FR2590081A1 - LINEAR POLARIZED GRID REFLECTING ANTENNA WITH IMPROVED TRANSVERSE POLARIZATION PERFORMANCE - Google Patents

Abstract

THE INVENTION CONCERNS AN ANTENNA WITH GRID REFLECTORS IN LINEAR POLARIZATION. A FIRST CONDUCTOR GRID 13A ARRANGED TO REFLECT SIGNALS OF A LINEAR POLARIZATION IS MOUNTED ABOVE A SECOND LINEAR POLARIZATION REFLECTOR 15 WHICH INCLUDES A SECOND CONDUCTOR GRID 15A REFLECTING ORTHOGONAL POLARIZATION SIGNALS. FIRST POLARIZATION 21 FEEDING HORNS AND SECOND POLARIZATION 23 FEEDING HORNS ARE AVAILABLE AT OFFSET FIREPLACES F1, F2 OF THE REFLECTORS. THE INVENTION APPLIES IN PARTICULAR TO AN ANTENNA FOR REUSE OF SPECTRUM FOR A TELECOMMUNICATION SATELLITE.

Description

The present invention relates to an antenna with

  linear polarization flier and more particularly

  an antenna with double reflectors

  perpendicular risings, attacked by feeding horns. This antenna with two grid reflectors

  comprises a first reflector constituted by a first

  re grid of linear conductors in an orientation

  to adapt to the polarization of a first horn of

  Power supply. The first reflector covers a second

  flector constituted by a second conductor grid ':

  which are oriented perpendicular to the first

  first orientation and to adapt to polarization

  thogonal of a second feed horn.

  An antenna of this kind in which each of the first and second feed horns consists of a network of horns is widely used in

  telecommunication satellites to produce

  shaped shafts with frequency reuse by orthogonal linear polarization. It is desirable

  in an application of this kind that the antenna is

  pact and light. Each of the reflectors is a section

  of a paraboloid of revolution with a grid of

  or closely spaced parallel elements which are oriented parallel to one of two orthogonal linear polarizations. The reflectors are arranged (the

  their axes are offset and parallel

  to be them. The grid of drivers in each of the

  parabolic disks or disks is arranged in such a way that

  drivers appear parallel to a distance

  this in the direction of propagation, in the direction of the parallel axes. The cornets are located at homes

  corresponding reflectors. An example of a provision

  this type is described in the United States patent.

of America No. 3,898,667.

  In an earlier antenna as described

  in the aforementioned patent, the reflectors with the axes de-

  stalled and staggered foci cause transver- sal (unwanted) polarization signals from elements parallel to the surface of a reflector to be scattered from the feed horn / co-polarized signal (desired) associated with the other reflector beam. It is desirable to have an inexpensive and lightweight means to further enhance the rejection of

  transversal polarization in an antenna of this kind.

  According to one embodiment, the invention relates to

  a spectrum reuse antenna comprising: a first reflector comprising a first grid of linear conductors of an orientation, covering a second reflector which comprises a second grid of a

  second perpendicular orientation and cornets of a-

  feeding or feed horn networks with

  polarizations corresponding to the staggered focal points

  or near these reflectors, the provision for improving polarization performance

  cross-section consisting of a grid of conductors

  neighboring nees from the opening of each of the cornets,

  the opening gate drivers being oriented

  pendicular to the conductors of the associated reflector

  with the particular feed horn.

  Other features and advantages of the

  will be better understood when reading the description of

  The following is a description of several exemplary embodiments and with reference to the appended drawings in which: FIG. 1 is a front view of a two-gate antenna intended for a satellite, according to one embodiment of the invention;

  FIG. 2 represents the reflection structure

  Figure 1, along lines 2-2 of the figure

  Fig. 3a is a view of the horizontally polarized cone network seen from the reflectors, Fig. 3b shows the vertical polarization cone array seen from the reflector, Fig. 4 illustrates the isolation contours without the grids on the horns, Figure 5 illustrates the insulation contours

  with the grids on the horns according to the present invention.

tion,

  FIG. 6 illustrates the diagram measured in

  polarization-beams of Figure 4 without the grills

  in front of the horn, and Figure 7 illustrates the diagrams measured in co-polarization of the beams of Figure 3 with the

grills in front of the cone.

  Figures 1 and 2 show an antenna 11

  on a wall of a satellite 10. Antenna 11 is

  carries a parabolic reflector 13 including a disk

  parabolic dielectric and a grid of

  horizontally polarized conductors 13a, the reflector 13 being mounted in overlap on a second parabolic reflector 15 consisting of a parabolic dielectric disk and a derrick grid 15a of

vertical polarization.

  In Figure 1, a portion of the front reflector

  13 is cut to show the reflector grid ar-

  15. The antenna 11 is mounted on a surface 10a

  of the main body 10 of a satellite by means of

  net dimensions 17, 18, 19 and 20. These balusters support

  carry the rear parabolic reflector 15 on the

  face 10a of the main satellite body 10. A reflection of

  parabolic fan 13 front or

  reflector 15, for example by means of a dielectric ring

  peripheral pole 16 disposed between the reflectors 13 and 15. These reflectors may also be mounted one

  on the other by stiffening ribs. An example

  Typical of these stiffening grooves is described in patent application No. RCA 81,336 entitled "Dual

Gridded Reflector Structure ".

  Reflectors 13 and 15 are sections of a paraboloid of revolution, the top of the reflectors are

  located near the lower edge, as shown by the

  2. The top of the parabolic reflector 13 is

  killed in V1 and the top of the second reflector 15 is located in V2. The two parabolic reflectors are mounted so as to be offset relative to one another as shown by the vertices V1 and V2 and the focal axes are

  slightly offset and parallel to each other. This corresponds

  the aforementioned patent, so that the fields of

  transversal development developed by the parallel elements

  on one surface of each reflector from one or more feed horns of a network associated with this reflector are diffused from the beam

copolarized from the other reflector.

  The antenna has networks of feed horns

  21 and 23; beam formation, such as the

  show FIGS. 3a and 3b for the polarizations

  pectives. The offset between the two reflectors is sufficient

  to ensure sufficient space around each

  fireplaces to receive the two networks of cones.

  The network of horizontal polarization cones 21

  tale is located at the F1 focus of the parabolic reflector 13 which features the horizontal grid drivers

  13a. See Figures 2 and 3a. Network 21 is generally

  centrally with respect to the F1 focus as shown in Figure 3a. The vertical polarization cone network 23 is located at the focal point F2 of the reflector 15 which includes the vertical grid conductors 15a. The network 23 is generally centered with respect to the focus

  F2 as shown in Figure 3b. Each network of cor-

  net is directed to the center of a respective reflector

  in order to completely irradiate the reflector,

at its center.

  Each of the polarization feed horns

  horizontal network 21 is arranged to transmit and receive high frequency signals of horizontal polarization. Similarly, each of the vertical bias feed horns of the array 23 is arranged to transmit and receive high frequency signals in vertical polarization. Figures 3a and 3b

  also show the entry waveguides to foreign

  horns. The input waveguides 22 of the turbines of the network 21 have a width less than their height so as to propagate signals with the fields

  Perpendicular to the vertical surfaces and consequently

  quent, to excite horizontal polarization signal waves. Entrance waveguides 24 of cornets

  network 23 are wider than they are tall so as to ex-

  cite waves of vertical polarization signals. The networks 21 and 23 are mounted on the satellite body 10

  by a support arm 30, according to Figure 2.

  According to the invention, a conductor grid 21a

  vertically is placed in front of the opening of the network of

  net 21 of horizontal polarization. So, the grid 21a

  is next to each net of network 21. See FIGS.

  res 2 and 3. This grid 21a of vertical conductors (shown in Figure 3a) may be constituted by a sheet of a dielectric, such as mylar or other

  dielectric material on which are printed or formulated

  by any other means of thin conductors. These

  ductors can be for example a sheet of

  with a thickness of 0.0075 mm. The leaf can be

  mounted on a frame 21b mounted on the support arm of

  net 30 by a rim 31, so that it is

  flat hold against the cornets. See Figure 2.

  The spacing between the conductors of the grid 21a and the dimension of the conductors are the same as for the grids 13a and 15a of the reflectors 15 and 13. They are arranged to couple signals between the horn and the reflector 13 with a weak attenuation while ensuring optimal rejection of

  vertical polarization from the conductor grid

  The width of the conductors is, for example, 0.075 mm and the center-to-center distance between them is 0.5 mm for one embodiment tested at frequencies of 11 to 14 GHz. The geometry of the grids (spacing and

  width) is chosen to give the best

  promised between the lowest transmission loss with

  the co-polarized component and the highest reflectance

  for the transverse polarization component.

  Across the opening of the vertically polarized cone network 23 is a grid 23a of

  horizontally oriented conductors with the same

  the same width and width as the reflective conductors

  13 and 15. Here again, the gate 23a is adjacent

  of each network horn 23. See Figure 3b. This grill

  is also preferably made from a sheet of paper

  electric as mylar on which are printed or otherwise formed thin conductors. The sheet can be mounted on a frame 23b fixed on the

  horn support arm 30 by a flange 33.

  Experience has shown that the rejection of

  transversal improvement is improved by using

  grids at the opening of the net

  tation. Figure 4 illustrates this transverse polarization effect in the absence of cone grids for a beam directed to the western half of the United States.

  of America and Figure 5 illustrates the reduction of

  transverse polarization fades with cone grids. These figures show diminished copolarization

  of transversal polarization, ie the con-

  insulation towers. The operating frequency is 11.76 GHz. The isolation contours at 44 dB, 40 dB, 36 dB and 32 dB are plotted in these two figures. In order to illustrate the improvement due to the installation of

  ahead of the cornets, the following observations should

  to be made: 1). In Figure 4, in the case where there is no

  in front of the horns, the insulation is poorer

  than 32db for most of western

  United States of America, as shown by the outer region

  greater than all dashed outlines; 2). According to Figure 5, in which grids are used in front of the horns, the insulation is better than 32db on the western part of the United States of America and it is 36db on a major part of

the covered area.

  In addition, Figures 6 and 7 show diagrams

  grams measured in co-polarization for both bundles, with and without grid in front of the cornets. These figures

  show that the grids in front of the horns

  not substantially the copolarization signal.

Claims (4)

CLAIMS.   1-Spectrum Reuse Antenna (Figure 2)   comprising: a first linear polarized reflector (13)   comprising a first linear conductor grid (13a) of a first polarization orientation (H) covering a second linearly polarized reflector (15) including a second linear conductor grid (15a) of a second polarization orientation ( V) orthogonal to said first orientation; a first   feed horn (21) arranged to couple   electromagnetic emissions in the said first   linear polarization on a given frequency band located at the focus (F1) or near the focus of the first polarized reflector; and a second feed horn (23) arranged to couple signals of said second linear bias orientation to said given frequency band located at or near said second polarized reflector; characterized in that to reduce the coupling of the polarization signals   cross-section, it comprises a third grid of   linear ducts (21a) of said second orientation   (V) near said first feed horn and a fourth   third grid of linear conductors (23a) of said   first orientation (H) near said second feed horn mentation.   Antenna according to Claim 1, characterized   in that the center-to-center distance between the conductors   linear motors and their width and thickness in each of said third and said fourth grids   leads to a reflection of unwanted signals from   cross-cutting without introducing a value   significant increase in the attenuation of the polarized signals read.   3-Antenna according to claim 1 or 2, characterized   in that the distance between the conductors and   their width of each of said third and said fourth   third grids are practically equal to the distance between the conductors and their width of the respective one said reflectors.   4-Antenna according to any one of claims 1 to 3, characterized in that each of said third and said fourth grids comprises. said   conductors formed on a thin dielectric sheet.   Antenna according to claim 4, characterized   in that each of the said third and fourth   third grid is a thin metal sheet.