FR3054044B1 - FREQUENCY SELECTIVE SURFACE COMMANDABLE AND MULTIFUNCTIONAL - Google Patents

Abstract

This device comprises a substrate, an array of conductive elementary patterns (8) printed on a surface of said substrate, and an array of coupling components (12, 12a, 12b), each connecting two adjacent conductive elementary patterns (8) and having a modifiable capacity. The device comprises a control assembly for controlling the value of the grouping capacitors (20a, 20b) of coupling components (12, 12a, 12b) selectively in a first notch mode, in which the capacity of all the groups (20a, 20b) is set to the same value, and a second bandpass mode, wherein the capacitance of the coupling components (12, 12a, 12b) of a first set of groups (20a) is set to a first value, and the capacity of the coupling components (12, 12a, 12b) of a second set (20b) of groups, complementary to the first set, is set to a second value.

Description

Controllable and multifunctional frequency selective surface

The present invention relates to a frequency-selective surface device comprising a substrate, an array of conductive elementary patterns printed on at least one surface of said substrate, and an array of coupling components, each coupling component connecting two adjacent conductive elementary patterns, each coupling component having a modifiable capacity by applying a command.

Frequency selective surface devices (also called FSS for "Frequency Selective Surface") are known elements in the field of electromagnetism, having the ability according to their configuration to reject certain frequencies or conversely to transmit certain frequencies. These devices are generally made in the form of periodic surfaces consisting of an ordered arrangement on a substrate of electrically conductive passive elements forming patterns. When this arrangement of elements is subjected to an incident plane electromagnetic wave, it is partly transmitted and partly reflected.

Under certain resonance conditions, the amplitude of the transmitted wave is equal to 0, the energy being reflected or scattered on the side of the incident wave. This type of surface thus behaves either as a bandpass filter, that is to say, letting electromagnetic waves pass at a given frequency, or as a notch filter, that is to say, rejecting waves. electromagnetic at a given frequency. Nevertheless, such a solution suffers from a double rigidity. On the one hand, the intended functional bandwidth is a direct consequence of the chosen periodic pattern, and can not be modified. On the other hand, it is not possible, with the same device, to switch from a function "pass band" to a function "cut strip" or vice versa.

In order to overcome these drawbacks, it has been proposed to integrate frequency-selective surface devices with variable capacitors or diodes that are electrically controllable, thus making it possible to vary the operating frequency of the device.

In particular, it has been proposed, for producing an active band-stop frequency-selective surface device, that is to say the frequency of which is rejected, to interconnect the patterns of the frequency-selective surface by means of electronic components, such as chokes and / or variable capacitances to make the FSS active. For example, a variation in the voltage applied across the variable capacitors brings about a change in the rejected frequency. Nevertheless, this solution does not make it possible to operate the device selectively in band-pass mode or in notch mode.

It has also been proposed to vary the operating mode, bandpass or notch, for the same pattern configuration, using different device metallization modes. For example, for the same configuration, when the substrate is dielectric and the metallized patterns, the device operates in notch mode, while when the substrate is metallized and the dielectric patterns, the device operates in bandpass mode. However, this solution also does not allow to operate a single device selectively in band-pass mode or notch mode.

An object of the invention is therefore to provide a frequency selective surface device which is multifunctional, that is to say which can operate selectively, in response to a command, in notch mode and in bandpass mode. . To this end, the subject of the invention is a device of the aforementioned type, characterized in that it further comprises a control assembly (14) configured to selectively control the value of the coupling component group capacities selectively according to: a first mode, in which the capacity of the set of coupling component groups is set to the same value, in order to operate said device in notch mode, and a second mode, in which the capacity of the components of coupling of a first set of groups of coupling components is set to a first value, and the capacity of the coupling components of a second set of groups of coupling components, complementary to the first set, is set to a second value, distinct from the first value, for operating said device in bandpass mode, each group of coupling components including a first component of uplage connecting a first elementary pattern to a second elementary pattern adjacent thereto, and a second coupling component connecting the first elementary pattern to a third elementary pattern adjacent thereto.

The device according to the invention may comprise one or more of the following characteristics, taken separately or in any technically possible combination: the elementary pattern network is a line-column network, each coupling component connecting two elementary patterns adjacent conductors along a line or in a column; each group of coupling components of the first set, respectively the second set, is adjacent only to groups of coupling components of the second set, respectively of the first set; each group of coupling components is a pair of coupling components, each pair of coupling components consisting of a first coupling component connecting a first elementary pattern to a second adjacent elementary pattern along a line, and a second coupling component coupling component connecting the first elementary pattern to a third adjacent elementary pattern in a column; in the first mode, said control unit is configured to vary the capacitance value of all groups of coupling components, in order to vary a resonant frequency of the device; in the second mode, said control unit is configured to vary the value of the capacitance of the coupling components of the first set and / or the second set, in order to vary a resonance frequency of the device; in the second mode, said control unit is configured to vary the value of the capacitance of the coupling components of the first set and / or the second set, in order to vary a bandwidth of the device; said coupling components are electrically controllable, and said control assembly is adapted to apply electrical control to the coupling components, to control the capacitance of the coupling component groups; said coupling components are thermally controllable, and said control assembly is adapted to apply thermal control to said coupling components, to control the capacitance of the coupling component groups; said coupling components are varicaps, in particular ferroelectric varicaps; the control unit comprises: an array of coupling component control modules, each control module being associated with a group of coupling components of said groups of coupling components and being configured to selectively control the value of the capacitors of the associated coupling component group, and - a control module of the control modules, configured to control said control modules so that each control module controls the value of the capabilities of the associated coupling component group, according to the first mode or according to the second mode selectively; said control unit is configured to control each control module by applying a predetermined electrical voltage across each coupling component of the coupling component group associated with the control module, and each control module is configured to applying the voltage commanded by said control unit across each coupling component of the associated coupling component group; said control unit is configured to control each control module the application of a predetermined temperature to the group of coupling components associated with said control module, and each control module is configured to apply said temperature controlled by said control unit; command to the associated coupling component group; each elementary conductive pattern is in the form of a ring. The subject of the invention is also a frequency selective surface system, said system being characterized in that it comprises a plurality of devices according to the invention, the substrates of said devices being common to said devices, the elementary conducting patterns of each device being printed on at least one surface of the substrate disjoined from any surface of the substrate on which the elementary conductive patterns of another device are printed. The invention will be better understood on reading the description which follows, given solely by way of example, and with reference to the appended drawings, in which: FIG. 1 is a diagram of a device with a selective surface in frequency according to one embodiment of the invention; FIG. 2 is a detailed diagram of a portion of the elementary pattern network and the coupling component network of the device of FIG. 1; FIG. 3 illustrates the reflection coefficient Su of a selective surface device in band-stop mode as a function of frequency, for various capacitance values; FIG. 4 illustrates the transmission coefficient S 2 1 of the device of FIG. 2 in band-stop mode as a function of frequency, for various capacitance values; FIG. 5 illustrates the reflection coefficient Su of the selective surface device of FIG. 2 in bandpass mode as a function of frequency, for various capacitance values; FIG. 6 illustrates the transmission coefficient S 2 1 of the selective-surface device of FIG. 2 in band-pass mode as a function of frequency, for various capacitance values; - Figure 7 is a diagram of a system according to one embodiment of the invention.

FIGS. 1 and 2 illustrate a frequency selective surface device 2 according to an embodiment of the invention, hereinafter referred to simply as device 2.

The device 2 comprises a substrate 4, and a network 6 of conductive elements 8 printed on at least one surface of the substrate.

The conductive elements 8 form on the surface of the substrate elementary patterns forming together a regular network, and will subsequently be called elementary conductive patterns 8.

The substrate 4 is for example flat. The substrate 4 is preferably made of a dielectric material, having dielectric characteristics, including a real permittivity and a tangent of losses, low. Preferably, the real permittivity of the material forming the substrate is less than 25 and its loss tangent is less than 0.1.

For example, the substrate is an NX9300 dielectric substrate marketed by the company NELTEC® having a real permittivity equal to 3 and a loss tangent equal to 0.0023.

Alternatively, the substrate may be made of a monolithic composite material.

The elementary conductive patterns 8 are made of an electrically conductive material.

The elementary conductive patterns 8 are of identical shapes.

In the example shown, the conductive elementary patterns 8 are circular patterns forming rings.

The diameter of the rings is chosen in particular according to the working frequency targeted for the application.

The elementary conductive patterns 8 are arranged to form a network, in particular a column line network. Column line network means that the conductive elementary patterns 8 are aligned both in rows and in columns.

In the example shown, each conductive elementary pattern 8, with the exception of elementary edge or edge conductive patterns, is thus adjacent to two conductive elementary patterns along one line and two other elementary conductive patterns along a column.

The elementary conductive patterns 8 are disjoint. By disjoint is meant that the elementary patterns are not connected to each other, in the absence of the coupling components described below.

In order to allow a controllability of the mode of operation of the network of conductive elementary patterns 8, that is to say of allowing to switch from a band-pass mode to a notch mode, and to modify the operating frequency by in the band-pass mode or in the notch mode, the device 2 furthermore comprises a plurality of coupling components 12 (not shown in FIG. 1), configured to couple the conductive elementary patterns 8 two-to-two, as well as to an assembly 14 for controlling the coupling components 12.

In the remainder of the description, bandpass mode will be referred to as a mode in which the device 2 transmits only electromagnetic radiations whose frequency is included in at least one frequency band comprised between a low cut-off frequency and a high cut-off frequency. , and centered around a resonance frequency.

A mode in which the device 2 transmits only electromagnetic radiations whose frequency is not included in a frequency band between a low cutoff frequency and a high cutoff frequency and centered around of a resonance frequency.

These resonant frequencies will be referred to by extension as the operating frequency of the device, in bandpass mode or in notch mode.

The coupling components 12 and the control unit 14 thus make it possible, in combination, to selectively vary the operating mode, notch or bandpass, of the device 2, which was, in the absence of these elements , fixed.

The coupling components 12 and the control assembly 14 also make it possible to selectively vary the operating frequency of the device 2, which device is also, in the absence of these elements, fixed.

The coupling components 12 connect the conductive elementary elements 8 two by two, each coupling component 12 connecting two adjacent conductive elementary patterns 8.

In particular, each elementary conductive pattern 8 is connected to each of the conductive elementary patterns 8 which are adjacent thereto by a single coupling component 12.

In the example shown, each coupling component 12 connects two adjacent conductive elementary patterns 8 along a line or in a column. The coupling components 12 therefore form, like the conductive elementary patterns 8, a column line network.

Coupling components 12 are capacitors with variable capacitance.

The operation of each coupling component 12, in particular the value of its capacitance, can therefore be modified by applying a command to this coupling component 12, the coupling component 12 being biased directly or in reverse.

The coupling components 12 are identical to each other.

The coupling components 12 are electrically controllable. Thus, each coupling component 12 is able to function as a capacitor, the capacitance of which is variable as a function of electrical control, in particular of the voltage applied to its terminals.

The coupling components 12 are, for example, varicaps, in particular MOS varicaps, varicaps diodes or ferroelectric varicaps.

Alternatively, the coupling components may be MEMS, NEMs, PIN diodes, liquid crystal based components, Schottky diodes, or FET transistors.

The coupling components 12 are electrically controllable.

When the varicaps 12 are ferroelectric varicaps, they can be controlled by being polarized in reverse or in direct.

Moreover, such ferroelectric varicaps can also be thermally controllable. Each ferroelectric varicap is then able to function as a variable capacitor, the capacity of which is variable according to a thermal control applied to it in order to fix its temperature at a given operating temperature.

For example, such thermally controllable ferroelectric varicaps may be BST (Ba1xSrxTiOs) varicaps. In particular, such varicaps BST are advantageous because they are controllable both electrically (in reverse and direct) and thermally, and essentially require the application of a potential difference, and therefore do not consume energy .

For example, a BST varicap may have a variable capacitance that can take values between 3.2 pF and 0.7 pF when the voltage at its terminals varies from 0 V to 20 V, the capacitance being a decreasing function of the value. absolute of the applied voltage.

The coupling components 12 are chosen according to the desired application, in particular depending on the range of capacitance obtainable by varying the voltage across their terminals or by varying their temperature.

When the coupling components 12 are electrically controlled, a variation in the capacitance of a coupling component 12 is obtained by varying the applied voltage across its terminals.

When the coupling components 12 are thermally controlled, a variation in the capacitance of a coupling component 12 is obtained by varying the temperature applied to this coupling component 12.

The coupling components 12 of the device 2 can be controlled in two distinct modes, corresponding to the two operating modes of the device, that is to say the band-pass mode and the notch mode.

The coupling components 12 are controlled in groups, each group of coupling components 12 comprising at least a first coupling component connecting a first elementary pattern to a second elementary pattern adjacent thereto, and a second coupling component, connecting the first elementary pattern to a third elementary pattern adjacent to it. The capacity of the coupling components of a given group are therefore equal to each other. Coupling component groups are disjoint, i.e., each coupling component belongs to a single group.

In particular, in the example shown, in which the elementary patterns form a line-column network, each group of coupling components is a pair of coupling components. Each pair is formed of a first coupling component 12a, connecting a first elementary pattern to a second elementary pattern adjacent thereto in a line, and a second coupling component 12b, connecting the first elementary pattern to a third elementary pattern. which is adjacent to it according to a column. The capacity of the first coupling component of a pair is therefore always identical to the capacity of the second coupling component of this pair. Coupling component pairs are disjoint, i.e., each coupling component belongs to a single pair. Nevertheless, it will be understood that the coupling components interconnecting the conductive elementary patterns of an end line (for example the last line), and the coupling components interconnecting the conductive elementary patterns of an end column. (eg the first column), do not belong to a group or pair of coupling components. These coupling components are therefore omitted.

By capacity of a group (for example a pair) of coupling components is therefore meant the common value of the capacity of the coupling components of this group (in particular of the first coupling component and the second coupling component of a coupling component). pair).

There is also a first set of groups of coupling components and a second set of groups of coupling components, which are disjoint and complementary.

In the example illustrated in FIG. 2, groups or pairs of coupling components of the first set are designated by the general reference 20a, while pairs of coupling components of the second set are designated by the general reference 20b.

As seen in FIG. 2, each of the first and second complementary sets is formed of pairs of non-adjacent, non-adjacent, non-adjacent, in-line non-adjacent coupling components in columns.

Thus, each pair of coupling components 20a of the first set is only adjacent pairs of coupling components 20b of the second set, and conversely, each pair of coupling components 20b of the second set is adjacent only to pairs of coupling components. 20a of the first set.

By pair of adjacent coupling components is meant two pairs of coupling components which both comprise coupling components connecting the same conductive elementary pattern to other elementary patterns. On the contrary, two pairs of non-adjacent coupling components are such that no elementary elementary pattern connected to an elementary pattern by a coupling component of a first of these pairs is connected to an elementary pattern by a coupling component of the second of these pairs.

In a first control mode, corresponding to the notch mode, the coupling components are controlled so that they all have the same capacity. Thus, the capacity of all groups of coupling components is set to the same value.

In a second control mode, corresponding to the bandpass mode, the capacity of the coupling component groups of the first set is set to a first value, and the capacity of the coupling component groups of the second set is set to a second value. , distinct from the first value, such that the ratio of the capacitance Cmin to the value of the capacitance Cmax (Cmin / Cmax) remains below 0.90. The control assembly 14 is configured to selectively control the capacitance value of the coupling component groups 12, in the first mode or in the second mode described above.

In particular, the control assembly 14 is configured to control the value of the capacitance of the groups 20a, 20b of coupling components selectively: according to the first mode, in which the control unit 14 sets the capacity of the set of groups of coupling components with the same value, in order to operate the device 2 in notch mode, according to the second mode, in which the control unit 14 sets the capacity of the coupling components of the first set of groups 20a coupling components to a first value, and sets the capacity of the coupling components of the second set of coupling component groups 20b to a second value, distinct from the first value.

In the first mode, the control assembly 14 is further configured to vary the capacitance value of all the coupling component groups 20a, 20b 12, in order to vary the operating frequency of the device by notch mode, that is, the center frequency of the non-transmitted band. In particular, the operating frequency increases when the value of the capacitance of the coupling components decreases.

In the second mode, the control assembly 14 is further configured to vary the capacitance value of the coupling components of the first set of coupling components and / or the second set of coupling components, in order to vary the operating frequency of the device 2 in bandpass mode, that is to say the center frequency of the transmitted band.

In order to vary the operating frequency of this second mode, the variation of the groups of coupling components must be of the same order, that is to say, for a group 20a of 2.7pF and a group 20b of 3, 2pF, decreasing the values of the variable capacities by -0.5 pF, ie 20a = 2.2 pF and 20b = 2.7 pF, the operating frequency increases. The reciprocity is valid, with a similar increase in coupling component values, the operating frequency decreases.

Further, in the second mode, the control assembly 14 is also configured to vary the capacitance value of the coupling components of the first set of coupling components and / or the second set of coupling components, in order to vary the width of the bandwidth. Increasing the value of the Cmin / Cmax ratio towards 1 decreases the width of the bandwidth and conversely, the decrease of the ratio Cmin / Cmax towards 0 increases the width of the bandwidth. To this end, the control assembly 14 comprises a plurality of control modules of the coupling components 12, configured to control the coupling components 12 to vary their capacity, and a control unit 26, configured to control the control modules according to the desired notch or band-pass mode and / or the desired operating frequency. In Figure 1, for simplification, only a control module is shown schematically and is designated by the general reference 24.

The control modules 24 are each associated with a given group of coupling components, each coupling component being associated with a single control module.

Each control module 24 is configured to control the value of the capabilities of the coupling components of the group associated with it. In particular, each control module is configured to control the value of the capabilities of the coupling components 12a, 12b of the group 20a or 20b associated therewith, in response to a command from the control unit 26. The control unit 26 comprises a processor 28 and a memory 30.

The memory 30 comprises at least one storage area 32 in which are stored, for each notch and band-pass mode, quantities representative of the values of the capacities associated with several given operating frequencies.

Thus, for the notch mode, the storage area 32 comprises, for each possible operating frequency, the value of the magnitude representative of the value of all the capacities making it possible to reach this operating frequency.

For the bandpass mode, the storage area 32 comprises, for each of a plurality of possible operating frequencies, possibly associated with a bandwidth, a pair of values, including the value of the magnitude representative of the capacity. groups of coupling components of the first set and the value of the magnitude representative of the capacity of the groups of coupling components of the second set, making it possible to reach this operating frequency and, if applicable, the bandwidth width.

Each magnitude representative of the value of a capacitance is, for example, the value of the capacitor itself, a voltage value to be applied across the coupling component to obtain this capacitance, or a temperature value to be imposed on the component. coupling to obtain this ability.

These data are for example from a calibration previously performed in real conditions. In particular, if the device 2 is intended to be integrated in a composite wall, the calibration is performed after integration of the device into the composite wall.

The memory 30 furthermore comprises a control application 36 capable of being executed by the processor 28.

When a given mode of operation, notch or bandpass, a given resonant frequency and possibly bandwidth are targeted, the control application 36 is configured to extract from the storage area 32 the values of the magnitudes representative of the capacities of the different groups of coupling components making it possible to obtain an operation of the device 2 according to the intended mode and the targeted operating frequency. Furthermore, the control application 36 is configured to control the control modules 24 by transmitting to each control module 24 the value of the quantity representative of the capacity of the group of coupling components associated with this module.

The operating mode, the operating frequency and the width of the bandwidth are for example entered by an operator by means of a suitable man-machine interface connected to the control unit 26, or are provided by another connected system. to the control unit 26.

According to one embodiment, the coupling components 12 being electrically controllable, the control assembly 14 is adapted to apply electrical control to the coupling components 12, to control the value of the capacitances of the coupling component groups 12.

In this embodiment, the magnitude representative of the value of the capacitance of a coupling component 12 is, for example, the voltage to be applied across the coupling component to obtain this capacitance value. The control unit 26 is thus configured to control at each control module 24 the application of a predetermined electrical voltage across the capacitors of a group 20a or 20b of coupling components 12, depending on the operating mode of operation. the target operating frequency, and possibly the target bandwidth, and each control module 24 is configured to apply the electrical voltage controlled by the control unit 26 to the terminals of the coupling components 12 of the coupling component group 12. For example, the control unit 26 comprises two variable voltage sources, each connected via electrical branches to the groups of coupling components of the first set or the second set respectively.

To achieve notch mode operation, both voltage sources generate a voltage at the same value, while for band-pass operation, the voltages generated by the two voltage sources differ. In these two modes, the voltages generated depend on the target operating frequency.

According to another embodiment, the coupling components 12 being thermally controllable, the control assembly 14 is adapted to apply thermal control to the coupling components 12, to control the value of the capacitances of the coupling component groups 20a, 20b. 12.

In this embodiment, the magnitude representative of the value of the capacitance of a coupling component 12 is, for example, the temperature to be imposed on the coupling component 12 to obtain this capacitance value. The control unit 26 is thus configured to control each control module 24 to apply a predetermined temperature to a group of coupling components, and each control module 24 is configured to apply the temperature controlled by the unit. 26 to the group of coupling components 12.

For example, the control modules 24 may be chosen from Peltier modules, heating resistors, or pyrooptic control means. By way of example, a frequency selective surface device has been manufactured from a 0.78 mm thick substrate made of a material having a real permittivity equal to 3 and a loss tangent of 0 , 0023. A plurality of circular shaped conductive elementary patterns has been printed on this substrate, the elementary patterns forming a row-column array. Each elementary pattern forms a ring of internal diameter equal to 23 mm, the width of the band forming the ring being 0.5 mm. Each elemental pattern occupies a 25 mm square cell. The different elementary patterns are therefore disjoint.

Varicaps were inserted to connect the different elementary patterns, as described above. The varicaps are BST varicaps, whose capacity varies from 3.2 pF to 0.7 pF when the voltage at its terminals varies from 0 V to ± 20 V.

Electrical branches have also been printed on the substrate in order to link each pair of varicaps of a first set, as described above, to a first voltage source, and to connect each pair of varicaps of a second together to a second source of voltage.

In a first step, the frequency response of this device was tested in notch mode by applying several voltage values across the varicaps, the same voltage being generated by the first and second voltage sources. Three voltage values were tested, corresponding to three capacitance values for all the varicaps, equal to 3.2 pF, 1.85 pF and 0.7 pF, respectively.

Electromagnetic waves were emitted on the device, with a zero angle of incidence and a vertical polarization, and the transmitted waves were analyzed to determine the reflection coefficient Su and the transmission coefficient S2i as a function of the frequency, for frequencies between 0.5 and 2.2 GHz.

Figures 3 and 4 thus illustrate the variation of the reflection coefficient Su and the transmission coefficient S2i respectively as a function of the frequency, for capacitance values equal to 3.2 pF (curve A), 1.85 pF (curve B) and 0.7 pF (curve C).

It can be seen from these figures that the operation of the device 1 is that of a notch filter.

Figure 4 shows in particular a displacement of the resonance frequency of the device, that is to say the central frequency of the non-transmitted band, to higher frequencies when the value of the capacitance decreases.

In a second step, the frequency response of this device was tested in bandpass mode by applying several pairs of voltage values across the varicaps, separate voltage values being generated by the first and second voltage sources.

Four pairs of voltage values were tested, corresponding to four pairs of capacitance values, respectively 2.3 / 3.2 pF, 1.5 / 2.9 pF, 0.7 / 3.2 pF, and 0.7 / 1.5 pF.

Electromagnetic waves were emitted on the device, with a zero angle of incidence and a vertical polarization, and the reflected and transmitted waves were analyzed to determine the reflection coefficient Su and the transmission coefficient S21 as a function of the frequency , for frequencies between 0.5 and 2.2 GHz.

Figures 5 and 6 thus illustrate the variation of the reflection coefficient Su and the transmission coefficient S21 respectively as a function of frequency, for these four pairs of capacitance values.

In these Figures, the curve D illustrates the variation of the reflection coefficient Su and the transmission coefficient S21 respectively as a function of the frequency for the pair of capacitance values 2.3 / 3.2 pF.

Curve E illustrates the variation of the reflection coefficient Su and the transmission coefficient S21 respectively as a function of the frequency for the pair of capacitance values 1.5 / 2.9 pF.

Curve F illustrates the variation of the reflection coefficient Su and the transmission coefficient S2i respectively as a function of the frequency for the pair of capacitance values 0.7 / 3.2 pF.

Finally, the curve G illustrates the variation of the reflection coefficient Su and of the transmission coefficient S2i respectively as a function of the frequency for the pair of capacitance values 0.7 / 1.5 pF.

It can be seen from these figures that the operation of the device is that of a band-pass filter whose operating frequency, corresponding to the central frequency of the transmitted frequency band, varies when the absolute values of capacity Cmin and Cmax of the couple varies. In addition, there is a variation in the width of the bandwidth when the value of the ratio Cmin / Cmax of the torque varies. In particular, there is a variation in the bandwidth, with an opening at -3 dB, from 0.010 GHz to 0.150 GHz. The 2.3 / 3.2 pF pair (Curve D) makes it possible to obtain a very narrow bandpass mode, with the CmJCmax ratio close to 1. By decreasing the absolute values of Cmin and Cmax with constant Cmin / Cmax ratio. , an increase in the value of the working frequency is obtained. The bandwidth is adjustable by the variation of the ratio Cmin / Cmax. Indeed, the 2.3 / 3.2 pF pair of ratio Cmin / CmaX = 0.72 has a very narrow bandwidth (0.010 GHz to -3 dB) at the center frequency of 0.96 GHz while the torque 0 , 7 / 3.2 pF ratio Cmin / Cmax = 0.22 has an enlarged bandwidth (0.150 GHz to -3 dB) at the center frequency of 1.26 GHz.

The frequency-selective surface device is thus multifunctional in that it is able to function selectively as a notch or as a band-pass in response to a command, depending on the intended applications. In addition, this device is frequency controllable, the operating frequency and the width of the bandwidth can be changed, by applying a command, depending on the need. In particular, the device offers bandwidth widths that can reach higher values than those offered by traditional devices.

Such a device is able to be integrated in a composite structural wall, without degrading the mechanical properties. It will be understood, however, that only the substrate on which the conductive elementary patterns and possibly the branches are printed, and the coupling components, are integrated into the wall, the control unit being able to be offset outside the wall.

In particular, this device can be integrated in a composite wall of the monolithic type or in a sandwich-type composite wall, in particular by insertion between two composite plies, or at the interface between the core and a skin of the sandwich, or still inserted into the core in a position perfectly parallel to the faces of the structure (for example by gluing between two plates of constituent materials of the soul).

In particular, because of the frequency controllability of the device according to the invention, such a device can be advantageously used: in a structural wall of a naval, land or air carrier, in an active radome wall, associated with an antenna, and / or as a carrier structure, for example a carrier structure of an antenna, in a scrambler, an electronic card, for performing spatial frequency filtering, in a filter antenna or a decoupler.

In particular, the integration of devices according to the invention in a structural wall of a carrier makes it possible to modify the radar signature. The use of devices according to the invention makes it possible to provide structures incorporating new functionalities, adding an added value to initially passive structures, while offering an extension of the life of these structures by its modularity .

According to one embodiment, illustrated in FIG. 6, several devices according to the invention can be used within the same system 30.

Such a system thus comprises several devices according to the invention which share the same substrate, and possibly the same control unit.

In the example illustrated in FIG. 6, the networks 6 of conductive elementary patterns 8 of the various devices 2, each of square shape, are arranged in rows and columns, to form a regular overall network of elementary patterns.

The frequency response of each of the devices 2, in particular its mode of operation as a notch or as a bandpass, its operating frequency and possibly its bandwidth, remains nevertheless controllable independently of the other devices 2 of the device. For example, some devices 2 may be controlled to function as a band pass, the other devices 2 being controlled to function as a tape cutter. Other embodiments may be envisaged. In particular, the conductive elementals are not necessarily circular (rings and solid discs) but can be elliptical, square, rectangular, hexagonal, cross of Jerusalem, etc.

Claims (15)

A frequency selective surface device (2) comprising a substrate (4), a network (6) of conductive elementary patterns (8) printed on a surface of said substrate (4) and forming together a regular network, and a network of coupling components (12, 12a, 12b), each coupling component (12) connecting two adjacent conductive elementary units (8), each coupling component (12, 12a, 12b) having a modifiable capacity by applying a command, said device (2) being characterized in that it further comprises a control assembly (14) configured to selectively control the value of the groups (20a, 20b) of coupling components (12, 12a, 12b) selectively according to a first mode, in which the capacity of all the groups (20a, 20b) of coupling components (12, 12a, 12b) is set to the same value, in order to operate said device (2) in the notch, and a second mode, wherein the capacitance of the coupling components (12, 12a, 12b) of a first set of groups (20a) of coupling components (12, 12a, 12b) is set to a first value, and the capacitance of the coupling components (12, 12a, 12b) of a second set (20b) of coupling component groups (12, 12a, 12b), complementary to the first set, is set to a second value, distinct from the first value, in order to operating said device (2) in bandpass mode, each group (20a, 20b) of coupling components (12, 12a, 12b) comprising a first coupling component (12a) connecting a first elementary pattern to a second elementary pattern adjacent thereto, and a second coupling component (12b) connecting the first elementary pattern to a third elementary pattern adjacent thereto. 2. - Device (2) according to claim 1, characterized in that the network (6) of elementary patterns is a row-column array, each coupling component (12) connecting two adjacent conductive elementary patterns (8) along a line or according to a column. 3. - Device (2) according to any one of claims 1 or 2, characterized in that each group of coupling components (12, 12a, 12b) of the first set, respectively the second set, is adjacent only to groups coupling components (12, 12a, 12b) of the second set, respectively of the first set. 4. - Device (2) according to claims 2 and 3, characterized in that each group (20a, 20b) of coupling components (12, 12a, 12b) is a pair of coupling components (12, 12a, 12b) each pair of coupling components (12, 12a, 12b) being formed of a first coupling component (12a) connecting a first elementary pattern to a second adjacent elementary pattern along a line, and a second coupling component ( 12b) connecting the first elementary pattern to a third adjacent elementary pattern in a column. 5. - Device (2) according to any one of claims 1 to 4, characterized in that in the first mode, said set (14) of control is configured to vary the value of the capacity of all groups (20a , 20b) of coupling components (12, 12a, 12b) for varying a resonance frequency of the device (2). 6. - Device (2) according to any one of claims 1 to 5, characterized in that in the second mode, said set (14) of control is configured to vary the value of the capacity of the coupling components (12). , 12a, 12b) of the first set and / or the second set, for varying a resonant frequency of the device (2). 7. - Device (2) according to any one of claims 1 to 6, characterized in that in the second mode, said set (14) of control is configured to vary the value of the capacity of the coupling components (12). , 12a, 12b) of the first set and / or the second set, for varying a bandwidth of the device (2). 8. - Device according to any one of claims 1 to 7, characterized in that said coupling components (12, 12a, 12b) are electrically controllable, and in that said set (14) of control is adapted to apply a electrically controlling the coupling components (12, 12a, 12b) to control the capacitance value of the coupling component groups (12, 12a, 12b). 9. - Device (2) according to any one of claims 1 to 8, characterized in that said coupling components (12, 12a, 12b) are thermally controllable, and in that said set (14) control is adapted for applying a thermal command to said coupling components (12, 12a, 12b) to control the capacitance value of the coupling component groups (12, 12a, 12b). 10. - Device (2) according to any one of claims 1 to 9, characterized in that said coupling components (12, 12a, 12b) are varicaps, including ferroelectric varicaps. 11. - Device (2) according to any one of claims 1 to 10, characterized in that the assembly (14) comprises: - an array of modules (24) for controlling the coupling components (12, 12a , 12b), each control module (24) being associated with a group (20a, 20b) of coupling components (12, 12a, 12b) among said groups (20a, 20b) of coupling components (12, 12a, 12b). ) and being configured to selectively control the value of the associated coupling component (12, 12a, 12b) group (20a, 20b) capabilities, and - a control module (24) control unit (26), configured to controlling said control modules (24) so that each control module (24) controls the value of the associated coupling group (12, 12a, 12b) group (20a, 20b) capabilities, in the first mode or in the second mode mode selectively. 12. - Device (2) according to claim 11, characterized in that said coupling components (12, 12a, 12b) are electrically controllable, said control assembly (14) is adapted to apply electrical control to the coupling components ( 12, 12a, 12b), in order to control the capacitance of the groups of coupling components (12, 12a, 12b), said control unit (26) is configured to control each control module (24) with the application a predetermined electrical voltage across each coupling component (12) of the group (20a, 20b) of coupling components (12, 12a, 12b) associated with the control module (24), and in that each module ( 24) is configured to apply the electrical voltage controlled by said control unit (26) across each coupling component (12) of the associated coupling component (12, 12a, 12b) group (20a, 20b). 13. - Device (2) according to claim 11, characterized in that said coupling components (12, 12a, 12b) are thermally controllable, said control assembly (14) is adapted to apply a thermal control to said coupling components ( 12, 12a, 12b), in order to control the capacitance of the groups of coupling components (12, 12a, 12b), said control unit (26) is configured to control each control module (24) with the application a predetermined temperature to the group (20a, 20b) of coupling components (12, 12a, 12b) associated with said control module (24), and in that each control module (24) is configured to apply said controlled temperature by said group control unit (26) to the group (20a, 20b) of associated coupling components (12, 12a, 12b). 14. - Device (2) according to any one of claims 1 to 13, characterized in that each elementary conductive pattern (8) is ring-shaped. 15.- system (30) with a frequency selective surface, said system (30) being characterized in that it comprises a plurality of devices (2) according to any one of claims 1 to 14, the substrates (4) of said devices (2) being common to said devices (2), the elementary conductive patterns (8) of each device (2) being printed on at least one surface of the substrate (4) disjoined from any surface of the substrate (4) on which are printed the elementary conductive patterns (8) of another device (2).