EP2169764B1 - Transmit/receive radiofrequency antenna with modifiable transmit/receive parameters - Google Patents

Description

TECHNICAL FIELD AND PRIOR ART

The present invention relates to a radiofrequency antenna whose transmission-reception parameters are modifiable.

Many antennas used in radiofrequency communication systems have a fixed geometry, i.e. their length and their configuration are determined during their manufacture and can not be modified later, or even with complex operations. Consequently, the operating frequency band of these antennas can not be modified, and more generally their transmission-reception parameters can not be modified.

In order to overcome this disadvantage and to make the operation of systems equipped with such an antenna type independent of its orientation, the antenna is generally dimensioned so that the radiation of the antenna is the most isotropic possible. that is, the transmitted energy is substantially the same in all directions. This is the case in wireless systems. Indeed, for example in the case of a mobile phone, the orientation of the antenna is almost permanently changed. With such antennas, the systems allow communication in any direction. However, this show multidirectional has the disadvantage of being energy-consuming. However, we seek to reduce the energy consumption of portable telecommunication systems.

In the case of systems requiring a regular change of frequency band, it is conceivable to use several antennas adapted to each of these frequency bands and to pass regularly from one antenna to another. However, this solution has a significant footprint and requires control means to switch from one antenna to another.

The document US 7,260,424 describes an antenna in several pieces connectable to each other by means of electrically controllable mechanical switches. It is then possible, by switching the switches, to modify the impedance of the antenna and to adapt it to different communication frequencies. However, apart from the complexity of producing the antenna and control, it is not possible to vary the impedance of the antenna only stepwise. Moreover, there is also the problem of congestion, this type of antenna is therefore poorly suited to implementation in mobile phone type systems.

In addition, the switches, even in the open state, have a capacitive impedance that does not allow to consider a total disconnection of the antenna element (or the parasitic element) that we want to disconnect. Finally, even if we can isolate each piece of this antenna, it can exist a radio frequency coupling between each of these pieces, which degrades the overall operation.

There are also antennas made from an electrically conductive liquid, the resonant frequency of the antenna being adapted by changing the length of the liquid antenna. This type of antenna is described in the document GB 2,435,720 . For this purpose, the liquid is contained in a tube having a given geometry, for example in the form of a helix, the length of the antenna being modified for example by a device for controlling the temperature, by a pump or a piston.

On the one hand the shape of the antenna is imposed by the shape of the tube, and therefore can not be changed during the use of the antenna. In addition, the modification of the length of the antenna requires cumbersome means and whose reaction time is relatively long.

Another editable antenna is described in the document US 2005/0057415 A1 . It is therefore an object of the present invention to provide a radio frequency antenna whose transmission-reception parameters can be modified rapidly and have a small footprint.

STATEMENT OF THE INVENTION

The previously stated goal is achieved by a radiofrequency antenna according to claim 1 comprising at least a portion made of a conductive liquid, whose shape is modified by electromagnetic forces.

In other words, liquid volumes are moved by electrowetting or by generating a magnetic field, to form, from the volumes of liquid, an antenna whose shape and / or length is adapted to a given frequency band and / or at a given orientation.

This antenna is of relatively simple construction, and allows for a large number of shapes. Moreover, the displacement of the drops of liquid is very fast. The frequency band of the antenna according to the invention can therefore be adapted very rapidly, depending on the orientation of the radiofrequency system.

The main subject of the present invention is therefore a radio transmission and reception antenna, comprising a transmission and reception zone, means of connection to a transmission and / or reception circuit, said transmission zone and receiver being formed at least in part by at least one volume of liquid, and means for modifying the shape of said liquid volume, said means for modifying the shape of said liquid volume using electromagnetic forces, in this case the liquid provides ferromagnetic properties, and a control unit means for deforming the fluid volume.

In one embodiment, most of the transmit and receive area of the antenna is in solid form, the volume of liquid forming an extension of the solid part of emission and reception, of adjustable form.

In an exemplary embodiment, the solid part may be a wire intended to be connected to a transmitting and / or receiving circuit, and the volume of liquid is provided at a free end of the wire, the means for modifying the shape the volume of liquid being formed by at least one electrode, the volume of liquid being deposited on an electrically insulating surface, providing low wettability with respect to the liquid, the electrode being disposed opposite the volume of liquid by relative to the insulating surface.

In another embodiment, the solid portion may be formed by two electrical conductive plates delimiting between them a slot to form a slot antenna, each plate being covered with a volume of liquid delimiting a slot superimposed substantially with the slot defined by the plates, the plates forming electrodes electrically insulated from the liquid volumes, a potential difference that can be imposed between the two plates to cause a change in the width of the slot, by bringing liquid volumes closer or further apart. It is also possible to provide a polarization electrode in the slot between the two plates, a potential difference can be imposed between the bias electrode and the two plates to cause a change in the width of the slot, by bringing together or removal volumes of liquid from the bias electrode. Advantageously, the antenna has a wall disposed at the slot to prevent contacting the two volumes of liquid.

In another embodiment, most of the emission and reception zone is in liquid form, the means for modifying the shape of the liquid volume or volumes comprising a plurality of electrodes or electromagnetic coils, distributed under an electrically insulating surface on which the liquid volume (s) can move, said surface having a low wettability with respect to the liquid.

The control unit can send individual commands to each of the electrodes or coils.

The radio antenna according to the invention may comprise a volume of liquid intended to be connected to the transmitting and / or receiving circuit and a ground plane connected to the transmitting / receiving circuit. The radio antenna can then form a GSM antenna.

The antenna according to the invention may comprise two liquid volumes separated by a slot whose width is substantially constant over its entire length and forming a slot antenna, or separated by a slot whose width increases along the slot and forming a broadband antenna.

The control unit can then advantageously generate orders to the electrodes or coils such that it causes the rotation of said slot to detect higher scanning energy orientation.

In another exemplary embodiment, the antenna comprises a ground plane and a substantially planar electrode maintained at a distance from this ground plane substantially parallel thereto, said electrode being covered with a liquid film, said electrode providing a very high good wettability with respect to the liquid, the adjustment of the potential between the ground plane and the electrode making it possible to modify the distribution of the film of liquid on the face of the electrode vis-à-vis the ground plane .

In another exemplary embodiment, the antenna may comprise a wire or point portion and a liquid portion remote from the wire portion, the liquid portion covering a surface provided with means adapted to modify the shape of the liquid portion. For example, the surface is spherical, so as to form a satellite dish.

The radio antenna advantageously comprises a sealed housing enclosing the transmitting and receiving part, said transmitting and receiving part being embedded in an electrically insulating liquid which is non-missible with the liquid forming at least a part of the antenna.

For example, in the case of the implementation of electrostatic forces, the liquid may be mercury, "Indalloy® 46L Ga-In-Sn-Zn Alloy" or water comprising one or more additives such as acid, a silver powder, a carbon powder, or in the In the case of the implementation of the electromagnetic forces, the liquid may be a magnetorheological liquid.

The present invention also relates to a portable communication device of the portable telephone type, comprising a transmission and reception circuit and at least one antenna according to the present invention connected to said circuit.

The present invention also relates to the use of means for modifying the shape of at least one volume of fluid of hydraulic fluid by electrostatic forces or by electromagnetic forces to modify the parameters of transmission and reception of an antenna radio.

BRIEF DESCRIPTION OF THE DRAWINGS

• les figures 1A et 1B sont des vues en perspective d'un exemple de réalisation d'une antenne de longueur variable selon la présente invention,
• la figure 2 est une vue de dessus d'un autre exemple de réalisation d'une antenne selon la présente invention,
• les figures 3A et 3B sont des schémas illustrant la polarisation des électrodes de l'exemple de la figure 2,
• les figures 4A et 4B sont des vues de dessus d'un exemple de réalisation d'une antenne de forme variable, les figures 4A et 4B illustrant une configuration en antenne fente et une configuration en antenne large bande respectivement,
• la figure 4A' est une vue de dessus de l'antenne de la figure 4A dans laquelle la fente a une orientation modifiée,
• la figure 5A est une vue en perspective d'une antenne selon la présente invention en trois dimensions,
• la figure 5B est une vue de côté de l'antenne de la figure 5A,
• la figure 5C est un exemple de réalisation de la figure 5A dans la zone d'émission liquide est enfermée dans un boîtier étanche,
• les figures 6 à 11 sont des vues en perspective d'autres exemples de réalisation d'antennes selon la présente invention,
• les figures 12A et 12B sont des vues de dessus d'un exemple de réalisation d'une antenne de forme variable utilisant les forces électromagnétiques, les figures 12A et 12B illustrant une configuration en antenne fente repliée et une configuration en antenne GSM repliée avec plan de masse respectivement.

The present invention will be better understood with the aid of the description which follows and the attached drawings, in which:

• the Figures 1A and 1B are perspective views of an exemplary embodiment of a variable length antenna according to the present invention,
• the figure 2 is a view from above of another embodiment of an antenna according to the present invention,
• the Figures 3A and 3B are diagrams illustrating the polarization of the electrodes of the example of the figure 2 ,
• the Figures 4A and 4B are views from above of an exemplary embodiment of an antenna of variable shape, the Figures 4A and 4B illustrating a slot antenna configuration and broadband antenna configuration respectively,
• the Figure 4A ' is a top view of the antenna of the Figure 4A in which the slot has a modified orientation,
• the Figure 5A is a perspective view of an antenna according to the present invention in three dimensions,
• the Figure 5B is a side view of the antenna of the Figure 5A ,
• the Figure 5C is an example of realization of the Figure 5A in the liquid emission zone is enclosed in a sealed housing,
• the Figures 6 to 11 are perspective views of other exemplary embodiments of antennas according to the present invention,
• the Figures 12A and 12B are top views of an exemplary embodiment of an antenna of variable shape using the electromagnetic forces, the Figures 12A and 12B illustrating a folded slot antenna configuration and a folded GSM antenna configuration with ground plane respectively.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

In the following description, we will mainly describe devices implementing a movement by electrowetting. We will therefore first describe in general the displacement of liquid drops using the principle of electrowetting. However devices using displacement means implementing electromagnetic forces are within the scope of the present invention, as will be discussed later.

The displacement by electrowetting of a drop of liquid on a dielectric is for example described in the article of MG Pollack, AD Shendorov, RB Fair, entitled "Electro-wetting-based actuation of droplets for integrated microfluidics", Lab Chip 2 (1) (2002) 96-101 .

The forces used for displacement are electrostatic forces.

The document FR 2 841 063 describes a device implementing a catenary facing electrodes activated for displacement.

The principle of this type of displacement is described below.

A drop is based on a succession of electrodes, from which it is isolated by a dielectric layer and a hydrophobic layer.

When an electrode located near the drop is activated, the dielectric layer and the hydrophobic layer, between this activated electrode and the electrode-polarized drop, act as a capacitor. The effects of electrostatic charge induce the displacement of the drop on this electrode. The electrode can be a catenary, it then maintains an electrical contact with the drop during its movement, as described in the document FR 2 841 063 .

The drop can thus be displaced step by step, or spread more or less on the hydrophobic surface, by successive activation of the electrodes of the matrix of electrodes.

On the Figures 1A and 1B an exemplary embodiment of an antenna 2 according to the present invention can be seen. In this example, it is a wired antenna.

The antenna 2 is formed by an electrical conducting wire 4 and a drop 6 of conductive liquid covering a free end 4.1 of the wire 4. The wire 4 and the drop 6 form a conductive element whose length determines the operating frequency band of the antenna.

The antenna also comprises means 8 for varying the length of the conductive element, by modifying the shape of the drop 6.

These means 8 are formed by a plane 10 on which the end 4.1 of the wire 4 and the drop 6 rest, and an electrode 12 disposed opposite the wire 4 relative to the plane 6. The wire 4 also forms a catenary.

The plane 10 comprises a dielectric layer for electrically isolating the drop 6 and the electrode 12, and a non-wetting layer vis-à-vis the liquid envisaged on the dielectric layer, ie hydrophobic for an aqueous or oleophobic solution, vis-à-vis screw of a fat body. The dielectric layer and the hydrophobic layer may be merged.

The liquid constituting the drop is chosen so that it is able to carry the electrical signal to be emitted. For example, water can be used. Advantageously, liquid forming is chosen good electrical conductors, such as mercury, "Indalloy® 46L Ga-In-Sn-Zn Alloy" or water with one or more additives such as acid, silver powder, carbon powder .... Indeed, the quality factor of the antenna is even higher than the liquid is good driver. The greatest possible conductivity is sought, for example at least 10 ⁵ Sm ^-1 .

Silver offers the highest conductivity at room temperature, it offers an electrical conductivity equal to 62.5.10 ⁶ Sm ^-1 . Copper has an electrical conductivity of 58.8 × 10 ⁶ Sm ^-1 , and mercury has an electrical conductivity of 1.04 × ⁶ Sm ^-1 .

Means (not shown) are provided to bias the electrode 12. The wire 4 is at a fixed potential, the drop 6 is at the same potential.

When the electrode 12 is not polarized, the drop 6 tends to be spherical because of its own properties and hydrophobic properties of the plane 10. It surrounds the end 4.1 of the wire 4 forming a small projection. Therefore, the length of the conductive element is substantially equal to that of the wire.

When the electrode 12 is biased so as to be brought to a significant potential with respect to the effective value of the information signal which passes on the antenna, a continuous electric field appears between the wire 4 and the electrode 12. It there is emergence of electrostatic forces, the liquid of the drop is then attracted by the electrode 12, the drop is deformed and tends to take the form of the electrode 12. This has the effect of increasing the length of the conductive element.

By varying the value of the bias potential of the electrode 12, it is then possible to vary the length of the conductive element of the antenna between the length of the wire 4 and the length of the wire to which is added the length of the deformed drop. It is therefore possible to adapt the antenna according to the wavelengths that we want it to transmit or receive. The higher the potential difference between the wire and the electrode, the more the drop tends to deform to cover the electrode and therefore to lengthen the conductive element.

The greater the length of the antenna, the lower the resonance frequency of the antenna, the lower the carrier used to transmit the signal.

In the example shown, a single electrode is used to change the length of the antenna, but it is understood that the use of several electrodes forming a path is within the scope of the present invention.

In addition, the representation of the antenna of the figure 1 is schematic. It is understood that in practice, it would be possible to contain the drop in a tube in which the wire 4 would penetrate, the electrode 12 being fixed on the tube, which would make it possible to offer an easily applicable antenna, for example to a portable device.

We will now give a numerical example of the wavelengths that can be obtained thanks to the invention.

Conventionally, the length of the antenna is equal to 1/2 or 1/4 of the wavelength or a multiple of the wavelength of the carrier.

The relation between the wavelength λ and the frequency f is: $$\mathrm{\lambda }=\mathrm{3.}{\mathrm{10}}^{\mathrm{8}}/\mathrm{f}$$

Consider that it is desired to provide an antenna for a four-channel transmission system, namely for example the frequency channels 2,411 GHz, 2,431 GHz, 2,451 GHz and 2,471 GHz used for the wireless transmission of home video. When one channel is used by another user, the system must be able to switch from one channel to another.

Moreover, we consider that we want to make an antenna in λ / 2, i.e. its length is equal to half of its wavelength.

Starting from the relation (I), one can calculate λ1 and λ2 for the two extreme values of the wavelengths of the channels, ie 2,411 GHz and 2,471 GHz respectively: $$\mathrm{<figure-callout\; id="2"\; label="\lambda "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\lambda </figure-callout>}2=0,1244\mathrm{m\; and\; <figure-callout\; id="2"\; label="\lambda "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\lambda </figure-callout>}2=0,1214m\mathrm{.}$$

We deduce the maximum length L1 and the minimum length L2 of the antenna: $$\mathrm{The}\mathrm{1}=\mathrm{62},\mathrm{2}\mathrm{mm\; and\; <figure-callout\; id="2"\; label="L"\; filenames="imgf0001.png"\; state="\{\{state\}\}">L</figure-callout>}\mathrm{2}=\mathrm{60},\mathrm{7}\mathrm{mm}\mathrm{.}$$

A maximum variation of 2.2 mm beyond 60 mm from the antenna is therefore required to reach the four channels. It is therefore possible to realize a wire 4 60 mm at the end of which is placed a drop of conductive liquid 6. Without electrostatic action, the drop 6 is collected and exceeds only 0.7 mm the end of the antenna wire (a drop of 0.7 mm radius of 2.05 μL), the antenna then has a length of 60.7 mm, which corresponds to the channel 2.471 GHz. The application of a polarization to the electrode 12 causes the electrostatic attraction of the drop 6 which can reach a length of 2.2 mm beyond the end of the antenna wire 4 (rod shape liquid of about 0.9 mm section and 2.2 mm long). The antenna then has a length of 62.2 mm, which corresponds to the 2.411 GHz channel.

On the figure 2 , we can see another embodiment of an antenna according to the invention. This is a slot antenna. In this case, the volumes of liquid are used to adjust the length of the slot, the greater part of the antenna being made of a highly conductive solid material, for example copper or gold.

In particular, the antenna 202 of the figure 2 comprises two plates 204 of highly conductive material, for example copper or gold, arranged next to each other and defining by their edges 204.1 vis-à-vis, a slot 208. Plus the material of the plates 204 is a good driver, the higher the quality factor of the antenna, and consequently its efficiency.

In the example shown, the antenna also comprises a polarization electrode 210 disposed in the slot 208.

Each plate 204 is covered with a volume of conductive liquid 206.

Each plate 104 is connected to a transmission / reception circuit.

It can be provided to cover the plates with a film having good wettability with respect to the liquid to ensure a spread of the liquid on the plates 204. However, the capillary forces may be sufficient.

We will now explain the operation of this antenna using the diagram of the electrical circuit of the figure 3A .

The width of the slot 208 makes it possible to adjust the transmission / reception characteristics of the antenna.

The two volumes of liquid define a slot 208 'by their edges 206.1 vis-à-vis. At rest, i.e. in the absence of polarization of the electrode 210, the slot 208 and the slot 208 'are identical. The width of the slot is therefore equal to the distance separating the plates 204.

The plates 204 form electrodes whose potential is imposed for example by a differential source via the signal to be transmitted 214. The potential of the two plates 204 may be different or not. The liquid volumes 206 are therefore at the potentials of the plates 204. The potential of the electrode 110 is imposed (schematized by the DC component 212). There is then the appearance of electrostatic forces tending to attract the liquid towards the electrode 210. The edges of the liquid volumes 206 are then attracted towards the electrode 210, overflowing with plates, which has the effect of reducing the width of the slot 208 '.

The more the electrode 210 is strongly polarized, the closer the edges of the liquid volumes are and the slit is narrower.

The width of the slot 208 'defined by the volumes 206 therefore varies as a function of the potential difference between the plates 204 and the bias electrode.

A central wall may be provided at the level of the electrode 210 to prevent the two liquid volumes 206 coming into contact, this wall defining a minimum slot width.

Alternatively, provision may be made to impose a substantially fixed potential on the electrode 210 and to vary the potential of the plates 204.

In another variant embodiment symbolized on the figure 3B it can be envisaged not to use an electrode 210, and to polarize the two plates 204 differently by superposing a DC component 212 on the signal to be transmitted 214. Indeed, if a relatively large potential difference is applied between the plates 204, the liquids placed on each of the solid conductive surfaces tend to attract at the slot 208 and therefore tend to reduce the width of this slot. This has the effect of increasing the frequency of operation of the antenna.

One could also plan to act only on a single volume of liquid 206 for change the width of the slot, there would then be an asymmetrical variation of the width of the slot.

The adjustment of the slot makes it possible to adjust, for example the resonance frequency, the directivity of the transmission, the bandwidth width ...)

On the Figures 4A and 4B other exemplary embodiments of a planar antenna according to the present invention can be seen for which a plurality of checkered electrodes are used. In these exemplary embodiments, the entire antenna is formed by the volumes of liquid, the liquid not only serving to adjust a relatively limited area of the antenna.

On the Figure 4A , is realized a bipolar slot antenna 102 comprising connection means 104 to a data transmission / reception circuit, two volumes of conductive liquid 106.1, 106.2 in electrical contact with the connection means 104, and means for modifying the form these volumes of liquid.

The two liquid volumes 106.1, 106.2 are intended to delimit between them a slot 108 of given width and orientation.

A ground plane may be provided above or below the liquid volumes.

The means for modifying the shape of these liquid volumes comprise a plurality of electrodes 112 distributed in a plane so as to allow the contour of each of the volumes 106.1, 106.2 to be modified with sufficient precision. In the example shown, the electrodes 112 are distributed in checkerboard, thus forming a surface divided into a multitude of sources of electrostatic force generation able to move the volumes 106.1, 106.2 with great precision. The electrodes are covered with a dielectric layer and a layer having a low wettability vis-à-vis the liquid volumes 106.1, 106.2, and on which the volumes 106.1, 106.2.

Each electrode 112 is individually connected to a control unit which applies a potential to specific electrodes in order to arrange the volumes 106.1, 106.2 to obtain the desired slot width and / or orientation of the desired band.

The conductive liquid spreads over all the electrodes to which a potential is applied.

In the configuration shown, all the hatched electrodes are polarized. If it is desired to change the width of the slot, it is sufficient to no longer polarize the designated electrodes 112.1 and / or the designated electrodes 112.2.

The width of the minimum slot is substantially equal to the width of the electrodes. The smaller the electrodes, the more precise the width of the slot can be, as well as the variation in wavelength.

You can also change the orientation of the slot. One can imagine delimiting a slot 108 'inclined by polarizing the electrodes as represented on the Figure 4A ' the hatched electrodes are polarized.

The size of the slot and its orientation can be changed in real time, during a conversation in the case of a mobile phone. The slot can therefore rotate to orient the transmission / reception in a high power direction. The slot can rotate so as to scan the directions to find the one of higher energy.

It is also possible to vary the wavelengths, and to adapt in real time the impedance of the antenna to the impedance of the transmission / reception circuit.

The antenna of the Figure 4A can allow to reach frequency channels of some Gigahertz.

On the Figure 4B , we can see the antenna of the figure 1 wherein the liquid volumes are in a configuration such that they form a broadband antenna. The liquid volumes have concave shapes facing each other and defining a slot 108 "substantially in the shape of an inverted triangle.This slot is obtained by a simple control of the electrodes.

This antenna makes it possible to transmit over a wide frequency band, for example it allows a higher bit rate transmission of a few megahertz. The structure of course makes it possible to produce antennas other than slot antennas or wide bands.

The liquid may be of the same type as that used in the antenna of the figure 1 .

On the Figures 5A and 5B we can see an application of the principle according to the invention applied to antennas in three dimensions.

Antenna 32 Figures 5A and 5B comprises a ground plane 303 connected to the ground and a solid electrode 304 disposed at a distance from the ground plane 303, for example by means of an electrical insulating support 305. The electrode 304 in the example shown has the shape of a disc, but this form is in no way limiting.

The electrode 304 is connected to the transmission / reception circuit.

According to the invention the electrode 304 is covered with a liquid film 306. At rest, the film is uniformly distributed on the upper face 304.1 and on the underside 304.2.

The desired parameter is the distance d between the plate and the ground plane, more particularly the distance between the ground plane 303 and the film covering the underside 304.2.

By superimposing a continuous value on the signal to be transmitted (or on the received signal), it is possible to move a part of the liquid situated on the upper face 304.1 of the electrode 304 towards the lower face 304.2 of the electrode 304. This displacement has the effect to reduce the distance d. The characteristics of the antenna are therefore modified.

Advantageously, it can be provided to use an electrode 304 having a very good wettability with respect to the liquid. When the electric polarization stops, the liquid is then distributed spontaneously around the electrode 304 to form a uniform layer all around the electrode 304.

On the Figure 5C , we can see a practical realization of the antenna of the Figures 5A and 5B wherein the electrode 304, which is covered with the film 306, and the ground plane 303 are enclosed in a sealed housing 308 to limit the risk of evaporation or loss of the conductive liquid.

In addition, it is advantageous to fill the housing 308 with an insulating liquid 310, of the dielectric oil type for example, to complete the overall volume of the antenna, which will not mix with the liquid of the film 306.

Drowning the antenna in an insulating liquid makes it possible to reduce the risks of evaporation, but also to make the antenna less sensitive to any sudden handling that could cause the conductive liquid to leave the support surfaces, despite the electrostatic forces attraction exerted by the electrodes. This is particularly interesting in the case of an antenna equipping a portable system.

It is understood that the structure of the antenna may be more complex, and it may be provided to add polarization electrodes to improve the control of the deformation of the liquid film.

On the figure 6 , we can see another embodiment of an antenna 402 in three dimensions.

The antenna 402 has a wire portion 403 and a cylindrical member 405 surrounding the portion wired, whose inner face is intended to be covered with a film of liquid 406.

For this, the cylindrical element 405 comprises a cylindrical support 410 electrical insulator whose inner face is covered with the film 406, and electrodes 408 disposed on its outer face. In the example shown, the electrodes 408 form a checkerboard on the entire outer face of the cylindrical support 410. Each electrode can be controlled individually or by row or column.

By modifying the potential between the wire portion 403 and the electrodes, it is possible to modify the distribution of the film on the inside face of the cylindrical support 410, so as to cover only a part of this inner face. This change in distribution has the effect of changing for example the direction of transmission and reception.

On the Figures 7, 8, 9 and 10 , we can see examples of shape that can take the liquid antenna for different types of controls of the structure of the figure 6 , the cylindrical support 410 not being shown.

On the figure 7 , we can see an antenna 702 whose control is such that the liquid is distributed on a cylinder strip 704

On the figure 8 an antenna 502 can be seen whose control is such that the liquid is in the form of a ring 504 centered on the catenary 403.

On the figure 9 , we can see an antenna 602 whose control is such that the liquid film forms a parallel wire 604 to the wire portion 403.

On the figure 10 , we can see an antenna 702 whose control is such that the liquid forms a helix 804 surrounding the wire part 403.

In the examples described above, the distance between the liquid portion and the wired part of the antenna can be adjusted by adding a DC component to the signal to be transmitted or received, and the shape of the antenna can be be adjusted by the electrical control of the electrodes, to cover more or less the liquid support.

On the figure 11 , an exemplary embodiment of a parabolic antenna according to the present invention can be seen.

For this, the antenna 902 comprises a wire or point portion 903 and a support 904 of spherical shape covered on its outer surface with individually controllable electrodes. The film 906 covers a portion of the inner face of the support 904 to form a cap whose concavity is orientable by means of the electrodes.

Advantageously, it can be expected that, thanks to the force of gravity, the concavity of the cap is automatically directed upwards to ensure satellite communications.

It is understood that the practical embodiment of the Figure 5C , applies to all described embodiments.

We have described embodiments in which the displacement of the liquid volumes is obtained by electrostatic forces, but we can also consider making them move via electromagnetic forces. For this, liquids are used which offer ferromagnetic properties and which can then be sensitive to the magnetic field, for example magneto-rheological liquids. Means can then be provided for generating magnetic fields, for example coils in replacement of the electrodes. This structure has the advantage of not presenting a risk of dielectric breakdown. It is understood that the configurations of the examples represented on the Figures 1 to 11 apply to the displacement means by the electromagnetic forces.

In the case of displacement by application of electrostatic forces, the application of a force is to place a certain electric charge on the electrodes. In the case of a displacement by application of electromagnetic forces, this amounts to applying a certain electric current in the coils.

On the Figures 12A and 12B another embodiment of antennas according to the present invention can be seen using electromagnetic forces to modify the shape of the antenna.

For this purpose, the electrodes are replaced by individually fed coils 1004 and a ferromagnetic liquid, for example a magneto-rheological liquid, is used as liquid 1006.

The coils, when powered by an electric current, generate a magnetic field and attract the magnetorheological fluid that deforms according to the presence or absence of a magnetic field

On the figure 12A , we can see an antenna that can be obtained by electromagnetic forces.

The coils 1004 are distributed in rows and columns under a surface 1008 insulating and having a low wettability with respect to the liquid 1006.

The liquid 1006 is an electrically conductive magnetorheological fluid.

The antenna also comprises two separate liquid volumes 1006.1, 1006.2 delimiting a slit 1010 of adjustable shape. Each volume of liquid 1006.1, 1006.2 is connected to the transmission / reception circuit by a conductor 1012. The volumes 1006.1 and 1006.2 are hatched to make them more visible.

In the example shown, it is a folded slot 1010, offering a large length for a small footprint.

The minimum width of the slot is determined by the spacing between the coils 1004.

Thanks to a suitable control of each of the coils, it is possible to realize any type of shape, as represented on the figure 12B , representing a folded GSM antenna with ground plane.

The antenna comprises a plurality of coils 1104 distributed in rows and columns under an insulating support 1108, a ground plane 1103 above the support and at a distance from it and the magnetorheological liquid 1006 deposited on the support.

The ground plane and the liquid 1106 are connected to the transmission / reception circuit by the connectors 1112.

The liquid 1106 (hatched for clarity on the figure 12B ) draws, in the example shown, spirals.

Antennas in three dimensions as represented on the Figures 5A to 11 are of course achievable by using the electromagnetic forces to adapt the distribution of the magnetorheological fluid.

Thanks to the present invention, it is possible to adjust the parameters of an antenna of conventional type, for example by changing its length, in the case of a wire antenna or the width of the slot in the case of an antenna. slot. It is also possible to make antennas shapes completely editable by performing most of the transmitting and receiving parts with a conductive liquid that can move, on command, on a surface.

Any type of antenna can be made, such as folded GSM antennas, rake antennas ...

Thus, thanks to the invention, simply adaptable antennas can be made according to the free frequency bands or the orientation thereof, making the transmission and reception of the device thus equipped more efficient.

In the examples described, the electrodes or the coils have identical sizes, but it is of course that one can provide to achieve structures whose electrode sizes vary. For example, in the case of a slotted antenna, it can be expected that the electrodes are smaller and more numerous at the slot, to increase the displacement sensitivity of the edges of the liquid volumes.

Claims (15)

1. Radio transmitting/receiving antenna, comprising a transmitting and receiving portion, connection means to a transmitting and/or receiving circuit, said transmitting and receiving portion being formed at least in part by at least one volume of liquid (1006.1, 1006.2, 1106), and means to modify the shape of said volume of liquid, said means to modify the shape of said volume of liquid using electromagnetic forces and comprising at least one coil (1004), the liquid volume being disposed on an electrically insulating surface which offers low wettability with respect to the liquid, said at least one coil (1004) being arranged in an opposite manner to the volume of liquid with respect to the electrically insulating surface, the liquid being electrically conductive and having ferromagnetic properties, and a control unit to control the means deforming the volume of liquid.
2. Radio antenna according to claim 1, wherein most of the transmitting and receiving portion of the antenna is in solid form, the volume of liquid forming an extension of the solid transmitting and receiving part of adjustable shape.
3. Radio antenna according to the preceding claim, wherein the solid part is a wire intended to be connected to a transmitting and/or receiving circuit, and the volume of liquid is provided at one free end.
4. Radio antenna according to claim 1, wherein most of the transmitting and receiving portion is in liquid form and in which the means to modify the shape of the volume or volumes of liquid comprise a plurality of electromagnetic coils (1004, 1104), distributed underneath the electrically insulating surface on which the volume or volumes of liquid (106.1, 106.2, 1006.1, 1006.2, 1106) may be moved, said surface having low wettability with respect to the liquid.
5. Radio antenna according to the preceding claim, wherein the control unit sends individual orders to each of the coils (1004, 1104).
6. Radio antenna according to claim 4 or 5, comprising a volume of liquid (1106) intended to be connected to the transmitting and/or receiving circuit, and a ground plane (1103) intended to be connected to the transmitting/receiving circuit.
7. Radio antenna according to the preceding claim, forming a GSM antenna.
8. Radio antenna according to claim 5 or 5, comprising two volumes of liquid separated by a slot which width is substantially constant over its entire length and forming a slot antenna, or separated by a slot which width increases along the slot and forming a broadband antenna.
9. Radio antenna according to the preceding claim, wherein the control unit generates orders to the coils (1004, 1104) so as to cause rotation of said slot (108') for detection by scanning of the direction with the highest energy.
10. Radio antenna according to claim 1, comprising a wire or point part (403, 503, 603, 703, 803, 903) and a liquid part spaced away from the wire part (403, 503, 603, 703, 803, 903), the liquid part covering a surface (405, 504, 604, 704, 804, 904) provided with means able to modify the shape of the liquid part.
11. Radio antenna according to claim 10, wherein the surface (904) is spherical, forming a parabolic antenna (902).
12. Radio antenna according to any of the preceding claims, comprising a sealed casing (308) enclosing the transmitting and receiving part, said transmitting and receiving part being embedded in an electrically insulating liquid (310) non-miscible with the liquid forming at least part of the antenna.
13. Radio antenna according to any of the preceding claims whereinthe liquid is a magneto-rheological liquid.
14. Mobile communication apparatus, of mobile telephone type, comprising a transmitting and receiving circuit and at least one antenna according to any of the preceding claims connected to said circuit.
15. Utilisation of means to modify the shape of at least one volume of a liquid which is electrically conductive and having ferromagnetic properties by electromagnetic forces to modify the transmitting and receiving parameters of a radio antenna according to claims 1 to 13.

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