FR2751471A1 - WIDE-BAND RADIATION DEVICE WHICH MAY BE MULTIPLE POLARIZATION - Google Patents

Abstract

The radiating device comprises, on a substrate (10), two pairs of thin conducting sectors (11A, 11B, 12A, 12B) arranged head to tail on either side of an axis of symmetry (AS), with planes of symmetry (PS1, PS2) passing through this axis. The conductive sectors (11A, 11B, 12A, 12B) have substantially the same surface as the insulating sectors (11P, 11Q, 12P, 12Q) defined between these conductive sectors.

Description

Broadband radiating device capable of multiple polarizations

  The invention relates to antennas or radiating devices.

  Although there are many types of antennas, it is always difficult to make an antenna that is wide

  strip, compact, and capable of processing more

  several polarizations, with good radio performance

  triques. These performances are measured in particular by the gain of the antenna, its radiation pattern, and the level

  residual transmission from one polarization to another.

  There are other components to this problem, such as the definition

  the exact phase center of such an antenna, as well as the correct electrical coupling of the antenna to the circuit

who cooperates with it.

  Works have already proposed a so-called radiating device

  "Bow-Tie antenna" or "dipole triangu-

  laire "which includes a pair of thin conductive sectors, arranged head to tail on either side of an axis of symmetry, with a plane of symmetry passing through this axis: -" Triangular dipole antennas ", Antenna Engineering Handbook, RC JOHNSON & H. JASIK, Mac Graw Hill Book Company, page -12, - "Experimentally Determined Radiation Characteristics of Conical and Triangular Antennas", GHBROWN & OM WOODWARD

  Jr, R.C.A. Review, Vol 3 N 4, December 1952.

  In its most general definition, the antenna according to the present invention comprises, on a substrate, said pair

  of conductive sectors and at least one other pair of sec-

  thin conductors, similar to the first, each arranged with a plane of symmetry passing through said axis, of

  so that the planes of symmetry are substantially regular

distributed around said axis.

  This in principle makes it possible to produce a selective antenna in several different directions (more precisely, master planes) relative to the axis of symmetry. However, in practice, most applications use only two directions perpendicular to each other: they correspond to two independent polarization vectors; as we will see later it is possible to treat,

  either the horizontal polarization and the vertical polarization

  wedge, that is the right circular polarization and the polarization-

circular left, in particular.

  Under these conditions, the proposed device comprises two pairs of conductive sectors whose planes of symmetry

are perpendicular.

  Although it is possible to do otherwise, it is very advantageous that the conductive sectors have substantially the same surface as the insulating sectors defined between these conductive sectors. A high performance radiating device is then obtained, without requiring recourse

  to amplifying active elements.

  In a particular embodiment, each of the conductive sectors of the two pairs already mentioned has a

  apex angle of about 45 degrees.

  Most often, means are provided which prevent the

  transmission of radiation from one side of the substrate.

  And, on the same side, a connection is provided, preferably by coaxial cables, to an adaptation assembly comprising two asymmetrizing baluns. At direct output, these provide vertical polarization and horizontal polarization, respectively. An interconnection assembly,

  with phase shift 0/90 degrees, allows polarization to be obtained

right and left circular tions.

  Other characteristics and advantages of the invention appear

  Upon examination of the detailed description below, as well as the accompanying drawings, in which:

  - Figure 1 is the general block diagram of a known radiating device of the "butterfly" type; - Figures 2, as well as 2A to 2I, illustrate different basic embodiments of an antenna according to the invention; - Figures 3 and 3A show two exemplary embodiments of pairs of conductive sectors; - Figures 4 and 4A show the use of a radiating element in combination with an electrical coupling device; - Figures 5A to 5D show an advantageous embodiment of such an electrical coupling;

  - Figures 6A to 6D show another advantageous embodiment -

  geuse of such an electrical coupling; and - Figure 7 illustrates an alternative embodiment of the

electrical outlet.

  The designs are essentially certain,

  and define geometric characteristics. Consequently, they are to be considered as an integral part of the description, and may not only allow a better understanding of it, but also contribute to the definition

of the invention, if applicable.

  Figure 1 illustrates the block diagram of a known antenna of the so-called "butterfly" type. This consists of two generally triangular sectors 11A and 11B, placed head to tail, opposite by their points. The two sectors are symmetrical with respect to a plane PS1, perpendicular to their own plane (in the hypothesis where these sectors are of planar shape). In this case, the sectors presented here are also symmetrical with respect to another plane PS2 perpendicular to the first, with respect to the axis of symmetry

AS of the two sectors 11A and 11B.

  This antenna was the subject of theoretical proposals according to which sectors 11A and 11B were in the air.

  In practice, the Applicant prefers to have these two sec-

  teurs on a substrate 10, which is for example a glass-teflon material such as "DUROID", sold by the company ROGERS

the United States.

  As shown in Figure 2, we have on the upper side

  flat plane of a substrate 10 not only the two opposite sectors 11A and 11B, but also two other sectors 12A

  and 12B, having a plane of symmetry PS2 perpendicular to the plane of symmetry PS1 (FIG. 1) of the sectors 11A and 11B.

  FIGS. 2A to 2D show that the upper face of the substrate 10 is not necessarily planar, but can correspond to any form of revolution (FIGS. 2A and 2B), or else to a prismatic shape having the same symmetries as the conductive sectors used (figures

2C and 2D).

  The peripheral edge of the sectors can be curvilinear,

  in principle convex. Likewise, FIGS. 2E to 2G show that the radial edges of the sectors can be curved-35 lines, with variable or evolving profile, in principle concave, to adjust the operating frequency band.

  In addition, one or more patterns can be engraved inside the "butterfly" sector, for example by holes (Figure 2H), or by triangular cutouts (Figure 2I). This

  also influences the frequency behavior of the an-

  clap. Figure 3 shows an example of application of the invention

  which is currently considered preferential. We pre-

  sees only two pairs of conductive sectors 11A, 12A, 11B, 12B, separated by insulating sectors

11P, 12P, 11Q, 12Q.

  And, according to another important characteristic of the invention-

  tion, it is ensured that the total area of the insulating and conductive sectors is substantially the same. A priori unexpectedly, it appeared that:

  - while the butterfly type dipole antennas have intrinsic-

  sequentially a relatively narrow bandwidth, it appeared that the use of two dipoles as defined above gives them a considerably higher frequency bandwidth. Typically, the bandwidth that could be expected from a butterfly dipole has

  found practically increased by a factor of 3 to 4.

  - moreover, insofar as two radius elements are used-

  nants crossed, that is to say at right angles to each other, there appeared a very weak parasitic coupling between the signals at the terminals of the two pairs of radiating elements. - finally, the pairs of radiating elements have a unique and well-defined phase center, which gives them

  important advantages for certain applications.

  On another level, it appears that the frequency band

  of operation that can thus be obtained would have required

  a dipole with an outside diameter twice as large,

  with the structure of the prior art.

  In other words, we obtain, with a structure whose transverse dimensions are two times smaller,

  a bandwidth three to four times greater.

  In view of the above, those skilled in the art will immediately understand

  The new radiating device is extremely interesting. The cross structure of Figure 3 has specific advantages. But it is also possible to use a structure with more than two pairs of dipoles, as for

  example the structure with three pairs of figure 3A.

  The devices which have just been described can be

  installed in modules, fitted with their coupling circuits

  electric range. The mechanical diagram of such a module is given, in simplified form, in FIG. 4, while a

  electrical diagram is given in FIG. 4A.

  The two pairs of dipoles such as 11A and 11B, which can be placed under a radome 20, are placed at the top of a

  module 21, delimited by a metal body. The rear part

  re of the substrate 10 is opposite an electromagnetic absorbent

  tick 22, placed in the upper housing of the housing 21.

  Instead of an electromagnetic absorbent, one can use an electromagnetic reflector, or a combination

  of the two, on different parts of the band of fre

  quence. Four coaxial cables are provided (one for each sector

  driver). The shields of the coaxial cables are interconnected

  connected to each other and to the metal case 21. The cores of the coaxial cables are respectively connected to the hot spots of one of the conductive sectors. This defines coaxial cables 31A, 31B, 32A, 32B, for the conductive sectors 11A, 11B, 12A, 12B respectively. Advantageously, in an intermediate housing of the housing 21, the coaxial cables form a loop, after which they

  join two de-symmetrizing baluns 41 and 42.

  The balun 41 receives the coaxial cables 31A and 31B, while

  that the balun 42 receives the coaxial cables 32A and 32B.

  Using the loops visible in FIG. 4, the electrical lengths of the coaxial cables from the hot point of the dipole concerned to the balun are made the same, so as to align the propagation times of the signals. In addition, it must be taken into account that the cables associated with the two opposite sectors 11A and 11B will have to meet on the same balun 41. As shown diagrammatically by the axis line 30, this results in a rotation of the cables, with crossing, to allow the junction which has just been described. Intermediate loops make it possible to catch up

  possible length differences due to this crossing.

  The baluns 41 and 42 each have two coaxial inputs, for an output, which is for example coaxial. A variant (figure 7) consists of an output on a microstrip line

  ("microstrip") which attacks a printed circuit: on a subs-

  trat 80, the microstrip line 81A is opposite to a ground plane

  81B, all under metal shielding 85.

  In one embodiment, these are the so-called "Miner-

  va ", or" Marchand ", described for example in: -" Transmission Line Conversion Transformer ", N. MARCHAND, Electronics, vol 17, pp 142-145, December 1944,

  - "100: 1 Bandwidth Balun Transformer", J.W.DUCAN & V.P.

MINERVA,

  Proceedings of the I.R.E., pp 156-164, February 1960, - "Design and performance of microstrip balun for Archimedes Spiral antennas", D.E. BAKER, J.R. NORTIER, C.A. VAN DER

  NEUT, Transaction of the SA Institute of electrical Engi-

neers, December 1987.

  In the case of four dipoles, we can first use the outputs of baluns 41 and 42, possibly through

  connecting stages 71 and 72, to provide on connectors

  teurs 91 and 92 of channels A and B respectively which correspond

  tooth with two crossed linear polarizations, like the

  horizontal and vertical polarizations.

  As a variant, as illustrated in FIG. 4A, the two channels are applied to subdividers (3 dB couplers in reverse) 71 and 72. One of the outputs of these is applied to a 0/90 degree phase shifter, 73 and 74, respectively. The output of each phase shifter goes to a 3dB coupler, 75 and 76 located on the other channel, and also receiving the other

  output of coupler 71 or 72 from the same channel.

  Those skilled in the art know that the coupling thus achieved allows

  to obtain circulating polarization signals at the output

  re right and left, respectively.

  Due to the small surface dimensions of the two pairs of base dipoles, the module according to the invention can be produced with a small lateral space requirement, the depth

  being slightly larger, as shown in Figure 4.

This arrangement is already satisfactory.

  However, for certain applications, it is desirable to have a large number of modules of this kind, in a volume as small as possible, and with a manufacturing

as simple as possible.

  We will now describe two alternative embodiments

  particularly interesting in this respect. FIGS. 5A to 5D relate to an alternative embodiment where one is only interested in one of the channels, for example the horizontal polarization defined by the sectors 11A

and 11B.

  The two coaxial cables 31A and 31B have cores which terminate

  feels respectively to two metallized faces of another

  41S substrate. This substrate 41S can also be made of DUROID.

  On one side, the substrate 41S carries a relative metallization-

  ment narrow 41A, which keeps the same transverse dimension over its entire length (or flares very slightly), to lead to the core of a coaxial connector 91 disposed at the other end.

  The underside of the substrate 41S is provided with a metallization

  41B which, on the web side of the 31B coaxial cable, pos-

  sedes practically the same width as metallization 41A.

  On the other hand, this metallization 41B widens rapidly, so that, on arrival, it is connected to the ground of the connector

  coaxial 91, with a much larger width.

  Those skilled in the art know that this achieves de-symmetrization

  in accordance with the principle of a balun.

  The advantage of the above embodiment is that it allows, with very few parts, to pass directly coaxial cables connecting the dipoles to the substrate 41S to a coaxial connector, immediately providing the output. All

  can be housed in a metal cavity 5, provided for example

  full of mode absorbers 51A, 51B, 51C and 51D.

  This is well suited for the case of transverse rectilinear polarizations. Reference is now made to FIGS. 6A to 6D, which illustrate an even more interesting variant, in particular

  bind for circular polarization.

  In these figures 6, there are two substrates 41S and 42S, for example made of DUROID. These are superimposed at the level of a zone 49 which is for example of generally rectangular shape. Outside of this area, they have practically the structure

  already described in connection with Figure 5.

  In short, assuming that the substrate 41S is at a lower level than the substrate 42S: - the substrate 41S carries below the metallization 41B which widens considerably, and above the metallization 41A

which widens little or not.

  - The substrate 42S carries above the metallization 42B which widens a lot, and below the metallization 42A which

widens little.

  Between the two substrates is provided a very thin insert, of material similar to the substrate, such as

DUROID.

  At the superposition part 49, the metallizations

  enlarged tions 41B and 42B spread out completely to define planmasses located above and below the sandwich thus formed by the two substrates 41S and 42S, thus

  than by the very thin intermediate layer (not shown).

  For their part, the metallizations 41A and 42A can be directly connected to the connectors 91 and 92, in the event that one wishes to operate this assembly in rectilinear polarization.

  But this assembly takes all its interest during polarization -

  circular tion: - it suffices to subject the metallizations 41A

  and 42A, to the right of overlay 49, the work

  jets that cross with very similar portions.

  This provides a coupling between the two channels, with the function

  0/90 degree phase shift. Polarization outputs are then obtained directly on connectors 91 and 92

right and left circular.

  Of course, instead of connectors 91 and 92, the variant

  of figure 7 is directly applicable.

  Other aspects of this achievement may appear

  in the patent application entitled "Balun hyperfré-

  integrated quence, in particular for dipole antenna ", deposited

  this day in the name of the Applicant, under the N 90 ......

  The present invention is not limited to the embodiments.

tion described.

  First of all, as already indicated, the shape of the substrate 10 is not necessarily planar. Approximately shapes

  flat, or of revolution, or prismatic can be used

  sées. The radome 20 (fig. 4) can be shaped to constitute

  kill a magnifying glass, or present any other desired effect of electromagnetic optics. The proposed antenna has dimensions in lambda / 4, instead of lambda / 2 for the prior art, lambda being the longest wavelength, that is to say on the bottom side of the wide operating band. In addition, at the bottom of the band, it has a progressive rise in gain with frequency. It may therefore be advantageous to use high impedance amplifiers to raise the gain in

band bottom.

  More generally, the condition of equality of surfaces con-

  conductive and non-conductive is not necessarily to

  respect, if we add to the radiating elements amplifiers

  that make it an active antenna.

  When we are interested in polarization, we should treat

  ter the potential difference between two sectors or dipoles

  opposites. With the embodiments with more than two dipoles,

  we can be interested in sums or differences,

  and more generally to any linear combination of poten-

in the conductive sectors.

  The processing of the collected signals can be carried out in parallel on different channels, or by multiplexing

of the same treatment route.

  Finally, the radiating elements according to the invention, with their coupler, suitably shielded, not only have a low

  lateral bulk, but also low lateral radiation

  ral, given their size and the frequencies processed.

  They are therefore particularly suitable for construction

network antennas.

  The invention can be applied to many fields: tele-

  communications, particularly in microwave, and other microwave applications, including broadband measurements

  band, for example on the radiation of other aerials.

Claims (12)

Claims   1.- Radiating device, of the type comprising a pair of thin conducting sectors (llA, 11B) arranged head to tail on either side of an axis of symmetry (AS), with a plane of symmetry (PSl) passing through this axis, characterized in that   that it comprises, on a substrate (10), said pair of sec-   thin conductors (11A, 11B) and at least one other pair of thin conductor sectors (12A, 12B) similar to the first, each arranged with a plane of symmetry (PS2)   passing through said axis (AS), so that the planes of symmetry   sorts are substantially evenly distributed around said axis. 2. Device according to claim 1, characterized in   what the conductive sectors (11A, 11B, 12A, 12B) have sensi-   the same surface as the insulating areas   (11P, 11Q, 12P, 12Q) defined between these conductive sectors.   3.- Device according to one of claims 1 and 2, charac-   characterized in that the conductive sectors are arranged on the same face of the substrate (10), the other face of which is   provided with means (22) preventing the transmission of the   is lying. 4.- Device according to claim 3, characterized in   what the means (22) preventing the transmission of the ray-   ment include absorbent means.   5.- Device according to one of claims 3 and 4, charac-   terized in that the means (22) preventing transmission   of radiation include reflecting means.   6.- Device according to one of claims 1 to 5, character-   laughed in that the sectors (11A, 11B, 12A, 12B) are shaped general triangular isosceles.   7.- Device according to one of claims 1 to 6, character-   laughed in that the sectors (llA, 11B, 12A, 12B) have edges curvilinear radials.   8.- Device according to one of claims 1 to 7, character-   laughed in that recesses of the chosen shape are engraved   inside the sectors (11A, 11B, 12A, 12B).   9.- Device according to one of claims 1 to 8, character-   laughed in that another dielectric coating is provided above the conductive areas.   10.- Device according to one of claims 1 to 9, charac-   terized in that it comprises two pairs of conduc-   tors (11A, 11B, 12A, 12B) whose apex angle is approximately degrees, the respective planes of symmetry of the two pairs being perpendicular.   11.- Device according to one of claims 1 to 10, charac-   terized in that it comprises four coaxial cables (31A, 31B, 32A, 32B) respectively connected on the one hand to the two pairs of conductive sectors, on the other hand to a mounting   adapter comprising two de-symmetrizing baluns (41,42).   12.- Device according to claim 11, characterized in   that the outputs of the de-balun baluns are intercon-   nectées (71,72) with phase shift 0/90 degrees, to provide   outputs (91,92) in right and left circular polarization che.