EP0446107B1 - Transmission system for electrical energy, in the microwave field, with gyromagnetic effect, such as a circulator, isolator or filter - Google Patents

Description

The invention relates to a system for transmitting electrical energy, at microwave frequencies, with a gyromagnetic effect, such as a circulator, insulator or filter, of the type described in the preamble of claim 1.

A system of this type is known from document DE-A-2 607 844.

We know that the limits of use of transmission systems of this type are imposed by the natural resonant frequency of the gyrator, that is to say by the frequency determined by parasitic capacities inherent in the configuration of the constituent elements and of the structure of the whole. A second limit appears when it is desired to transmit power through the system. Generally, the power transmitted is proportional to the diameter of the gyromagnetic pad used and inversely proportional to the transmission losses. Now, the increase in the dimensions of the gyrator device increases the parasitic capacity and is therefore accompanied by a reduction in the natural resonance frequency. It is also known that the transmission losses can be minimized by an appropriate choice of the appropriate magnetic parameters and thus of an optimum coupling coefficient, that is to say close to 1. Such a coupling coefficient is obtained by increasing the number of conductive strands which constitutes the inductance. However, the increase in the number of strands again leads to an increase in the parasitic capacity and consequently a reduction in the natural resonant frequency.

The system according to DE-A-2 607 844 does not give or suggest a solution to this problem.

The present invention aims to propose a transmission system of the type stated above, which at least makes it possible to greatly reduce this parasitic capacity so as to increase the natural frequency and that the other parameters of the system such as the geometric dimensions of the gyrator device , the number of conductive strands of the inductors and the coupling coefficient can be advantageously chosen without this being detrimental to the natural resonant frequency.

To achieve this object, a transmission system according to the invention comprises the characteristics set out in the characterizing part of claim 1.

By document US Pat. No. 349953, a circulator is already known, comprising in the middle between the two gyromagnetic disks and the set of conductors, on either side thereof, stacked one on the other, a dielectric disk. and a disc of metal sheets. The dielectric discs are produced in the form of discs of thin thickness determined to allow the adaptation of the input impedance to the value of the resistance of the load. To this end, the thickness of the discs should be reduced.

Due to this fundamentally different object from that aimed by the invention and to the fact that the dielectric discs must have a small thickness, which is contrary to the invention, the object of document US-A-349953 is fundamentally distinguished from the invention.

Other advantageous features of the invention are described in the dependent claims.

The invention will be better understood and other objects, characteristics, details and advantages thereof will appear more clearly during the explanatory description which follows, made with reference to the appended schematic drawings given solely by way of example illustrating several modes. of the invention and in which.

Figure 1 is a perspective and exploded view of a dielectric power transmission system according to the present invention.

Figure 2 is a sectional view along a vertical plane passing through the line II-II of Figure 1, in the assembled state and on a larger scale.

FIG. 3 is a perspective and exploded view of a first embodiment of the gyrator device 1 according to FIG. 1.

FIG. 4 is a perspective and exploded view of a second embodiment of the gyrator device 1 of FIG. 1.

FIG. 5 is a third embodiment of the gyrator device according to FIG. 1.

Figures 6 and 7 show curves defining the relationship respectively between the limit frequency on the one hand and the admissible power and on the other hand, the diameter of the gyromagnetic pellet.

Referring to Figures 1 and 2, we see that an electrical energy transmission system, microwave, gyromagnetic effect essentially comprises a gyrator device 1 capable of being mounted on a printed circuit board 2 disposed between plates upper and lower respectively 3 and 4 made of metal or a non-magnetic alloy, for example aluminum, each provided with a central bore 5 intended to receive a pole piece 7 for example of steel and a magnet 8. An upper magnetic closure plate 10 and a lower magnetic closure plate 11 are disposed respectively on the free outer surfaces of the upper and lower magnets 8. The assembly is surrounded by a belt 12 consisting of several elements 13, 14, 15 and magnetically connecting the plates upper and lower closure 10 and 11 to close the magnetic circuit. The belt has three connectors 16 which are fixed to three sides of the plates 3 and 4 in the assembled state of the system.

The printed circuit board 2 has in its center a recess 17 adapted to receive the gyrator device 1. The board 2 carries on its upper surface a pattern of bands and electrically conductive zones, namely three substantially radial bands 19 which extend from the edge of the recess 17 to the edge of the plate and are intended to be electrically connected each to the conductor 18 (FIG. 2) of one of the connectors 16, and three zones 20 which are electrically isolated at 21 from the bands 19 and are intended to be in electrical contact with the upper plate 3 which bears on each zone 20 by a pin 22 and constitutes a ground electrode.

It should be noted that each strip 19 is generally connected to the corresponding conductor 18 via an adaptation network, not shown, and comprising LC type cells, in a manner known per se.

Referring to FIGS. 3 to 5, three embodiments of a gyrator device 1 according to the present invention will be described below.

According to a first embodiment, represented in FIG. 3, the gyrator device 1 comprises a configuration of three inductors 23, 24, 25 each comprising two conducting strands 27, 28 arranged in the same plane which are parallel and connected at their indicated ends at 29 and 30. These ends are produced in the form of electrical connection lugs, one of which, for example the lug 29 is connected to one of the earth zones 20 of the printed circuit on the wafer 2 and of the gyrator device while the other tab bearing the reference 30 will be electrically connected to one of the conductive strips 19 of the printed circuit. These inductors 23 to 25 can be made of any suitable conductive metal and have a self-supporting structure. The inductors are electrically isolated from each other by interposition an appropriate insulator. The inductors are arranged so as to be angularly offset by 120 °.

Two discs 32, 33, of circular shape in the example shown, made of an electrically insulating material and of low permittivity are arranged on either side of the configuration of the three inductors 23 to 25. These discs could be discs Teflon or a dielectric material such as ceramic. On each disc 32, 33 is placed a disc 34, 35 respectively of a gyromagnetic material, such as ferrite material. The external face of each gyromagnetic disc is therefore, in the assembled state of the system, in contact with a metallic plane which may or may not be connected to the ground of the system. As can be seen from FIG. 1, the various connecting lugs 29, 30 radially project from the assembly formed by the stack of disks 32 to 35 on the central configuration of the inductors 24, 25, so that they can be electrically connected to the circuit printed brochure 2.

FIG. 4 shows an embodiment of the gyrator device 1 in which the insulating layer, of low permittivity is formed by four discs or plates of thinner thickness 37 to 40 which are stacked between the upper and lower gyromagnetic discs 34, 35. three inductors 23 to 25 are each arranged between two neighboring insulating discs, being angularly offset by 120 °, as shown in Figure 3. In this embodiment each inductor has ten parallel strands. Each inductor can be made so as to present a self-supporting structure or be laid, in the form of a printed circuit on a surface of one of the discs 37 to 40, of course providing a support for the connecting lugs 29, 30. In this embodiment, the discs 37 to 40 are advantageously made made of a dielectric material such as ceramic.

In the embodiment according to FIG. 5, the insulating layer of low permittivity is formed by seven disks 42 to 48 which are stacked between the gyromagnetic disks 34, 35 while sandwiching the inductances therebetween. In this embodiment, each inductor is divided into two halves which, in the whole of the gyrator are juxtaposed and electrically connected in parallel. For example the inductance 23 of FIGS. 3 and 4 is now formed by the two half-inductors 23a and 23b, interposed respectively between the disks 43, 44 and 46, 47, that is to say between two pairs of different disks . In the same way the inductors 24 and 25 are formed respectively by the half-inductors 24a, 24b and 25a, 25b and arranged between two pairs of different discs, as shown in FIG. 5.

The operation of a system according to the present invention, which has just been described by way of example with reference to the figures, will be described below.

The general structure of such a transmission system is known per se and therefore does not need to be described in more detail. The discs made of a gyromagnetic material 34, 35 are immersed in the static magnetic field generated by the magnets 8, as is clear from FIGS. 1 and 2. The magnetic circuit is closed by the plates of upper 10 and lower 11 closure and the belt 12. Via the connectors 16, a perpendicular microwave field is applied to the gyromagnetic material, the wavelength of this field being very large compared to the length of the axes of the gyromagnetic discs, so that the field is uniform in the volume of these.

où L_o est la valeur pour la valeur d'une inductance pour une perméabilité µ_eff = 1 et C' la somme des capacités parasites.The interposition of an insulating layer, of low permittivity between the configuration of the inductors and each disc made of gyromagnetic material makes it possible to reduce considerably, the parasitic capacity due to the dimensions of the conductive strips, of the inductors and of their number of strands and of the thickness of the gyromagnetic material. The strong reduction of this parasitic capacity makes it possible to increase the natural resonant frequency of the gyratory system which is given by the equation: $$\text{F = [2π (}\underline{\text{3}}{\text{L}}_{\text{o}}{\text{.C 'µ}}_{\text{eff}}{\text{)]}}^{\text{-1/2}}$$

where L _o is the value for the value of an inductance for a permeability µ _eff = 1 and C 'the sum of the stray capacitances.

It thus becomes obvious that the natural frequency, that is to say the operation of the gyrator device 1, can be increased by reducing the parasitic capacity C ′. This operating frequency constitutes the limit frequency of the system. Indeed, the frequency to which the system will be granted is determined by the paralleling on each input or access of the gyrator device 1 of a capacity (not shown) and the relative bandwidth as well as the resistance can be modified by means of LC type cells inserted at the entrance of the gyrator device.

où εo, εr, e et S désignent respectivement la permittivité du vide, la permittivité relative de l'isolant, l'épaisseur et la surface de la couche isolante.By placing the insulating layer of low permissibility, in the form of one or more discs, between the two tyromagnetic discs 34, 35 of the device 1, a capacitor C "is introduced which can be written in the form: $$\text{C "= εo. Εr.}\frac{\mathit{\text{S}}}{\mathit{\text{e}}}$$

where εo, εr, e and S denote respectively the permittivity of the vacuum, the relative permittivity of the insulator, the thickness and the surface of the insulating layer.

O% H est l'épaisseur du disque gyromagnétique.This capacity C "can be assumed to be in series with the parasitic capacity C 'and by choosing the smallest possible εr and the greatest possible thickness, the introduced capacity C' takes on a value so small that the total capacity is strongly For example, the product protected by the Teflon mark has an εr = 2. Concerning the thickness of the insulating layer, in the embodiment according to FIG. 5, each Teflon disc could have a thickness of 0 , 1 mm, which gives a total thickness of the insulation of 0.7 mm. Generally, the maximum thickness is a function of the thickness of the gyromagnetic discs and is roughly determined by the term $${\text{E}}_{\text{max}}\text{=}\frac{\text{2}\mathit{\text{H}}}{\text{3}}$$

O% H is the thickness of the gyromagnetic disc.

It has been found that the limit frequency F of a gyrator according to the invention is multiplied by √K compared to a conventional gyrator if K is the coefficient by which the parasitic capacity has been reduced by providing the insulating layers of low permittivity , as just described.

The addition of insulator of low permittivity and relatively high thickness of 1 to several tenths of a millimeter also makes it possible to increase the dimensions of the discs of gyromagnetic material and the number of strands constituting the inductors and thus improve the coefficient of coupling. The admissible power can be multiplied by two or three taking into account the lower thermal resistance, the larger heat exchange surfaces and a better distribution of energy inside the gyromagnetic material. Thanks to the measures which have just been indicated, it is possible to reduce the losses and increase the relative frequency band.

Figures 6 and 7 which respectively show the limit frequency F (in MHz) and the admissible power Pa (in Watts), as a function of the diameter D of the disc made of gyromagnetic material, such as ferrite material, (in cm) confirm what has just been said. In each figure, curve A gives the values of a system typical of the conventional technique, while curve B gives the values which have been measured, under the same conditions as for curve A, of a system according to the invention, that is to say comprising an insulator of low permittivity and a high thickness between the configuration of the inductors and the gyromagnetic ferrite discs.

It has further been found that the relative passing frequency bands of a system according to the invention can have a width which is twice that of a known system in the low frequency zone of 30 MHz.

The improvements which have just been stated can be applied to various types of systems, in particular all those which require reciprocal coupling or not, such as circulators, isolators and filters.

The techniques for implementing the invention can be diverse. The layer added to reduce the parasitic capacity can be an insulator of the adhesive type or not, a dielectric such as ceramic of low permittivity, or the like. The printed circuits can be simple or double-sided or of the multilayer type. The shape of the pellets of gyromagnetic material can have any other known suitable shape. It is the same with regard to the insulating layer 8 and the inductors. The number of pads and insulating layers may vary. The invention is also applicable to a system structure using only one gyromagnetic pad on which the configuration of the inductors will be placed, with interposition for curve A, of a system according to the invention, that is to say comprising an insulator of low permittivity and of a high thickness between the configuration of the inductors and the gyromagnetic ferrite discs.

It has further been found that the relative passing frequency bands of a system according to the invention can have a width which is twice that of a known system in the low frequency zone of 30 MHz.

The improvements which have just been stated can be applied to various types of systems, in particular all those which require reciprocal coupling or not, such as circulators, isolators and filters.

The techniques for implementing the invention can be diverse. The layer added to reduce the parasitic capacity can be an insulator of the adhesive type or not, a dielectric such as ceramic of low permittivity, or the like. The printed circuits can be simple or double-sided or of the multilayer type. The shape of the pellets of gyromagnetic material can have any other known suitable shape. It is the same with regard to the insulating layer 8 and the inductors. The number of pads and insulating layers may vary. The invention is also applicable to a system structure using only one gyromagnetic pad on which the configuration of the inductors will be placed, with interposition at least one insulating layer of low permittivity. Of course, the number of access fittings can be different and vary between two and a higher number.

Claims (9)

1. Electric power transmission system for hyperfrequencies with a gyromagnetic effect such as a circulator, isolator or filter, comprising a gyrator device (1) including at least one advantageously disk-shaped chip made from gyromagnetic material such as ferrite material, one side of which being coupled to a reference potential, and a device of at least two tuning inductors (23 to 25) electrically insulated from one another and arranged on the other face of said chip and at least one end thereof is coupled to the ground of the gyrator device (1) whereas the other end is coupled to the depend input terminal of the transmission system, the gyrator device (1) being subjected to a homogeneous magnetostatic field for activating the gyrator, characterized in that a disk from an electrically insulating material of a small permittivity is mounted at least between the inductor device and the corresponding gyromagnetic material disk, said disk having a predetermined thickness forming as capacitor means mounted in series with the interference capacities of the gyrator device a means for increasing the natural resonance frequency of the gyrator device (1) by increase of its thickness and reduction of its relative permittivity.
2. System according to claim 1, characterized in that the overall thickness of the said insulating disk material depends from the thickness of the gyromagnetic device and is approximately determined by the terms $${\text{E}}_{\text{max}}\text{=}\frac{\text{2H}}{\text{3}}$$

   

   where H is the thickness of the gyromagnetic disk and E_max is the overall maximum thickness of the insulating layer means.
3. System according to any of claims 1 or 2, comprising two chips (34, 35) made from a gyromagnetic material on both sides of the device of the inductor set (23 to 25), characterized in that a chip (32, 33) from an electrically insulating material of small permittivity is provided between the inductor device (23 to 25) and each gyromagnetic chip (34, 35).
4. System according to claim 3, comprising three inductors (23 to 25) angularly espaced by 120° from each other, characterized in that an electrically insulating disk of small permittivity (38, 39) is mounted between the central inductor (25) and each of the other inductors (23, 24).
5. System according to claim 4, characterized in that the inductors (23 to 25) are stacked and realised as flat circuit elements formed by two portions mounted electrically in parallel relationship with one another and each inductor portion is located in a different plane in the stack and that a said disk of small permittivity electrically insulating material (43 to 47) is placed between two juxtaposed inductor portions.
6. System according to any of claims 3 to 5, characterized in that one inductor (23 to 25) or inductor portion (23a, 23b to 25a, 25b) is realised as printed circuit on one face of an insulating plate (37 to 40 ; 42 to 48).
7. System according to any of claims 1 to 6, characterized in that an inductor (23 to 25) comprises a certain number of conducting elements, advantageously between 2 and 10.
8. System according to any of the foregoing claims, characterized in that it comprises three inductors angularly shifted by 120°.
9. System according to any of the foregoing claims, characterized in that the total thickness of the insulating disks is about 0,7 mm for an isolator having a relative permittivity of about 2, such as Téflon.

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