveguide of good non-magnetic conductive metal the ends of which are closed by metal plates welded to the guide (isotropic short circuits which do not change the plane of polarization of the waves).

Parts A, B and C contain air as insulation and are connected by flanges 2, 2 ', 3 and 3'. Although the flanges are not essential, they have been shown in FIG. 1 because they allow easy disassembly, which is very useful on a prototype by making the parts interchangeable, for example to search for the slot or the slots giving the result. better.

The antenna of FIG. 1 is supplied by two generators, the emitting parts of which (generally called antennas but which we will call transmitters to avoid any confusion) are placed in the orifices 4 and 5, along the directions of the axes of the ellipse and at distances from the ends e and d respectively equal to (2 n + 1) λ _ga / 4 and (2 n + 1) λ _gb / 4. The adapter screws (stubs), sometimes necessary depending on the type of generator, have not been shown in Figure 1.

These two generators emit, in TE₁₁ mode, orthogonally polarized waves, therefore are completely decoupled and can neither react nor interfere with each other; if in each plane of polarization there were reflections, the wavelengths being different the nodes and the bellies would not coincide which makes the diffusion more homogeneous.

The electric field lines are shown in the cross sections of the flanges 2-2 'and 3-3' in Figure 1.

Part B has only one wave diffuser slot 6 of constant width, the ends of which are adapted by narrower parts 7 and 8 of lengths substantially equal to a quarter of the wavelengths (λ _gb / 4 for 7 and λ _ga / 4 for 8).

FIG. 2 shows the straight sections at the ends 7 and 8 of the slot to specify the angles at the center α _a and α _b between the polarization planes (coincident with the axes a and b ) and the rays passing through the axis of the slot. The wave diffuser slot is therefore included in a dihedron whose edge coincides with the axis of the antenna and whose angle β = 90 ° - (α _a + α _b ). The dotted lines in Figure 2 correspond to the traces of the dihedral in the planes of straight sections and show the angle β.

This angle β defines the inclination or "bias" with respect to the generatrices (and to the axis) and is partly responsible for the multiple polarizations of the waves emitted, all the more so as the emitters are in orthogonal positions one to one. 'other. The angles β, α _a and α _b are a function for identical generators, the dimensions (length and width) of the slit (s), the ellipticity of the guide, of ε _B and µ _B and of the medium outside, α _a and α _b are generally between 0 ° and 25 ° and β is between 90 ° and 40 °.

For an elliptical antenna fed by two magnetrons at 2450 MHz, with values 2a = 93 mm, 2b = 76 mm, d = 93 mm, e = 49 mm and a slot of 950 mm in length and 9.8 mm in width , the angles α _a and α _b were respectively 10 ° and 12 ° and β = 68 °. These values are not critical and may vary by a few degrees.

Figure 3 shows an antenna powered by a single generator (real) whose part A is similar to that of part A of figure 1 and whose part B differs only by the width of the slot (the values of α _a , α _b , β, and the length remaining the same), on the other hand part C does not contain a real generator but a virtual or fictitious generator polarized along the axis a of the ellipse makes an anisotropic short-circuit or active.

In the case of figure 3, one used in the part C an active short-circuit, giving a reflection with change of polarization of 90 ° what minimizes the phenomena of interference, gives a more uniform distribution and a more important multipolarization .

In this example, the anisotropic (or active) short-circuit used is composed of a quarter-wave birefringent element 10, the neutral lines of which are directed along the bisectors of the axes of the ellipse, attached to a metal plate. From the practical point of view, this quarter wave birefringent element can be produced in many ways, in this example it consists of a "Teflon" blade 10 11 mm thick placed at 45 ° from the axes of the ellipse and attached to the metal plate closing off part C. This "Teflon" plate 10 shown in dotted lines in FIG. 3 is shown in detail in FIG. 4.

In FIG. 4, it will be noted that the 11 mm thick "Teflon" blade 10 is cut in double bevels to avoid parasitic reflections. The vibration which returns to B after passing back and forth in the quarter wave birefringent has rotated 90 ° and everything happens as if there was a fictitious generator giving, in the direction of the axis α , vibrations polarized orthogonally to those of the generator of part A. The wave which returns to a wavelength λ _ga different from λ _gb and can in no case (if it returns to A) disturb the generator placed in A, we find the advantages of the antenna in FIG. 1. In this example, the total available power (only one magnetron) being lower, we used a 6.5 mm wide wave diffuser slot, of the same length and the same α _a , α _b and β as in the previous example.

FIG. 5 illustrates an alternative embodiment and represents an antenna of sealed and rotating circular section, supplied by four generators and having four wave diffusing slots in part B. The parts A and C each contain two generators in orthogonal positions 5, 5 'and 4, 4' whose distances from the transmitters to the short-circuits, (2 n + 1) λ _g / 4, are two by two different for reasons of congestion. Between the flanges 2, 2 'and 3, 3' have been inserted two rotary joints 9 which do not disturb the propagation of the TE₁₁ mode and which make it possible to rotate B leaving the parts A and C fixed. On the other hand, the circular guide of B is placed in a 2 mm thick "Teflon" tube which thus makes the antenna watertight and prevents the entry of powdery solids, vapors or liquids into the antenna. . The antenna in this example for four identical magnetrons of 2450 MHz frequency had a diameter of 85 mm with d = e = 57 mm and d ' = e' = 171 mm. The slits in part B were 950 mm long, 9 mm wide and their ends were fitted with pointed parts 7 and 8 (not starting in the same plane of cross section to reduce reflections).

Each of the wave diffusing slots was contained in a diopter with an angle β = 80 ° (the angles α _a and α _b no longer make sense since B turns), which defines their inclination or bias relative to the generatrices of the cylinder. During the rotation of part B, all the space along B is irradiated under multiple polarizations: the antenna is in this case omnipolarizing.

We can also use the antenna in a fixed position, by changing the angle of B with respect to A and C we modify the distribution of the scattered waves (in the position of the figure, the distribution is uniform, α _a = α _b = 5 °).

FIG. 6 shows a distribution of the different slots and differs from FIG. 5 only in part B which contains 8 concurrent slots of 950 mm in length and 5 mm in width with β angles of 80 °. These slots are concurrent in pairs and are adapted differently 7, 7 'and 8, 8' which reduces reflections.

FIG. 7 illustrates another alternative embodiment: it is an antenna of circular, rotating, sealed section and of reduced section in parts B and C which contain the same dielectric (ε _B = ε _C ). Part A connected to B by flanges 2, 2 'fixed on a rotating joint 9 contains air and four generators emit there in 5, 5 and 5', 5 'so that they are two by two in orthogonal positions , the magnetrons which are in the same plane being supplied by two different phases of the sector to avoid interactions as much as possible. In the example, the diameter of part B is 85 mm, the generators transmit at the frequency of 2450 MHz, the distances d and d ' are respectively 57 mm and 171 mm. The dielectric used in parts B and C is "Teflon", the diameter of B and C is 60 mm. Part B contains four wave diffusing slots 6 4 mm wide and 900 mm long adapted to the ends by pointed parts 7 and 8. Each slot occupies a dihedral with an angle β = 85 ° in this example.

Part C contains a birefringent ceramic element of the same shape as that of FIG. 4 intended to change the polarizations during reflections of the different waves and therefore avoid interactions and improve the pluripolarization of the radiation. This part C could be connected to B by a rotating joint and would then remain fixed during the rotation of B but, in our example, FIG. 7, for reasons of simplicity, the antenna having to be immersed in a fluid, the flanges of B and C, 3 and 3 ', were connected directly and therefore C rotated with B.

Finally, the seal was achieved (doubly since B and C are filled with "Teflon") by the fact that B and C were placed in a "Teflon" tube not shown, closed at one end and the other end of which is fixed to the fixed part of the rotary joint 9, part connected to A. Therefore, the antenna can be immersed in a fluid, the parts B and C rotating inside (the mechanism has not been shown).

(les isolants de A et de B n'étant pas magnétiques); dans l'exemple ε_AB = 1,41, l'épaisseur de la lame quart d'onde = 57,5 mm et les rayons des guides sont: R_A = 42,5 mm ; R_AB = 35,75 mm et R_B = 30 mm.FIG. 8 shows the section along the axis of the cylinder of the adaptation carried out, in the example of FIG. 7, between A and B. This adaptation uses the properties of quarter-wave plates but it could be carried out well in other ways. The non-absorbent dielectric sheet of thickness equal to (2 n + 1) λ _g / 4 has a permittivity ${\text{ε}}_{\text{AB}}\text{=}\sqrt{{\text{ε}}_{\text{AT}}{\text{ε}}_{\text{B}}}$

(the insulators of A and B are not magnetic); in the example ε _AB = 1.41, the thickness of the quarter-wave plate = 57.5 mm and the radii of the guides are: R _A = 42.5 mm; R _AB = 35.75 mm and R _B = 30 mm.

Finally, the invention is obviously not limited to the embodiments shown and described above but, on the contrary, covers all variants thereof, in particular as regards the shapes, dimensions, arrangements and inclinations of the (or) slots (s).

Claims (10)

1) microwave antenna of the type consisting of a cylindrical enclosure (1) made of a good conductive metal, preferably non-magnetic, characterized in that it is closed at each of its ends by a short circuit with anisotropic or isotropic reflection, of oval or elliptical circular cross-section, provided over almost the entire length of its central part (B) - fixed or rotating - with one or more wave diffusing passages in the form of elongated non-resonant slots (6) generally suitable ( 7, 8) and inclined with respect to the generators of the cylinder, empty or containing one or more suitable low-absorbency dielectrics, supplied directly in TE₁₁ mode by one or more generators with orthogonal or parallel polarizations, emitting waves with multiple polarizations. 2) Antenna according to claim 1 characterized by the use of short circuits with anisotropic reflection which rotate the plane of polarization of the waves during reflection and can for example consist of either a ferrite or a cold magnetized plasma , or of a quarter wave birefringent element having its neutral lines at 45 ° from the direction of the incident polarization attached to a metal plate. 3) Antenna according to claims 1 and 2 characterized in that the anisotropic reflection short-circuit is preferably made so as to rotate the polarization by 90 ° during reflection. 4) Antenna according to claim 1, characterized in that the (or) slot (s) wave diffuser (s) is (or are) elongated (s) (6) preferably of the same widths parallel or crossed but generally inclined, identically or not, with respect to the generatrices of the cylinder and each included in a dihedral determined by two planes passing through the axis (edge of the dihedral) and containing the two rays passing through the ends of the slot, for each slot l angle β of the dihedron is between approximately 40 ° and 90 °, this angle β characterizes the average inclination of the slit relative to the generators, inclination as well as width of the slit which can vary locally according to the distribution, the desired multipolarization and the nature of the product to be treated. 5) Antenna according to one of claims 1 to 4, filled with air, intended for two 2450 MHz microwave generators of elliptical section, of axes 93/2 mm and 76/2 mm including the transmitters (antennas) are at distances d = 93 mm and e = 49 mm from short circuits characterized in that the wave diffuser slot of length 950 mm has a constant width of between 7.5 and 10 mm depending on the power and the medium to irradiate and is adapted at its two ends (7,8) by narrower parts, slit whose angles α _a and α _b are between 8 ° and 14 ° and whose angle β is between 62 ° and 74 ° . 6) Antenna according to claim 1 characterized in that it is supplied directly in general by one or more generators, which may have different frequencies but compatible with the propagation of TE₁₁ mode alone, of which the part (s) ) transmitter (s) (antennas) is (or are) located at distances ( e , d ) from the nearest short-circuit, close to (s) an odd number of times a quarter of the length d 'corresponding guided wave. 7) Antenna according to claims 1 and 6 characterized in that if it is supplied at the same end by several generators, if they transmit simultaneously they give TE₁₁ modes with orthogonal polarizations, if they do not transmit simultaneously, they give TE₁₁ modes with orthogonal or parallel polarizations. 8) Antenna according to claim 1 characterized in that the part (B) provided with one or more slots can rotate through the use of rotary joints (9) not disturbing TE₁₁ mode. 9) Antenna according to claim 1 characterized in that, whatever (or the) dielectric (s) placed (s) inside so that the TE₁₁ mode only propagates the section is reduced depending on the characteristics of dielectric and dioptres are adapted to avoid multiple reflections. 10) Antenna according to claim 1 characterized in that it can be made watertight thanks to the presence of one or more solid dielectrics with little absorption inside, "Teflon" for example, by covering the slots with a little material absorbent or by placing part B (where the slots are located) in a closed tube made of insulating material which is not very absorbent, in particular "Teflon".

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