WO1999028991A1

WO1999028991A1 - Transducer for transmitting-receiving microwave radio energy

Info

Publication number: WO1999028991A1
Application number: PCT/FR1998/002523
Authority: WO
Inventors: Maurice Chive; Luc Dubois
Original assignee: Universite Des Sciences Et Technologies De Lille
Priority date: 1997-11-27
Filing date: 1998-11-25
Publication date: 1999-06-10
Also published as: FR2771552B1; FR2771552A1

Abstract

The invention concerns a transducer for transmitting-receiving microwave radio energy, comprising first (1) and second (2) electrically conducting zones connected to a third electrically conducting zone (3) placed in the same plane. A transmission line (4) is coupled with the first (1) and second (2) electrically conducting zones. The invention is applicable to treatment by radiation hyperthermia and the measurement of temperature of a body by capturing its radiation.

Description

Microwave radio transmission-reception transducer

The present invention relates to a microwave radio transmission-reception transducer.

At present, the transducer elements used to bring microwave radio energy onto or into a body, or to capture the electromagnetic radiation of thermal origin from the latter, are essentially of the following type:

- waveguides open or loaded with an appropriate impedance;

- radiant cones; - wire antennas;

- applicators in plated structure.

The last type of transducer elements have many advantages, they are easy to implement, light, inexpensive and can easily be combined to form a network configuration.

Transducer elements of this type have been the subject of specific studies and of a description in French patent applications No. 2,539,035 published on July 13, 1984, No. 2,703,871 and No. 2,703,872 published on October 14, 1994.

In general, these transducer elements have two separate electrically conductive structures, at least one of these structures playing the role of radiating element and the other that of an element brought to a reference potential. The operation of such transducers can be globally assimilated to that of a radiating dipole.

Due in particular to the distinct nature of the two electrical structures, and in order to ensure, on the one hand, an electrical separation, and, on the other hand, sufficient mechanical and geometric cohesion thereof, as well as a simplification of implementation by use of a manufacturing technique similar to that of printed circuits, such elements are produced from dielectric supports, such as for example epoxy-fiberglass used for the production of quality printed circuits allowing transmission and processing microwave signals.

However, the necessary presence of such a support imperatively imposes a power limitation on the use of these transducer elements, in particular when these are used as microwave energy emission transducers. This limitation is in fact due to the losses of microwave energy in the electrical support. Although small, these losses can lead to excessive heating of the dielectric support, and ultimately the destruction of the latter.

In addition, when these transducer elements are used in reception, in the context of radiometric applications consisting in capturing radiation of thermal origin emitted by a body placed opposite the transducer element, the presence of this dielectric support, although at low losses, generates, due to its own temperature, a parasitic thermal noise, very difficult to quantify. This noise is added to the signals received from the medium or the body analyzed and thus falsifies the temperature measurement by radiometry.

Such a disturbance in the radiometric temperature measurement is particularly harmful when the radiometric temperature measurement operation is carried out for a body brought to high temperature, above 50 ° C., or to low temperature, below 5 ° C.

The use of systems for thermostating the dielectric support, cooling or heating at constant temperature, does not in any way eliminate the thermal noise due to the losses of the latter. The subject of the present invention is the implementation of a radioelectric energy transmission-reception transducer microwave stick to overcome the drawbacks of plated transducer elements 1 prior art.

Another object of the present invention is in particular the implementation of a microwave radio transmission-reception transducer in which the dielectric support is completely eliminated or, where appropriate, whose contribution to thermal noise is substantially scaled down. Another object of the present invention is finally the use of specific microwave radio-frequency energy transmission-reception transducers, allowing the production of transducer networks adapted to various applications. The microwave radio emission-reception transducer, object of the present invention, is remarkable in that it comprises at least a first zone, electrically conductive, substantially planar, brought to a reference potential, a second zone, electrically conductive, superimposed in the same plane on the first electrically conductive zone, and a third, intermediate zone, partially connecting the first and the second electrically conductive zone. A transmission line comprising a first and a second electrically conductive element is coupled to the electrically conductive zones, the first conductive element being interconnected to the first electrically conductive zone and brought to the reference potential, and the second conductive element being electrically coupled to the second electrically conductive area.

It will be better understood on reading the description below and on observing the drawings in which:

- Figures la, 2a, 3a and 4a show a transducer for transmitting and receiving microwave radio energy in various particular, non-limiting embodiments; FIGS. 1b, 2b, 3b and 4b represent the adaptation diagrams which make it possible to judge the quality of the transfer of energy in transmission or in reception of each transducer of transmission / reception of radio frequency microwave energy represented in FIGS. 2a, 3a and 4a respectively;

- Figures 5a to 5g show different alternative embodiments of transmission / reception transducers of microwave radio energy, according to the object of the present invention;

- Figure 6a shows an advantageous, non-limiting embodiment of a network of transducers formed from a plurality of transducers corresponding to a type of transducer as shown in Figures la, 2a, 3a or 4a;

- Figure 6b shows an advantageous variant of a transducer used in a network of transducers as shown in Figure 6a;

FIG. 6c represents a detail of execution of a transducer used in a network of transducers represented in FIGS. 5a or 5b, or even for any type of transducer represented in FIGS. 1a, 2a, 3a or 4a;

FIG. 7 represents a network of transducers in accordance with the object of the present invention more particularly intended for successive irradiation operations for treatment of a body by hyperthermia, then of thermometric measurement of this body by microwave radiometry;

FIG. 8 represents, in a sectional view along a radial plane of symmetry, an installation for treating a body, constituting a dissipative medium, this installation comprising a network of transducers as shown in FIG. 7.

A more detailed description of a microwave electrical energy transmission-reception transducer, in accordance with the object of the present invention, will now be given in conjunction with FIG. 1a and FIG. 1b. With reference to the aforementioned figures, it is indicated that, in general, the microwave radio emission-reception transducer, object of the present invention, comprises, at least, a first substantially planar electrically conductive area, denoted 1 , which is brought to a reference potential such as a ground potential for example.

The transceiver transducer, object of the present invention, further comprises a second zone, denoted 2, electrically conductive, substantially planar, which is superimposed in the same plane on the first electrically conductive zone 1. The first zone 1 and the aforementioned second zone 2 are then, as shown in the same figure, connected by a third intermediate zone 3. This third zone 3 partially connects the first 1 and the second electrically conductive zone 2 and makes it possible to ensure electrical continuity between this first and this second zone mentioned above.

It is thus understood, on observation of the aforementioned figure, that the first 1, the second 2 and the third zone 3 are thus placed in the same plane, all the zones thus arranged having substantially the shape of a U, as shown in the drawings.

In addition, a transmission line, denoted 4, comprises a first and a second electrically conductive element, denoted 41 and 42, the first conductive element 41 being interconnected with the first electrically conductive zone 1 and therefore being brought to the reference potential. , while the second conductive element 42 is itself electrically coupled to the second electrically conductive zone 2.

In a nonlimiting embodiment given by way of example only in FIG. 1a, it is indicated that the aforementioned transmission line 4 can advantageously be constituted by a coaxial cable of which the external metal shield 41 constitutes the first element electrically conductive and whose central core 42 constitutes the second conductive element.

In such a case, both the external conductor 41 and the central core 42 can be brazed respectively on the first electrically conductive zone 1 and on the second electrically conductive zone 2.

With regard to the operating mode of the microwave radio transmission-reception transducer represented in FIG. 1a, it is indicated that this, unlike the transducers currently known implementing a resonance or at least tuning process. the geometry of the radiating elements with respect to the radiated wavelength, that is to say emitted or received, the transducer of emission-reception of radioelectric energy, object of the present invention, operates so different in that it constitutes in fact a reflector making it possible to ensure a reflection coefficient substantially equal to 1 for a very wide frequency spectrum, except for a determined frequency band for which the reflection coefficient is greatly degraded, the microwave radio transmitting and receiving transducer, object of the present invention, therefore acting in this band of fr equences as an element allowing the transmission in transmission, and respectively in reception, from the transmission line, of radioelectric energy whose frequency band corresponds to the frequency band not reflected by the latter.

A diagram representing the reflection coefficient defined by | S _X1 1 expressed in decibels for the transceiver of microwave radioelectric energy transmission, object of the present invention, as represented in FIG. 1a, is represented in FIG. 1b, the abscissa axis being graduated in GHz and the ordinate axis being graduated in attenuation expressed in dB relative to the reflection value thus constituting the zero level.

First, it is indicated that, as the central quence of the radioelectric energy thus transmitted as the bandwidth of frequencies transmitted by the transceiver transducer of microwave radioelectric energy represented in FIG. la, are physically dependent on the geometric dimensions of the latter.

In a particularly advantageous embodiment of the microwave radio transmission-reception transducer, object of the present invention, it is indicated that the first 1, the second 2 and the third 3 electrically conductive zones have come from a single sheet of electrically conductive material, such as a metallic sheet. This sheet of electrically conductive material is then provided with a cutout 5 with substantially parallel edges, this cutout thus making it possible to materialize the first 1, the second 2 and the third 3 electrically conductive zones.

It will of course be understood that the characteristics relating to the central frequency and to the width of the frequency band of the radioelectric energy transmitted, either in transmission or in reception, by the transducer which is the subject of the present invention, closely depend on the geometric dimensions constituting the latter.

With reference to FIG. 1a, these parameters or geometric dimensions will be defined in the following manner:

- a and b denote the maximum external dimensions of the microwave radio transmission-reception transducer, in accordance with the subject of the present invention, or, more precisely, the dimensions of a rectangle or a square in which the first, second and third electrically conductive zones are inscribed. When a = b, the electrically conductive areas are inscribed in a square;

- c ₂ and c ₂ denote the maximum dimension of the first, respectively of the second electrically conductive area 1, 2, in a direction parallel to the dimension a;

- d denotes the length of the slot 5 with parallel edges in a direction substantially parallel to dimension b;

- e denotes the width of the slot 5 in a direction substantially parallel to the dimension a;

- h denotes the dimension of the third electrically conductive zone in a direction parallel to the dimension b;

- f denotes the distance from the coupling point of the second electrically conductive element of the transmission line to the second electrically conductive area 2 relative to the external edge of the transducer on the slot 5;

g denotes the distance separating this same interconnection point from the internal edge of the slot 5, that is to say from the third electrically conductive zone 3.

For parameter values as represented in FIG. 1a, given by the table below:

the central frequency of the transmitted radioelectric energy, as represented in figure lb, was worth 9.21 GHz for a bandwidth at -10 dB, that is to say an attenuation of 10 dB compared to the zero level , equal to 1.73 GHz. It will thus be understood that the microwave radio emission-reception transducer, object of the present invention, is of a particularly simple implementation insofar as the production of the first, second and third zones from a single sheet of electrically conductive material can be made in a particularly simple manner from a rectangle of metal sheet or plate, in the absence of any dielectric support, with determined outer external dimensions a and b, in which a slot 5 is cut having the dimensions d and e previously mentioned.

When the transmission line is formed by a coaxial cable 4, the latter is then stripped at its connection end, so as to release the central core 42. The central core 42 and the electrically conductive envelope 41 are then connected by soldering, for example, to the second 2 and to the first 1 electrically conductive zones respectively offset from the third 3 zone of dimension g. Various descriptive elements making it possible to illustrate the physical dependence of the adaptation parameter | S ₁ 1 in transmission of the transducer, object of the present invention, with respect to the geometric dimensions of the latter, will now be given by way of illustration. For a substantially rectangular slot 5, the transducer, object of the present invention, has a maximum external dimension, that is to say a dimension a, b, between λ _0/4 and λ _0/2 , with λ ₀ = c / f ₀ where f ₀ represents the central frequency of the frequency band transmitted or received by the transducer, object of the present invention, and c represents the speed of light in air.

The influence of the different geometric parameters of the structure on the value of the central frequency f ₀ is illustrated below for a transducer element according to FIG. 1 taken as a reference, having the following initial dimensions: a = 28 mm; b = 32 mm; vs. = c ₂ = 12 mm, d = 28 mm; e = 4 mm, f = 17 mm; g = 13 mm.

With regard to the central frequency f ₀ of the transmitted or received frequency band, it is indicated that this is inversely proportional to the length d of the cutout or slot 5, that is to say to the dimension d of this one, as illustrated by the table below.

Table variation of the frequency f of use as a function of da = 28 mm; c _α = c ₂ = 12 mm; e = 4 mm; g = 13 mm.

Likewise, in general, the transducer, object of the present invention, has a central transmit-receive frequency of the frequency band of transmitted or received radio energy inversely proportional to the distance e separating the parallel edges of cutout 5, as illustrated by the table below.

Table variation of the frequency f _A of use as a function of ea = 28 mm; b = 32 mm; d = 28 mm; g ≈ 13 mm

In a preferred embodiment, the third electrically conductive zone 3 in fact forms a short circuit between the first 1 and the second 2 electrically conductive zones and the cutout 5 has, at the level of the third electrically conductive zone 3, a substantially orthogonal to the parallel edges of the cutout 5. In this case, the central frequency f ₀ of the strip of frequencies of transmitted or received radioelectric energy is proportional to the distance g separating the connection point offset from the coaxial line from the edge orthogonal to the parallel edges of the cutout 5 and materializing the third electrically conductive area 3, as illustrated by the table below.

Frequency variation table f. use depending on ga = 28 mm; b = 32 mm; c _x = c ₂ = 12 mm; e = 4 mm.

The central frequency f ₀ of the frequency band transmitted or received by the transducer is inversely proportional to the maximum external dimension of the transducer in the direction of the coaxial cable, that is to say in the direction of the dimension a, reduced by the distance e separating the parallel edges of the cutout 5. In other words, the central frequency f ₀ of the frequency band transmitted in transmission or reception is therefore inversely proportional to the sum of the parameters c and c ₂ , as well as 'illustrated by the table below.

Frequency variation table f. of use as a function of c ₁ and c ₇ b = 32 mm; d = 28 mm; e = 4 mm; g = 13 mm

Finally, for a central frequency f ₀ of the frequency band transmitted or received by the transducer according to the object of the present invention, the width of the frequency band transmitted or received is substantially inversely proportional to the distance separating the parallel edges of the cutout 5, that is to say the parameter e, and substantially proportional to the maximum external dimension of the transducer in the direction of the coaxial cable, or of the transmission line, that is to say substantially proportional to the sum of the parameters c_ and c ₂ .

In order to materialize the laws of dependence of the radioelectric parameters' adaptation in transmission and reception of the transducer, object of the present invention, with respect to the geometric dimensions of the latter, various examples of embodiment of particular transducers, in accordance with the object of the present invention will be described in connection with Figures 2a and 2b, 3a and 3b, 4a and 4b.

In the context of the embodiment shown in FIG. 2a, the general shape of the transducer, that is to say of the first 1, of the second 2, of the third 3 zones is substantially circular. In general, the geometric shape formed by the outer edge of the first 1, the second 2, and the third 3 zones, is substantially polygonal or circular.

In addition, the assembly formed by the first, 1, the second 2 and the third 3 zone, as well as the cutout 5 with substantially parallel edges, advantageously has symmetry with respect to the longitudinal axis of symmetry, materialized by X ' X on the set of the aforementioned figures of cutout 5.

In the context of the embodiment of FIG. 2a, the different geometric parameters had the following values:

As also shown in FIG. 2b, the central frequency f ₀ is equal to 3.23 GHz and the bandwidth at -10 dB is equal to 0.6 GHz.

In the case of the embodiment of FIG. 3a, the geometric parameters had the following value:

In this embodiment, as shown in FIG. 3b, the central frequency f ₀ is equal to 3.0 GHz and the bandwidth width at -10 dB of the radio energy transmitted in transmission-reception is equal to

0.43 GHz.

Finally, the embodiment of FIG. 4a corresponds to a particular polygonal shape of the assembly formed by the first, the second, the third electrically conductive zone previously mentioned, in which the general, polygonal shape is inscribed in a rectangle of corresponding dimension a and b.

In the embodiment shown in FIG. 4a, the values of the geometric parameters are indicated in the table below:

While the general shape corresponds to that of a rectangle completed by a circular part constituting the common external edge of the first, second and third zones opposite to the opening of the slot 5, the central frequency f ₀ in this embodiment is equal to 3.27 GHz and the bandwidth at -10 dB of the radio energy transmitted in transmission-reception is equal to 0.278 GHz. In general, it is indicated that, at the first

1, second 2, and third 3 zones interconnected by the coaxial cable 4, can also be associated with a metal plate 6, or, where appropriate, a metal housing placed in a plane parallel to the electrically conductive zones, as shown in FIG. 5a. The metallic casing or reflective metallic plane 6 is then placed substantially in a plane parallel to the electrically conductive zones 1, 2 and 3, on the transmission line or coaxial cable side, as shown in the above-mentioned figure. The metal plate or the metal case open on one side thus improves the directivity of the transducer. The microwave radio emission-reception transducer, object of the present invention, as shown in FIG. 5a, can then be easily installed on an industrial site in the absence of significant modifications to the environment of the transducer.

It will be noted, as shown previously in the description in conjunction with FIGS. 1a to 5a, that the transducer in transmission-reception of radioelectric energy that, in accordance with the object of the present invention, can easily be implemented in the absence of any dielectric support of the first, second and third electrically conductive zones previously mentioned. In such a case, the absence of dielectric material results in the possible use of this type of transducer, both on emission and on reception, in hyperthermia treatment applications when the transducer is used for emission, respectively measurement of the internal temperature of a body by radiometry when this transducer is used in reception.

It will be understood in particular that this type of transducer is particularly well suited to a dual use of this "type, ^by switching the transmission or reception channels of an appropriate device, not shown in the drawings, for internal temperature measurement. of the body, by radiometry, which can particularly advantageously be carried out in the absence of any temperature error introduced by the own radiation of a dielectric support which would be added in order to ensure the implementation of such a transducer .

However, when the transducer, object of the present invention, is intended for a single use in reception for the measurement of the temperature of a body by radiometry for medical applications, it may be advantageous, as shown in FIG. 5b , to produce all of the first, second and third electrically conductive zones from a sheet of KAPTON metallized on one of its faces, in which, in addition to the cut allowing the materialization of the polygon or of the outer circle of the assembly, the slot is then cut. In this case, all of the electrically conductive zones are then supported by the KAPTON sheet with the same dimensions as those of the metallization constituting the aforementioned assembly and bearing the reference 7 in FIG. 5b. The clean KAPTON sheet- ment said 7 may be of small thickness, 1 mm for example, or even 50 μm, in order to thus constitute a strip of dielectric material common to the aforementioned electrically conductive areas. The dielectric material chosen, such as KAPTON, is a dielectric material with low radioelectric losses.

Different advantageous embodiments of a microwave radio transmission-reception transducer, in accordance with the object of the present invention, in the case where this transducer formed by the first, second and third electrically conductive zones 1 , 2, 3 above, further comprises a layer or substrate of dielectric material supporting one set thereof, will now be given in connection with Figures 5c, 5d and 5e.

FIG. 5c corresponds to the case where the transmission line coupled to the first and to the second electrically conductive zone is constituted by a coaxial line, as shown in FIG. 1a for example. However, the aforementioned first, second and third electrically conductive zones can in this case be produced from a dielectric substrate comprising a metallization on one of its faces, the cutout 5 being formed for example on the single metallization. In the same way, FIGS. 5d and 5e also show the implementation of a microwave radio transmission-reception transducer, in accordance with the object of the present invention, in which a dielectric substrate is associated with 1 'set of electrically conductive areas, but where however the transmission line coupled to the latter is constituted by a microstrip or microstrip line. In such a case, the transducer, object of the present invention, comprises successively, in successive parallel planes distributed in a direction orthogonal to the plane containing the first, the second and the third zone, a first layer of dielectric material provided, on the face opposite to the plane containing the electrically conductive areas, with a line of microstrip type replacing the coaxial line. Such an embodiment is represented in figure

5d.

In addition, as shown in FIG. 5e, a second layer of dielectric material 41 can be provided so as to cover the first layer 40 of dielectric material and the microstrip line to produce a protected microstrip line.

Finally, a metallization playing the role of reflective plane 6 can then be provided, so as to cover the opposite face of the second layer of dielectric material covering the first.

In the case of the embodiments of FIGS. 5d and 5e, the microstrip or microstrip line is then coupled in a manner known per se in the context of the implementation of the microstrip and microstrip lines, so capacitive to the aforementioned electrically conductive zones 1, 2 and 3. The reflective plane 6 of FIG. 5e plays the same role as in the case of FIG. 5a.

FIGS. 5f and 5g relate to a more particular embodiment of the transducer in transmission-reception of microwave radio energy, object of the present invention, more particularly intended for medical or biomedical applications.

Figure 5f shows a front view of such a transducer and Figure 5g shows a sectional view along the section plane Q of Figure 5f of the same transducer.

In such a type of application, all of the electrically conductive zones 1, 2 and 3 can advantageously be produced from a thin sheet of KAPTON with a thickness of the order of 75 μm, metallized on a of its faces, this sheet of KAPTON bearing the reference 40 on the Figure 5g. The assembly constituted by the transducer and the transmission line represented in the form of a coaxial line for example in the case of FIGS. 5f and 5g, can then advantageously be coated in a flexible non-allergenic material, bearing the reference 43. The coating thus formed advantageously makes it possible to produce an application tablet on sensitive biological tissues for example. The thickness of the assembly, represented in the cutting plane of FIG. 5g, does not then exceed a value of one order of 5 mm and the diameter of the circular zone constituting the application patch as shown in figure 5f or 5g does not exceed 30 mm. Metallization playing the role of reflective plane 6 is produced on the external face of the non-allergenic material in a plane parallel to the electrically conductive zones 1, 2 and 3.

Of course, because of its particularly simple mechanical structure, the radio-electric transmission-reception transducer, object of the present invention, lends itself particularly well to the production of elementary form-transmitting and / or receiving transducers. complex, which can then be organized into networks, as will be described below in the description.

As shown in particular in FIG. 6a, such a network of microwave radio transmission-reception transducers may comprise a plurality of radio-frequency transmission-reception transducers, as described previously in the description. In FIG. 6a, these transducers are shown in a nonlimiting manner as having a rectangular shape, the opening of the slot 5 or cutout being oriented in the same direction.

As will be observed in FIG. 6a above, the plurality of radio-frequency transmission-reception transducers is then arranged in a common plane in a bidirectional matrix, in an XY direction along two substantially orthogonal directions. Each transducer, noted T _{± i} in FIG. 6a, can then be identified by its address in XY as shown in FIG. 6a. Preferably, the arrangement of transducers can be produced from a dielectric support, denoted SD, substantially rigid, in which different windows are provided at the location of each of the transducers T _i . Each window Fi _j is then adapted so as to have suitable dimensions so as to provide a space communicating with the cutout or slot 5. This space communicating with the slot or cutout 5 makes it possible to ensure the operation of each transducer ^r ∑ _ij in suitable radiation conditions in transmission and reception, independently of the presence of neighboring transducers. Preferably, each transducer _i can be provided with an independent microwave power supply / reception control system.

Preferably, and in order to simplify the implementation of a network of radio-electric transmission-reception transducers as shown in FIG. 6a, it is indicated that each transducer T _{i; j} advantageously has the same geometric dimensions and, consequently, the same radiation parameters, center frequency and width of the transmitted frequency band at -10 dB. Under such conditions, it is indicated that the independent microwave radio power / reception control system can advantageously be constituted by coaxial cables, represented in dotted lines in FIG. 6a due to the fact that these coaxial cables are placed by example behind the plan of the dielectric support SB, these coaxial cables being able to be connected by magic tees, ensuring a suitable transmission of the radio frequency microwave energy in emission and reception, as well as microwave switches allowing the control of the separate supply of either of the transducers Finally, in a particularly advantageous embodiment, as shown in FIG. 6b, each transceiver transducer T _{± j} can advantageously be mounted for rotation relative to an axis of rotation contained in the common plane of the electrically conductive areas 1 , 2 and 3, this axis of rotation being symbolized by the axis of a motor bearing the reference R in FIG. 6b. The axis of rotation R and consequently each transmit-receive transducer T _ii is also mechanically coupled to a rotation drive means, designated by M, around the aforementioned axis of rotation R. The drive means M can be produced for example by a micro-motor, such as a stepping micro-motor, for example. This embodiment thus makes it possible to modify the orientation in inclination of each transmission-reception transducer with respect to the common plane and thus to adapt the transmission-reception diagram resulting from the network, for a given application.

In addition, FIG. 6c represents a possible mode of connection of each magic tee, denoted TE _{i :)} in FIG. 6a, to the electrically conductive zones constituting each transducer T _{± J.}

The embodiment of the network of microwave radio transmission-reception transducers, as shown in FIGS. 6a to 6c, makes it possible to minimize the parasitic radiation due to the dielectric substrate SB. In fact, unlike conventional type plated antennas for which the electric field is very large inside the dielectric substrate, this field thereby introducing a non-negligible contribution into the total radiometric signal, the arrangement of each transducer T _ii in each window formed in the dielectric substrate SB thus makes it possible to greatly reduce the parasitic signal introduced into the resulting radiometric signal. Of course, other forms of networks using a plurality of transmit-receive transducers in accordance with the object of the present invention, can be envisaged.

A particularly advantageous embodiment, intended for biomedical applications for example, will now be described in conjunction with FIGS. 7 and 8.

According to FIG. 7, the microwave radio emission-reception transducer comprises a set of transducers, which are organized with respect to a center of symmetry, denoted C. These transducers are organized according to an elementary emission transducer, this elementary emission transducer being formed by a plurality of transducers, denoted TE .., TE ₂ , TE ₃ and TE ₄ , which are oriented at 90 ° from each other in the plane of the figure. The abovementioned emission transducers are supplied from a common source of microwave energy, for example by means of a coaxial cable and magic tees, as described previously in relation to FIG. 6a.

The microwave radio emission-reception transducer represented in FIG. 7 also comprises, organized with respect to this same common center of symmetry C, a plurality of microwave radio energy transducers, denoted T ^ TR ₂ , TR ₃ and TR ₄ , which are connected to a common microwave energy receiving circuit. The above transducers can be connected via a coaxial line and magic tees in the same way as in the case of emission transducers. The transducers TR_ to TR ₄ are organized into an elementary transducer called reception.

In a particularly advantageous embodiment, as shown in FIG. 7, the microwave radio transmission-reception transducers 1E ₁ to TE ₄ and TR _} to TR ₄ each consist of a first 1, a second 2 and a third 3 electrically conductive zones, forming a circular sector provided with a cutout 5, which is placed on the longitudinal axis of symmetry of each of the aforementioned circular sectors. The transducers TR _X to TR ₄ are also distributed in the plane at 90 ° from each other, the transducers TE- _L to TE ₄ and TR _X to TR ₄ being furthermore nested and distributed in petals relative to the center of symmetry C, as shown in FIG. 7.

In FIG. 7, the constituent elements of each of the aforementioned transducers have thus been shown for the TE _X and TR _X transducers alone, so as not to overload the drawing. It is thus understood that the transducers TE _X to TE ₄ operate as applicators of radioelectric energy, while the transducers TR _X to TR ₄ operate on the contrary in radiometric sensors. FIG. 8 shows a complete installation enabling hyperthermia treatment and a radiometric temperature measurement of a dissipative medium to be carried out, this installation being provided with a transducer as shown in FIG. 7. FIG. 8 is shown in a section plane corresponding to the section plane X'X of FIG. 7. The installation therefore includes a metal case, denoted BM, provided at its open end with a peripheral tube made of plastic material, denoted TU, this tube being intended to receive a circulation of water at constant temperature. The metal housing is provided at its top with an infrared sensor centered on the center of symmetry C of the transducer, this infrared sensor thus being in direct vision of the central opening of the transducer shown in FIG. 7. The IRC infrared sensor makes it possible to carry out radiation measurements of the dissipative medium, in order to control the temperature evolution of the assembly, mainly of its surface.

A particularly efficient microwave radio transmission-reception transducer has thus been described, insofar as this type of transducer can be used in treatment by micro- hyperthermia. wave controlled by microwave radiometry for medical treatment. In such a case, the transducer can then be designed so as to operate both in transmission and in reception, alternately. This type of microwave radio transmission-reception transducer can also be used as a temperature sensor. A particular embodiment made it possible to produce a specific sensor of small size, intended to operate in a range of temperatures between 25 and 45 ° C., in order to non-invasively monitor the internal temperature of premature newborns. In such a case, of course, the structure of the transducer is substantially simplified and may correspond to that shown in FIG. 5f. Another particular embodiment made it possible to produce a specific sensor intended to operate in a range of temperatures between -40 ° C. and + 50 ° C., in order to non-invasively control the internal temperature of materials of the agro-food type. in the freezing or deep-freezing phase. In such a case, the structure of the transducer corresponds to that shown in FIG. 5a.

Claims

1. Transceiver for transmission and reception of microwave radio energy, comprising at least a first zone, electrically conductive, substantially planar, brought to a reference potential, a second zone, electrically conductive, substantially planar, superimposed in the same plane at the first electrically conductive zone, a third, intermediate zone, partially connecting the first and the second electrically conductive zone and ensuring the electrical continuity between the first and the second electrically conductive zone, the first, the second and the third zone having come from a single sheet of electrically conductive material, said sheet of electrically conductive material comprising a cut, with substantially parallel edges, materializing the first, the second and the third zone, a transmission line comprising a first and a second element electrically c a conductor, the first conductive element interconnected to said first electrically conductive area being brought to the reference potential and the second conductive element being electrically coupled to the second electrically conductive area, characterized in that said cutout is substantially rectangular, said transducer having an external dimension maximum between λ _0/4 and λ _0/2 with λ ₀ = c / f ₀ where f ₀ represents the center frequency of the frequency band transmitted or received by said transducer and c represents the speed of light in the air .

2. Transducer according to claim 1, characterized in that said transmission line is formed by a coaxial cable stripped at its connection end, so as to release the central core, the central core and the electrically conductive casing being connected to the second respectively the first electrically conductive zone offset from said third zone.

3. A transducer according to claim 1, character- ensures that said transducer has a central frequency f ₀ of the frequency band transmitted or received inversely proportional to the length of said cut.

4. Transducer according to claim 1, characterized in that said transducer has a central frequency f ₀ of the frequency band transmitted or received inversely proportional to the distance separating said parallel edges of the cutout.

5. Transducer according to claims 1 and 2, characterized in that said third zone forming a short circuit between the first and the second zone, said cutout has at said third zone an edge substantially orthogonal to said substantially parallel edges, said frequency center of the transmitted or received frequency band being proportional to the distance separating the connection point offset from the coaxial line of the substantially orthogonal edge materializing said third zone.

6. Transducer according to claims 1 and 2, characterized in that it has a central frequency f ₀ of the frequency band transmitted or received inversely proportional to the maximum external dimension of the transducer in the direction of the coaxial cable, reduced by the distance between the parallel edges of said cut.

7. Transducer according to one of claims 1 to 6, characterized in that, for a central frequency f ₀ of the frequency band transmitted or received by said transducer, said frequency band is substantially inversely proportional to the distance between the edges parallel to said cut and substantially proportional to the maximum external dimension of said transducer in the direction of the coaxial cable, reduced by said distance separating the parallel edges of said cut.

8. Transducer according to one of claims 1 or

2, characterized in that, in said first, second and third zones interconnected by said coaxial cable, is further associated with at least one metal plate, placed in a plane parallel to said zones on the coaxial cable side, said metal plate making it possible to improve the direction of said transducer.

9. Transducer according to one of claims 1 to 7, characterized in that the assembly formed by the first, the second, the third zone and the cut with substantially parallel edges has symmetry with respect to the longitudinal axis of symmetry of said cut.

10. A transducer according to claim 9, characterized in that the geometric figure formed by the outer edge of said assembly is substantially polygonal or circular.

11. Transducer according to one of claims 1 to

10, characterized in that said first, second and third zones are also added to a strip of common dielectric material, with low radioelectric losses.

12. A transducer according to claim 11, characterized in that the latter successively comprises, in successive parallel planes distributed in a direction orthogonal to the plane containing the first, the second and the third zone: - a first layer of dielectric material, provided on the face opposite to the plane containing said areas of a line of micro-ribbon type replacing the coaxial line; a second layer of dielectric material covering the first layer of dielectric material and the microstrip line;

- a metallization covering this second layer of dielectric material, playing the role of reflective plane.

13. Microwave radio transmission-reception energy transducer, characterized in that it comprises at least, organized with respect to a center of symmetry according to an elementary emission transducer:

a plurality of first microwave radio emission-reception transducers according to claim 1, these first microwave radio emission-reception transducers being supplied from a common source of microwave energy, and, organized with respect to this same center of symmetry according to an elementary receiving transducer, - a plurality of second transmitting / receiving transducers of microwave radio energy according to claim 1, these second transmitting and receiving transducers of microwave radio energy being connected to a common microwave energy reception circuit, said transducer further comprising means for controlling the supply and transmission respectively of reception of said first and second transmission-reception transducers.

14. A transducer according to claim 13, characterized in that said first and second transmitting-receiving transducers of microwave radio energy consist each of a first, a second and a third zone forming an assembly whose external edge has a shape of circular sector provided with a cutout placed on the longitudinal axis of symmetry of each of the circular sectors, the first and second transmitting-receiving transducers of microwave radio energy being nested and distributed in petals with respect to said center of symmetry.

15. Network of microwave radio transmission-reception transducers, characterized in that it comprises a plurality of radio-transmission-reception transducers according to one of claims 1 to 10, said plurality of radio transmission-reception transducers being arranged in a common plane in a matrix X, Y, in two substantially orthogonal directions, each transceiver transducer being provided with independent control means for supplying / receiving radio frequency microwave energy.

16. Array of transducers according to claim 15, characterized in that each emission-reception transducer is mounted for rotation relative to an axis of rotation contained in said common plane, each of the emission-reception transducers being coupled mechanically to a means for driving in rotation about said axis of rotation, which makes it possible to modify the orientation in inclination of each transmitter-receiver transducer with respect to said common plane and to adapt the emission-reception diagram resulting from said network.