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

p0001The invention relates to the field of the reflector antenna arrays (or "reflectarray antennas"), especially the phase-shifting cells which equip such antennas.

p0002The reflector array antennas is one of two main families of array antennas, the other family consisting of the phased array antenna (or "Phased Array Antennas"). These array antennas are particularly interesting because they can be reconfigured, for example to allow the passage of a coverage area (or "spot") to another.

p0003A reflector array antenna consists of radiating elements responsible for intercepting with minimal losses waves comprising signals to be transmitted, delivered by a primary source, to reflect them in a chosen direction, called pointing direction. To allow the reconfigurability of the antenna pattern, each radiating element is equipped with a phase control device with which it is an active or passive phase-shifter cell.

p0004By "phase-shifting cell" here means both structures cavity and radiating slot that planar resonant structures radiating patch (or "patch").

p0005The invention relates more particularly to the active phase-shifting cells, linearly polarized. These typically comprise a phase-shifting cell is provided with a switch (or switch) consisting of diodes (usually PIN type) or MESFETs, or varactors, or mechanical control means (such as a loaded motor moving a dielectric bar).

p0006The phase-shifting cells to switch consume significant amounts of energy and are subject to significant losses and overheating. The phase-shifting cells to mechanical control are complex to implement, especially in the case of large size networks, and consumers of energy. In one case as in the other, the disadvantages induced phase control techniques limit the applications of phase-shifting cells, especially in the space sector and more specifically in the viewing platforms such as satellites.

p0007The invention therefore aims to improve the situation in the case of phase-shifting reflector array antennas linearly polarized cells active.

p0008It proposes for this purpose a phase-shifting cell having a resonant characteristic length and comprising at least one location selected a mist electromechanical device, type MEMS (for "Micro ElectroMechanical System") which can be placed in at least two different states allowing and prohibiting respectively establishing a short-circuit for varying the resonant characteristic length, to vary the phase shift of the waves to be reflected which have at least one linear polarization.

p0009Each MEMS device may for example include a flexible conductive bridge whose states are controlled by two substantially superimposed control electrodes and one of which is constituted by the bridge. Alternatively, each MEMS device can include a flexible conductive beam suspended (or "cantilever") whose states are controlled by a control electrode placed beneath its suspended part.

p0010The cell of the invention comprises a resonant planar structure comprising at least one rectangular upper patch placed substantially parallel to a lower ground plane, at a chosen distance, the lower ground plane defining at least a "pellet" conductive, for example rectangular , fully surrounded by a nonconductive area, located below the upper patch and of smaller dimensions than the own. In this case, the cell includes at least one metallized bushing connecting the pad to the upper pad and the MEMS device is placed at the non-conductive area in order to establish in one of its states a link between the wafer and the rest of the ground plane to control the resonant length of the upper patch.

p0011The lower ground plane may possibly define at least two pellets (eg rectangular) fully surrounded by a nonconductive area, placed below the upper pad and lower dimensions to his. In this case, the cell comprises at least two metallized bushings respectively connecting the pad than to the pellets, and at least two MEMS devices each placed at one of the non-conductive areas to establish connections between one at least of the pellets and the rest of the ground plane, thereby defining at least three different resonant lengths of the upper patch according to their states.

p0012In a variant of this last embodiment, the cell may have an upper ground plane comprising at least one radiating slot, provided with a MEMS device controlling its resonant characteristic length, a lower ground plane, and metallized vias connecting plane lower mass at peripheral portions of the upper ground plane to define a resonant cavity. For example, the top ground plane may comprise at least two radiating slots each provided with a single MEMS device controlling their resonant characteristic length. Each MEMS device can then preferably be located substantially in the middle of a radiating slot. Moreover, 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 circuited annular gap at two points substantially opposite.

p0013Alternatively, the top ground plane may include a slot antenna, provided with at least two MEMS devices to define at least three different resonant lengths according to their states.

p0014Furthermore, the upper ground plane may optionally comprise at least one rectangular radiating slot having long sides parallel to a first direction, and at least one other rectangular radiating slot having long sides parallel to a second direction perpendicular to the first, to to allow a double linear polarization.

p0015In another family of embodiments, the cell may comprise a resonant planar structure comprising an upper patch placed substantially parallel to a lower ground plane, at a selected distance. In this case, the pad comprises at least a slot provided with at least one MEMS device controlling its characteristic resonant length.

p0016The cell may then comprise a single slot (half wave length) provided with at least two MEMS devices, to define at least three different resonant lengths according to their states. Alternatively, the upper pad may be substantially square, and the cell may comprise at least a first and a second rectangular slots (quarter wave length) placed substantially opposite one another, opening out on two opposite sides non-radiating of the square, and each comprising at least two MEMS devices to define at least three different resonant lengths according to their states. In the latter case, the cell may also comprise at least third and fourth rectangular slots (quarter wave length) placed substantially opposite one another, opening out on two other opposite sides of the non-radiating square, and each comprising at least two MEMS devices, to define at least three other different resonant lengths depending on their length, to allow a double linear polarization. One can also provide more upper blocks each provided with at least one half slot quarter-wave pairs of slots opposite halves then constituting a half wave slots.

p0017In the presence of a MEMS device to bridge and slot (s) rectangular (s), the bridge is preferably placed substantially parallel to the long sides of the slot. In contrast, in the presence of a MEMS device and beam slot (s) rectangular (s), said beam is preferably placed substantially perpendicularly to the long sides of the slot.

p0018In addition, the lower ground plane may define a lower tile placed below the upper patch and of smaller dimensions than the own In this case, the cell includes metallized vias that connect the ground plane to the peripheral portions of the upper patch to define a resonant cavity. This structure Cobble and cavity defined yet another family of phase-shifting cells.

p0019The invention also provides a reflector array antenna equipped with at least two phase-shifting cells of the type presented above.

p0020The invention is particularly well adapted, although not exclusively, to geostationary telecommunication antennas Ku-band (12-18 GHz), reconfigurable coverage (change of orbital position, adaptation of traffic), and the band radar antennas C (4-8 GHz) or X-band (8-12 GHz), especially for the type of radar SAR (synthetic aperture radar).

p0021Other features and advantages of the invention will appear on examining the detailed description below and the appended drawings, in which:<ul><li>the <figref idrefs="f0001">figure 1</figref> schematically illustrates, in a top view, a first embodiment of a phase-shifter cell of the invention,</li><li>the <figref idrefs="f0001">2</figref> is a cross-sectional view along the axis II-II of the phase-shifter cell of the <figref idrefs="f0001">figure 1</figref>,</li><li>the <figref idrefs="f0001">3</figref> schematically illustrates, in a top view, a second embodiment of a phase-shifter cell of the invention,</li><li>the <figref idrefs="f0001">4</figref> is a cross-sectional view along line IV-IV of the phase-shifter cell of the <figref idrefs="f0001">3</figref>,</li><li>the <figref idrefs="f0002">5</figref> schematically illustrates, in a top view, a third embodiment of a phase-shifter cell of the invention,</li><li>the <figref idrefs="f0002">6</figref> is a cross-sectional view along the axis VI-VI of the phase-shifter cell of the <figref idrefs="f0002">5</figref>,</li><li>the <figref idrefs="f0002">7</figref> schematically illustrates, in a top view of a fourth embodiment of a phase-shifter cell of the invention, </li><li>the <figref idrefs="f0003">8</figref> is a cross-sectional view according to VIII-VIII line of the phase-shifter cell of the <figref idrefs="f0002">7</figref>,</li><li>the <figref idrefs="f0003">9</figref> schematically illustrates, in a top view of a fifth embodiment of a phase-shifter cell of the invention,</li><li>the <figref idrefs="f0003">Figure 10</figref> schematically illustrates, in a top view of a sixth embodiment of a phase-shifter cell of the invention,</li><li>the <figref idrefs="f0004">11</figref> is a cross sectional view along the XI-XI axis of the phase-shifting cells of <figref idrefs="f0003">figures 10</figref> and <figref idrefs="f0004">12</figref>,</li><li>the <figref idrefs="f0004">Figure 12</figref> schematically illustrates, in a top view of a seventh embodiment of a phase-shifter cell of the invention,</li><li>the <figref idrefs="f0004">13</figref> schematically illustrates, in a top view of an eighth embodiment of a phase-shifter cell of the invention,</li><li>the <figref idrefs="f0004">Figure 14</figref> schematically illustrates, in a top view, a ninth embodiment of a phase-shifter cell of the invention,</li><li>the <figref idrefs="f0004">Figure 15</figref> schematically illustrates, in a top view of a tenth embodiment of a phase-shifter cell of the invention,</li><li>the <figref idrefs="f0005">Figure 16</figref> schematically illustrates, in a top view, an eleventh embodiment of a phase-shifter cell of the invention,</li><li>the <figref idrefs="f0005">Figure 17</figref> is a cross-sectional view along line XVII-XVII of the phase-shifter cell of the <figref idrefs="f0005">Figure 16</figref>,</li><li>the <figref idrefs="f0005">Figure 18</figref> is a perspective view detailing a portion of the phase-shifter cell of the <figref idrefs="f0005">Figure 16</figref>,</li><li>the <figref idrefs="f0006">Figure 19</figref> schematically illustrates, in a top view, a twelfth embodiment of a phase-shifter cell of the invention,</li><li>the <figref idrefs="f0006">Figure 20</figref> is a cross-sectional view along line XX-XX of the phase-shifter cell of the <figref idrefs="f0006">Figure 19</figref>,</li><li>the <figref idrefs="f0007">Figure 21</figref> schematically illustrates, in a top view, a thirteenth embodiment of a phase-shifter cell of the invention, without its MEMS devices,</li><li>the <figref idrefs="f0007">Figure 22</figref> schematically illustrates, in a top view, a fourteenth embodiment of a phase-shifter cell of the invention, without its MEMS devices,</li><li>the <figref idrefs="f0008">Figure 23</figref> schematically illustrates, in a top view, a fifteenth embodiment of a phase-shifter cell of the invention,</li><li>the <figref idrefs="f0008">Figure 24</figref> schematically illustrates, in a top view, a sixteenth embodiment of a phase-shifter cell of the invention,</li><li>the <figref idrefs="f0008">Figure 25</figref> is a cross-sectional view along line XXV-XXV of the phase-shifter cell of the <figref idrefs="f0008">Figure 24</figref>and</li><li>the <figref idrefs="f0009">Figure 26</figref> is a diagram illustrating the evolution of the phase shift (Δφ in degrees) as a function of the length of a slit (b mm) for several different values ​​of upper patch length (x = 3, 4, 5, 7.5 and 8 mm respectively from top down) and for a substrate thickness (d ').</li></ul>

p0022The attached drawings may not only serve to complete the invention, but also contribute to its definition, if appropriate.

p0023The invention relates to an active phase-shifting cell with linear polarization for an active reflecting array antenna.

p0024The antenna reflector array can for example be dedicated to telecommunications, such kind of geostationary Ku-band (12-18 GHz), reconfigurable coverage (change of orbital location, or adaptation of traffic) or the C-band radars ( 4-8 GHz) or X-band (8-12 GHz), especially for the type of radar SAR (synthetic aperture radar) or the RF ISL-type bonds to broadband, especially in d a small constellation of satellites flying in formation.

p0025In its most general, a phase-shifting cell, according to the invention comprises one or more selected locations a mist electromechanical device, MEMS (for "Micro ElectroMechanical System"). Each MEMS device can be placed, with the aid of electrical control, in at least two different states allowing and prohibiting respectively the establishment of a short-circuit for varying a characteristic resonant length of the cell, in order to vary the phase shift of the waves to be reflected (from the source of the antenna) having at least one linear polarization.

p0026Such a phase-shifting cell can be broken down into three large families as its radiating structure. A first family includes structures cavity and slot (s) radiating a second family includes planar resonant structures to blocks (or "patches") and a third family includes planar resonant cavity structures.

p0027Referring initially to <figref idrefs="f0001 f0002 f0003">Figures 1 to 9</figref> to describe embodiments of phase-shifting cells belonging to the first family.

p0028On the <figref idrefs="f0001">Figures 1 and 2</figref> is illustrated a first CD phase-shifting cell sample comprising a substrate SB having a "rear" surface (or "lower"), fastened to a ground plane "lower" PM1, and a "front" face (or "upper") , secured to a ground plane "superior" PM2.

p0029The substrate SB is made, for example Duroid or TMM and has a thickness equal to, for example, λ / 4, where λ is the wavelength in the vacuum of the waves to reflect, from the source antenna .

p0030Lower PM1 and PM2 upper ground planes are electrically connected together by means of holes (or vias) formed in the TM metallized substrate SB. These plans are made for example from alumina substrates, silicon or glass which, due to their low thickness (typically 500 microns) should be reported on a substrate SB Duroid or TMM to allow the obtaining a thickness equal to λ / 4. The metallized holes TM are preferably fitted at the lower periphery of the PM1 and PM2 upper ground planes so as to define a resonant cavity.

p0031Two techniques can be envisaged to achieve this assembly. A first technique consists in superimposing a Duroid substrate (or Metclad), for example equal to about 3 mm thickness, on an alumina substrate, for example a thickness of about 0.254 mm, and then depositing a ground plane lower PM1 on the underside of the substrate in Duroid and a ground plane upper PM2, on the upper face of the alumina substrate, said upper ground plane PM2 being locally interrupted by the slots. A second technique consists in using a Duroid substrate (or Metclad), for example a thickness of about 2 or 3 mm, and to form on its upper side portions of an intermediate ground plane in which are formed of the voltage control lines and to report on this upper face portions of alumina substrates, for example a thickness of about 0.254 mm, with an upper face on an upper ground plane PM2 each having one or more slots, then depositing a lower PM1 ground plane on the underside of the substrate in Duroid, and finally to connect the lower ground planes, intermediate and upper levels by two holes (or vias) metallized.

p0032Furthermore, the upper PM2 ground plane comprises a single radiating slot FR, preferably rectangular shape defined by two sides (longitudinal), of length b and two short sides (transverse) width a.

p0033This radiating slot FR is for example made by etching the upper ground plane PM2.

p0034Furthermore, the radiating slot FR has an LC resonant parallel. The parameters of such a resonator (resonance frequency and bandwidth) depend mainly on the length b and width a of the radiating slot FR, and the permittivity ε_r the substrate SB.

p0035Several modes can propagate in the cavity defined by the metallized holes TM. Each of these modes has its own propagation constant β and a characteristic impedance Z₀ clean. The cutoff frequency modes in the cavity depends mainly on the length m_x m and width_there lower ground planes PM1 and PM2 higher, and the permittivity ε_r the substrate SB. It is also recalled that a vertical resonance can occur in this type of cavity when its thickness is equal to nλ_g/ 2, where n is an integer and λ_g is the wavelength of the (the) mode (s) guided (s) propagating into the cavity.

p0036For example, one may choose a square mesh network wherein m_x = m_there = 0,7λ = 8 mm. In this case, and in the presence of a wavelength λ corresponding to an operating frequency of 26.4 GHz, the cavity has a cutoff frequency equal to 18.75 GHz and works only in its fundamental mode, which corresponds to a guided wave length λ_g equal to about 16.14 mm, in the case of an air cavity.

p0037In the presence of a cavity thickness d equal to λ / 4 (in this case approximately λ_g/ 5.7), the phase shifts of up to 360 ° can be obtained for widths of a slot FR between about 0.25 mm and about 1 mm. For example, in the presence of a width a equal to 0.5 mm, the inflection point of the phase shift is obtained at the resonance of the slot E, which corresponds to a length b equal to about 5.5 mm, taking into account other aforesaid.

p0038In this embodiment, the radiating slot FR is preferentially centered in the middle of the upper ground plane PM2. But it could be otherwise, especially in the presence of a possible additional parasitic slot. In the latter case, the slots are preferably located symmetrically with respect to the cell center.

p0039Furthermore, in this embodiment, the radiating slot FR is provided with three DC MEMS devices each constituting a two-state switch. Of course, the radiating slot may comprise a different number of DC MEMS devices since the latter is at least equal to one.

p0040Each DC MEMS device is here made of a flexible conductive bridge PT whose two ends are secured to support studs PL themselves secured to the upper face of the substrate SB. PL These pads are for example made of gold or aluminum and have a slightly higher than the upper ground plane PM2 thickness. The flexible bridge PT is implemented in the form of a blade made conductive, for example by a metallization of gold or aluminum, and installed in the slot EN substantially parallel to its longitudinal edges.

p0041In addition, each MEMS device DC comprises two substantially superimposed control electrodes, one of them being formed by a flexible bridge PT, and the other being, for example, placed at a higher level above the flexible bridge PT (not shown), these two electrodes being connected to a supply circuit (not shown).

p0042Is also provided on the upper face of the substrate SB, within the radiating slot FR and substantially at a central portion of its longitudinal edges, two small THE access lines placed substantially opposite one of other, perpendicularly to the flexible bridge PT, and electrically connected to the upper ground plane PM2.

p0043In the presence of a control current selected at the control electrodes, the suspended part of the PT is attracted to said bridge THE access lines. The suspended portion then flexes to come into contact with two access lines LA, which locally generates a short circuit in the radiating slot FR and reduces its resonant characteristic length (b), which is its electrical length. This is one of two states of the MEMS device DC.

p0044In the absence of control current, the PT bridge The distance LA access lines, so that the length of the radiating slot FR is not disturbed. This is the other state of the MEMS device DC.

p0045Order separately the various MEMS devices DC, so it is possible, in this embodiment, set in three different positions three short circuits corresponding to at least four different resonant lengths for the slot FR. Of course, the positions of the DC MEMS devices are selected so as to achieve a regular quantization of the phase law. This positional constraint favors the introduction of MEMS devices slit edge. These resonant different lengths corresponding to different phase shifts of the reflected wave by the phase-shifting cell CD.

p0046On the <figref idrefs="f0001">Figures 3 and 4</figref> is shown a second example of the phase-shifting cell first family CD. This is a variant of the phase-shifting cell CD described above with reference to<figref idrefs="f0001">Figures 1 and 2</figref>. Specifically, what differentiates the first embodiment of the second is the embodiment of MEMS devices.

p0047Here, each MEMS DC 'comprises a flexible beam (or "cantilever") PE conductor having one end fastened to a holding pad PL' device driver formed in the radiating slot FR along one of the longitudinal edges and connected electrically the upper ground plane PM2.

p0048This stud PL is for example made of gold or aluminum and is slightly higher than the upper PM2 ground plane thickness, so the PE beam is suspended above the radiating slot FR and the ground plane level higher PM2. The flexible PE beam is made in the form of a blade made conductive, for example by means of a metallization of gold or aluminum, mounted substantially perpendicular to its longitudinal edges. The free end of the PE beam passes through the slot FR in width and slightly overlaps the upper ground plane PM2 in a place is preferably placed a contact pad electrically conductive PLC.

p0049In addition, each MEMS device DC 'has a control electrode CE' placed below the suspended central portion of the beam PE, and connected to a power supply circuit (not shown), another electrode being formed by the flexible beam conductive PE. The control electrode CE is formed on the upper face of the substrate SB, within the radiating slot FR.

p0050In the presence of a control current selected at the control electrode of EC ', the suspended part of the PE beam is attracted to said electrode. It then flexes until its free end comes into contact with the contact pad PLC, 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 two states of the MEMS device DC '.

p0051In the absence of control current, the free end of the beam PE is remote PLC contact pad, so that the length of the radiating slot FR is not disturbed. This is the other state of the MEMS device DC.

p0052Order separately the different MEMS DC 'devices, so it is also possible, in this embodiment, set in three different positions three short circuits corresponding to at least four different resonant lengths for the slot FR. Of course, the positions of the various MEMS devices DC 'are chosen so as to achieve a regular quantization of the phase law. These resonant different lengths corresponding to different phase shifts of the reflected wave by the phase-shifting cell CD.

p0053In this embodiment, the radiating slot FR is provided with three MEMS devices DC '. But, the EN radiating slot may comprise a different number of MEMS devices DC 'since the latter is at least equal to one.

p0054On the <figref idrefs="f0002">Figures 5 and 6</figref> is shown a third example of the phase-shifting cell first family CD. In this example the phase-shifting cell CD follows the structure of the first example described above with reference to<figref idrefs="f0001">Figures 1 and 2</figref>But instead of a single radiating slot there are multiple (N = 5), and each slot comprises a single MEMS device DC PT bridge. Of course, the number N of radiating slots shown is not limiting. It can take any value greater than or equal to two. Furthermore, it is conceivable that at least one of the slots is not equipped with a MEMS device.

p0055The radiating slots present, some of different lengths. More specifically, in the example illustrated, the upper ground plane PM2 comprises two radiating slots FR1 end, having a first resonant characteristic length L1, two intermediate radiating slots FR2 having a second resonant characteristic length L2 greater than L1, and a central radiating slot FR3, having a third resonant characteristic length L3 greater than L2. Alternatively, the five slots could present five different lengths.

p0056Here, five radiating slots FR1 to FR3 are substantially centered relative to the center of the upper ground plane PM2, and PT bridge MEMS device DC is also installed in a centered position. But we could do differently. Indeed, in the example described above is short circuited the unwanted slots, but you could also change the resonant length of some of them to excite many resonances and to master the phase difference between slots with coupling.

p0057The distance separating two adjacent slots can be fixed or variable. It varies according to need. It is typically between about 100 .mu.m and 500 .mu.m.

p0058This is not to use one or more radiating slots by placing their respective DC MEMS devices in their second state (not flexed). The slots or that we do not want to use are shorted by placing their MEMS devices DC in their first state (down). The reflected wave phase variation is here achieved by the selection of one of the combinations of shorted and not shorted slots. Each combination corresponds in fact a particular phase shift and discreet depending primarily upon the ratio between the smallest characteristic resonant length and the longest length resonant characteristic.

p0059Each slot shorted in the middle is somewhat like a parasitic element for not short-circuited adjacent slot. This is to excite many resonances to have a range of acceptable phase shifts, while avoiding highly resonant response leading to low band performance. The coupling between the different resonances, directed by coupling between a slot and a pad (or patch), attenuates the resonant response.

p0060On the <figref idrefs="f0002">figures 7</figref> and <figref idrefs="f0003">8</figref> is shown a fourth example of the phase-shifting cell first family CD. This is a variant of the phase-shifting cell CD described above with reference to<figref idrefs="f0002">Figures 5 and 6</figref>.

p0061Specifically, what differentiates the fourth embodiment of the third is the embodiment of MEMS devices. In this example, each PT bridge MEMS device DC is indeed replaced by a MEMS device DC 'PE beam, of the type described with reference to<figref idrefs="f0001">Figures 3 and 4</figref>.

p0062The operation of this phase-shifting cell CD is identical to that of the phase-shifting cell described above with reference to <figref idrefs="f0002">Figures 5 and 6</figref>.

p0063As shown in the fifth example of the <figref idrefs="f0003">9</figref>, It is possible to form a phase-shifting cell CD belonging to the first family and adapted for dual linear polarization.

p0064To do this, use at least one radiating slot FRV oriented in a first direction ( "vertical"), and at least one FRH radiating slot oriented in a second direction ( "horizontal"), perpendicular to the first. Of course, as illustrated in<figref idrefs="f0003">9</figref>, The phase-shifting cell CD can comprise one or more radiating slots LIF and one or more radiating slots HRF, as required. The cell is then preferably rectangular and has a width substantially equal to the half of its length.

p0065It is possible to use radiating slots LIF and HRF having only one MEMS device PT bridge or PE beam, but it is preferable to use radiating slots LIF and HRF comprising at least two MEMS devices bridge PT or PE beam (as shown).

p0066Referring now to <figref idrefs="f0003 f0004 f0005">Figures 10-18</figref> to describe embodiments of phase-shifting cells belonging to the second family.

p0067On the <figref idrefs="f0003">figures 10</figref> and <figref idrefs="f0004">11</figref> is shown first CD phase-shifting cell sample comprising a substrate SB having a rear face (or lower), fixed to a lower ground plane PM1 defining a pad (or "patch") below, and a front face (or higher) , secured to an upper ground plane defining a box (or "patch") greater PS. PS blocks higher and lower PM1 define a resonant planar structure.

p0068The substrate SB is made, for example Duroid or TMM and has a thickness of low, typically of the order of λ / 10 to λ / 5 where λ is the wavelength in the vacuum of the waves to reflect, from the source to the antenna.

p0069The upper patch PS is placed substantially parallel to the lower ground plane PM1 and has smaller dimensions than the own. For example, and as shown, the upper patch PS is rectangular and preferably square.

p0070Furthermore, the upper patch PS comprises a single slot FP, preferably of rectangular shape defined by two sides (longitudinal), of length b and two short sides (transverse) width a.

p0071FP This slot is for example made by etching the ground plane constituting the upper patch PS.

p0072In this embodiment, the FP slot is provided with three MEMS devices DC PT bridge each constituting a two-state switch of the type described above with reference to <figref idrefs="f0001">Figures 1 and 2</figref>. Of course, the FP slot could have a different number of DC MEMS devices since the latter is at least equal to one.

p0073The principle of operation of this phase-shifting cell CD, and more precisely of its DC MEMS devices is identical to that described previously with reference to <figref idrefs="f0001">Figures 1 and 2</figref>. Only the involved physical effect differs. The FP slot is here intended to disrupt the path of currents flowing through the upper patch PS. By varying the length of the disturbance slot FP, by establishing short (s) -Circuit (s) chosen (s) by means of at least one MEMS DC devices placed in its first state (bent), is varied the currents path disturbances, thereby varying the resonant characteristic length (or electrical length) of the upper patch PS and thus the phase shift of the reflected wave.

p0074It is important to note that the invention can here be applied only if the upper patch PS is resonant at λ / 2.

p0075On the <figref idrefs="f0004">Figure 12</figref> is shown a second example of the second phase-shifting cell family CD. This is a variant of the phase-shifting cell CD described above with reference to<figref idrefs="f0003">figures 10</figref> and <figref idrefs="f0004">11</figref>. Specifically, what differentiates the first embodiment of the second is the embodiment of MEMS devices.

p0076Here, each MEMS device DC 'is type PE beam, as in the example described above with reference to <figref idrefs="f0001">Figures 3 and 4</figref>. Furthermore, in this embodiment, the disturbance FP slot is provided with three MEMS DC 'devices. But the disturbance FP slot could have a different number of MEMS devices DC 'since the latter is at least equal to one.

p0077As is illustrated in <figref idrefs="f0004">Figures 13 and 14</figref>Can be envisaged at least third and fourth embodiments, variants of the first and second embodiments described above with reference to <figref idrefs="f0003 f0004">Figures 10 to 12</figref>.

p0078More specifically, the third example shown in <figref idrefs="f0004">13</figref> comprises two holes (or vias) metallized TM for electrically coupling the upper patch PS and the lower ground plane PM1 hand side of the two opposite ends of the disturbing FP slot. These metallized holes MT are for supplying the DC upper patch PS to bias the MEMS device.

p0079In the fourth example illustrated in <figref idrefs="f0004">Figure 14</figref>The upper patch PS has two small interference slots F1 and F2 whose resonance corresponds approximately to a length equal to a quarter of the wavelength, placed substantially opposite one another and opening on the opposite edges, not radiating. Every little slot F1, F2 is provided with at least one (here two) MEMS device to bridge PT (but it could be a PE beam). Moreover, a hole (or crossing) Metallic TM enables electrically coupling the upper patch PS and the lower ground plane PM1 in a central portion located between the two small interference slots F1 and F2. This metallized hole MT is for supplying DC the upper patch PS to bias the MEMS device. It is conceivable to make two small slits disruptive quarter wave, or more, resulting in at least one non-radiating sides.

p0080Of course, it is also possible that the upper patch PS (substantially square) does not comprise a rectangular slot opening on a non-radiating side of the square and having at least two MEMS devices DC or DC '.

p0081As shown in the fifth example of the <figref idrefs="f0004">Figure 15</figref>, It is possible to form a phase-shifting cell CD belonging to the second family and adapted for dual linear polarization.

p0082To do this, you can for example use two small interference slots F1 and F2 oriented in a first direction, and at least two small interference slots F3 and F4 oriented in a second direction perpendicular to the first. Here, the term "small crack" disruptive FP slot of the type described above with reference to<figref idrefs="f0004">Figure 14</figref>.

p0083It is possible to use small interference slots F1 to F4, quarter wave length, having only one MEMS device PT bridge or PE beam, but it is preferable to use small interference slots F1 to F4 having at least two MEMS devices PT bridge or beam PE (as shown). The number of MEMS devices used in each slot depends on the number of phase states that are desired.

p0084As in the previous example, a hole (or crossing) Metallic (e) TM enables electrically coupling the upper patch PS and the lower ground plane PM1 in a central portion between the four small interference slots F1 to F4, of length quarter wave. This metallized hole MT is for supplying DC the upper patch PS to bias the MEMS device.

p0085In the last three embodiments (<figref idrefs="f0004">Figure 13-15</figref>), The upper patch PS power supply is by means of at least one metallized hole TM. But alternatively this can be fed by means of a quarter wave line high impedance.

p0086On the <figref idrefs="f0005">16 to 18</figref> is shown a sixth CD phase-shifting cell sample comprising a substrate SB having a rear face (or lower), fixed to a lower ground plane PM1, and a front face (or higher), secured to a top ground plane defining a pad (or patch) greater PS 'rectangular. The upper patch PS 'and the lower ground plane PM1 is a short paved circuited structure that defines a resonant planar structure. It is important to note that the length of the upper patch PS is selected so that it is resonant at λ / 4.

p0087The substrate SB is made, for example Duroid or TMM and has a thickness of low, typically of the order of λ / 10 to λ / 5 where λ is the wavelength in the vacuum of the waves to reflect, from the source to the antenna.

p0088The upper patch PS 'is positioned substantially parallel to the lower ground plane PM1 and has much lower dimensions to hers at least in one direction.

p0089As illustrated in <figref idrefs="f0005">Figure 18</figref>The lower ground plane PM1 comprises at least a small "pellet" PI conductive, insulated from its own conductive portion by a nonconductive area Z, made for example by etching. Each small conductive pad Pl is electrically connected to the upper patch PS 'via a hole (or crossing) Metallic TM. Moreover, each small conductive pad Pl is preferably rectangular, more preferably square.

p0090Each via TM is connected to the upper patch PS 'in a chosen location, the locations being preferably substantially aligned along a line parallel to the longitudinal sides of said upper patch PS.

p0091Moreover, each small conductive pad PI is provided with a MEMS device PT bridge or PE beam (as illustrated in <figref idrefs="f0005">Figure 18</figref>), Of the type described above. Each MEMS device DC '(or DC) is to establish an electrical connection between his little lower pavement Pl and the conductive part of the lower ground plane PM1, when placed in its first state (down). Thus, when one of the MEMS devices CD '(or CD) is placed in its first state (bent), the metallized hole TM, which is connected at its small conductive pad Pl, bypasses the upper patch PS' substantially the place where it is connected to it, which has the effect of varying its resonant characteristic length (or electrical length) and hence the phase shift of the reflected wave.

p0092This structure is advantageous because its devices being placed on the rear side they are more protected from the radiation.

p0093In the example illustrated in <figref idrefs="f0005">Figures 16 and 17</figref>Five TM metallized holes are used to define corresponding five short circuits at least six different resonant lengths of the upper patch PS '. Therefore, by controlling separately the different MEMS DC 'devices (or DC), it is possible to obtain several different phase shifts of the reflected wave by the phase-shifting cell CD.

p0094Of course, the CD phase-shifting cell may comprise a number of MEMS devices (DC or DC ') different from five, since the latter is at least equal to one. The number of MEMS devices used depends on the number of phase states that are desired.

p0095It is important to note that in this embodiment, the resonance frequency, the sum of the length of the dipole "active" (that is to say between the short-circuit and the other end of the dipole) and the short-circuit length must be equal to a quarter of the wavelength of the guided mode λ_g.

p0096This exemplary embodiment can allow the formation of a phase-shifting cell dual linear polarization of the type shown in <figref idrefs="f0003">9</figref>. This requires it to combine dipoles "horizontal" and dipoles "vertical" of the type described above with reference to<figref idrefs="f0005">16 to 18</figref>.

p0097Referring now to <figref idrefs="f0006">Figures 19 and 20</figref> to describe an example of a phase-shifting cell embodiment belonging to the third family.

p0098This embodiment is in a way an intermediate structure between the embodiments illustrated in <figref idrefs="f0002 f0003">Figures 5 to 8</figref> and examples of embodiments shown in <figref idrefs="f0003 f0004">Figures 10 to 12</figref>.

p0099Here, the phase-shifting cell CD includes a substrate SB having a rear face (or lower), fixed to a lower ground plane PM1, and a front face (or higher), secured to an upper patch PS.

p0100The substrate SB is made, for example Duroid or TMM and has a thickness equal to λ / 4, where λ is the wavelength in the vacuum of the waves to reflect, from the source of the antenna.

p0101The substrate SB is crossed, on its periphery, through holes (or vias) Metallic (s) TM connected to the lower ground plane PM1 and surrounding the upper patch PS so as to define a resonant cavity. For example, for operation in the Ku band, the upper patch PS is a square of length between about 15 mm and about 17 mm.

p0102Furthermore, the upper patch PS comprises at least two (five) radiating slots each comprising a single MEMS device (DC or DC ') to PT bridge or beam PE. Of course, the number N of radiating slots shown is not limiting. It can take any value greater than or equal to two. For example, the slots have a long side length of between about 5 mm and about 7 mm and a short side width of between about 0.3 mm and about 0.7 mm.

p0103The radiating slots present, some of different lengths. More specifically, in the example illustrated, the upper patch PS comprises two radiating slots FR1 end, having a first resonant characteristic length L1, two intermediate radiating slots FR2 having a second resonant characteristic length L2 greater than L1, and a slot FR3 central radiant having a third resonant characteristic length L3 greater than L2. Alternatively, the five slots could present five different lengths.

p0104Here, five radiating slots FR1 to FR3 are substantially centered relative to the center of the upper patch PS, and MEMS devices PT DC bridge (or DC 'PE beam) are also installed in a centered position (for example).

p0105This is not to use one or more radiating slots by placing their respective DC MEMS devices in their second state (not flexed). The slots or that we do not want to use are shorted by placing their MEMS devices DC in their first state (down). The reflected wave phase variation is here achieved by the selection of one of the combinations of shorted and not shorted slots. Each combination corresponds in fact a particular phase shift and discreet depending primarily upon the ratio between the smallest characteristic resonant length and the longest length resonant characteristic.

p0106Each slot shorted in the middle is somewhat like a parasitic element for not short-circuited adjacent slot. Therefore, it can improve the bandwidth of the non-short-circuited slot.

p0107In the example described above is short circuited the unwanted slots, but can be done differently. For example, you can change the resonant length of some slots to excite many resonances and to master the phase difference between slots with the coupling. This can for example be done by placing one or more (e.g. two or three) MEMS devices, preferably cantilever-type DC 'in the opposite end portions of the slots, and not in their central part.

p0108Of course, one may use slots of substantially identical shape and dimensions.

p0109Some holes (or vias) Metallic (s) TM, eg two, can be advantageously used for conveying the voltage commands in the various MEMS devices DC or DC '.

p0110In the foregoing, we have described the cells with simple slots long quarter wave or half wave. But, it is possible to produce cells having composed slots, as illustrated in<figref idrefs="f0007">Figures 21 and 22</figref>.

p0111More specifically, cells of the exemplary embodiments illustrated in <figref idrefs="f0007">Figures 21 and 22</figref> show substantially the structure illustrated on cells <figref idrefs="f0003 f0004">Figures 10 to 12</figref>. Here, each half wavelength slot is constituted by two half-length of quarter wave slots. The MEMS devices DC or DC 'have been omitted to avoid overloading the drawings.

p0112In the example illustrated in <figref idrefs="f0007">Figure 21</figref>, Two upper blocks PS1 and PS2 are placed substantially parallel to the lower ground plane PM1 and distance thereof. These two upper blocks PS1 and PS2 are spaced from each other a selected distance so as to define between them a capacitive region. They have different shapes and each have a half slot quarter wave FR1, FR2. These two half FR1 and FR2 slots together constitute a half wave slot and an inductive field whose effect is advantageously compensated for (at least partially) by the capacitive region inter blocks.

p0113For example, the stones have a width of about 3.7 mm and are separated by a distance forming a gap equal to about 0.1 mm.

p0114Such asymmetrical structure offers a frequency response of good stability due to efficient coupling between the two resonances.

p0115In the example illustrated in <figref idrefs="f0007">Figure 22</figref>, Three upper blocks PS1, PS2 and PS3 are placed substantially parallel to the lower ground plane PM1 and distance thereof. The upper two paved PS1 and PS3 are substantially identical and frame the PS2 pad. Moreover, the two upper blocks PS1 and PS3 each comprise a half slot quarter wave FR1, FR4, while the upper patch PS2 comprises two half slots quarter wave FR2 and FR3 opening on two opposite sides, one placed opposite the half of FR1 slot PS1 upper patch and defining therewith a first half wave slot, and the other placed opposite the half slot FR4 PS3 upper patch and defining therewith a half second wave slot.

p0116Such a symmetrical structure also offers a frequency response of good stability due to efficient coupling between the resonances.

p0117Many other combinations of upper pavers can be considered. Thus, one can consider a combination of upper blocks separated from each other by spaces constituting slit widths chosen with which they constitute what skilled in the art calls a "cross of Jerusalem." Reducing, with a MEMS device, the width of the slots facing each other, can be acted on the resonant frequency of such a structure, and thus modify the reflected wave phase. A dual structure consisting of metal lines of the shape of a cross of Jerusalem is particularly described in the document<nplcit id="ncit0001" npl-type="s"><text>Simovski C. et al, "High-impedance surfaces with angular and polarization stability," 27th ESA Antenna Workshop on Innovative Technology Periodic Antennas, pp 176-184</text></nplcit>. The resonance of such a structure is mainly provided by the inductive and capacitive parts specific to the cross of Jerusalem, not by the resonance of the pavers. This structure type called "metamaterial" then operates on frequency bands much lower.

p0118It is also possible to add to the phase-shifting cells, which comprise at least one pad provided with at least one FP slot, as described above, one or more auxiliary blocks and at least one MEMS coupling device, so as to vary the dimension of the pad 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 FP slots. A phase-shifting cell of this type is illustrated CD<figref idrefs="f0008">Figure 23</figref>.

p0119Specifically, the phase-shifting cell CD illustrated in <figref idrefs="f0008">Figure 23</figref> from a structure such as that illustrated in <figref idrefs="f0003 f0004">Figures 10 to 12</figref>. It thus includes a substrate SB having a rear face (or lower), secured to a lower ground plane PM1, and a front face (or higher), bonded to at least one pad (or patch) higher PS and at least one auxiliary pad PA1, PA2. Here shows two auxiliary cobblestones PA1 and PA2, placed on either side of two parallel sides of the PS block (themselves parallel to the long side (Y) of the slot FP). But, one could envisage to provide only a single auxiliary pad PA. Moreover, it is also possible, alternatively or additionally, to place an auxiliary pad along at least two non-radiating sides of the PS block (parallel to the short side (X) of the slot FP).

p0120PS senior pavers, PA1 and PA2 and the lower ground plane PM1 define a resonant planar structure.

p0121The phase-shifting cell CD also includes at least one MEMS device DC coupling or DC 'installed between the PS pad and an auxiliary pad PA1, PA2 and charged with establishing whether or not a contact between the cobblestones in the condition in which it is placed.

p0122In the example illustrated the PS block is capable of being connected to each auxiliary pad PA1, PA2 via three MEMS devices DC ', a central and two end. The two MEMS devices DC 'end are preferably arranged symmetrically relative to the center of the auxiliary pad PA1, PA2.

p0123The various MEMS devices DC 'or DC linking the PS block to one of the auxiliary blocks PA1, PA2 are preferably controlled by the same control current. In other words, they are preferably simultaneously placed in the same state so as to ensure an electrical connection, an absence of electrical connection between the PS and the auxiliary pad pad PA1, PA2 concerned.

p0124When a link is established between the PS pad and an auxiliary pad PA1, PA2, the physical length (along X) PS pad can be increased. By acting simultaneously on the pair length and length of the PS block of the FP slot, can then be simultaneously varying the torque phase of the incident wave on an upper 360 ° range, and dispersion of this phase shift in frequency. The ability to control the dispersion of this phase shift in frequency is particularly interesting to compensate for the frequency dispersive illumination of a reflector array plane by a primary source.

p0125It is important to note that several (at least two) auxiliary blocks, preferably of the same dimensions may be placed parallel to each other, on at least both sides of the PS block, the blocks being connected in pairs by one or more DC coupling MEMS devices' or DC, and preferably three. This will vary even more the physical length of the PS pad, as needed, by adjusting the respective states of MEMS devices DC 'or DC coupling the auxiliary cobblestones.

p0126Furthermore, the auxiliary blocks which are located on either side of the two parallel sides of the PS pad does not necessarily have the same dimensions. This is particularly the case in the example illustrated in<figref idrefs="f0008">Figure 23</figref>Wherein the auxiliary pad PA1 has a length (in the X direction) larger than that of the auxiliary pad PA2, but a width (in the Y direction) substantially identical to that of the auxiliary pad PA2. For example, if the PS block has a length equal to L, the lengths of the auxiliary blocks PA1 and PA2 can be respectively equal to L / 2 and L / 3.

p0127As in the examples described above, the PS block may include one or more MEMS devices DC or DC '. The number of MEMS devices used depends on the number of phase states that are desired.

p0128This type of phase-shifting cell CD allows to vary dynamically, as required, the phase and the dispersion phase in frequency, which is particularly advantageous for an active antenna (or reconfigurable). The choice of the phase shift and of the dispersion of the phase shift is in fact fixed by the physical length of the PS block and the electrical length of each slot FP of each PS block, according to the respective states of various MEMS devices used.

p0129To provide a phase-shifting cell passive type CD for a non-reconfigurable antenna, we can overcome the MEMS devices at the slots. More specifically, as illustrated in<figref idrefs="f0008">Figures 24 and 25</figref>, One may use a structure of the type illustrated in <figref idrefs="f0003 f0004">Figures 10 to 12</figref>But without MEMS device.

p0130This CD structure thus comprises a substrate SB having a rear face (or lower), fixed to a lower ground plane PM1, and a front face (or higher), secured to at least one pad (or patch) top PS having at FP least one slot. The upper patch PS and the lower ground plane PM1 define a resonant planar structure.

p0131By judiciously choosing the dimensions of the upper patch PS, including its length x (the X direction), and FP slot, including its length b (the Y direction) and the thickness of the substrate SB, can be placed on both a chosen phase shift and a phase dispersion chosen frequency.

p0132The dimensions and thicknesses can be deduced curves of the kind illustrated in <figref idrefs="f0009">Figure 26</figref>, Giving the change ΔΦ of the phase shift depending on the length b of the FP slot for several different values ​​of x upper patch length and PS to a thickness of SB substrate (for example equal to about 2 mm).

p0133When the upper patch PS contains only one FP slot, the latter is preferably positioned substantially at its center. But, the upper patch PS may comprise several FP slots, possibly of different dimensions.

p0134Such a phase-shifting cell CD provides any phase, including phase shifts (very) higher than 360 °. It also helps control the dispersion of this phase shift in frequency. The phase-shifting cells of the prior art that achieve such characteristics include three pavers placed parallel to each other over and above a lower ground plane (they are in particular described in the article<nplcit id="ncit0002" npl-type="s"><text>JA Encinar et al, "Design of a three-layer printed reflectarray for dual polarization and dual coverage", 27th ESA Antenna Workshop, Santiago de Compostel, Spain, March 2004</text></nplcit>). The phase-shifting cells CD of the invention comprise a single metallization level (upper pad), in addition to the lower ground plane PM1, and therefore are much easier to perform than the phase-shifting cells of the prior art.