FR2460051A1 - ROW DIPOLA CROSS WITH REFLECTOR FOR RADIATION OF A CIRCULAR POLARIZATION WAVE COMPOSED OF TWO WAVE LINEAR POLARIZATION - Google Patents

Abstract

ROW OF CROSS-DIPOLES WITH REFLECTOR FOR THE RADIATION OF A CIRCULAR POLARIZED WAVE COMPOSED OF TWO LINEAR POLARIZATION WAVES. THE REFLECTOR 11 FOR THE TRANSVERSAL POLARIZATION IS MADE IN THE FORM OF A FLAT REFLECTOR AND, BY PLACING CONDUCTIVE ELEMENTS 21, 22, IT IS AT THE SAME TIME MADE IN THE FORM OF AN ANGULAR REFLECTOR FOR THE LONGITUDINAL POLARIZATION.

Description

Row of cross dip8les with reflector for the radiation of a wave

  circular polarization composed of two waves

linearly polarized.

  The present invention relates to a row of cross dipeles comprising a reflector for the radiation of a circularly polarized wave composed of two waves with

linear polarization.

  In the upper atmosphere, there are different ionized layers that contain free electrons and ions in large numbers. The ionization is generally carried out by photoelectric effect, that is to say under the effect of

  ultraviolet shortwave solar radiation which is complete

  absorbed in the upper atmosphere. As the density of

  the air is very weak at these heights, the charges recombine

  are very slow, so that a high balanced ionization value is established. In the highest layer,

  it disappears slowly enough to keep

you stay until morning.

  During the day, a division into three layers is possible, these three layers being designated by D, E and F. For the propagation of electromagnetic waves, the outer layer F, designated layer F-2, is decisive. Its ionization state does not follow any simple rules. The curve of the day

  is very different depending on the season and the degree of

of and latitude.

  For transmissions by satellites and spacecraft, it is necessary to know exactly the nature of the outer ionosphere and the magnetosphere. For their

  study, the technique of incoherent dispersion is used.

  In this process, short-wave radiation is sent to the atmosphere from a high-power transmitter and a highly focussing antenna. Part of the radiated energy is backscattered to the point of emission by

  the upper edge of the cloud type of layer E after reflection

  on the high layer F-2. According to the importance of

  backscattering we can draw conclusions about the behavior

  layer F-2. In this case the rotation of the direction of polarization is particularly important. The study of the outer ionosphere therefore requires antennas

  strongly focussing that can emit and receive indif-

  all polarizations, that is to say linear (horizontal, vertical), circular left, circular right. But not only the study of the ionosphere by means of radars, but also other cases, for example the suppression of rain echoes, require radars with purely circular polarization. Furthermore, for radio links 10, particularly with satellites and spacecraft, it is necessary to

  preferably a circular polarization.

  For the emission of electromagnetic waves with polar

  linear or circular, for example, it is known to use

  to draw dipoles in crosses. If you want to obtain a highly focused radiation pattern, you must install several cross-shaped dipoles arranged in line in front of a reflector. In

  however, the diagrams of the two di-

  are not identical for the longitudinal polarization (that is to say in the direction of the collinear dipelins) and the

  transversal polarization (that is, in the plane perpendicular

  eyepiece with collinear diplexes). Moreover, the diagram for the longitudinal polarization in the plane perpendicular to the collinear dipoles has a greater width of radiation. Such an antenna is however not suitable, for example for the study of the outer ionosphere. In particular, it is not possible, as a primary transmitter for a reflector antenna, to use a row of dipoles in a cross to obtain an even more pronounced directional characteristic. To achieve a high surface efficiency for circular polarization, it is also necessary that the radiation patterns in the plane perpendicular to the focal line have the same shape for both directions

of polarization.

  The present invention therefore has as its object

  to make a row of cross-shaped dia-

  flector for the emission of a circularly polarized wave consisting of two linearly polarized waves, which, thanks to simple technical means, presents radiation patterns of the same shape in the plane perpendicular to the collinear dipoles, for the two polarizations linear and

  which, in connection with a reflector, gives a very high

  overperforming with reflectors of

  as well as a good circular polarization of the entire antenna. Moreover, it is necessary to adapt the difference

  impedance between dipoles radiating long polarization

  tudinal and transverse polarization.

  With a row of cross dipoles of the aforementioned type this result is achieved according to the invention in that the reflector for the transverse polarization is realized under

  the shape of a flat reflector and that, by setting up

  conductive elements it is at the same time realized in the form

  an angular reflector for the longitudinal polarization.

  The advantages obtained with the invention reside in particular in the fact that by adapting the shape of the two

  radiation patterns produced by the longitudinal diplexes

  nal and transverse, we emit in the plane perpendicular to

  collinear dipoles a circular polarization with high efficiency

  is lying. If the row of cross dipoles according to the invention is

  used as the primary transmitter of a cylindroparabolic antenna

  with an off-center power supply, we obtain a super-

  greatly increased. The use of the row of cross dipoles according to the invention as a primary emitter allows thus to deconstruct antennas with reflectors moreover.

  weak dimensIas. In particular with antennas of very high

  in the case of a reflector diatre the present invention realizes

  an important saving of material and price. By eliminating

  of the difference in impedance between the dipoles radiating the longitudinal polarization and the transverse polarization on

  further increases the overall efficiency of these antennas.

  The invention will be better understood with the aid of

  description of two embodiments taken as examples, but not limited to, and illustrated by the appended drawing, in which: Figure la shows a side view or sectional view of the row of cross dipoles according to the invention; Figure 1b is a plan view of Figure 1a; e $$ e uemoauawTeTnolpuadaed sesodsTp quos u '..... I' .... C 't xToaz ua salgdTp sep' eiTsaoAsuPaq uoTeslaelod e. epuo, I qugeqawa IsaeIdTp sel go to EnbloqueedopulIu anaeaoel $ a 'np aIeToO auSiT el suep sesodslp quos u' ...

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  focal line. The emission of the radiation of the electromagnetic wave

  Circular polarization gnetic is performed in the direction of the

  cylindroparabolic reflector 12. The dimensions of the reflec-

  cylindroparabolic nozzle 12 have been selected in this embodiment so that the quotient of the length of the

  reflector in the focal line by its perpendicular diameter

  to this one is about 0.45. In this way, in addition

  of high mechanical stability, a satisfactory yield is obtained

  optimum perfection of the antenna by about 90% in the event of

  supposedly uniform representation of the row of dipoles in crosses.

  The operating mode of the row of dip8les

  according to the invention for transmitting a polar wave.

  Circular production consists in using a type of reflector

  polarization-dependent, which for the trans-

  versale, acts as a planar reflector and simultaneously

  as an angular reflector for longitudinal polarization

  Dinale. This is achieved by setting up the elements

  bar-shaped conductors 21, 22 above a reflec-

  planar conductor 11. The conductive elements in the form of bars 31,

  32 are used to adapt the impedance of the dipeles longi-

  tudinal and transversal. Their action for the longitudinal polarization corresponds to a shift of the reflector 11

  without however modifying the impedance and the radius diagram.

  of transverse polarization. The influence of these conductive elements 31 32 on the radiation pattern

  longitudinal polarization is relatively low.

  The row of cross dipoles according to the invention is particularly suitable as the primary transmitter of the antennas

  with reflectors having a focal line or a focal plane.

Claims (9)

  1. Row of dipoles in a cross with a reflector for the radiation of a circularly polarized wave   composed of two waves with linear polarization, characteris-   in that the reflector (11) for the transverse polarization is in the form of a planar reflector and that, by placing conducting elements (21, 22), it is at the same time realized in the form of a reflector   angular for the longitudinal polarization.   2. Row of cross dipoles according to the claim   1, characterized in that the conductive elements   tors (21, 22) are bar-shaped, arranged symmetrically and parallel to the collinear dipoles of the cross dipoles (1, 2, ....., 1 ....., n) and that they are placed at a determined distance from the reflector and parallel to it.   3. Row of cross dipoles according to the claim   2, characterized in that the conductive elements (21, 22) are arranged above the reflector (11) at a distance h which is smaller than the half-wavelength   operating (i) cross dipoles (1, 2, ..... not).   4. Row of cross dipoles according to the claim   3, characterized by the fact that at a distance of   crosses 1, 2, .........., n) 1/4 of times the length   the reflector operating wave on both sides of the collinear dipoles are respectively installed bar-shaped conductor elements at a distance (a) of 0.45 times the operating wavelength and that the   two conductive elements have relative to the reflec-   also a distance (h) of 0.45 times the length of operating (1)   5. Row of cross-hatches according to any one   than claims 1 to 4, characterized in that   both sides and parallel to the collinear dip8les are   in addition arranged in the same way other conductive elements   bar-shaped conductors (31, 32) which have a low   distance from the reflector (11).   6. Row of cross dipoles according to the claim   5, characterized in that the further bar-shaped conductor elements (31, 32) are preferably arranged at a distance from the reflector of about 0.1 times the   operating wavelength (a).   7. Row of cross dipoles according to any one of   Claims 2 to 6, characterized in that the   bar-shaped conductive elements (21, 22; 31, 32)   feel a diameter of the order of magnitude of 0.025 times the   operating wavelength ()).   8. Row of cross dipoles according to any one of   Claims 1 to 7, characterized in that the   conductive elements (21, 22; 31, 32) have the same longitudinal only the reflector (11).   9. Row of cross dipoles according to any one of   Claims 1 to 8, characterized in that the   diphas, radiating the longitudinally polarized wave of   diodes (1, 2, ...., i, ...., n) are arranged in parallel   in the focal line of a cylindroparabolic reflector   (12) and that the dipoles, radiating the polarized wave trans-   transversal dipoles (1, 2, ...., i, ....., n) are available.   perpendicular to this focal line, the radiation being effected in the direction of the cylindroparabolic reflector (12).