EP1580844A1 - Phase shifter with linear polarization and a resonating length which can be varied using mem switches. - Google Patents

Abstract

The phase shifter has a slot radiator (FR) provided with micro electromechanical systems (DC). The systems are to be placed in two different states permitting and prohibiting respectively creation of a short circuit intended to vary a characteristic resonating length of the slot radiator, in order to shift a phase of wave reflected by the phase shifter. An independent claim is also included for a reflectarray antenna comprising a phase shifter.

Description

The invention relates to the field of reflector array antennas (or "Reflectarray antennas"), and more particularly the phase-shifter cells who equip such antennas.

Antenna reflector network is one of the two main families of antennas network, the other family consisting of antennas phased array (or "Phased Array Antennas"). These network antennas are particularly interesting because they can be reconfigured, for example to allow the passage of a zone of cover (or "spot") to another.

A reflector array antenna consists of radiating elements intercepted with minimal losses of waves, including signals to be transmitted, delivered by a primary source, in order to reflect them in a chosen direction, called the pointing direction. In order to allow reconfigurability of the antenna pattern, each radiating element is equipped with a phase control device with which it constitutes a cell passive or active phase shifter.

By "phase-shifting cell" is meant here as well the structures to cavity and radiating slit as planar resonant structures to paved radiating (or "patch").

The invention more particularly targets phase-shifting cells active, linearly polarized. These usually include a cell phase shifter provided with either a switch (or switch) consisting of diodes (usually PIN type), or MESFETs, or varactors, either mechanical control means (for example an engine charged with moving a dielectric bar).

Switched phase shifters consume an important amount of energy and are subject to significant losses and overheating. Mechanically controlled phase shifters are complex to put particularly in the case of large networks, and energy consumers. In either case, the disadvantages induced by the phase control techniques used limit the applications of phase-shifting cells, particularly in the space domain and more specifically in observation platforms such as satellites.

The purpose of the invention is therefore to improve the situation in the case of reflective grating antennas with active polarization phase shifters linear.

For this purpose, it proposes a phase-shifting cell presenting a resonant length characteristic and comprising in at least one place chosen a micron electromechanical device, of the MEMS type (for "Micro ElectroMechanical System"), which can be placed in at least two different states allowing and prohibiting the establishment of a short circuit intended to vary the resonant characteristic length, so to vary the phase shift of the waves to reflect which present at least a linear polarization.

Each MEMS device may for example comprise a flexible bridge conductor whose states are controlled by two electrodes of control substantially superimposed and one of which is constituted by the bridge. Alternatively, each MEMS device may comprise a flexible beam suspended conductor (or "cantilever") whose states are controlled by a control electrode placed below its suspended part.

In a family of embodiments, the cell may comprise a planar resonant structure comprising at least one upper block rectangular placed substantially parallel to a lower ground plane, at a selected distance, the lower ground plane defining at least one Conductive "pad", for example rectangular, fully surrounded a non-conductive zone, placed below the upper pavement and dimensions smaller than his. In this case, the cell less a metallized crossing connecting the upper block to the pellet, and the MEMS device is placed at the level of the non-conductive area in order to establish in one of its states a connection between the pellet and the rest of the ground plane to control the resonant length of the upper pad.

The lower ground plane can possibly define at least two pellets (for example rectangular) completely surrounded by a zone non-conductive, placed below the upper pad and dimensions less than his. In this case, the cell comprises at least two metallized crossings respectively connecting the upper pavement to one of the pellets, and at least two MEMS devices each placed at the level of one of the non-conducting areas in order to establish links between the one less lozenges and the rest of the ground plane, thus allowing to define at least three resonant lengths of different upper pavement according to their states.

In a variant of this family of realization, the cell can have a top ground plane including at least one slot radiating, provided with a MEMS device controlling its resonant length characteristic, a lower ground plane, and metallic crossings connecting the lower ground plane to the peripheral parts of the plane of higher mass in order to define a resonant cavity. For example, the plan of upper mass may comprise at least two radiating slots each provided with a single MEMS device controlling their length resonant characteristic. Each MEMS device can then be preferentially placed substantially in the middle of a radiating slot. By elsewhere, the slots are preferably substantially parallel to each other and may have slightly different lengths. But, they can also have a curved shape, so as to achieve together a short annular slot circuited at two substantially opposite points.

Alternatively, the upper ground plane may comprise a slot radiator, provided with at least two MEMS devices for defining at least three different resonant lengths depending on their states.

Moreover, the higher ground plane can possibly comprise at least one rectangular radiating slot having long sides parallel to a first direction, and at least one other slot radiating rectangular with long sides parallel to a second direction perpendicular to the first, to allow a double linear polarization.

In another family of embodiments, the cell may comprise a planar resonant structure comprising a top paver placed substantially parallel to a lower ground plane at a distance chosen. In this case, the block comprises at least one slot provided with at least a MEMS device controlling its characteristic resonant length.

The cell can then comprise a single slot (of length half wave) provided with at least two MEMS devices, allowing to define at least three different resonant lengths depending on their states. In a variant, the upper block may be substantially square, and the cell may comprise at least first and second rectangular slots (in length quarter wave) placed substantially opposite one another, leading to two opposite non-radiating sides of the square, and each having minus two MEMS devices to define at least three lengths resonant different according to their states. In the latter case, the cell can also include at least third and fourth slots rectangular (of quarter-wave length) placed substantially opposite from each other, leading to two other opposite non-radiating sides square, and each having at least two MEMS devices, to define at least three other different resonant lengths according to their states, to allow a linear double polarization. We can also provide several upper pavers each provided with at least half a slot quarter of wave, pairs of half-slots facing each other then constituting half wave slots.

In the presence of a bridge MEMS device and slot (s) rectangular (s), the bridge is preferably placed substantially parallel to the long sides of the slot. On the other hand, in the presence of a MEMS device with beam and slot (s) rectangular (s), said beam is preferentially placed substantially perpendicular to large sides of the slot.

By the way, the lower ground plane can define a lower pavement placed below the upper block and of dimensions smaller than his In this case, the cell comprises metallized vias which connect the plane mass to peripheral parts of the upper pavement in order to define a resonant cavity. This paved and cavity structure defines yet another family of dephasing cells.

The invention also proposes a reflective array antenna equipped with at least two dephasing cells of the type presented above.

The invention is particularly well adapted, although in a non exclusive, to Ku-band geostationary telecommunication antennas (12 to 18 GHz), with reconfigurable coverage (change of orbital position, adaptation of traffic), and to C-band radar antennas (4 to 8 GHz) or X band (8 to 12 GHz), in particular for SAR-type radars (radar synthetic opening).

• la figure 1 illustre de façon schématique, dans une vue du dessus, un premier exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 2 est une vue en coupe transversale selon l'axe II-II de la cellule déphaseuse de la figure 1,
• la figure 3 illustre de façon schématique, dans une vue du dessus, un deuxième exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 4 est une vue en coupe transversale selon l'axe IV-IV de la cellule déphaseuse de la figure 3,
• la figure 5 illustre de façon schématique, dans une vue du dessus, un troisième exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 6 est une vue en coupe transversale selon l'axe VI-VI de la cellule déphaseuse de la figure 5,
• la figure 7 illustre de façon schématique, dans une vue du dessus, un quatrième exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 8 est une vue en coupe transversale selon l'axe VIII-VIII de la cellule déphaseuse de la figure 7,
• la figure 9 illustre de façon schématique, dans une vue du dessus, un cinquième exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 10 illustre de façon schématique, dans une vue du dessus, un sixième exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 11 est une vue en coupe transversale selon l'axe XI-XI des cellules déphaseuses des figures 10 et 12,
• la figure 12 illustre de façon schématique, dans une vue du dessus, un septième exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 13 illustre de façon schématique, dans une vue du dessus, un huitième exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 14 illustre de façon schématique, dans une vue du dessus, un neuvième exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 15 illustre de façon schématique, dans une vue du dessus, un dixième exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 16 illustre de façon schématique, dans une vue du dessus, un onzième exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 17 est une vue en coupe transversale selon l'axe XVII-XVII de la cellule déphaseuse de la figure 16,
• la figure 18 est une vue en perspective détaillant une partie de la cellule déphaseuse de la figure 16,
• la figure 19 illustre de façon schématique, dans une vue du dessus, un douzième exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 20 est une vue en coupe transversale selon l'axe XX-XX de la cellule déphaseuse de la figure 19,
• la figure 21 illustre de façon schématique, dans une vue du dessus, un treizième exemple de réalisation d'une cellule déphaseuse selon l'invention, sans ses dispositifs MEMS,
• la figure 22 illustre de façon schématique, dans une vue du dessus, un quatorzième exemple de réalisation d'une cellule déphaseuse selon l'invention, sans ses dispositifs MEMS,
• la figure 23 illustre de façon schématique, dans une vue du dessus, un quinzième exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 24 illustre de façon schématique, dans une vue du dessus, un seizième exemple de réalisation d'une cellule déphaseuse selon l'invention,
• la figure 25 est une vue en coupe transversale selon l'axe XXV-XXV de la cellule déphaseuse de la figure 24, et
• la figure 26 est un diagramme illustrant l'évolution du déphasage (Δ en degrés) en fonction de la longueur d'une fente (b en mm), pour plusieurs valeurs différentes de longueur de pavé supérieur (x = 3, 4, 5, 7,5 et 8 mm respectivement en allant du haut vers le bas) et pour une épaisseur de substrat (d').

Other characteristics and advantages of the invention will become apparent upon examination of the following detailed description, and the accompanying drawings, in which:

• FIG. 1 schematically illustrates, in a view from above, a first embodiment of a phase-shifting cell according to the invention,
• FIG. 2 is a cross-sectional view along axis II-II of the phase-shifting cell of FIG. 1;
• FIG. 3 schematically illustrates, in a view from above, a second exemplary embodiment of a phase-shifting cell according to the invention,
• FIG. 4 is a cross-sectional view along the axis IV-IV of the phase-shifting cell of FIG. 3;
• FIG. 5 schematically illustrates, in a view from above, a third embodiment of a phase-shifting cell according to the invention,
• FIG. 6 is a view in cross section along the axis VI-VI of the phase-shifting cell of FIG. 5,
• FIG. 7 schematically illustrates, in a view from above, a fourth embodiment of a phase-shifting cell according to the invention,
• FIG. 8 is a cross-sectional view along the axis VIII-VIII of the phase-shifting cell of FIG. 7,
• FIG. 9 schematically illustrates, in a view from above, a fifth exemplary embodiment of a phase-shifting cell according to the invention,
• FIG. 10 schematically illustrates, in a view from above, a sixth exemplary embodiment of a phase-shifting cell according to the invention,
• FIG. 11 is a cross-sectional view along the axis XI-XI of the phase-shifting cells of FIGS. 10 and 12,
• FIG. 12 schematically illustrates, in a view from above, a seventh embodiment of a phase-shifting cell according to the invention,
• FIG. 13 schematically illustrates, in a view from above, an eighth embodiment of a phase-shifting cell according to the invention,
• FIG. 14 schematically illustrates, in a view from above, a ninth embodiment of a phase-shifting cell according to the invention,
• FIG. 15 schematically illustrates, in a view from above, a tenth exemplary embodiment of a phase-shifting cell according to the invention,
• FIG. 16 schematically illustrates, in a view from above, an eleventh embodiment of a phase-shifting cell according to the invention,
• FIG. 17 is a view in cross section along the axis XVII-XVII of the phase-shifting cell of FIG. 16,
• FIG. 18 is a perspective view detailing a portion of the phase shifter cell of FIG. 16,
• FIG. 19 schematically illustrates, in a view from above, a twelfth embodiment of a phase-shifting cell according to the invention,
• FIG. 20 is a cross-sectional view along the axis XX-XX of the phase-shifting cell of FIG. 19,
• FIG. 21 schematically illustrates, in a view from above, a thirteenth embodiment of a phase-shifting cell according to the invention, without its MEMS devices,
• FIG. 22 schematically illustrates, in a view from above, a fourteenth embodiment of a phase-shifting cell according to the invention, without its MEMS devices,
• FIG. 23 schematically illustrates, in a view from above, a fifteenth embodiment of a phase-shifting cell according to the invention,
• FIG. 24 schematically illustrates, in a view from above, a sixteenth embodiment of a phase-shifting cell according to the invention,
• FIG. 25 is a cross-sectional view along the axis XXV-XXV of the phase-shifting cell of FIG. 24, and
• FIG. 26 is a diagram illustrating the evolution of the phase shift (Δ in degrees) as a function of the length of a slot (b in mm), for several different values of greater paver length (x = 3, 4, 5 , 7.5 and 8 mm respectively from top to bottom) and for a substrate thickness (d ').

The accompanying drawings may not only serve to supplement the invention, but also contribute to its definition, if necessary.

The invention relates to a polarization-active phase shifter cell linear for an active reflector array antenna.

The reflector array antenna can for example be dedicated to telecommunications, for example of the Ku-band geostationary type (12 to 18 GHz), with reconfigurable coverage (change of orbital position or adaptation of traffic), or to C-band (4 to 8 GHz) or band radars X (8 to 12 GHz), especially for SAR type radars synthetic), or high-speed ISL-RF type links, in particular inside a small constellation of satellites flying in formation.

In its greater generality, a phase-shifting cell, according to the invention comprises in one or more selected locations a device electromechanical micrometer, MEMS type (for "Micro ElectroMechanical System "). Each MEMS device can be placed at using electrical controls, in at least two different states permitting and prohibiting respectively the establishment of a short circuit intended to vary a characteristic resonant length of the cell, in order to to vary the phase shift of the waves to be reflected (from the source of the antenna) having at least one linear polarization.

Such a phase-shifting cell can be divided into three major families according to its radiant structure. A first family groups together cavity and slit (s) radiating structures, a second family groups together resonant planar paved structures (or "patches") and a third family groups planar resonant cavity structures.

Reference is first made to Figures 1 to 9 to describe examples of phase-shifting cells belonging to the first family.

In FIGS. 1 and 2 is illustrated a first example of a cell CD phase shifter comprising a substrate SB having a "rear" face (or "lower"), secured to an "inferior" ground plane PM1, and a face "before" (or "superior"), solidarized to a plane of mass "Superior" PM2.

The SB substrate is for example made of Duroid or TMM and has a thickness d equal, for example, to λ / 4, where λ is the length wave in the void of the waves to be reflected, coming from the source of the antenna.

The ground planes lower PM1 and higher PM2 are connected electrically between them via holes (or bushings) TM metallized formed in SB substrate. These plans are for example made from alumina, silicon or glass substrates which, because of their their small thicknesses (typically 500 μm) must be reported on a SB substrate in Duroid or TMM so as to allow obtaining a thickness equal to λ / 4. The metallized holes TM are preferentially implanted at the periphery of the lower mass planes PM1 and higher PM2 in order to define a resonant cavity.

Two techniques can be envisaged to achieve this assembly. A first technique consists in superimposing a substrate in Duroid (or Metclad), for example with a thickness of about 3 mm, on a alumina substrate, for example with a thickness of approximately 0.254 mm, and then depositing a lower ground plane PM1 on the underside of the substrate in Duroid and an upper ground plane PM2, on the upper face of the alumina substrate, said upper ground plane PM2 being locally interrupted by the slits. A second technique is to use only one substrate Duroid (or Metclad), for example of thickness equal to about 2 or 3 mm, then to form on its upper face portions of a plane of intermediate mass in which control lines are formed of tension, then to report on this upper face portions of alumina substrates, for example with a thickness of approximately 0.254 mm, having on an upper face an upper ground plane PM2 each having one or more slots and then depositing a ground plane lower PM1 on the underside of the Duroid substrate, and finally to connect the lower, middle and upper ground planes by two levels of holes (or traverses) metallized.

Moreover, the upper ground plane PM2 comprises a single radiating slot FR, preferably of rectangular shape defined by two long sides (longitudinal), of length b, and two short sides (transverse), of width a.

This radiating slot FR is for example made by etching the upper plane of mass PM2.

Moreover, the radiating slot FR has a resonance of parallel LC type. The parameters of such a resonator (resonant frequency and bandwidth) depend mainly on the length b and width a of the radiating gap FR, as well as the permittivity ε _r of the substrate SB.

Several modes can propagate in the cavity delimited by the metallized holes TM. Each of these modes has a clean propagation constant β and a characteristic impedance Z _{0 of its} own. The cut-off frequency of the modes in the cavity depends mainly on the length m _x and width m _y of the lower mass planes PM1 and higher PM2, as well as the permittivity ε _r of the substrate SB. It is also recalled that a vertical resonance can occur in this type of cavity when its thickness d is equal to nλ _g / 2, where n is an integer and λ _g is the wavelength of the mode (s) ) guided (s) propagating in the cavity.

For example, one can choose a square mesh network in which m _x = m _y = 0.7λ = 8 mm. In this case, and in the presence of a wavelength λ corresponding to a working frequency of 26.4 GHz, the cavity has a cutoff frequency equal to 18.75 GHz and operates only in its fundamental mode, this which corresponds to a guided wavelength λ _g equal to approximately 16.14 mm, in the case of an air cavity.

In the presence of a cavity with a thickness d equal to λ / 4 (in this case approximately λ _g / 5.7), phase shifts of up to 360 ° can be obtained for slot widths FR of between approximately 0.25 mm. and about 1 mm. For example, in the presence of a width equal to 0.5 mm, the point of inflection of the phase shift is obtained at the resonance of the slot FR, which corresponds to a length b equal to about 5.5 mm, taking into account other values mentioned above.

In this embodiment, the radiating slot FR is preferentially centered in the middle of the upper mass plane PM2. But he could be otherwise, especially in the presence of a possible slot complementary parasite. In the latter case, the slots are located preferentially symmetrically with respect to the center of the cell.

Moreover, in this exemplary embodiment, the radiating slot FR is provided with three MEMS DC devices each constituting a switch two-state. Of course, the radiating slot could have a number different from MEMS DC devices as long as it is at least equal to one.

Each MEMS DC device here consists of a flexible bridge PT conductor whose two ends are secured to studs of holding PL themselves secured to the upper face of the substrate SB. These plots PL are for example made of gold or aluminum and have a thickness slightly greater than that of the upper ground plane PM2. The PT flexible bridge is made in the form of a blade made conductive, by example by metallization in gold or aluminum, and installed in the slot FR substantially parallel to its longitudinal edges.

Moreover, each MEMS DC device comprises two electrodes substantially superimposed control, one of them being constituted by the flexible bridge PT, and the other being, for example, placed at a level above the flexible bridge PT (not shown), these two electrodes being connected to a supply circuit (not shown).

It is also provided on the upper face of the substrate SB, the inside of the radiating slot FR and substantially at the level of a part central to its longitudinal edges, two small access lines LA placed substantially facing each other, perpendicular to the flexible bridge PT, and electrically connected to the PM2 upper ground plane.

In the presence of a control current selected at the level of control electrodes, the suspended part of the PT bridge is drawn towards said LA access lines. The suspended part then flexes until it comes to contact of the two access lines LA, which locally generates a short circuit in the radiating slot FR and reduces its characteristic resonant length (b), which is its electrical length. This is one of the two states of the DC MEMS device.

In the absence of control current, the PT bridge is remote from access lines LA, so that the length of the radiating gap FR is not disrupted. This is the other state of the MEMS DC device.

By controlling separately the different MEMS devices DC, it is therefore possible, in this embodiment, to define in three different positions three short circuits corresponding to at least four different resonant lengths for the FR slot. Of course, the positions different MEMS DC devices are chosen so as to achieve a regular quantification of the phase law. This positional constraint favors the implementation of MEMS devices at the edge of the slot. These different resonant lengths correspond to different phase shifts of the wave reflected by the phase shifter cell CD.

In Figures 3 and 4 is illustrated a second example of CD phase shifter cell of the first family. This is a variant of the phase-shifting cell CD described above with reference to FIGS. 1 and 2. More precisely, what differentiates the first embodiment of the second this is the embodiment of the MEMS devices.

Here, each MEMS device DC 'comprises a flexible beam (or "Cantilever") conductive PE having an end secured to a stud PL conductor, formed in the radiating slot FR along one longitudinal edges and electrically connected to the ground plane higher PM2.

This pad PL 'is for example made of gold or aluminum and has a thickness slightly greater than that of the ground plane upper PM2, so that the beam PE is suspended above the radiating slot FR and the level of the upper ground plane PM2. Beam flexible PE is made in the form of a blade made conductive, by example using a metallization in gold or aluminum, installed substantially perpendicular to its longitudinal edges. The free end PE beam crosses the slot FR in its width and overflows slightly on the upper mass plane PM2 in a place where is preferentially placed an electrically conductive PLC contact pad.

Moreover, each MEMS device DC 'comprises a EC 'command placed below the suspended central part of the PE beam, and connected to a supply circuit (not shown), another electrode being constituted by the flexible conducting beam PE. The electrode of EC 'command is formed on the upper face of the SB substrate, inside of the radiating gap FR.

In the presence of a control current chosen at the level of the control electrode EC ', the suspended part of the beam PE is attracted towards said electrode. She then flexes until her free end come into contact with the PLC contact pad, which locally generates a short circuit in the radiating slot FR and reduces its resonant length characteristic (b), which is its electrical length. This is one of the two states of the MEMS device DC '.

In the absence of control current, the free end of the beam PE is away from the PLC contact pad, so that the length of the slot radiating FR is not disturbed. This is the other state of the device MEMS DC.

By controlling separately the different MEMS devices DC ', it is therefore also possible, in this embodiment, to define in three different positions three short circuits corresponding to the minus four different resonant lengths for the FR slot. Good understood, the positions of the different MEMS devices DC 'are chosen from in order to carry out a regular quantification of the phase law. These different resonant lengths correspond to different phase shifts of the wave reflected by the phase shifter cell CD.

In this embodiment, the radiating slot FR is provided of three DC MEMS devices. But, the radiating slot FR could have a different number of MEMS devices DC 'when this one is at least equal to one.

In FIGS. 5 and 6 is illustrated a third example of a cell CD phase shifter of the first family. In this example the cell CD phase shifter takes up the structure of the first example described above in reference to Figures 1 and 2, but instead of a single radiating slot she has several (N = 5), and each slot has a single device MEMS DC with PT bridge. Of course, the number N of radiating slits illustrated is not limiting. It can take any higher value or equal to two. Moreover, it can be envisaged that at least one of the slots is not equipped with a MEMS device.

The radiating slots have, for some, lengths different. More precisely, in the illustrated example, the ground plane upper PM2 has two radiating end slots FR1, having a first characteristic resonant length L1, two slots intermediate radiators FR2, having a second length resonant characteristic L2 greater than L1, and a radiating slit central FR3, having a third characteristic resonant length L3 greater than L2. In one variant, the five slots could have five different lengths.

Here, the five radiating slots FR1 to FR3 are substantially centered with respect to the middle of the upper mass plane PM2, and their MEMS DC PT bridge device is also installed in centered position. But, we could do differently. Indeed, in the example described above we run around the undesirable slots, but we could also modify the resonant length of some of them to excite several resonances and well control the phase shift between slots, with the coupling.

The distance separating two adjacent slits may be fixed or variable. It varies according to the needs. It is typically between about 100 μm and 500 μm.

This is to use one or more radiating slots in placing their respective MEMS DC devices in their second state (no decreased). The slot or slots that you do not want to use are short-circuited by placing their MEMS DC devices in their first state (flexed). The phase variation of the reflected wave is thus obtained here by selecting one of the combinations of short-circuited and non-short-circuited slots. AT each combination corresponds in fact to a particular and discrete phase shift mainly function of the ratio between the smallest resonant length characteristic and the greatest characteristic resonant length.

Each slot short-circuited in the middle acts as it were as a parasitic element for the neighboring non-shorted slot. It's about here to excite several resonances to have a range of phase shifts acceptable, while avoiding a very resonant response leading to low band performance. The coupling between the different resonances, achieved by coupling between a slot and a pad (or patch), can mitigate the resonant answer.

In FIGS. 7 and 8 is illustrated a fourth example of CD phase shifter cell of the first family. This is a variant of the CD phase-shifting cell described above with reference to Figures 5 and 6.

More specifically, what differentiates the fourth example of realization of the third is the embodiment of MEMS devices. In this example, each MEMS DC device with a PT bridge is indeed replaced by a MEMS DC 'PE beam device, of the type of those described in reference to Figures 3 and 4.

The operation of this phase-shifting cell CD is identical to that of the phase-shifting cell described above with reference to FIGS. 5 and 6.

As illustrated in the fifth example of Figure 9, it is possible to form a CD phase-shifting cell belonging to the first family and adapted to a linear double polarization.

To do this, at least one radially oriented FRV slot is used in a first direction ("vertical"), and at least one radiating slot HRF oriented in a second ("horizontal") direction, perpendicular to the first one. Of course, as illustrated in FIG. 9, the cell CD phase shifter may have one or more FRV radiating slots and one or more FRH radiating slots as required. The cell is then preferably rectangular and has a width substantially equal to half of its length.

It is possible to use FRV and FRH radiating slots having only one MEMS device with PT bridge or PE beam, but however, it is preferable to use FRV and FRH radiating slots having at least two PT bridge or PE beam MEMS devices (as shown).

Reference is now made to Figures 10 to 18 for describing embodiments of phase-shifting cells belonging to the second family.

In Figures 10 and 11 is illustrated a first example of CD phase-shifting cell comprising a substrate SB having a face back (or lower), secured to a lower ground plane PM1 defining a lower tile (or "patch"), and a front (or upper) face, solidarized to a higher ground plane defining a block (or "patch") higher PS. The upper PS and lower PM1 tiles define a planar resonant structure.

The SB substrate is for example made of Duroid or TMM and has a thickness of weak, typically of the order of λ / 10 to λ / 5, where λ is the wavelength in the vacuum of the waves to reflect, coming from the source of the antenna.

The upper block PS is placed substantially parallel to the plane lower mass PM1 and has dimensions smaller than hers. For example, and as illustrated, the upper PS pad is shaped rectangular, and preferentially square.

In addition, the upper block PS has a single slot FP, preferentially of rectangular shape defined by two long sides (longitudinal), of length b, and two small sides (transverse), of width at.

This slot FP is for example made by etching the plane of mass constituting the upper pavement PS.

In this embodiment, the slot FP is provided with three MEMS DC devices with PT bridge each constituting a two-way switch states, of the type of those described above with reference to Figures 1 and 2. Of course, the FP slot could have a different number of MEMS DC devices as long as it is at least one.

The operating principle of this phase-shifting cell CD, and more precisely of its MEMS DC devices, is identical to that described previously with reference to Figures 1 and 2. Only the physical effect involved differs. The slot FP is here intended to disrupt the path of currents that circulate in the upper pavement PS. By varying the length of the slot FP, by the establishment of short-circuit (s) chosen by means of at least one of the MEMS devices DC placed in its first state (bent), the currents disturbances of the currents are varied, which varies the characteristic resonant length (or electrical length) of the pavement higher PS and therefore the phase shift of the reflected wave.

It is important to note that the invention can only apply here to condition that the upper PS is resonant at λ / 2.

In FIG. 12 is illustrated a second example of a cell CD dephaser of the second family. This is a variant of the cell CD phase shifter described above with reference to Figures 10 and 11. More precisely, what differentiates the first embodiment of the second this is the embodiment of the MEMS devices.

Here, each MEMS device DC 'is of PE beam type, as in the embodiment described above with reference to Figures 3 and 4. Moreover, in this embodiment, the disturbing slot FP is equipped with three MEMS DC devices. But, the disruptive crack FP could have a different number of MEMS devices DC 'when this one is at least equal to one.

As illustrated in FIGS. 13 and 14, it is possible to envisage least third and fourth exemplary embodiments, variants of first and second exemplary embodiments described above with reference Figures 10 to 12.

More specifically, the third example illustrated in FIG. 13 has two holes (or crossings) metallized TM to couple electrically the upper pavement PS and the lower ground plane PM1 of either side of the two opposite ends of the disturbing slot FP. These MT metallized holes are intended to supply DC power to the pavement higher PS so as to bias the MEMS device.

In the fourth example shown in Figure 14, the upper pavement PS has two small disturbing slots F1 and F2, whose resonance is approximately one quarter of the length wave, placed substantially opposite one another and opening onto opposite, non-radiating edges. Each small slot F1, F2 is provided of at least one (here two) MEMS device with PT bridge (but it could be a PE beam). Moreover, a hole (or crossing) metallized TM allows electrically couple the upper PS block and the lower ground plane PM1 in a central part located between the two small slots disruptive F1 and F2. This metallized hole MT is intended to supply direct current the upper pad PS so as to bias the device MEMS. We can consider making two small quarter disruptive slots wave, or more, opening on at least one of the non-radiating sides.

Of course, one can also consider that the PS upper pad (substantially square) includes only a rectangular slot opening on a non-radiating side of the square and having at least two devices MEMS DC or DC '.

As illustrated in the fifth example of Figure 15, it is it is possible to form a phase-shifting cell CD belonging to the second family and adapted to a linear double polarization.

To do this, one can for example use at least two small disruptive slots F1 and F2 oriented in a first direction, and at minus two small disturbing slots F3 and F4 oriented according to a second direction, perpendicular to the first. Here we mean "small split "a disturbing FP slot of the type shown above in reference to Figure 14.

It is possible to use small disturbing slots F1 to F4, quarter-wave length, with only a single MEMS bridge device PT or PE beam, but it is however preferable to use small disruptive slots F1 to F4 having at least two MEMS devices to PT bridge or PE beam (as shown). The number of MEMS devices used in each slot depends on the number of phase states that one wish to obtain.

As in the previous example, a hole (or crossing) metallized TM makes it possible to electrically couple the upper block PS and the plane of lower mass PM1 in a central part located between the four small disruptive slots F1 to F4 of quarter-wave length. This MT metallized hole is intended to supply DC power to the upper pad PS so as to polarize the MEMS device.

In the last three embodiments (FIGS. 13 to 15), the upper PS block is powered by at least one hole Metallic TM. But, as a variant, this feed can be carried out by means of a quarter-wave line with high impedance.

In Figures 16 to 18 is illustrated a sixth example of CD phase-shifting cell comprising a substrate SB having a face back (or lower), secured to a lower ground plane PM1, and a front (or upper) side, secured to a ground plane upper defining a patch (or patch) upper PS 'shape rectangular. The upper pavement PS 'and the lower ground plane PM1 constitute a short-circuited cobblestone structure that defines a structure planar resonant. It is important to note that the length of the pavement higher PS is chosen so that it is resonant at λ / 4.

The SB substrate is for example made of Duroid or TMM and has a thickness of weak, typically of the order of λ / 10 to λ / 5, where λ is the wavelength in the vacuum of the waves to reflect, coming from the source of the antenna.

The upper pavement PS 'is placed substantially parallel to the plane lower mass PM1 and has much smaller dimensions than at least in one direction.

As illustrated in FIG. 18, the lower ground plane PM1 has at least one small conductive "pellet" PI, isolated from its own conductive part by a non-conducting zone Z, made for example by engraving. Each small conductive pad Pl is electrically connected to the upper pavement PS 'via a hole (or crossing) metallized TM. Moreover, each small conductive pad P1 is preferably rectangular shape, and more preferably square.

Each metallized hole TM is connected to the upper pavement PS 'in one chosen place, the different places being preferentially aligned along a straight line parallel to the longitudinal sides of said pavement higher PS.

Moreover, each small conductive pad PI is provided with a MEMS device with PT bridge or with PE beam (as illustrated in FIG. 18), of the type described above. Each MEMS device DC '(or DC) is intended to establish an electrical connection between its lower pavement Pl and the conductive part of the lower ground plane PM1, when placed in his first state (bent). So when one of the devices MEMS DC '(or DC) is placed in its first state (flexed), the metallized hole TM, which is connected at its small conductive pad Pl, bypasses the upper pad PS ' substantially at the point where it is connected to it, which has the effect of vary its characteristic resonant length (or electrical length) and therefore the phase shift of the reflected wave.

This structure is advantageous because its devices are placed on the backside they are further protected from radiation.

In the example illustrated in FIGS. 16 and 17, five metallized holes TM make it possible to define five short circuits corresponding to at least six different resonant lengths for the upper pad PS '. Therefore, by separately controlling the different MEMS devices DC '(or DC), it is possible to obtain several different phase shifts of the wave reflected by the CD phase shifter cell.

Of course, the phase-shifting cell CD may comprise a number MEMS devices (DC or DC ') different from five, provided that the latter is less equal to one. The number of MEMS devices used depends on the number of phase states that one wishes to obtain.

It is important to note that in this exemplary embodiment, at the resonant frequency, the sum of the length of the "active" dipole (that is to say between the short circuit and the other end of the dipole) and the length of the short-circuit must be equal to one quarter of the wavelength of the guided mode λ _g .

This embodiment may allow the constitution of a cell linear polarization phase shifter, of the type illustrated in FIG. figure 9. To do this, it is necessary to combine "horizontal" dipoles with "vertical" dipoles of the type described above with reference to FIGS. 16 to 18.

Reference is now made to Figures 19 and 20 to describe an example of phase-shifting cell belonging to the third family.

This exemplary embodiment constitutes, in a way, a structure intermediate between the exemplary embodiments illustrated in FIGS. 5 to 8 and the exemplary embodiments illustrated in FIGS. 10 to 12.

Here, the phase shifter cell CD comprises a substrate SB comprising a rear face (or lower), secured to a lower ground plane PM1, and a front face (or upper), secured to an upper pad PS.

The SB substrate is for example made of Duroid or TMM and has a thickness d equal to λ / 4, where λ is the wavelength in the vacuum waves to reflect, from the source of the antenna.

The substrate SB is crossed, on its periphery, by holes (or crossings) TM connected to the lower ground plane PM1 and surrounding the upper pad PS to define a resonant cavity. By example, for operation in the Ku band, the upper pad PS is a square of length between about 15 mm and about 17 mm.

In addition, the upper block PS has at least two (here five) radiating slots each having a single MEMS device (DC or DC ') with PT bridge or PE beam. Of course, the number N of slots radiating illustrated is not limiting. It can take any value greater than or equal to two. For example, the slots have a large side of length between about 5 mm and about 7 mm, and a small side of width between about 0.3 mm and about 0.7 mm.

The radiating slots have, for some, lengths different. Specifically, in the example shown, the upper PS block has two radiating end slots FR1, presenting a first resonant length characteristic L1, two radiating slots intermediate FR2, having a second resonant length characteristic L2 greater than L1, and a central radiating slot FR3, having a third characteristic resonant length L3 greater than L2. In one variant, the five slots could have five lengths different.

Here, the five radiating slots FR1 to FR3 are substantially centered relative to the middle of the upper PS block, and their devices MEMS DC to PT bridge (or DC 'to PE beam) are also installed in centered position (for example).

This is to use one or more radiating slots in placing their respective MEMS DC devices in their second state (no decreased). The slot or slots that you do not want to use are short-circuited by placing their MEMS DC devices in their first state (flexed). The phase variation of the reflected wave is thus obtained here by selecting one of the combinations of short-circuited and non-short-circuited slots. AT each combination corresponds in fact to a particular and discrete phase shift mainly function of the ratio between the smallest resonant length characteristic and the greatest characteristic resonant length.

Each slot short-circuited in the middle acts as it were as a parasitic element for the neighboring non-shorted slot. By therefore, it is likely to improve the bandwidth of the slot not short-circuited.

In the example described above, the slots which are not desirable, but we could proceed differently. For example, we can modify the resonant length of some slots to excite several resonances and well control the phase shift between slots, with the coupling. This can for example be done by placing one or more (for example two or three) MEMS devices, preferably of the DC 'cantilever type, in the parts of opposite ends of the slots, and not in their central part.

Of course, it is possible to use slots of shapes and dimensions substantially identical.

Some holes (or crossings) metallized TM, for example one on two, can be advantageously used to route orders voltage at the different MEMS devices DC or DC '.

In the foregoing, cells with slots have been described. simple of quarter-wave or half-wave length. But, it is possible to make cells with compound slots, as shown in the Figures 21 and 22.

More specifically, the cells of the exemplary embodiments illustrated in FIGS. 21 and 22 substantially show the structure of the cells illustrated in FIGS. 10 to 12. Here, each slot of half-wave length is consisting of two half-slits of quarter-wave length. The devices MEMS DC or DC 'have been voluntarily omitted so as not to overburden the drawings.

In the example illustrated in FIG. 21, two upper pavers PS1 and PS2 are placed substantially parallel to the lower ground plane PM1 and away from it. These two upper pavers PS1 and PS2 are spaced from each other by a selected distance so as to define between them a capacitive area. They have different shapes and each a half quarter wave slot FR1, FR2. These two half slits FR1 and FR2 together constitute a half-wave slot and an inductive zone whose effect is advantageously compensated (at least partially) by the inter-paved capacitive area.

For example, the pavers have a width equal to about 3.7 mm and are separated by a distance, forming a slot, equal to about 0.1 mm.

Such an asymmetrical structure offers a frequency response of good stability due to an effective coupling between the two resonances.

In the example illustrated in FIG. 22, three upper blocks PS1, PS2 and PS3 are placed substantially parallel to the ground plane lower PM1 and away from it. The two upper pavers PS1 and PS3 are substantially identical and frame the PS2 pad. Moreover, both upper pavers PS1 and PS3 each have half a quarter slit wave FR1, FR4, while the upper pad PS2 has two halves quarter-wave slots FR2 and FR3 opening on two opposite sides, one placed next to the half slot FR1 of the upper block PS1 and defining with it a first half wave slit, and the other placed next to the half slot FR4 of the upper block PS3 and defining with it a second split half wave.

Such a symmetrical structure also offers an answer in frequency of good stability due to effective coupling between resonances.

Many other combinations of upper pavers can be envisaged. Thus, it is possible to envisage a combination of several upper pavers separated from one another by spaces constituting slits of selected widths with which they constitute what the person skilled in the art calls a "Jerusalem cross". By reducing, with a MEMS device, the width of the slots opposite, one can act on the resonance frequency of such a structure, and thus modify the phase of the reflected wave. A dual structure comprising metallic lines of the form of a Jerusalem cross is described in particular in C. Simovski et al., High-impedance surfaces with angular and polarization stability, 27 ^th ESA Antenna Technology Workshop on Innovative Periodic Antennas, pp 176-184. The resonance of such a structure is mainly ensured by the inductive and capacitive parts of the Jerusalem cross, and not by the resonance of the pavement. This structure, called "metamaterial" type, then operates in much lower frequency bands.

It is also possible to add to the phase-shifting cells, which comprise at least one block provided with at least one slot FP, described above, one or more auxiliary blocks and at least one MEMS device of coupling, so as to vary the size of the pavement according to at least one of its two directions (X and Y), and preferably along its length X which is parallel to the direction defining the length b (or long side) of the slots FP. A CD phase shifter cell of this type is illustrated in FIG.

More precisely, the phase-shifting cell CD illustrated in FIG. 23 from a structure of the type illustrated in Figures 10 to 12. It therefore comprises a substrate SB having a rear face (or lower), secured to a lower mass plane PM1, and a front face (or upper), secured to at least one block (or patch) upper PS and to minus one auxiliary pad PA1, PA2. Here, there are two auxiliary blocks PA1 and PA2, placed on both sides of two parallel sides of the PS pad (themselves parallel to the long sides (Y) of the FP slot). But, we could consider providing only one auxiliary pad PA. Moreover, we can also consider, alternatively or in addition, to place a paving stone auxiliary along at least one of the two non-radiating sides of the PS block (parallel to the small side (X) of the slot FP).

The upper pavers PS, PA1 and PA2 and the lower ground plane PM1 define a resonant planar structure.

The phase-shifting cell CD also comprises at least one device DC or DC Coupling MEMS 'Installed Between PS Keypad and Auxiliary Keypad PA1, PA2 and responsible for establishing, or not, a contact between these blocks according to the state in which he is placed.

In the example shown, the PS block is likely to be connected to each auxiliary pad PA1, PA2 via three MEMS devices DC ', a central and two end. The two devices MEMS DC ' end are preferably placed symmetrically with respect to the center of the auxiliary pad PA1, PA2.

The different DC or DC MEMS devices that connect the PS pad to one of the auxiliary blocks PA1, PA2 are preferably controlled by the same control current. In other words, they are preferentially placed simultaneously in the same state so as to ensure either an electrical connection or an absence of an electrical connection, between the PS block and the auxiliary block PA1, PA2 concerned.

When a link is established between the PS block and an auxiliary keypad PA1, PA2, the physical length (according to X) of the PS pad can therefore be increased. By acting simultaneously on the pair length of the PS pad and length of the slot FP, we can then simultaneously change the torque phase shift of the incident wave over a range greater than 360 °, and dispersion of this phase shift in frequency. The possibility of controlling the dispersion of this phase shift in frequency is particularly interesting for to compensate for the frequency-dispersive illumination of a plane reflector by a primary source.

It is important to note that several (at least two) pavers auxiliaries, preferably of the same size, may be placed parallel to each other, on at least one of the two sides of the pavement PS, the tiles being connected in pairs by one or more MEMS devices coupling DC 'or DC, and preferably three. This makes it possible to vary even more the physical length of the PS block, as needed, in playing on the respective states of the MEMS devices DC 'or DC coupling the auxiliary pavers.

In addition, the auxiliary pavers which are located on both sides of two parallel sides of the PS block do not necessarily have the same dimensions. This is particularly the case in the example illustrated on the Figure 23, where the auxiliary pad PA1 has a length (in the direction X) greater than that of the auxiliary pad PA2, but a width (according to the direction Y) substantially identical to that of the auxiliary pad PA2. By for example, if the length of the PS pad is equal to L, the lengths of the tiles auxiliary PA1 and PA2 can be respectively equal to L / 2 and L / 3.

As in the examples previously described, the PS block can have one or more MEMS devices DC or DC '. Number of MEMS devices used depends on the number of phase shift states that one wish to obtain.

This type of phase-shifting cell CD therefore makes it possible to vary dynamically, as needed, the phase shift and dispersion of frequency phase, which is particularly advantageous for a active antenna (or reconfigurable). The choice of phase shift and dispersion of the phase shift is indeed fixed by the physical length of the PS pad and by the electrical length of each FP slot of each PS pad, according to the states respective MEMS devices used.

In order to constitute a passive-type CD phase-shifting cell, for a non-reconfigurable antenna, one can dispense with MEMS devices at level of the slots. More specifically, as illustrated in Figures 24 and 25, a structure of the type illustrated in FIGS. 10 to 12 can be used, but without MEMS device.

Such a structure CD therefore comprises a substrate SB comprising a rear face (or lower), secured to a lower ground plane PM1, and a front face (or upper), secured to at least one block (or patch) PS upper having at least one FP slot. The upper pad PS and the lower mass plane PM1 define a resonant planar structure.

By judiciously choosing the dimensions of the upper PS block, and in particular its length x (in the X direction), and the slot FP, and in particular its length b (in the Y direction), as well as the thickness d of substrate SB, it is possible to impose both a chosen phase shift and a dispersion selected frequency phase.

The dimensions and thicknesses can be deduced from the curves of type of those illustrated in Figure 26, giving the evolution of the phase shift ΔΦ depending on the length b of the slot FP, for several different values x of upper paver length PS and for a thickness of SB substrate (for example equal to about 2 mm).

When the upper PS block has only one FP slot, it is preferably placed substantially at its center. But, the pavement PS could have multiple FP slots, possibly different dimensions.

Such a phase-shifting cell CD makes it possible to obtain any phase shift, and in particular phase shifts (very) greater than 360 °. It also controls the dispersion of this phase shift in frequency. The phase-shifting cells of the prior art, which make it possible to obtain such characteristics, comprise three blocks placed parallel to one another above and above a lower ground plane (they are described in particular in the article by JA Encinar et al, "Design of a three-layer printed reflectarray for dual polarization and dual coverage", 27 ^th ESA Antenna workshop, Santiago Compostel, Spain, March 2004). The phase-shifter cells CD according to the invention comprise only one level of metallization (upper block), in addition to the lower ground plane PM1, and are therefore much simpler to achieve than the phase-shifting cells of the prior art.

The invention is not limited to cell embodiments phased array and reflector array antenna described above, only as example, but it encompasses all the variants that may be considered those skilled in the art within the scope of the claims below.

Claims (25)

Phase-shifting cell (CD), for a reflector array antenna, defined by a characteristic resonant length, characterized in that it comprises, in at least one selected location, a micron electromechanical device (DC, DC '), of the MEMS type, suitable for being placed in at least two different states allowing and respectively prohibiting the establishment of a short circuit intended to vary said resonant length, so as to vary the phase shift of a reflection wave having at least one linear polarization. Cell according to claim 1, characterized in that said MEMS device (DC) comprises a conductive flexible bridge (PT) whose states are controlled by two substantially superimposed control electrodes and one of which is constituted by said bridge (PT). Cell according to claim 1, characterized in that said MEMS device (DC ') comprises a suspended conductive flexible beam (PE) whose states are controlled by a control electrode (EC') placed below a suspended part of said beam (PE), which constitutes another electrode. Cell according to one of claims 1 to 3, characterized in that it comprises a resonant planar structure comprising an upper block (PS) placed substantially parallel to a lower ground plane (PM1), at a selected distance, said upper block (PS) having at least one slot (FP) provided with at least one MEMS device (DC, DC ') controlling the characteristic resonant length of said upper pad (PS). Cell according to Claim 4, characterized in that it comprises a single slot (FP) provided with at least two MEMS devices (DC, DC '), making it possible to define at least three different resonant lengths (FP) according to the states in which they are respectively placed. Cell according to one of claims 4 and 5, characterized in that it comprises at least one auxiliary block (PA1, PA2) placed along at least one of the sides of said upper pad (PS), at a selected distance thereof, and at least one coupling MEMS device (DC ', DC), placed between said auxiliary pad (PA1, PA2) and said upper pad (PS) and making it possible to establish or not an electrical connection between said auxiliary and upper blocks according to the state in which it is placed. Cell according to Claim 6, characterized in that it comprises at least two parallel auxiliary blocks parallel to one another, of substantially identical dimensions and placed along at least one of the sides of said upper block (PS), and at least one MEMS coupling device (DC ', DC) placed between said neighboring auxiliary blocks and making it possible to establish or not an electrical connection between them according to the state in which it is placed. Cell according to claim 4, characterized in that said upper block (PS) is substantially square, and in that it comprises at least one rectangular slot opening on a non-radiating side of said square and comprising at least two MEMS devices (DC, DC '), making it possible to define at least three different resonant lengths according to the states in which they are respectively placed. Cell according to claim 4, characterized in that said upper block (PS) is substantially square, and in that it comprises at least first (F1) and second (F2) rectangular slots placed substantially facing one of the other and opening on two opposite sides of said square, non-radiating, each slot (F1, F2) comprising at least two MEMS devices (DC, DC '), making it possible to define at least three different resonant lengths according to the states in which they are respectively placed. Cell according to claim 9, characterized in that it comprises at least third (F3) and fourth (F4) rectangular slots placed substantially opposite one another and opening on two other opposite sides of said square, each slot (F3, F4) comprising at least two MEMS devices (DC, DC '), making it possible to define at least three other different resonant lengths according to the states in which they are respectively placed, so as to allow a linear double polarization. Cell according to one of claims 4 to 10 in combination with claim 2, characterized in that each slot (FP, F1-F4) is rectangular, and in that each bridge (PT) of MEMS device (DC) is placed substantially parallel to large sides of said slot. Cell according to one of Claims 4 to 10 in combination with Claim 3, characterized in that each slot (FP, F1-F4) is rectangular, and in that each MEMS device beam (PE) (DC ') is positioned substantially perpendicular to the long sides of said slot. Cell according to one of claims 4, 5, 11 and 12, characterized in that said upper block (PS) has dimensions smaller than the dimensions of the lower ground plane (PM1), and in that it comprises metallized bushings (TM) connected to said lower ground plane (PM1) and surrounding said upper pad (PS) so as to define a resonant cavity. Cell according to one of claims 4 to 13, characterized in that said resonant planar structure comprises at least two upper blocks (PS1, PS2) distant from each other by a selected distance, each block comprising at least one half slot (FR1, FR2, FR3, FR4) opening on one of its sides and two half slots facing constituting a slot. Cell according to one of claims 4 to 13, characterized in that said resonant planar structure comprises several upper blocks spaced from each other by spaces constituting slots of selected widths, said blocks and said slots constituting a "Jerusalem cross" . Cell according to one of claims 1 to 3, characterized in that it comprises, on the one hand, a resonant planar structure comprising a rectangular upper block (PS) placed substantially parallel to a lower ground plane (PM1), to a selected distance, said lower ground plane (PM1) defining at least one pellet (P1) completely surrounded by a non-conductive zone (Z), placed below said upper pad (PS) and of dimensions smaller than the dimensions of the latter; and on the other hand, at least one metallized bushing (TM) connecting said upper pad (PS) to said pad (Pl), and in that said MEMS device (DC, DC ') is placed at said area ( Z) so as to establish in one of its states a connection between said pad (PI) and the remainder of said ground plane (PM1) to control the resonant length of said upper pad (PS). Cell according to claim 16, characterized in that said lower ground plane (PM1) defines at least two pellets (P1) integrally surrounded by a non-conductive zone (Z), placed below said upper pad (PS) and of dimensions less than the dimensions of the latter, and in that it comprises, on the one hand, at least two metallized crossings (TM) respectively connecting the upper block (PS) to one of said pads (PI), and on the other on the one hand, at least two MEMS devices (DC, DC ') each placed at one of the zones (ZI) so as to establish connections between at least one of said pads (P1) and the remainder of said ground plane (PM1), thus making it possible to define at least three different resonant lengths of the upper block (PS) according to the states in which they are respectively placed. Cell according to one of claims 1 to 3, characterized in that it comprises an upper ground plane (PM2) comprising at least one radiating slot (FR) provided with a MEMS device (DC, DC ') controlling its characteristic resonant length, a lower ground plane (PM1), and metallized vias (TM) connecting said lower ground plane (PM1) to peripheral portions of said upper ground plane (PM2) so as to define a resonant cavity. Cell according to claim 18, characterized in that said upper ground plane (PM2) comprises at least two radiating slots (FR1, FR2, FR3) each provided with a single MEMS device (DC, DC ') controlling their characteristic resonant length . Cell according to claim 19, characterized in that each MEMS device (DC, DC ') is placed substantially in the middle of a radiating slot (FR1, FR2, FR3). Cell according to one of claims 19 and 20, characterized in that said slots (FR1, FR2, FR3) are substantially parallel to each other and have different lengths. Cell according to claim 18, characterized in that said upper ground plane (PM2) comprises a radiating slot (FR), provided with at least two MEMS devices (DC, DC ') making it possible to define at least three different resonant lengths of slot according to the states in which they are respectively placed. Cell according to one of claims 18 to 22, characterized in that said upper ground plane (PM2) comprises at least one rectangular radiating slot (FRV) having long sides parallel to a first direction, and at least one other radiating slot Rectangular (RVE) having long sides parallel to a second direction perpendicular to the first, so as to allow a linear double polarization. A phase shifter (CD) cell, for a reflector array antenna, characterized in that it comprises a resonant planar structure comprising an upper pad (PS) placed substantially parallel to a lower ground plane (PM1), at a selected distance, and comprising at least one slot (FP), the dimensions of the keypad (PS) and the slot (FP) and said distance being chosen so as to impose a selected phase shift and a selected phase phase dispersion at a reflection wave having at least one a linear polarization. Reflecting array antenna, characterized in that it comprises at least two phase-shifting cells (CD) according to one of the preceding claims.

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