FR2905803A1 - ROTARY DIELECTRIC PHASING DEVICE FOR RADIANT ELEMENTS - Google Patents

Abstract

The rotary phase shifter comprises an electrically conductive track (7) having a plurality of concentric segments (7a, 7b, 7c) about an axis X-X ', at least one input (30) and at least two outputs (31, 32). The track (7) is placed in a matrix with a low dielectric constant. The rotary phase shifter also comprises an upper piece (6) and a lower piece (5) disposed on either side of the track (7), a material having a dielectric constant greater than that of the matrix. Each of these parts (5, 6) having on its outer face a conductive surface (2, 3) connected to the ground. The upper part (6) and the lower part (5) are able to move in rotation around the axis X-X 'with respect to the track (7) to modify the overlap of the segments (7a, 7b, 7c).

Description

Rotary dielectric phase shifter device for radiating elements

  The present invention relates to a rotary phase-shifting device, comprising a dielectric material, making it possible to apply a phase shift on radiating elements, or groups of radiating elements, in particular belonging to antennas for the base stations of the cellular communication networks. (GSM, UMTS, ...). This phase shift aims to detach the direction of the main lobe of the antenna, and thus achieve antennas dynamic depointing, or otherwise called variable tilt antennas. The invention relates more particularly to the field of microstrip type structures. In general, these are conductive surfaces formed on one of the faces of a planar dielectric substrate, on the other side of which is contiguous a continuous conductive sheet commonly referred to as the ground plane. The radiating members with microstrips are generally in the form of a printed circuit plated on the dielectric substrate.

  There are several major families of phase shift systems according to their mechanical mode of operation. On the one hand the longitudinally displaced systems (for example described in US-5,949,303 or WO-02/35651) where a high and low loss dielectric constant material is used to create a relative phase shift between two radiating elements, or two groups radiating elements, an antenna. The material is inserted near the conductive line which may be planar stripline or microstrip structure. The speed of propagation of the signal flowing on this conductive line is reduced as the dielectric constant of the material is high, the thickness of the piece of dielectric material is substantial, and this piece is placed so as to cut the current lines that lie between the power lines and the earth. The major disadvantage of this system is that it requires a large enough area to be activated, since the piece of dielectric material must move from one end of the system to the other in the longitudinal direction. The limits of the displacement of the part therefore limit the amplitude of phase shift of the system.

  On the other hand the transverse displacement systems (for example described in EP-1 215 752), where a high dielectric constant material and low loss is used to create a relative phase shift between two radiating elements. The movement 2905803 2 is transverse to the supply line of the various radiating elements. Each of the phase shifts adds up to each other until the last radiating element is energized. The disadvantage of this system is that it is necessary to set in motion each of these phase shifters, while they are physically far apart from each other. Finally rotary systems (for example described in US-6,850,130 or JP-09-246,846), wherein one or more metal parts provide the connection between various conductive lines. These metal parts provide an ad hoc coupling between the conductive lines most often in the form of a contactless connection, ie where a capacitive effect between two metal parts provides RF coupling between the lines. However, the coupling between lines has the disadvantage that these systems can hardly have good performance over a wide band of frequency without the need to make compromises harmful to the coupling losses, so the overall efficiency of the phase shift system. Another disadvantage of these systems is that it is difficult to multiply the conductive lines that will be connected to the radiating elements. The present invention aims to eliminate the disadvantages of the prior art, and in particular to provide a system for detaching a compact antenna comprising a phase shift device of simple structure, economical and reliable. In particular, it proposes a rotary electric phase-shifter, continuously variable and with low losses. The object of the present invention is a rotary phase shifter comprising: an electrically conductive track, comprising a plurality of concentric segments around an axis, at least one input and at least two outputs, placed in a matrix with a low dielectric constant an upper part and a lower part arranged on either side of the track, in a material having a dielectric constant greater than that of the matrix, each of these parts having on its outer face a conductive surface connected to the ground; , Characterized in that the upper piece and the lower piece are able to move in rotation about the axis relative to the track to modify the overlap of the segments.

The rotary device according to the invention allows the misalignment of the antenna through the use of a relatively high dielectric constant material (Er> 1) and low loss to create a phase shift. This system comprises a fixed part, including a stripline or microstrip type feed line. This line is of circular or semicircular type, it is embedded in a material or a gas of relatively low dielectric constant, this gas can be simply air. The invention further comprises one or more plates of a material having a dielectric constant greater than that used for the supply line alone, thus making it possible to achieve a substantial phase shift in the long term.

The track further includes a first section for impedance transformation and a second section for current division. These sections are placed between the input and the outputs and are connected to the concentric segments. Advantageously, the first section is at least partially covered by a dielectric material. Such coverage helps to improve the performance of the device. According to a particular embodiment of the invention, the average dielectric constant of the upper part and the lower part is modified by removal of material. The present invention has the advantage of allowing great ease of mechanical movement of the parts and ensuring perfect continuity between the different supply lines of the radiating elements microstrip structure or stripline. Another advantage of the invention is that the rate of modification of the phase is different depending on whether stripline or microstrip lines are considered that are more or less distant from the center of rotation of the assembly. For the lines placed near the center, the phase shift is relatively slow whereas for the lines distant from the center it is much faster, and for the same angular movement. This is in contrast to mechanical phase-shift systems of the longitudinal type. In fact, in the case of longitudinal systems, the mechanical displacement of the dielectric block is constant by construction, whereas the phase change should be progressive and linear (ie radiating elements at the ends of the antenna must be out of phase much faster than those present in the center). Depending on whether the radiating elements to be powered are at the ends or at the center of the antenna, it is necessary to use different dielectric media, ie having a different average dielectric constant value. This can be achieved by choosing either a different dielectric material for each section of radiating elements to be fed or by recessing all or part of the dielectric material (for example by creating recesses or reducing the thickness) so that its value average is changed. In the context of the invention, it suffices to choose the lines which are outside to feed the radiating elements which are placed at the ends of the antenna, and the lines which are inside to feed the radiating elements which are placed in the center of the antenna, to be sure that the phase difference between dipoles will be progressive and constant. To control the phase shift rate between dipoles, the spacing between the tracks during the construction of the phase shift system will be appropriately selected. In particular, if the phase shift between the radiating elements of the antenna must be linear and progressive, an equal and constant distance between the lines will be adopted.

Of course, a change in dielectric medium may also be associated with the method so that an additional construction variable can be used. According to the invention, the dielectric material is preferably selected from a plastic material and / or a ceramic material. According to a particular embodiment, the plastic material constituting the dielectric material contains one or more polymers.

The dielectric material may in particular consist of a mixture, an alloy or a superposition of layers of different materials. The invention also relates to an antenna comprising a phase shift device as described above. Other features and advantages of the present invention will appear on reading the following description of an embodiment, given of course by way of illustration and not limitation, and in the appended drawing in which - FIG. Schematic exploded view of a first embodiment of a phase shifter according to the invention, - Figure 2 shows the device of Figure 1 to which the cover has been removed, - Figure 3 shows the bottom of the device. FIG. 1 shows the electrical network of the device of FIG. 1, FIG. 5 shows a dielectric part of the device of FIG. 1, FIGS. 6A and 6B are sectional views AA 'of FIG. two variant embodiments of the dielectric part of FIG. 5; FIG. 7 represents a diagrammatic exploded view of a second embodiment of a phase shifter according to the invention; FIG. Figure 9 shows the upper dielectric part of the device of Figure 6, Figure 10 shows the lower dielectric part of the device of Figure 6, Figure 11 is a sectional view BB of the device of Figure 7; 1 of the dielectric part of FIG. 9, FIG. 12 is a sectional view C-C 'of the dielectric part of FIG.

The phase shifter illustrated in these figures corresponds to a phase-shifter designed to work in the AMPS (Advanced Mobile Phone System) and GSM (Global System for Mobile Communications) frequency bands, ie 824 MHz to 960 MHz. Of course a phase shifter according to the invention can work in any frequency band.

In the embodiment of the invention illustrated in Figures 1 and 2, the phase shifter 1 comprises a housing consisting of a cover 2 and a bottom 3 of conductive material arranged parallel to each other , connected by a central mechanical axis 4 coaxial with the direction X-X ', and constituting the ground plane. The phase shifter 1 also comprises a lower part 5 and an upper part 6 made of dielectric material placed in contact with the cover 2 and the bottom 3 respectively. The phase shifter further comprises a power supply line in the form of an electrically conductive track 7 composed of a plurality of concentric segments 7a, 7b, 7c, provided with a power supply, which are represented in the form of a network of lines. The two pieces 5, 6 made of dielectric material are able to be displaced in rotation relative to the track 7, to modify the overlap of the segments by the two parts 5, 6. FIG. 3 schematically represents the bottom 3 of the housing. The bottom 3 consists of a conductive material, at least on the surface. The lid 2 and the bottom 3 are connected to each other and to the ground; they are thus brought to the same potential. The bottom 3, as well as the cover 2, are here formed of an aluminum block, whether folded, molded or machined. The bottom 3 and the cover 2 could equally well be made of other materials, such as aluminum, copper, brass or any other metal or alloy.

The bottom 3 here has a shape S2 which covers the total surface of the phase shifter, but it could also be made in many configurations other than that shown. The bottom 3 has at least one input and two outputs. The minimum access number is therefore 3, and there are only physical congestion constraints that can limit the number (without being limited to an even or odd number). In this case, the inlet 30 is shown in the central position but, it could as well be placed on one of the sides of the bottom 3. The outputs 31 and 32 are carried by each end of Q. The input 30 and outputs 31, 32 are here connectors, but they could also be made in the form of direct links to the radiating elements by means of coaxial cables or by extending the microstrip or triplate lines. FIG. 4 shows the electric track 7 placed in the center of the phase shifter, which is in the form of a microstrip line punched in a brass sheet, but it could equally well be made of any other material having good electrical conductivity, as well as in the form of a printed circuit. The track 7 comprises several segments 40 placed concentrically with respect to the axis of rotation X-X 'of the phase shifter. The segments 40 are parallel to each other. During the realization, one makes sure to separate these segments so as to minimize the coupling.

The access to the runway is in the center. A first section 42 of the track 7, located in the extension of the access 41, is composed of several segments. The section 42 is used to allow a correct impedance transformation between the access 41 and the number N of connections to be provided at the output (N 2). The width of the segments forming the section 42 is adapted to respect the desired input and output impedance, generally 50 ohms. Typically the segments may have a width of the order of 7.35 mm to 7.5 mm for a thickness of about 1 mm, when the ribbon line is inscribed between two parts 2, 3 connected to earth and spaced 7 mm apart. In this case, the distance between the access 41 and the set of segments 40 to be fed is quite large. This distance can be used to allow this transformation of impedance under excellent conditions. The section 42 can be made for example by a progressive impedance transformation Klopfenstein type. This section 42 can be made either in the form of an air stripline line or dielectric material. This is one of the great advantages of the invention.

The known systems require accepting compromises that are harmful to the usable frequency bandwidth and overall losses of the phase-shifter systems, and in return offer little opportunity for adapting the input impedance of the phase-shifter.

A second section 43 is used to allow the division of power to the different segments 40. Indeed, the segments 40 do not necessarily have to have the same operating amplitude, but often they must allow a weighting of the power available in the different outlets 32, 33. The arrangements for weighting these powers are most often in the form of a change in the section width of the segments 40 or in the form of adding recesses within them. It goes without saying that given the reciprocal nature of an antenna, a receiving element (or an antenna composed of a network of reception elements) is able to operate as a radiating element (or radiating antenna) without any 15 modification of its characteristics. On the bottom 3 is deposited a piece 5 dielectric material shown in Figure 5. A part 6 is also deposited in the same lid 2. The parts 5,6 can be made in different ways. For ease of design, parts 5 and 6 are in the present example of identical shape. Typically, the pieces 5, 6 are made of plastic, such as, for example, polypropylene polypropylene (PPS RYTON) having a dielectric constant of the order of 4 to 6. Although more expensive and requiring greater precision, it is also possible to use a ceramic-type material as a dielectric material whose dielectric constant Er is of the order of 10.

Part 5 only partially covers the surface of the bottom 3 and can be broken down into three subassemblies: - a central part 51 full, - two lateral wings 52 and 53 which ensure a suitable impedance transformation between the different heterogeneous media of the stripline device, and the peripheral portion 54 provides the phase shift function of the system. The central portion 51 does not have its own electrical function, unless it covers all or part of the access 41 of the track 7. In this case the dielectric can be used 2905803 8 so as to increase the capabilities of the line of progressive impedance transformation. In the present case, the impedance transformation takes place between the part of the track 7 which is in contact with the air, and the part of the track 7 which is enclosed between the solid parts of the two parts 5, 6 made of dielectric material. In the embodiment of FIG. 1, this impedance transformation function is provided by creating recesses in the dielectric material. These recesses can have the shape that you want. By way of example, they have been represented here by simple recesses made in parts 5 and 6. In FIG. 6A, these recesses 55 10 pass through the part 5, 6 from one side to the other; while in Figure 6B, the recesses 56 are formed on either side of the part 5, 6 and do not communicate. The configuration of the dielectric part of FIG. 5 thus makes it possible, of course, to obtain a gradual phase shift by resorting to localized, complete or partial evidence of the dielectric medium.

By calculation or simulation, the appropriate succession of the modifications to be made in the section of the parts 5, 6 is obtained in order to obtain a suitable impedance transformation between the two media using an equivalent diagram of the dielectric medium of elements. located under the succession of discrete elements: resistance R, inductances L and capacitors C.

The rotation about the central axis XX 'of the peripheral portion 54 of the part 5, 6, consisting of a material of relatively high dielectric constant and low loss (of the order of less than one per thousand), allows to create a relative phase shift between the radiating elements (or groups of radiating elements) of the antenna. The dielectric material used is disposed near the conductive track in a triplate (stripline) configuration in the present case. The part 5, 6 is placed so as to cut the current lines between the power supply segments 7a, 7b and 7c and the ground. The piece 5, 6 dielectric material should not cause loss of signal intensity, but has the role of delaying the propagation. The speed of propagation of the signal flowing on this conductive line is reduced as the dielectric constant of the part 5, 6 is high and the thickness of the part 5, 6 is substantial. In the embodiment of FIG. 7, the phase-shifter 71 comprises a housing composed of a cover (not shown) and a bottom 72 of conductive material, an upper part 73 and a lower part 74 made of dielectric material placed in contact with the cover and the bottom 72 respectively, and an electrically conductive track 75 composed of several concentric segments. The two pieces 73, 74 of dielectric material are likely to be displaced in rotation relative to the track 75, to change the recovery of the line. FIG. 8 shows an example of a diagram of an electrical track 81, obtained by simulation. It includes the access 82 to the runway 81 which is in the center, a first section 83 of the runway 81 in the extension of the access 82 composed of several segments, and a second section 84 used to allow the division towards the different segments 85a, 85b, 85c, 85d each provided with an output 86. FIGS. 9 and 10 respectively represent two embodiments 91, 101 of embodiment of a piece of dielectric material according to the embodiment of FIG. Part 91, 101 has a central portion 92, 102, two side wings 92, 93 and 103, 104 which provide the impedance transformation, and a peripheral portion 95, 105 which provides the phase shift function of the system. The wings 92, 93 and 103, 104 are simplified since they are reduced here to a single quarter-wavelength section of reduced thickness. In FIGS. 9 and 10, quarter-wave-type sections are used, the average value of dielectric constant being varied by varying the thickness of the material at each stage, as represented for example in FIGS. 11 and 12. The central portion 92, 102 does not have its own electrical function unless it covers all or part of the access 41 of the track 7. In Figure 9, the central portion 92 is full. However, in the case where this choice is not chosen, recesses 106 can be made in the central portion 102 as shown in FIG. 10 for example. The invention is not limited to the embodiments described but is capable of numerous variants easily accessible to those skilled in the art.

Claims (7)

  Rotating phase shift device comprising: an electrically conductive track (7) comprising a plurality of concentric segments (7a, 7b, 7c) about an axis X-X ', at least one input (30) and at least two outputs (31, 32), placed in a matrix with a low dielectric constant, - an upper part (6) and a lower part (5) arranged on either side of the track (7), in a material having a dielectric constant greater than that of the matrix, each of these parts (5, 6) having on its outer face a conductive surface (2, 3) connected to the earth, characterized in that the upper part (6) and the lower part (5) ) are able to move in rotation around the axis XX 'with respect to the track (7) to modify the overlap of the segments (7a, 7b, 7c).   2. Device according to claim 1, wherein the track (7) further comprises a first section (42) for the impedance transformation and a second section (43) for the current division, the sections (42, 43). being connected to the segments (7a, 7b, 7c).   3. Device according to claim 2, wherein the first section (42) is at least partially covered by a dielectric material.   4. Device according to one of the preceding claims; wherein the average dielectric constant of the upper part (6) and the lower part (5) is modified by removal of material.   5. Device according to one of the preceding claims, wherein the dielectric material is selected from a plastic material and a ceramic material.   6. Device according to claim 5, wherein the dielectric material contains one or more polymers.   7. An antenna comprising a phase shift device according to one of the preceding claims. 10