FR2799580A1 - PRINTED BROADBAND PRINTED ANTENNA WITH LOW CROSS POLARIZATION LEVEL AND CORRESPONDING ANTENNA ARRAY - Google Patents

Abstract

The invention relates to a printed antenna, of the type comprising: a substrate plate; a metallic deposit, located on one side of said substrate plate and defining a resonant pad (2); a supply means (3), making it possible to supply said resonant pellet. According to the invention, the antenna further comprises at least one reactance arm (141 to 144) extending from a cold point (9A, 9B) of said resonant pellet. The invention also relates to an array of Antennas comprising at least two printed antennas as mentioned above.

Description

Antenna with broad bandwidth and low level of cross polarization, and corresponding antenna array.

The field of the invention is that of antennas made in printed technology.

It is recalled that this technology makes it possible to obtain light, compact and inexpensive printed antennas if mass-produced. They are now found in all types of applications (reception of satellite television, telecommunications, portable radars, ...). They can be used alone or networks.

More specifically, the invention relates to an improvement to conventional printed antennas.

Traditionally, a printed antenna comprises in particular - a substrate plate (or dielectric); a metal deposit, located on one face of the substrate plate defining a resonant pellet (or "patch"). Generally, the resonant chip is of square or circular shape, and its dimensions are of the order of half a wavelength. ; - Supply means, for supplying the resonant chip, by contact (line or coaxial probe) or by coupling (line or slot cut in a ground plane).

If such a conventional printed antenna has several advantages (lightness, low cost compactness), it also has some disadvantages. First of all, the bandwidth of such a conventional printed antenna is not wide enough a few% to ROS (Stationary Wave Ratio) less than 2. It is recalled that this percentage is obtained by division of the bandwidth by center frequency of this band. A known solution for increasing the bandwidth is to increase the thickness of the substrate plate. Unfortunately this solution generates spurious radiation that makes it unusable in practice. Indeed, the ideal operation corresponds to the excitation of a particular mode (generally a fundamental mode), but when the thickness of the substrate becomes important with respect to the wavelength (approximately 0.1A ,, with k, the operating wavelength), then unintentionally excited other modes (usually higher modes), said parasitic modes. Waves of parasitic surfaces are also excited which reduce the efficiency of the antenna.

Moreover, such a conventional printed antenna generates a level of cross polarization that is too high. This level reflects the capacity of the antenna, when it operates according to a first polarization (main component, for example horizontal), to reject a second polarization (cross component, for example vertical). Ideally, the level of cross polarization is zero.

Current antenna arrays, because they are obtained by juxtaposition of a plurality of conventional printed antennas (so-called sources), have the same disadvantages as those mentioned above (bandwidth too narrow and cross polarization level too high) .

Such an antenna array can be used either to maximize the radiation pattern in a predetermined principal direction (eg, the normal Oz to the (0x, Oy) plane containing the antenna array), or to generate a depointed radiation pattern relative to this predetermined main direction. The second case corresponds in particular, but not exclusively, to obtaining a radiation pattern of the "cosecant" type, making it possible to vary the transmission (and / or reception) power of the network as a function of at least one angular parameter. This angular parameter is, for example, the angle θ between the axis Oz and the direction away from the radiation pattern, and / or the angle cp between the axis Ox and the projection in the plane (0x, Oy) of the de-emphasized direction of the radiation pattern.

Currently, the implementation of an antenna array in the aforementioned second case (depointed radiation diagram) requires the use of additional means for playing on the phase and the amplitude of each of the elementary antennas. these additional means are complex and expensive.

The invention particularly aims to overcome these disadvantages of the state of the art.

More precisely, one of the objectives of the present invention is to provide a printed antenna having an enlarged bandwidth and a low level of cross polarization. The invention also aims to provide such a printed antenna which has a manufacturing cost substantially equal to that of a conventional printed antenna.

Another object of the invention is to provide such a printed antenna having dimensions close to those of a conventional printed antenna.

An additional object of the invention is to provide an array of antennas from a plurality of such printed antennas.

Another object of the invention is to provide such a network of printed antennas to obtain an off-line radiation pattern without additional resources (to play on the phase and amplitude) complex and expensive.

These various objectives, as well as others which will appear subsequently, are achieved according to the invention using a printed antenna, of the type comprising - a substrate plate, - a metal deposit, located on the face of said substrate plate and defining a resonant pad - a supply means for supplying said resonant pad, and further comprising - at least one reactor arm extending from a cold spot of said resonant pad.

The printed antenna of the invention is therefore different from that of the prior art in that, from one or more cold spots the resonant chip, extend one or more reactance arms. Each "reactance arm" (or stub, or "mustache") may be either in the plane containing the resonant pellet, or in a plane inclined relative to the latter. The second case (arm in an inclined plane) includes, but is not limited to, the upwardly extending, monopole-type reactance arms and the downwardly extending reactance arms of the coaxial line type.

It is clear that all or only some of the cold spots may be involved. It is also clear that each cold point concerned can be a starting point for one or more reactance arms. It is recalled that a cold point, for a given mode, is a point in the resonant pellet where the current is maximum and the voltage is zero. The reactance arms make it possible to eliminate, by short-circuiting them, unwanted modes (or parasitic modes), and thus to improve markedly - cross-polarization level, by increasing the useful radiation according to the main polarization, with respect to parasitic radiation, according to cross polarization; - the bandwidth, by bringing a reactance to certain frequencies. in other words, the variation of reactive energy is minimized. In a first advantageous embodiment of the printed antenna according to the invention, said supply means does not substantially "wedge" said resonant chip, said chip resonant thus presenting a unique fundamental mode. Said cold point from which said at least one reactance arm extends is a cold spot for said single fundamental mode.

Thus, in this first embodiment of the antenna according to the invention, the undesired modes that are suppressed are the higher modes.

In a second advantageous embodiment of the printed antenna according to the invention, said supply means supplies substantially "wedge" said resonant chip, said resonant chip thus having at least two fundamental modes. Said cold point from which said at least one reactance arm extends is cold point for the superposition of said at least two fundamental modes.

Thus, in this second embodiment of the antenna according to the invention, the undesired modes that are suppressed are the higher modes.

In a third advantageous embodiment of the printed antenna according to the invention, said supply means supplies said "resonant" wafer substantially "in wedge", said resonant wafer thus presenting at least two fundamental modes. Said cold point from which said at least one reactance arm extends is a cold point for one of said fundamental modes.

Thus, in this third embodiment of the antenna according to the invention, the undesired modes that are suppressed are on the one hand the other fundamental mode (a cold point of one of the two fundamental modes being a hot point of the other) and on the other hand the higher modes. Advantageously, said at least one reactance arm is formed in said metal deposit. In this way, the reactance arms are very simple to perform and do not generate additional costs compared to resonant pellet alone.

Advantageously, said at least one reactance arm is a section of line formed in said metal deposit and extending outwardly of said resonant chip.

According to an advantageous variant, said at least one reactor arm is a slot section formed in said metal deposit and extending inwardly of said resonant chip.

With this variant, one gains even more in compactness since the reactance arms do not extend towards the outside of the pellet. In this case, the size of the printed antenna according to the invention is the same as that of a conventional printed antenna.

Preferably, said feeding means belongs to the group comprising - direct drive lines - direct attack probes; - contactless coupling lines; - Non-contact coupling lines cooperating with slots. This list is by no means exhaustive.

Preferably, so as to obtain a predetermined operation of said printed antenna, at least one parameter belonging to the group comprising the length of each reactance arm is played during the design of said antenna; the width of each reactor arm; the geometrical shape of each reactor arm; the position of each reactor arm; the number of cold spots from which at least one reactor arm extends; the number of reactance arms extending from each cold point. Thus, there are many possible strategies for controlling the global reactance introduced by all the reactance arms. Advantageously, said at least one reactance arm has a length substantially equal to a, / 4, with k the operating wavelength. In this way, the reactor arm constitutes an open-circuit stub close to a quarter wave.

Advantageously, said at least one reactor arm has at least one elbow. The elbows allow the reactance arms to stay closer to the resonant chip. The antenna is therefore more compact.

In a particular embodiment of the invention, said resonant chip has at least two cold spots, said antenna comprises at least a first pair of reactance arms. The reactance arms of said at least one first pair of reactance arms have substantially symmetry to a first axis, passing through said at least two cold points.

This first symmetry between pairs of reactance arms reduces the amount of noise, and thus improve the performance of the antenna. Advantageously, said resonant pellet has at least two cold spots.

The antenna comprises at least a second pair of reactance arms. The reactance arms of said at least one second pair of reactance arms have substantially symmetry with respect to a second axis, forming an axis of symmetry for said resonant chip and passing through a point of excitation said resonant chip by said means of food.

The combination of two symmetries between pairs of reactance arms, along two separate axes, further improves the performance of the antenna.

The invention also relates to an antenna array comprising at least two printed antennas as mentioned above.

In a first advantageous embodiment of printed antenna array according to the invention, each of said antennas comprises even set of at least one reactance arm, so as to maximize a radiation of said antenna array in a predetermined main direction.

Advantageously, said network comprises at least a first pair of antennas and at least a second pair of antennas. The reactance arms of the antennas of said at least one first pair of antennas have between them substantially symmetry with respect to a third axis, forming an axis of symmetry for said antenna array and passing through a feed point of said network of antennas. antennas. The antenna reactance arms of said at least one second pair of antennas have between substantially symmetry with respect to a fourth axis, forming an axis of symmetry for said antenna array, perpendicular to said third axis and passing through said feed point of said antenna network.

Thus, it is assumed that the network is in a plane (0x, Oy), the predetermined main direction is the axis Oz, and the third and fourth axes are for example respectively the axes Ox and Oy (or conversely the axes Oy and Ox).

This double symmetry between antenna pair reactance arms makes it possible to reduce the amount of noise and thus improve the performance of the antenna array. It is appropriate to distinguish these symmetries, within the antenna array, between reactance arms of antenna pairs, and the aforementioned symmetries, within the antenna used alone, between pairs of reactance arms. Indeed, the axes of symmetry concerned are not the same in both cases (some are specific to the antenna, while the others are specific to the antenna array).

In a second advantageous embodiment of the antenna array printed according to the invention, at least two of said antennas each comprise a distinct set of at least one reactance arm, so as to induce a radiation misalignment of said antenna array by referred to a predetermined main direction.

Thus, by appropriately choosing the reactance arms, it is possible to detach the radiation pattern from the antenna array. By "predetermined main direction" means here the direction that would take the radiation pattern if there was no misalignment. If it is again assumed that the network is in a plane (0x, Oy), the predetermined main direction, relative to which the misalignment is performed, is the Oz axis. In contrast to the conventional solution discussed above, the invention makes it possible to perform such a defocusing without any additional means (neither phase-shifter nor amplifier).

Advantageously, said network comprises at least a first pair of antennas. antenna reactance arm of said at least a first pair of antennas do not have a symmetry with respect to a third axis, forming an axis of symmetry for said antenna array and passing through a feed point of said network of antennas; antennas. In this way, said misalignment is performed around said third axis. Thus, the misalignment is for example around the axis Ox (or Oy).

Advantageously, said network comprises at least a second pair of antennas. The reactance arms of the antennas of said at least one second pair of antennas do not have a symmetry with respect to a fourth axis, forming an axis of symmetry for said antenna array, perpendicular to said third and passing through said d-point. supplying said antenna array. In this way, said misalignment is also performed around said fourth axis. Thus, the misalignment is for example around the axis Oy (or Ox).

Other features and advantages of the invention will become apparent on reading the following description of a preferred embodiment of the invention, given by way of indicative and nonlimiting example, and the appended drawings, in which - FIG. 1 (prior art) has a perspective view of a first known printed antenna with a "non-wedge" power supply; FIG. 2 (prior art) illustrates the distribution of the electric field around the pellet of the first known antenna of FIG. 1; FIG. 3 (prior art) shows a view from above of a second known printed antenna, with a "wedge" power supply; FIGS. 4A, 4B and 4C (prior art) each illustrate the distribution of the electric field around the pellet of the second known antenna of FIG. 3, respectively for a first fundamental mode (FIG. 4A), a second fundamental mode (FIG. .4B) and the superposition of the first second fundamental modes (fig.4C); - each of Figures 5 to 12 shows a top view of a separate embodiment of a printed antenna according to the present invention; and FIG. 13 shows a perspective view of a particular embodiment of an array of printed antennas according to the present invention. For the sake of simplification, identical elements in different figures retain the same numerical reference. In order to explain the notion of the cold point of a printed antenna, two examples of antennas printed according to the prior art are presented in relation to FIGS. 1 to 4.

The first known printed antenna fig.l and 2) comprises, conventionally - a substrate plate 1; a metal deposit, located on the upper face of the substrate plate 1 and defining a resonant pellet of rectangular shape (length a and width b); - A supply line (microstrip line) 3, feeding the resonant chip 2 by direct contact. width b of the pellet 2 is much greater than the width of the feed line 3; - A ground plane 4, located on the underside of the substrate plate 1. For this first known antenna, the excitation point 6 of the pellet is not wedge. Therefore, the pellet has only one fundamental mode. The dimensions of the pellet are of the order of half a wavelength. This causes a non-uniform distribution of the electric field under around the resonant chip 2. FIG. 2 illustrates an example of such a non-uniform distribution, for a TMO mode, 1. The two cold spots 5A, 5B of this mode appear clearly in the figure.

The second known printed antenna (see Fig. 4) differs from the first only in that the excitation point 7 of the chip 3 is here in wedge. Therefore, the pellet has two basic modes: mode 0.1 and mode 1.0. Indeed, each of the two sides of the pellet to which the excitation point belongs is associated with a distinct fundamental mode. The global non-uniform distribution (see figAC) is obtained by summation of the non-uniform distributions of the two fundamental modes (see fig.4A and 4B). For each fundamental mode, the pellet has two distinct cold points: 7A, 7B (see Fig. 4A) and 8A, 8B (see Fig. 4B). In addition, for the superposition of the two fundamental modes, the pellet also has two distinct cold spots: 9A, 9B (see Fig.4C).

Several particular embodiments of a printed antenna according to the present invention will now be presented in connection with FIGS. 5 to 12. It is recalled that the general principle of the invention is to add, in at least one cold point of the pellet 2, at least one reactor arm. These reactance arms allow to reduce the level of cross polarization and increase the bandwidth of the antenna.

In the first embodiment, illustrated in FIG. 5, the resonant chip is not supplied with a wedge (the antenna is therefore of the same type as the first known antenna, presented above in relation with FIGS. 1 and 2). . On the contrary, in the second to eighth embodiments, illustrated in FIGS. 6 to 12 respectively, the resonant chip is supplied with a wedge (the antenna is therefore of the same type as the second known antenna, presented above in relation to the Figures 3 and 4).

In the first embodiment (see Fig. 5), two reactance arms 101, 102 and extend from each cold point 5A, 5B for the single fundamental mode. Each reactor arm is a section of line formed in the metal deposit and which extends outwardly of the pellet. Each reactor arm has a length substantially equal to V4, with k the operating wavelength. For the sake of compactness, each arm has a bend 11.

The reactance arms have between them two types of symmetry - a first symmetry with respect to a first axis 12 passing through the two cold points 5A, 5B (and forming an axis of symmetry for the pellet). Thus, it is possible to distinguish two first pairs of reactance arms (101, 102), (103, 10a) for each of which there exists this first symmetry; a second symmetry with respect to a second axis 13 forming an axis of symmetry for the pellet and passing through the excitation point 6 of the pellet. Thus, it is possible to distinguish two second reactance arm pairs (10, 103), (102, 104) for each of which there is this second symmetry.

In the second embodiment (see FIG. 6), two reactance arms 142 and 143, 144 extend from each cold point 9A, 9B for the superposition of the two fundamental modes. The first and second axes of symmetry are here referenced 15 and 16 respectively. The other features are unchanged from the first embodiment described above. In the third embodiment (see Fig. 7), two reactance arms 171, 172 and 173, 174 extend from each cold point 7A, 7B for the first fundamental mode ( mode 0.1).

In the fourth embodiment (see Fig. 8), two reactance arms <B> 181, 182 </ B> and 183 extend from each cold point 8A, 8B for the second fundamental mode (mode 1.0).

The fifth embodiment (see Fig. 9) is a variant of the second embodiment, in which the reactance arms have a larger width. sixth embodiment (see Fig. 10) is a variant of the second embodiment in which the reactance arms do not have bend.

The seventh embodiment (see Fig. 11) is a variant of the second embodiment in which the reactance arms have no elbow and are split.

The eighth embodiment (see Fig. 12) is a second embodiment variant, wherein the reactance arms 191 to 194 are slot sections formed in the metal deposit and extending inwardly of the resonant chip. 2.

It is clear that many other embodiments of the printed antenna according to the present invention can be envisaged. In particular, it is possible to provide other forms of reactance arm; other forms of pellets (square, round, ...); - other types of food. In particular, it is possible to replace the direct drive line with a direct drive probe (for example a coaxial probe), a non-contact coupling line, a non-contact coupling line cooperating with a slot, etc. - etc.

In general, in order to obtain a predetermined operation of the printed antenna according to the invention, it is possible to play during the design of this antenna on various parameters, such as in particular: the length and / or the width and / or or the geometrical shape of each reactor arm, the number of cold points from which at least one reactor arm extends, the number of reactance arms extending from each cold point, and so on. A particular embodiment of the network of antennas printed according to the present invention will now be presented in connection with FIG. 13.

In a particular embodiment, the network comprises four printed antennas 20 to 204. Each is supplied with a wedge. Each comprises an elbow reactance arm 21, 214, of length L1 to L4, respectively, which extends from a cold point for one of its two fundamental modes (see the fourth embodiment, shown here). above in relation to Figure 8).

It is assumed that the feed point of the network corresponds to the center 0 of the reference (O, Ox Oy). It is assumed that, in a conventional manner (and independently of the reactance arms), the pellets of the network have a double symmetry with respect to the axes and Oy. In general, the main direction of radiation 22 of the network passes through O and is defined by the angle pair (6, cp), with 6 the angle between the axis and the main radiation direction 22, and cp the angle between the axis Ox and projection 23 in plane (0x , Oy) of the main radiation direction 22.

Several cases can be distinguished according to the possible symmetries between them the reactance arms of the printed antennas of the network. In particular, the following four cases can be distinguished: if L1 = L2 = L3 = L4 (double symmetry with respect to the Ox and Oy axes), there is no misalignment, the radiation of the grating is effected along the main direction coinciding with the Oz axis (that is 6 = 0 mod Z); if L1 = L3, L2 = LA. and Ll # L2 (symmetry with respect to the Oy axis): it has a simple misalignment, with respect to the axis Ox but not with respect to the axis Oy (ie cp = 90 mod n and 0; E 0 mod # - if L1 = L2, L3 = L4 and L1; d L3 (symmetry with respect to the Ox axis): it a simple misalignment, with respect to the axis Oy but not with respect to the axis Ox (ie cp = 0 mod n and 0; t 0 mod n); - if L1; É L2; i L3 (no symmetry): there is a double misalignment, relative to the axis Oy and relative to the axis Ox (that is to say cp; é 0 mod on, cp 90 mod ju and 0; É 0 mod # It is clear that many other embodiments of the antenna array The present invention may be provided with: - a higher number of antennas printed within the network, - a higher number of reactance arms per printed antenna (one or more arms from one or more points). cold of each antenna); not tending in the plane containing the resonant pellet but in a plane inclined with respect thereto; other types of antennas printed with a reactor arm according to the invention (such as in particular, but not exclusively, the eight embodiments described above, in relation to FIGS. 5 to 12); etc.

Claims (1)

 A printed antenna, of the type comprising - a substrate plate (1), - a metal deposit, located on one side of said substrate plate and defining a resonant chip (2), - a power supply means (3), allowing feeding said resonant pellet, characterized in that it further comprises; at least one reactor arm (101 to 104, 14, 144, 171 to 174, 181 to 184 191 to 194, 211 to 214) extending from a cold point (5A, 5B, 7A, 8A); , 8B, 9A, 9B) of said resonant pellet. Antenna printed according to claim 1, characterized in that said means (3) for feeding does not substantially "wedge" said resonant chip said resonant chip thus having a single fundamental mode, and in that said cold point (5A, 5B) from which said at least one of the reactance extends is a cold spot for said single fundamental mode. A printed antenna according to claim 1, characterized in that said supply means (3) supplies said "resonant" wafer substantially "corner" with said resonant wafer thereby presenting at least two fundamental modes, and in that said cold point (9A, 9B) from which said at least one reactor arm extends is a cold spot for the superposition of said at least two fundamental modes. 4. Antenna printed according to claim 1, characterized in that said means (3) feeds substantially "wedge" said resonant chip (2), said resonant chip thus having at least two fundamental modes, and in that said cold point (7A, 7B, 8A, 8B) from which said at least one reactance arm extends is a cold spot for one of said fundamental modes. Antenna printed according to any one of claims 1 to 4, characterized in that said at least one reactor arm is formed in said metal deposit. Antenna printed according to claim 5, characterized in that said at least one reactance arm is a line section (101 to 104; 141 to 144; 171 to 174; <B> 18, </ B> to 1; 21, 214) formed in said metal deposit and extending outwardly of said resonant chip. Antenna printed according to claim 5, characterized in that said at least one reactor arm is a slot section (19I to 194) formed in said metal deposit and extending inwardly of said resonant chip. A printed antenna according to any one of claims 1 to 7, characterized in that said feeding means belongs to the group comprising - direct drive lines (3); - direct attack probes; - contactless coupling lines; - Non-contact coupling lines cooperating with slots. 9. Antenna printed according to any one of claims 1 to 8, characterized in that, so as to obtain a predetermined operation said printed antenna is played during the design of said antenna on at least one parameter belonging to the group comprising: the length of each reactor arm; the width of each reactor arm; the geometrical shape of each reactor arm; the position of each reactor arm; the number of cold spots from which a reactance arm extends less; the number of reactance arms extending from each cold point. Antenna printed according to any one of claims 1 to 9, characterized in that said at least one reactance arm has a length substantially equal to k./4 with #. the operating wavelength. 11. Antenna printed according to any one of claims 1 '10, characterized in that said at least one reactor arm has at least one elbow (11). Antenna printed according to any one of claims 1 to 11, characterized in that said resonant chip has at least two cold spots, in that said antenna comprises at least a first pair of reactance arms, and that the arms The reactance of said at least one first pair of reactance arms is substantially symmetrical about a first axis, passing through said at least two cold spots. Antenna printed according to any one of claims 1 to 12, characterized in that said resonant chip has at least two cold spots, in that said antenna comprises at least a second pair of reactance arms, and that the reactance arms said at least one second pair of reactance arms have substantially symmetry with respect to a second axis, forming symmetry for said resonant chip and passing through a point of excitation of said resonant chip by said supply means. 14. Antenna array, characterized in that it comprises at least two antennas printed according to any one of claims 1 to 13. Antenna network according to claim 14, characterized in that each of said antennas comprises the same set at least one reactance arm, so as to maximize a radiation of said antenna array in a given principal direction. 16. Antenna array according to claim 15, characterized in that it comprises less a first pair of antennas and at least a second pair of antennas, in that the reactance arms of the antennas of said at least one first pair of antennas have substantially symmetry with respect to the third axis, forming an axis of symmetry for said antenna array and passing through a feed point of said antenna array, and in that the reactance arms of the antennas of said at least one second pair of antennas have between them substantially symmetry with respect to fourth axis, forming an axis of symmetry for said antenna array, perpendicular to said third axis and passing through said feed point of said antenna array. 17. Antenna array according to claim 14, characterized in that at least two of said antennas each comprise a distinct set of at least one reactance arm, so as to induce a radiation misalignment of said antenna array relative to to a predetermined main direction. 18. Antenna array according to claim 17, characterized in that it comprises at least a first pair of antennas, and in that the reactance arms of the antennas of said at least one first pair of antennas do not present to each other. a symmetry with respect to a third axis, forming an axis of symmetry for said antenna array and passing through a feed point of said antenna array, so that said misalignment is performed around said third axis. 19. Antenna array according to claim 18, characterized in that it comprises at least a second pair of antennas, and in that the reactance arms of the antennas of said at least one second pair of antennas have not between them a symmetry with respect to a fourth axis, forming an axis of symmetry for said antenna array, perpendicular to said third axis and passing through said feed point of said antenna array, so that said misalignment is also effected around said fourth antenna; axis.