EP0278867B1 - Integrated microwave circulator - Google Patents

Description

The present invention relates to a waveguide circulator, for microwave waves, in which the gyrator can be integrated. The circulator object of the invention is a model in which the power can reach and exceed the kilowatt, in a frequency range between 1 and 100 GHz.

In its general definition, a circulator is a microwave component having a number of doors, at least three, which transmits the energy it receives from one door to another door. This component has the property of non-reciprocity, that is to say that, if the direction of the incident energy is modified, the function of the entry and exit gates is not exchanged. This condition of non-reciprocity is introduced by the use in such a component of a gyrator comprising ferrites. These are ceramic magnetic materials mainly constituted by metal oxides which, however, differ from conventional metallic magnetic materials in that they are non-conductive and have low losses of magnetic origin at microwave frequencies.

Among the different classes of circulators, those called junctions consist of a junction with three or four doors made as a waveguide in which is inserted, in its center, at least one ferrite rod subjected to a transverse external magnetic field.

• soit en plusieurs parties assemblées : il est alors facile d'y coller et positionner les ferrites,
• soit monobloc, ce qui signifie qu'on ne peut accéder à l'intérieur du corps, pour y fixer un gyrateur, que par les portes du circulateur, ce qui suppose donc qu'il soit démonté du matériel dans lequel il est en service.

The waveguide circulators are made from a metal body which is either machined in the mass, or welded, and whose body is:

• either in several assembled parts: it is then easy to stick to it and position the ferrites,
• is monobloc, which means that you can access the inside of the body, to fix a gyrator, only by the doors of the circulator, which therefore assumes that it is dismantled from the equipment in which it is in service.

The waveguides are either made of welded sheet metal or molded, and it is difficult to precisely position and fix the ferrite piece (s) of the gyrator there, especially since the waveguides must not not have - apart from the doors - slots or air gaps, which have the double disadvantage of having a high impedance, and of presenting a microwave leak, dangerous for the user.

It is therefore an object of the invention to provide a solution to the problem of integrating a gyrator in a waveguide structure, without requiring access to the interior of the waveguide.

It is another object of the invention to solve this problem in the case of a monobloc waveguide, welded or molded, but not formed from two removable half-shells.

It is also an object of the invention to solve this problem in the case of high-power circulators, provided on their main surfaces with air or liquid radiators.

It is also the object of the invention to produce an industrial power circulator little sensitive to dust, thanks to the absence of free gap between the ferrites.

Finally, it is an object of the invention to ensure easy and economical integration of the gyrator in the circulator, without loss of additional insertions or stray radiation.

According to the invention, which is defined in claim 1, the circulator is pierced with two opposite circular holes, in its two parallel walls, and at the location where the gyrator must be located. The gyrator is, for its part, in one piece and constituted by the stack of parts of cylindrical shape which are, for example, glued together. This gyrator comprises, at least, a pole piece, a ferrite, a solid dielectric such as silica, a ferrite and a second pole piece. One or two magnets are also bonded to the two pole pieces. All components of the gyrator have substantially the same diameter at most equal to the diameter of the holes, so that the gyrator is in the form of a cylindrical part, which can be introduced through the holes made in the circulator. Only the pole pieces can have, at a level corresponding to the main walls of the waveguide, a projecting flange of larger diameter, but equal to the diameter of the holes in the waveguide: the two radiators, which are also drilled with holes corresponding to the passage of the gyrator, block it in position, by resting on the external faces of the edges of the pole pieces. The gyrator is therefore fixed by means of the radiators. A special glue joint or a "microwave" seal can be added to eliminate any leakage of microwave radiation, and ensure thermal continuity for the cooling of the gyrator.

• le gyrateur est un cylindre monobloc, qui comporte au moins un aimant, une première pièce polaire, un premier ferrite, un diélectrique solide, un second ferrite et une seconde pièce polaire, pièces dont le diamètre est au plus égal au diamètre des trous, le dit gyrateur passant à travers les trous pratiqués dans les faces principales du guide d'onde.
• les plaques de refroidissement immobilisent le gyrateur dans le guide d'onde.

More specifically, the invention relates to an integrated microwave circulator, comprising a waveguide junction, and a gyrator placed at the center of symmetry of the junction, as well as cooling plates applied to the main faces of the guide. wave which are pierced by two circular holes, facing one another, and centered on the center of symmetry of the junction, this circulator being characterized in that:

• the gyrator is a monobloc cylinder, which comprises at least one magnet, a first pole piece, a first ferrite, a solid dielectric, a second ferrite and a second pole piece, pieces whose diameter is at most equal to the diameter of the holes, the said gyrator passing through the holes made in the main faces of the waveguide.
• the cooling plates immobilize the gyrator in the waveguide.

• fig. 1 : vue en plan, simplifiée, d'un circulateur selon l'art connu,
• fig. 2 : exemple de montage d'un gyrateur dans un circulateur, selon l'art connu,
• fig. 3 : autre exemple de montage d'un gyrateur dans un circulateur, selon l'art connu,
• fig. 4 : vue en coupe de la partie d'un circulateur dans lequel est monté un gyrateur selon l'invention (vue partielle), avec un premier type de joint.
• fig. 5 : vue en coupe du montage d'un gyrateur, selon l'invention (vue partielle), avec un second type de joint,
• fig. 6 : vue en coupe d'un gyrateur selon l'invention, selon un perfectionnement destiné à augmenter la puissance commandée.
• fig. 7 : vue en coupe d'un gyrateur selon l'invention (vue d'ensemble).

The invention will be better understood, and other characteristics will appear on reading the description which follows, illustrated by the attached figures, which represent:

• fig. 1: simplified plan view of a circulator according to known art,
• fig. 2: example of mounting a gyrator in a circulator, according to known art,
• fig. 3: another example of mounting a gyrator in a circulator, according to known art,
• fig. 4: sectional view of the part of a circulator in which a gyrator according to the invention is mounted (partial view), with a first type of seal.
• fig. 5: sectional view of the mounting of a gyrator, according to the invention (partial view), with a second type of seal,
• fig. 6: sectional view of a gyrator according to the invention, according to an improvement intended to increase the controlled power.
• fig. 7: sectional view of a gyrator according to the invention (overview).

Figures 1 to 3 define what a circulator, and how to integrate a gyrator, but this preliminary reminder will simplify the explanations, thereafter, and to make more clear the presentation of the invention.

Figure 1 gives the plan of a three-door circulator produced from a T or Y junction and three arms formed by waveguides whose openings are called doors 1, 2, 3. A step 4 ensures the ternary symmetry of the junction, so that the triangle ABC, formed between the points common to the three waveguides - in the plane of the figure - is an equilateral triangle. In the axis of this junction, that is to say in the axis of the center of the triangle ABC, are placed two ferrite discs 6 and 7 subjected to a transverse magnetic field applied by one or two magnets 8 and 9, by l 'through pole pieces 10 and 11.

Figure 1 is a plane which passes through the plane of symmetry of the circulator, Figure 2, which is a section along X′X, allows to see the parts not shown in Figure 1. We will call the main faces of the circulator the faces 12 and 13 planes and parallel to the plane of symmetry of the circulator.

In such a circulator, the microwave energy entering through door 1 exits through door 3, and the energy entering through door 3 exits through door 2.

However, a circulator constituted as described above does not work correctly because it is not suitable. For the circulation conditions in the circulator to be satisfied, the impedance of the waveguides must be reduced at the ferrites. The rectangular waveguides which are commonly used are standardized guides whose side ratio is of the order of 2 to 1 and which propagate the TE 10 mode. To reduce the impedance of the waveguides, it is necessary reduce the height "h". This reduction is achieved by the introduction into the junction of metal plates 14 and 15 constituting an impedance transformer. These plates are arranged against the main faces of the junction and the ferrite discs 6 and 7 are bonded opposite one another against these plates. It is obvious that the necessary introduction of these plates reduces the distance separating the ferrite discs and therefore increases the risk of breakdown at this level. The power handling of a junction circulator of the prior art is therefore limited, thereby resulting in a significant limitation of its use.

Figure 2 shows how the elements just described are positioned and held in place.

According to French patent No. EP-A-0 012 682, filed on December 8, 1978 and belonging to the Applicant, the main faces 12 and 13 of the waveguide are each provided with a hole bordered by a shoulder 16 and 17 on which the impedance transformer 14 and 15 is brazed. In each hole penetrates an assembly constituted by a ferrite 6, a pole piece 10, a radiator, and a magnet 8, all the pieces of which are brazed together, l 'assembly being further brazed on the shoulder 16.

• des épaulements 16 et 17 pour bien positionner chaque ensemble de pièces brasées,
• des transformateurs d'impédances 14 et 15
• des cotes très précises, pour que la distance nécessaire entre les pastilles de ferrite 6 et 7 soit respecté,
• que le circulateur, une fois monté, ne soit plus démonté.

This type of mounting of two sets which are independent and separated by an air dielectric supposes:

• shoulders 16 and 17 to properly position each set of brazed parts,
• impedance transformers 14 and 15
• very precise dimensions, so that the necessary distance between the ferrite pads 6 and 7 is respected,
• that the circulator, once mounted, is no longer disassembled.

Indeed, this type of mounting requires access to the interior of the waveguide, for soldering for example. This is a drawback with respect to the power waveguides, which are one-piece, of molded metal.

This is the reason why, in certain circulators, a block of ferrite is introduced between two dielectric discs, and the assembly is compressed inside the waveguide, which must necessarily be formed from at least two parts. , and not monobloc. The ferrites and magnets which complete the gyrator give it the appearance of a cylinder which crosses the waveguide, but this gyrator is not a single piece and cannot be installed from the outside. US-A-3,466,571 gives an example of such a compressed gyrator.

However, it is also known that the decoupling between the doors of a circulator decreases when the power of the incident wave exceeds a threshold which is a function of the choice of ferrite, the frequency of the wave and the way in which the circulator is produced, and that, for a high power in a circulator whose ferrite discs are spaced by a determined distance, there is a risk of breakdown, which eliminates the presence of dielectric.

French patent FR-A-2 208 202, filed on November 28, 1972, in the name of the plaintiff, provides a solution to the increase in power in a junction circulator. Figure 3, which recalls the basis, is simplified and limited to only the parts necessary for understanding: a power circulator is in this case in the form of two low impedance junction circulators, electrically connected in series.

In a circulator of main faces 12 and 13, a metal plate 20 is introduced at the height of the longitudinal plane of symmetry, which has the effect of dividing the junction as well as the standard waveguides used in two junctions and associated guides of reduced height. This plate occupies the entire area of the junction. However it can extend beyond and occupy both the area of the junction and the arms.

According to the remark made in the foregoing, two junctions in reduced impedance guides are obtained in this way with which two circulators are produced by placing in the axis of the junctions, on either side of the wall 20, two ferrite pads 18 and 19 which are thus opposite respectively the pads 6 and 7. This gives two circulators which are stacked, that is to say that electrically they are shown in series. They are easily adaptable without metal element for reduction of impedance, being already made in low impedance guides. Each of these circulators receiving only half of the incident energy, the total admissible power in the circulator obtained by stacking the two elementary circulators and practically double that of a normal circulator.

This type of mounting requires a tool for mounting the ferrites 6, 7, 18, 19 relative to the pole pieces 10 and 11.

The drawbacks of the known art are avoided by the structure of the circulator according to the invention, a partial view of which, of the gyrator region, is given in section in FIG. 4. To facilitate understanding, the same reference indices are preserved if they designate the same objects.

In a circulator whose general forms are those of FIG. 1, the junction with ternary symmetry is constituted by a waveguide of reduced height, the reduction ratio compared to the standard waveguides depending on the frequency and the power flowing through it. The coupling of microwave waves to the gyrator takes place directly, without an impedance transformer. This means that the main faces 12 and 13 of the waveguide are flat, inside the cavity, and that no impedance transformer, such as 14-15 in FIG. 2, is soldered there. or molded.

The main faces 12 and 13 each have, at the base of the ternary center of symmetry, a circular hole 22 and 23.

• un résonateur composite monobloc comprenant deux disques de ferrite 6 et 7 collés sur les deux faces d'un disque de diélectrique 21, tel que silice ou céramique,
• deux pièces polaires 10 et 11, en acier doux, dont la forme cylindrique adaptée aux fonctions à remplir sera analysée ultérieurement,
• un ou deux aimants 8 et 9, cylindriques de diamètre inférieur à celui des pièces polaires.

The integral monobloc gyrator is a set of cylindrical external shape, constituted by:

• a one-piece composite resonator comprising two ferrite discs 6 and 7 bonded to the two faces of a dielectric disc 21, such as silica or ceramic,
• two pole pieces 10 and 11, made of mild steel, whose cylindrical shape adapted to the functions to be fulfilled will be analyzed later,
• one or two magnets 8 and 9, cylindrical with a diameter smaller than that of the pole pieces.

All of these parts are glued, so as to form a monobloc gyrator which can be manipulated and introduced through the two opposite holes 22 and 23.

They all have a diameter which is substantially constant, except for the two pole pieces 10 and 11 which have at their base, that is to say at the level where they pass through the main faces 12 and 13, a projecting rim 24 and 25, of diameter equal to the diameter of the holes 22 and 23 in the faces 12 and 13 of the waveguide. The flanges 24 and 25 have an outer face - relative to the waveguide - planar 26 and 27, and coplanar with the outer surface of the faces 12 and 13 of the waveguide.

Two microwave energy seals - which will be detailed later - are interposed between the monobloc gyrator and the waveguide.

Finally, the power circulator according to the invention comprises cooling means constituted either by two fin plates 28 and 29, air cooling, as shown in FIG. 4, or by two liquid circulation boxes, as shown in FIG. 7. These cooling means are also pierced with two holes 30 and 31, of diameter corresponding to the small diameter of the pole pieces 10 and 11.

The monobloc gyrator being positioned in the holes 22 and 23 of the waveguide, the fact of attaching the cooling plates 28 and 29 immobilizes the gyrator, because the internal faces, turned towards the waveguide, of the plates 28 and 29 come to bear on the external faces 26 and 27 of the edges of the pole pieces 10 and 11, and block the gyrator.

A circuit made of soft magnetic material 32, having one or more removable parts, or alternatively constituting a return circuit of the partially open magnetic flux, completes the power circulator according to the invention. This magnetic circuit 32 is visible in FIG. 7, which gives a view - along the axis Y′Y of FIG. 1 - more general but less detailed than fig. 4.

The structure of the circulator according to the invention is such that one can check before integrating each of the parts, which will now be each better detailed, and the complete gyrator.

Unlike the known solutions in waveguide structure and more especially those for power applications, the monobloc resonator is produced without air gap between the ferrites 6 and 7, the air gap being replaced by a dielectric or a plate metal 21. It is mainly constituted by at least two thin ferrites, produced either in the form of discs or with a section having a ternary symmetry. By thin ferrites is meant ferrites of small thickness compared to the wavelength in the composite resonator.

The dimensions of the ferrites and the dielectric are calculated so as to obtain a gyromagnetic resonator whose impedance is practically the same as that of the waveguide of reduced height constituting the ports of the junction.

Such a structure avoids the intrusion of dust or the condensation of material in the critical zone located between the ferrites.

It is therefore the dimensions calculated for the ferrites which impose the diameter of the projecting flanges 24 and 25 of the pole pieces 10 and 11 and, consequently, the diameter of the holes 22 and 23 in the faces 12 and 13 of the guide. wave.

The pole pieces 10 and 11, of mild steel or other, cylindrical, have a small diameter at the height of the cooling plates 28 and 29, and a large diameter, that of the protruding rim 24 and 25, at the height of the faces 12 and 13 of the waveguide. They can easily penetrate inside the waveguide, depending on the total thickness of the one-piece resonator 6 + 21 + 7. The important thing is that the distance between the two faces 26 and 27 of the edges is equal to the distance between the two outer faces of the walls 12 and 13 of the waveguide.

• l'insertion du gyrateur monté et testé préalablement dans la structure hyperfréquence compacte, où seul un trou central calibré est réalisé à l'endroit où doit être incorporé le gyrateur.
• après l'insertion du gyrateur, le montage aisé des joints d'étanchéité et des plaques de refroidissement.
• la réalisation d'une interface thermique à résistance faible.

Their shapes allow simultaneously:

• the insertion of the gyrator assembled and tested beforehand in the compact microwave structure, where only a calibrated central hole is made at the place where the gyrator must be incorporated.
• after insertion of the gyrator, easy mounting of seals and cooling plates.
• the creation of a low resistance thermal interface.

This can be achieved by a film of adhesive or conductive lacquer 34 and 35 between the cylindrical surfaces of the pole pieces 10 and 11, and the internal surfaces of the holes 22 and 23 in the waveguide, and 30 and 31 in radiators. This film does not have to provide a rigid mechanical connection.

The diameter of the pole pieces 10 and 11, at the level of the insertion zone in the waveguide junction, must be as close as possible to that of the ferrites 6 and 7, in order to reduce the rate of energy coupled by the gap inevitably existing between these pole pieces and the metallic body of the junction, the coupling thus produced being of the magnetic type in a region where the magnetic fields have no transverse components.

It is to avoid high-precision machining of the holes 22 and 23 and the flanges 24 and 25 that the invention provides for microwave sealing bonding, and because the air knives have a very high impedance.

Figure 5 - which gives only part of fig. 4 - shows another microwave sealing system, without glue or conductive lacquer. In this case, the hole 31 in the cooling plate 29 is of a diameter such that the plate 29 is hooped onto the body of the pole piece 11. There is therefore mechanical fixing of the one-piece gyrator by the cooling plate 29, and there is no microwave leakage since there is hooping. However, there is however a special seal 33, absorbing the microwaves, around the pole piece 11, and between the plate 29 on the one hand, and the flange 25 and the face 13 on the other hand. In this case, the plate 29 is machined to create a housing there for the seal 33, and a second projecting rim 36, around the pole piece 11, facilitates the centering of the seal 33.

The cooling means 28 and 29 comprise at least one flat plate in close contact with the external surfaces of the faces 12 and 13 of the waveguide. They are wider than the waveguide width, so that they overlap. These plates, once made integral, for example by screws which do not pass through the waveguide, ensure the mechanical rigidity of the gyrator, in its receiving structure and participate in the production of microwave seals.

The plates 28 and 29 may include fins, as in FIG. 4, or tubes allowing the circulation of a fluid, as in fig. 5, or even constitute "water boxes" as in fig. 7. The coolant can still circulate in tubes welded to these plates.

The magnets 8 and 9 can be made of ferrite, or other materials such as samarium-cobalt. They can be glued to the monobloc gyrator, but they can also be positioned by the cooling plates 28 and 29, and held in place by the magnetic circuit 32.

It has been said that the circulator according to the invention has a waveguide of very reduced height, therefore of impedance adapted to that of the gyrator. However, it is known that, in this case, the power which can pass through the circulator is less than if the waveguide is of greater height.

If a large power is required, it is possible to apply the structure described in FIG. 3 and which depends on the French patent FR-A-2 208 202 already cited. The gyrator is then that of FIG. 6.

It is still a monobloc cylinder, but the resonator comprises, between the ferrites 6 and 7 and the dielectric 21 already described, at least a third ferrite 34 and a second dielectric 35, which means that the high-height circulator functions as two low height circulators mounted in parallel. Such a resonator is mounted without a metal plate 20 (see fig. 3) being mounted in the waveguide.

• soit passe à travers un trou pratiqué dans la plaque 20,
• soit est divisé en deux moitiés, chacune étant monobloc et comportant une pièce polaire, un premier ferrite, un diélectrique et un second ferrite, la plaque 20 n'étant pas percée.

However, a metal plate 20 can be mounted in the median plane of the waveguide, in accordance with patent FR-A-2 208 202. In this case, the gyrator:

• either passes through a hole in the plate 20,
• or is divided into two halves, each being a single piece and comprising a pole piece, a first ferrite, a dielectric and a second ferrite, the plate 20 not being pierced.

The circulator according to the invention has been described as a power circulator: the models produced carry 1 KW at 2.45 GHz. However, the structure according to the invention applies to low power circulators. In this case, it may have only one magnet, and the pole piece devoid of a magnet either rests on the main face not pierced with the waveguide, or is blocked by the cooling plate.

The applications of the circulator according to the invention are numerous. In the field of power, they relate to industrial heating, such as the drying of paper or inks, polymerizations, ... In the field of signal processing, the circulator can be integrated in a microwave head, and this up to '' at very high frequencies (at 94 GHz, for example).

The field of the invention is specified by the following claims.

Claims (11)

1. An integrated microwave circulator comprising a waveguide-type junction, a gyrator placed in the center of symmetry of the junction, as well as cooling plates (28, 29) applied to the main faces (12, 13) of the waveguide which are pierced by two circular holes (22, 23), one facing the other and centered onto the center of symmetry of the junction, characterized in that

- the gyrator is a monobloc cylinder comprising at least one magnet (28), a first pole piece (10), a first ferrite (6), a solid state dielectric material (21), a second ferrite (7) and a second pole piece (11), wherein the diameter of these pieces is at most equal to the diameter of the holes (22, 23), said gyrator passing through the holes (22, 23) pierced through the main faces (12, 13) of the waveguide,

- the cooling plates (28, 29) immobilize the gyrator in the waveguide.

2. A circulator according to claim 1, characterized in that the height (h) of the waveguide is adapted to the impedance of the gyrator (8 ... 9), and that its main faces (12, 13) are plain faces inside the waveguide and do not include impedance matching components.

3. A circulator according to claim 1, characterized in that the diameter of the components constituting the gyrator is determined by the concept of the resonator constituted by the ferrites (6, 7) and the solid state dielectric material (21) in accordance with the frequency at which the circulator operates and with the power passing therethrough, and that all these components are glued together.

4. A circulator according to claim 1, characterized in that each pole piece (10, 11) of the gyrator comprises a projecting edge (24, 25) of larger diameter than the remaining parts of the gyrator, each edge (24, 25) being provided with a face (26, 27) outside with respect to the waveguide, which face is coplanar with the outer surface of a main face (12, 13) of the waveguide.

5. A circulator according to claim 4, characterized in that the holes (22, 23) in the main faces (12, 13) of the waveguide present a diameter equal to that of the projecting edges (24, 25) of the pole pieces (10, 11).

6. A circulator according to claim 5, characterized in that each cooling plate (28, 29) is supplied with a hole (30, 31) along the axis of the gyrator, this hole having the same diameter as the pole pieces (10, 11), and that a seal (34, 35), made of conducting glue or varnish and interposed between the pole pieces and the main faces (12, 13) of the waveguide as well as the cooling plates (28, 29), ensures the sealing against microwaves and the thermal continuity between the gyrator and the cooling plates (28, 29).

7. A circulator according to claim 5, characterized in that each cooling plate (28, 29) is supplied with a hole (30, 31) which is coaxial with the gyrator and has the same diameter as the pole pieces (10, 11), and that at at least one cooling plate (29) is press-fitted onto a pole piece (11), a flat seal (33) for protecting against the microwave energy being placed between the cooling plate (29) and the upper face (27) of the projecting edge (25) of said pole piece (11).

8. A circulator according to claim 1, characterized in that the cooling plates (28, 29) are of larger size than the waveguide and are applied against the waveguide by threaded rods outside of the waveguide, thus securing the monobloc gyrator in position.

9. A circulator according to claim 1, characterized in that in case of a high power model, the gyrator comprises at least two series-connected resonators: a first pole piece (10), a first ferrite (6), a first dielectric (21), a second ferrite (34), a second dielectric (35), a third ferrite (7) and a second pole piece (11).

10. A circulator according to claim 1, characterized in that in case of a high power model comprising a metal plate (10) in the central waveguide plane, the gyrator is composed of two monobloc half-gyrators each one comprising a pole piece (10), a first ferrite (6), a solid state dielectric (21) and a second ferrite (34), and each monobloc half-gyrator being secured in position on either side of the metal plate (10) by a cooling plate (28, 29).

11. A circulator according to claim 1, characterized in that in case of a low power model, the circulator only includes one magnet (8), the pole piece (10) which hashaving no magnet being secured either by a cooling plate (28) or by the main face (12) without hole of the waveguide.

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