EP1139484B1 - Microwave phase shifter and phased array antenna with such phase shifters - Google Patents

Abstract

A microwave phase-shifter including a coupler in a waveguide form, at least one pair of phase-shifter cells, and a conductive strip positioned between each phase shifter cell and configured with a conductive plane to form a guided space where a wave cannot propagate. An incident wave entering a first input of the coupler is subdivided into two waves. Each of the waves are reflected on an elementary cell with identical phases to the incident wave and are recombined into a resultant phase-shifted wave prior to exiting the coupler by an output juxtaposed with the first input.

Description

The present invention relates to a phase shifter. It applies in particular for an electronic scanning antenna. The invention also applies in particular for low cost electronic scanning antennas, used both in the radar field, such as for example the management of air traffic at airports, and in the field of telecommunications, for example civil ones.

Passive electronic scanning antennas use phase shifters to ensure the mobility of their beam. These phase shifters can act directly on the radiated wave constituting what is known as a microwave lens. These phase shifters can still act within an energy distribution device. The amplification of the wave to be transmitted is centralized then the wave thus amplified is distributed to the phase shifters. There are one-plane electronic scanning antennas and two-plane electronic scanning antennas. An antenna "a plane" comprises a linear array of radiating sources each in series with a phase shifter. The direction of the beam is then electronically controlled in a single plane, comprising the radiating sources and the direction of radiation. To point a beam in a given direction θ, each phase shifter is controlled so as to create a wave plane perpendicular to the radiation direction θ. To obtain a "two-plane" scan, it is necessary to extend the linear array of radiating sources in a second direction.

Phase shifters are basic components that typically combine heterogeneous technologies to achieve microwave and control functions. The microwave functions are in particular provided by waveguides or ceramic substrates. The control functions are in particular ensured by logic circuits and power circuits. These different functions are dissociated and require interconnections. Controlling a group of phase shifters also requires interconnections. This results in a high cost of producing these phase shifters and therefore scanning antennas which includes them, and all the more so as the number of phase shifters is important.

A document US-A-4,568,893 describes a microwave phase shifter using a waveguide coupler coupled to phase shift cells.

An object of the invention is notably to allow the realization of a low cost electronic scanning antenna. For this purpose, the subject of the invention is a microwave phase shifter, comprising at least one waveguide coupler 3db and a pair of phase shift cells, the incident wave E entering a first input of the coupler to be divided into two waves E1, E2, these two waves each reflecting on one of the pair of elementary cells with identical phases and recomposing into a phase-shifted resulting wave output from the coupler juxtaposed to the first input.

In order to obtain a more compact and economical phase shifter, an elementary phase-shifting cell comprises a phase shift circuit in front of a conductive plane whose function is to reflect the incident wave and disposed substantially parallel to the phase-shift circuit, the phase-shifting circuit comprising at least two half-waves. phase-shifters, the incident waves E1, E2 being linearly polarized in a first given direction Oy. A half-phase-shifter comprises at least one dielectric support, at least two electrically conductive wires substantially parallel to the given direction Oy, arranged on the support and carrying the each minus a two-state semiconductor element D1, D2, each wire being connected to control conductors of the semiconductor elements, these conductors being substantially normal to the wires, and two conductive zones disposed towards the periphery of the cell, substantially parallel to the control conductors. The control conductors are at least three in each half-phase-shifter and are electrically isolated from one half-phase-shifter to the other to control the state of all the semiconductor elements independently of each other . The geometric and electrical characteristics of the half-phase-shifters being such that at each of the states of the semiconductor elements corresponds a given phase-shift value (dφ ₁ , ... dφ ₈ ) of the electromagnetic wave which is reflected by the cell, the state of the semiconductor elements being controlled by an electronic circuit.

The dielectric support may advantageously carry the electronic control circuit semiconductors and their interconnections, these semiconductors being for example diodes.

The invention also relates to a microwave antenna with electronic scanning comprising phase shifters as defined above.

Advantageously, the phase shifters are distributed in at least one block, a block comprising a set of pairs of phase shift cells made on the same part and a set of couplers forming a single piece. This allows collective tests of phase shifters. In case of failure of a phase shift block, it can easily be replaced by another. The test and maintenance of the antenna are thus particularly simplified, and increased reliability.

• la figure 1, par un synoptique, la structure d'une antenne à balayage électronique alimentée par un émetteur de puissance centralisé ;
• les figures 2a et 2b, des exemples de réalisation de déphaseurs selon l'invention ;
• les figures 3a et 3b, la structure d'un circuit imprimé comportant des déphaseurs selon l'invention et leurs commandes associées ;
• la figure 4, un premier exemple de réalisation d'une cellule élémentaire d'un déphaseur selon l'invention ;
• la figure 5, un deuxième exemple de réalisation d'une cellule élémentaire d'un déphaseur selon l'invention ;
• la figure 6, un exemple de réalisation d'une antenne selon l'invention ;
• les figures 7 et 8, des exemples de réalisation de blocs de déphasage.

Other characteristics and advantages of the invention will become apparent with the aid of the following description made with reference to appended drawings which represent:

• the figure 1 by a synoptic, the structure of an electronic scanning antenna fed by a centralized power transmitter;
• the Figures 2a and 2b , exemplary embodiments of phase shifters according to the invention;
• the Figures 3a and 3b , the structure of a printed circuit comprising phase shifters according to the invention and their associated controls;
• the figure 4 , a first embodiment of an elementary cell of a phase shifter according to the invention;
• the figure 5 a second embodiment of an elementary cell of a phase shifter according to the invention;
• the figure 6 an embodiment of an antenna according to the invention;
• the Figures 7 and 8 , exemplary embodiments of phase shift blocks.

The figure 1 illustrates with a synoptic an electronic scanning antenna "a plane". This antenna comprises a linear network of phase shifters where the microwave wave is amplified by a centralized transmitter. The network includes associated radiating sources 1 each phase shifter 23. Each phase shifter 23 is for example supplied by distribution means, that is to say it receives the microwave provided by these distribution means 4 from the microwave provided 5 by the issuer. On reception, the received wave is transmitted to the reception circuits by the distribution means 4. Each phase-shifter is controlled so as to create a wave plane 6 perpendicular to the radiation direction θ, this angle defining the direction of rotation. pointing the antenna beam in the plane of the radiating sources 1.

The Figures 2a and 2b illustrate a possible embodiment of an antenna according to the invention. More particularly, these figures illustrate the production of phase shifters 23 according to the invention. In this embodiment, the cost is reduced and the implementation of phase shifters, and more generally of the antenna, is considerably simplified. For this purpose, a support or multilayer printed circuit 21 forming a phase shift device, represented in a plane Oxy, is for example associated with a coupling device 22 waveguide. This makes it possible in particular to perform and test the phase shifters collectively, thus greatly reducing the cost and facilitating their integration into the antenna.

The figure 2b illustrates part 23 of the figure 2a , this part actually representing an elementary phase shifter according to the invention. The figure 2b illustrates in particular a waveguide coupler 3db 24 associated with a pair of phase shift cells 25, 26. The elementary phase shifter 23 is thus produced by associating the coupler 3dB 24 with a pair of cells 25, 26 of the phase-shifter 21 functioning in reflection. In particular the incident wave E, passing through a first input 27 of the coupler 24, is divided into two incident waves E1, E2 to the two phase shift cells 25, 26. These two cells reflect the incident waves with identical phase shifts. The reflected waves enter the coupler to recompose with each other and the resulting wave S out of phase with respect to E is found on the output 28 of the coupler, juxtaposed with the first input 27. The phase shift device consisting of the two cells 25, 26, is equivalent to two variable shorts electrically controlled. This device is made for example on the support 21 comprising semiconductors in look at the coupler to ensure the phase shift. Moreover, the control circuits 29 of these semiconductors are for example implanted on the same support, on its face opposite the semiconductors, the multilayer support then ensuring the interconnections between the control circuits and the semiconductors. These are for example diodes. The incident microwave frequency E entering the coupler is for example derived from the distribution circuit 4.

The figure 2a shows an example of phase shift device 21 where the pairs of elementary cells 25, 26 are formed on the same part, for example of the printed circuit type. The couplers 24 associated with each of these pairs can form a single piece 22 as illustrated by this same figure 2a . This piece 22 is then attached to the phase shifter 21. The guides constituting the couplers are for example machined in the same metal part. However, it is of course possible to make a phase shifter according to the invention which is not produced collectively, as illustrated for example by the figure 2b . The implementation of the couplers, individual or collective, may include using molding techniques, injection or metallization of a plastic part that can reduce costs.

The figure 3a schematically shows a portion of the phase shifter shown in the Oxy plane, in a view from above, according to F. This phase shifter comprises an alignment of pairs of phase shift cells 25, 26 forming a linear array of phase shift cell pairs. It should be noted that other forms of alignment are feasible, in particular on a circle to form a cylindrical antenna, as will be shown by Figures 7 and 8 thereafter. In association with a 3dB coupler, a pair forms an elementary phase shifter 23 as described with respect to the figure 1 . The phase shift cells 25, 26 are separated by zones 20, used in particular for the microwave decoupling of these cells. These last realize the reflection and the phase shift of the waves which they receive. An elementary cell 25, 26 comprises a phase-shifting microwave circuit disposed in front of a conductive plane.

The figure 3b is a schematic sectional view in the plane Oxz of an exemplary possible embodiment of the phase shift device. The device phase shift consists of a microwave circuit 31 distributed in the elementary cells 25, 26 and a conductive plane 32, disposed substantially parallel to the microwave circuit 31, at a distance d predefined. This microwave circuit receives the incident waves E1 and E2 coming from the coupler 24.

The conductive plane 32 has the particular function of reflecting the microwave waves. It can be constituted by any known means, for example parallel wires or wire mesh, sufficiently tight, or a continuous plane. The microwave circuit 31 and the conductive plane 32 are preferably made on two sides of a dielectric support 33, for example of the printed circuit type. The assembly 21 also comprises, preferably on the same printed circuit 33, which is then a multilayer circuit, the electronic circuit necessary for the control of the phase values. On the figure 3b there is shown a multilayer circuit whose front face 34 carries the microwave circuit 31, the rear face 35 carries components 36 of the aforementioned electronic control circuit, and the intermediate layers form the conductive plane 32 and for example two planes 37 of interconnections of the components 36 to the microwave circuit 31.

The figure 4 illustrates an elementary phase-shift circuit 10 included in the microwave circuit 31. Each phase-shift circuit is separated from another by a decoupling zone 20 comprising for example a conductive strip 48 parallel to the direction Oy and a conductive strip 49 parallel to the direction Ox. It therefore comprises for example at its periphery two conductive strips 48 in the direction Oy and two conductive strips in the direction Ox. Each phase shift circuit associated with the corresponding portion of the conductive plane 32 forms a phase shift cell 25, 26.

A phase shift circuit 10 comprises a plurality of conductive wires 42 substantially parallel to the direction Oy and each carrying a semiconductor element D1, D2 with two states, for example a diode. The phase shift circuit also comprises conductive zones connecting the diodes to reference potentials and control circuits. More particularly, a phase shift circuit consists of two circuits 50 subsequently called half-phase-shifter. We first describe a half-phase shifter.

A half-phase-shifter 50 comprises a dielectric support 33, two wires 42 each carrying a diode D1, D2. The two wires are connected to the ground potential, or to any other reference potential, via a conductive line 43. This line 43 is for example of the microstrip type made by metal deposition on the front face of the dielectric support 33 for example by a screen printing technique. The diodes D1 and D2 are thus wired in opposition so that, for example, their anodes are connected to the ground potential via this line 43. For this purpose, the latter is for example connected to a conductive strip 48 of the decoupling means 20. Diode supply voltage D1 and D2 is supplied by control conductors 44. The anode of the diodes being connected to the ground potential, the control conductors are then connected to the cathode of the diodes. The supply voltage supplied by these conductors is for example of the order of -15 volts. The control leads are controlled to have at least two voltage states. In a first state, their voltage is for example at the supply voltage, which makes the diode pass, or in other words polarized live. In a second state, their voltage is such that the diode is blocked, or in other words polarized in reverse. The controls of the two control conductors 44, 45 are independent of one another so as to control the diodes independently of one another. The control conductors 44, 45 and the connected ground conductor 43 are substantially parallel to the direction Ox and therefore perpendicular to the wires 42. figure 4 the ground conductor 43 is common to the two son especially for space and material gains, it could however provide a specific driver for each wire. It could also be expected to connect not directly these conductors directly to a reference potential but through a control circuit.

The control conductors 44, 45 are connected to the electronic control circuit carried by the reflector, via metallized holes 46 made for example at the decoupling zone 20, in particular for reasons of space, but also for do not disturb the functioning of the elementary cells. Metallic holes 46 are of course electrically isolated from the conductive strips of the decoupling zone. For this purpose, there is provided an interruption of the strip 20 around the ends of the control conductors directly connected to the metallized holes 46.

A half-phase-shifter 50 may have four different values for its susceptance B _D , these values being denoted B _D1 , B _D2 , B _D3 and B _D4 , according to the command (direct or inverse bias) applied to each of the diodes D1, D2. The susceptance values B _D1 , B _D2 , B _D3 and B _D4 are a function of the parameters of the circuit, that is to say the values chosen for the geometrical parameters, in particular as regards the dimensions, shapes and spacings of the different conductive surfaces 43, 44, 45, and electrical phase shifter, particularly with regard to the electrical characteristics of the diodes. In particular, it is necessary to take into account the definition constraint of the conductive strip of the decoupling zone 20 mentioned above during the determination of the different parameters for fixing phase shifts dφ ₁ - dφ ₄ .

où λ est la longueur d'onde correspondant à la pulsation ω précédente.If, now, we study the behavior of the entire half-phase-shifter 50 in association with the conductive plane 32, we must take into account the susceptance due to this plane 32, brought into the plane of the half-phase shifter and denoted B _CC , which is written: $${\mathrm{B}}_{\mathrm{CC}}\mathrm{=}\mathrm{-}\mathrm{cotg}\frac{\mathrm{2}\mathrm{\pi d}}{\mathrm{\lambda }}$$

where λ is the wavelength corresponding to the preceding puls pulse.

The susceptance B _C of the cell is then given by: $${\mathrm{B}}_{\mathrm{VS}}\mathrm{=}{\mathrm{B}}_{\mathrm{VS}}\mathrm{+}{\mathrm{B}}_{\mathrm{CC}}$$

It follows that the susceptance B _C can take four distinct values (denoted B _C1 , B _C2 , B _C3 , and B _C4 ) respectively corresponding to the four values of B _D , the distance d representing an additional parameter for the determination of the values B _C1 - B _C4 .

It is also known that the phase shift dφ printed by an admittance Y to a microwave wave is of the form: $$\mathrm{d\phi }\mathrm{=}\mathrm{2}\mathrm{arctg\; Y}$$

et qu'on obtient quatre valeurs possibles dϕ₁ - dϕ₄ de déphasage par demi-déphaseur 50, selon la commande appliquée à chacune des diodes D₁ et D₂. Les différents paramètres sont choisis pour que les quatre valeurs dϕ₁ - dϕ₄ soient équiréparties, par exemple mais non obligatoirement : 0°, 90°, 180°, 270°. Ces quatre états correspondent à une commande numérique codée sur deux bits.It thus appears that, neglecting the real part of the admittance of a cell, we have: $$\mathrm{d\phi }\mathrm{\cong }\mathrm{2}\arctan {\mathrm{B}}_{\mathrm{VS}}$$

and that four possible values dφ ₁ - dφ ₄ of phase shift per half-phase-shifter 50 are obtained, according to the command applied to each of the diodes D ₁ and D ₂ . The different parameters are chosen so that the four values dφ ₁ - dφ ₄ are equidistributed, for example but not necessarily: 0 °, 90 °, 180 °, 270 °. These four states correspond to a two-bit digital control.

It should be noted that the case in which the parameters of the circuit have been chosen is described above so that the null susceptances (or substantially zero) are such that they correspond to the diodes polarized in the forward direction, but that can of course choose a symmetrical operation; more generally, it is not necessary for one of the susceptances B _d or B _{r to} be zero, these values being determined so that the equidistribution condition of the phase shifts dφ ₁ -dφ ₄ is fulfilled.

To show how an elementary cell 25, 26 allows eight possible phase shifts, that is to say a control of three-bit phase shifts, we now consider the set of two half-phase shifters 50. By operating the two half-phase shifters 50 independently of one another, one can obtain twice as many states, that is to say phase shifts, than in the case of a single half-phase-shifter. Nevertheless, it is necessary to provide electrical insulation between the two half-phase shifters. The latter two being for example juxtaposed, the control conductors 44, 45 are isolated for example by a line 47 of dielectric, corresponding in fact to a cut-off line in the metallization of the conductors 44, 45. This first insulation allows in fact a insulation of the electrical controls of the diodes.

At the four susceptance values B _D1 , B _D2 , B _D3 , B _D4 obtained by the influence of a half-phase-shifter, we thus obtain four new values B ' _D1 , B' _D2 , B ' _D3 , B' _D4 obtained by the influence of the second phase shifter.

The geometric and electrical parameters of the phase shifter are for example defined to obtain eight phase shifts equidistant between 0 ° and 360 °.

Depending on the desired phase shifts are defined susceptance B values of _C and hence susceptance B _D values according to the equations (1) and (2), distance d being known. The geometric and electrical parameters of the phase-shifter can then be obtained by conventional simulation means.

A phase shift circuit as illustrated by the figure 4 is simple to implement, it makes it possible to obtain eight phase shifts by simply playing on geometric parameters of conductors and on the choice of diodes. The phase shifter 21 which comprises an array of phase shift cell pairs can therefore be obtained economically. The printed circuit supporting the microwave circuits and the electronic control circuits is also thin.

As indicated above, the phase shifter comprises decoupling means 20 between the cells 25, 26. The microwave wave E received by the cells is polarized linearly, parallel to the direction Oy. It is desirable that this wave be does not propagate from one cell to another, in the Ox direction. To avoid such propagation, the decoupling means comprise at least the conductive zone 48. It is therefore expected to provide this substantially strip-shaped conductive zone 48, made by metal deposition on the surface 34, for example, between the cells, parallel to the direction Oy. This strip 48 forms, with the reflective plane 32 which is below, a waveguide-like space whose width is the distance d. The distance d is chosen to be less than λ / 2, λ being the length of the microwave wave, knowing that a wave whose polarization is parallel to the bands can not propagate in such a space. In practice, the reflector according to the invention operates in a certain frequency band and d is chosen to be less than half the smallest of the wavelengths of the band. Of course, it is necessary to take this constraint into account when determining the different parameters for fixing phase shifts dφ ₁ , ... dφ ₈ . In addition, the band 48 must have a width, in the direction Ox, sufficient for the effect described above is sensitive. In practice, the width may be of the order of λ / 5.

Moreover, it may be parasitically created in a cell, a wave whose polarization is directed in the direction Oz, perpendicular to the plane formed by the directions Ox and Oy containing a phase shift circuit. It is also desirable to prevent its spread to neighboring cells.

For neighboring cells in the Ox direction, it is possible to use as shown in FIG. figure 4 the metallized holes 46 for connecting the control conductors to the electronic circuits. Indeed, these being parallel to the polarization of the parasitic wave, they are equivalent to a shielding conductive plane if they are sufficiently close together (at a distance from each other much less than the length of the operating wave of the reflector), so many, for the operating wavelengths of the reflector. If this condition is not fulfilled, additional metallized holes can be formed, having no connection function. It should be noted that the metallized connection holes 46 are preferably made at the level of the strips 48 so as not to disturb the operation of the cells. This provision also provides a saving of space.

Finally, with regard to two neighboring cells in the Oy direction, it is possible to use metallized holes 40 similar to the connection holes 46 but aligned in the Ox direction opening into the conductive strip 49. These metallized holes 40, such as the metallized holes of FIG. connection 46 are made in a direction Oz substantially perpendicular to the plane Oxy. For example, it is still possible to provide a continuous conductive surface in the xOz plane.

The figure 5 illustrates a phase shifter according to the invention for controlling the phase shifts on 4 bits, thus on an additional bit compared to the circuit illustrated by the figure 4 . The phase shifting circuit always comprises two half-phase shifters 50 made as previously described. However, the two half-phase-shifters are no longer separated by a line 47 isolating the controls of the diodes, but by two conductive zones 71, 72 connected by a diode D3, or any other semiconductor with two states. These two zones 71, 72 are for example made by metal deposition on the front face 34 of the dielectric. These zones form control conductors of the diode D3. For this purpose, a conductive zone 71 is for example connected to the electronic control circuits by a metallized hole 46. Depending on the state of the electronic control, this zone 71 is at a supply potential, for example -15 volts or to another potential, for example the mass potential. The other conductive zone 72 is for example connected to the ground potential. For this purpose, it is for example connected to the conductive strip 48 parallel to the direction Oy of the decoupling means 20.

When the conductive zone 71 is controlled to be at the ground potential, or more generally to make the diode D3 blocked, that is to say in reverse bias, the phase shift circuit is similar to that of the figure 4 , it presents in this state eight possible phase shifts. It is of course necessary to redefine its geometrical and electrical parameters because of the introduction of the additional zones 71, 72. When the conductive zone 71 has a potential that makes the diode D3 conducting, that is to say in direct polarization , the electrical parameters of the phase shift circuit are modified compared to the previous state. In particular, the capacity formed of the space between the two conductive zones 71, 72 becomes short-circuited by the diodes D3. The eight susceptances possible of the previous state, controlled on three bits, are then modified by the conduction of the diode D3. The eight new susceptances thus obtained make it possible to obtain eight additional phase shifts. A total of sixteen phase shifts are possible. The geometric and electrical characteristics of the two half-phase-shifters 50 but also the additional conductive zones 71, 72 and their diode D3 must be defined so as to obtain the sixteen desired phase-shifts for each of the states of the diodes.

The figures 4 and 5 show examples of possible realization of the phase shifter 21, and more particularly the phase shift cells 25, 26. Other embodiments on multilayer support are possible. In general, the phase shift cells 25, 26 of the same pair, associated with a coupler 24, produce the same phase shift. They can, for example, be controlled by the same circuit.

The figure 6 illustrates an exemplary embodiment of an antenna according to the invention comprising phase shifters as described above. The antenna comprises a linear array of phase shifters providing, for example, electronic scanning in azimuth, for example in the context of an air traffic surveillance application. This antenna comprises means 4 of energy distribution, and more particularly the microwave provided by a power transmitter. It comprises radiating elements 1. Finally it comprises a phase shift block 81 itself composed of phase shifters according to the invention. This phase shift block is for example that illustrated by the figure 2a . In this case, the pairs of phase shift cells 25, 26 are made on the same dielectric support. The dielectric support 33 is then common to all the cells. The phase shift block therefore comprises a set of couplers 22 placed on a phase shift device 21 as illustrated by the Figures 3a, 3b to 5 . More particularly, the phase shift block 81 consists for example of several assemblies conforming to the figure 2a arranged end to end. An assembly 21, 22 comprises several phase shifters, for example 16 as illustrated by this figure 2a . For example, a phase shift block comprising 5 sets 21, 22 then has 80 phase shifters. The microwave links are such that the outputs of the distribution means 4 are connected to the inputs 27 of the couplers 24, which also form the inputs of the phase shifters. Similarly, the outputs of the latter, which are the outputs 28 of the couplers are connected to the radiating elements. Waveguides 82, 83 conduct the microwave from the transmitter to the distribution circuit 4, and similarly conduct the received wave to the receiving circuits. A first guide 82 corresponds, for example, to the sum path of the antenna pattern and a second guide 83 corresponds, for example, to the difference path, thus enabling deviation measurements.

In the exemplary embodiment of the figure 6 , the radiating sources are arranged linearly, that is to say rectilinearly. It is possible to envisage examples of realization where the sources radiators, and also the phase shifters are not aligned rectilinearly. Other examples of embodiments are proposed to Figures 7 and 8 .

The figure 7 shows, in a partial perspective view, an embodiment where the phase shift block 81 is cylindrical. It is then in particular composed of elementary phase shifters arranged side by side on a cylindrical surface, in particular the phase shifter 21 has in this case a cylindrical shape. The figure 8 shows, in a partial view, an embodiment where the phase shift block 81 is in the form of a ring. The elementary phase shifters are then arranged in a ring, the phase shifter having for example in this case a ring shape. They are in this figure seen from above, that is to say for example on the side of the input of the microwave wave.

The transmitter which feeds the distribution circuits 4 may be tube or solid state. The technological choice may depend in particular on the powers involved.

An antenna according to the invention, produced for example according to the figure 6 , is economical and very compact. In particular, it is economical because of the considerable simplification of connections and the reduction in the number of construction and assembly operations. It is also economical because of the simplification of testing, debugging and maintenance. In particular, the phase shifters are tested collectively, hence saving time. In case of problems, replacing one phase-shifter with another is very easy. In particular, if a phase shifter of an assembly 21, 22 is faulty, it is very easy to replace the assembly comprising the faulty phase shifter by another set of phase shifters. The maintenance of the antenna is thus simplified.

The invention is particularly well suited for an electronic scanning antenna "a plane". It can nevertheless be applied for a "two-plane" electronic scanning antenna. In particular in the latter case, the support of the phase shifter 21 contains, for example, several rows of pairs of phase shift cells 25, 26 instead of just one, in particular to obtain a planar array of phase shifters. Other means of supplying the couplers 24 are possible. In particular the power supply may be of the "Rattle Snake" type where the elementary phase shifters 23 are arranged on a snaked line. In this type of power supply, the electric field is perpendicular to the field by guide feed, that is to say parallel to the direction Ox of the figure 4 instead of the direction Oy. It is then necessary to rotate the phase shifters by 90 ° so that the orientation of the wires 42 carrying the diodes are in the direction of the electric field. The power supply of the couplers 24 can also be done by active sources, the two field directions being possible. In this case, the antenna comprises active microwave sources, an active elementary source is for example associated with each coupler 24.

If less economy and compactness are sufficient, the phase shift device 21 of the printed circuit type can be replaced by ferrite circuits or any other type of phase shift circuit.

Claims (14)

1. A microwave phase shifter, comprising at least one 3db coupler in waveguide form (24) and a pair of phase-shifting cells (25, 26), the incident wave (E) entering into a first input (27) of the coupler in order to be divided into two waves (E1, E2), these two waves each being reflected on one of the pair of phase-shifting cells (25, 26) with identical phases and being recomposed into a resultant phase-shifted wave (S) exiting via the output (28) of the coupler juxtaposed with the first input (27), an incident wave (E1, E2) being linearly polarised in a first given direction (Oy), a phase-shifting cell (25, 26) comprises a phase-shifting circuit (10) before a conducting plane (32) having the function of reflecting the incident wave (E1, E2) and arranged substantially parallel to the phase-shifting circuit, the phase-shifting circuit (10) comprising at least two half phase shifters (50),
   one half phase shifter (50) comprising at least one dielectric substrate (33), at least two electrically conductive wires (42) substantially parallel to the given direction (Oy), arranged on the substrate and each one comprising at least a two-state semiconductor element (D1, D2), each wire being connected to control conductors (43, 44, 45) for the semiconductor elements, these conductors being substantially normal to the wires, and two conductive zones (49) arranged towards the periphery of the cell, substantially in parallel to the control conductors,
   the control conductors being at least three in number in each half phase shifter and being isolated electrically from one half phase shifter to the other in order to control the state of all the semiconductor elements independently of one another,
   the geometric and electrical characteristics of the half phase shifters being such that a given phase-shift value (dϕ₁, ... dϕ₈) of the electromagnetic wave which is reflected by the cell corresponds to each of the states of the semiconductor elements, the state of the semiconductor elements being controlled by an electronic circuit (36).
2. A phase shifter according to Claim 1, characterised in that the two half phase shifters (50) are separated by two conductive zones (71, 72) connected by a two-state semiconductor element (D3), at least one of the zones (71) being connected to the electronic control circuit (36) for controlling the state of the semiconductor, the geometric and electrical characteristics of the half phase shifters and of the conductive zones (71, 72) and of their semiconductor elements being such that a given phase-shift value (dϕ₁, ... dϕ₁₆) of the electromagnetic wave which is reflected by the cell corresponds to each of the states of the semiconductor elements.
3. A phase shifter according to any one of the preceding claims, characterised in that a conductive strip (48) is arranged between each cell, parallel to the given direction (Oy), which forms with the conducting plane a guided space where the wave cannot be propagated.
4. A phase shifter according to any one of the preceding claims, characterised in that the dielectric substrate (33) is of the multilayer printed board type, a first face (34) of which bears the microwave circuit, a first intermediate layer of which bears the conducting plane (32) and the second face (35) of which bears components of the control circuit.
5. A phase shifter according to Claim 4, characterised in that the dielectric substrate (33) furthermore comprises at least a second intermediate layer (37) bearing interconnections of the control circuit.
6. A phase shifter according to any one of the preceding claims, characterised in that it comprises metal-coated holes (40, 46) made in the dielectric substrate (33), in the direction (Oz) perpendicular to the plane (Oxy) of the phase-shifting circuit, at a distance one from the other which is very much less than the electromagnetic wavelength, some at least of these metal-coated holes providing a link between the control circuit and the control conductors.
7. A phase shifter according to any one of the preceding claims, characterised in that the semiconductor elements are diodes.
8. A phased-array microwave antenna, characterised in that it comprises at least radiating elements (1), phase shifters (23) according to any one of the preceding claims and means (4, 5) for supplying these phase shifters, the inputs of the couplers (24) which form the inputs of the phase shifters being connected to the supply means (4), the outputs of the couplers being connected to the radiating elements.
9. An antenna according to Claim 8, characterised in that the phase shifters are distributed in at least one block (81), a block comprising a set (21) of pairs of phase-shifting cells (25, 26) which are produced on one and the same piece and a set (22) of couplers (24) forming a single piece.
10. An antenna according to any one of Claims 8 or 9, characterised in that the phase shifters (23) are distributed on a cylinder.
11. An antenna according to any one of Claims 8 or 9, characterised in that the phase shifters (23) are distributed on a ring.
12. An antenna according to any one of Claims 8 or 9, characterised in that it comprises a planar array of phase shifters (23).
13. An antenna according to any one of Claims 8 to 12, characterised in that the supply means for the phase shifters (23) comprise means (4) for distribution of a microwave (5) provided by a centralised transmitter.
14. An antenna according to any one of Claims 8 to 12, characterised in that it comprises active microwave sources supplying the phase shifters (23).

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