CA1039842A - Compact frequency reuse antenna - Google Patents
Compact frequency reuse antennaInfo
- Publication number
- CA1039842A CA1039842A CA218,547A CA218547A CA1039842A CA 1039842 A CA1039842 A CA 1039842A CA 218547 A CA218547 A CA 218547A CA 1039842 A CA1039842 A CA 1039842A
- Authority
- CA
- Canada
- Prior art keywords
- reflector
- reflectors
- waves
- parallel
- elements
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
- H01Q19/10—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces
- H01Q19/12—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces wherein the surfaces are concave
- H01Q19/17—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces wherein the surfaces are concave the primary radiating source comprising two or more radiating elements
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q25/00—Antennas or antenna systems providing at least two radiating patterns
- H01Q25/001—Crossed polarisation dual antennas
Landscapes
- Aerials With Secondary Devices (AREA)
- Variable-Direction Aerials And Aerial Arrays (AREA)
Abstract
Abstract of the Disclosure A compact antenna system that permits orthogonally polarized frequency reuse operation is achieved by two overlapping parabolic reflectors. Each of the reflectors has a reflecting surface comprised of parallel, reflecting, conductive elements with the reflecting elements of one reflector polarized orthogonally to the reflecting elements in the other.
each reflector has an associated feed copolarized with the reflecting elements of the particular reflector. The two reflectors are overlapped, without coinciding their respective focus points, near their vertices and at their more nearly flat ends. Consequently, cross-polarized fields generated by the parallel elements in the surface of each reflector from its associated feed are scattered away from the copolarized beam of each reflector and further the structure is compact, particularly along the desired axis of reflection.
each reflector has an associated feed copolarized with the reflecting elements of the particular reflector. The two reflectors are overlapped, without coinciding their respective focus points, near their vertices and at their more nearly flat ends. Consequently, cross-polarized fields generated by the parallel elements in the surface of each reflector from its associated feed are scattered away from the copolarized beam of each reflector and further the structure is compact, particularly along the desired axis of reflection.
Description
~CA 67,698 his invention relates to a compact frequency reuse antenna system and more particularly to an antenna system which achieves frequency reuse by or-thogonally polarized sources and reflectors.
With the ever increasing demand for more frequency spectrum, it is imperative that greater use be made of the allocated spectrum. This is particularly true in satellite communications where the coverage area is a substantial portion of the earth's surface. It is also desirable on a cost basis to achieve more channel space per frequency spectrum. A practical way of achieving spectrum reuse is oy communicating with waves of orthogonal polarization. Isolation of the orthogonally polarized waves can be achieved by separating a great distance from each other the feeds and the associated reflectors com-municating these orthogonally polarized waves. However, in addition to the desirability of spectrum reuse in satellite communication antennas particularly, there is a need for a highly compact antenna. This is particularly true of the satellite antenna itself. Providing a compact frequency reuse antenna in view of such factors as dis-cussed above poses a problem.
The invention may be practiced in an antenna arrangement for communicating electromagnetic waves of the ~5 same frequency with a given orthogonal polarization. The arrangement includes first and second reflectors, each -reflector comprising a portion of a parabaloid and having resultant focus point. Each of the reflectors comprises parallel reflecting elements, with the elements of one reflector oriented in a first direction to reflect waves
With the ever increasing demand for more frequency spectrum, it is imperative that greater use be made of the allocated spectrum. This is particularly true in satellite communications where the coverage area is a substantial portion of the earth's surface. It is also desirable on a cost basis to achieve more channel space per frequency spectrum. A practical way of achieving spectrum reuse is oy communicating with waves of orthogonal polarization. Isolation of the orthogonally polarized waves can be achieved by separating a great distance from each other the feeds and the associated reflectors com-municating these orthogonally polarized waves. However, in addition to the desirability of spectrum reuse in satellite communication antennas particularly, there is a need for a highly compact antenna. This is particularly true of the satellite antenna itself. Providing a compact frequency reuse antenna in view of such factors as dis-cussed above poses a problem.
The invention may be practiced in an antenna arrangement for communicating electromagnetic waves of the ~5 same frequency with a given orthogonal polarization. The arrangement includes first and second reflectors, each -reflector comprising a portion of a parabaloid and having resultant focus point. Each of the reflectors comprises parallel reflecting elements, with the elements of one reflector oriented in a first direction to reflect waves
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-- RCP~ 67, 698 ~0398~2 1 polarized in a first direction and with the elements of the other reflector oriented in an orthogonal direction to reflect waves polarized in an orthogonal direction. A
first antenna feed means is located at the focus of the first reflector for communicating electromagnetic waves copoiarized with the elements of the first reflector. A
second antenna feed is located at the focus of the second reflector for communicating electromagnetic waves co-polarized with the elements of the second reflector. The reflectors are mounted one behind the other, with the focus points of the reflectors separated from each other and with the focal axes parallel to each other. Consequently, cross-po~arized waves generated by the parallel elements at the surface of the respective reflectors are scattered away from the copolarized beam of each reflector, and co-polarized waves generated at the respective reflectors arecommunicated parallel to a given, common direction.
According to the preferred embodiment of the invention, the reflectors are overlapped near their more nearly flat ends and near the vertices of the respective reflectors and are essentially symmetrical with respect to the given, common direction. -In the following description of the preferred embodiment of the invention reference is made to the drawings which accompany the description and in which:
Figure l is a front elevation drawing of a satellite antenna system mounted to the satellite according to one embodiment of the present invention;
Figure 2 is a side elevation view of the arrange-
-- RCP~ 67, 698 ~0398~2 1 polarized in a first direction and with the elements of the other reflector oriented in an orthogonal direction to reflect waves polarized in an orthogonal direction. A
first antenna feed means is located at the focus of the first reflector for communicating electromagnetic waves copoiarized with the elements of the first reflector. A
second antenna feed is located at the focus of the second reflector for communicating electromagnetic waves co-polarized with the elements of the second reflector. The reflectors are mounted one behind the other, with the focus points of the reflectors separated from each other and with the focal axes parallel to each other. Consequently, cross-po~arized waves generated by the parallel elements at the surface of the respective reflectors are scattered away from the copolarized beam of each reflector, and co-polarized waves generated at the respective reflectors arecommunicated parallel to a given, common direction.
According to the preferred embodiment of the invention, the reflectors are overlapped near their more nearly flat ends and near the vertices of the respective reflectors and are essentially symmetrical with respect to the given, common direction. -In the following description of the preferred embodiment of the invention reference is made to the drawings which accompany the description and in which:
Figure l is a front elevation drawing of a satellite antenna system mounted to the satellite according to one embodiment of the present invention;
Figure 2 is a side elevation view of the arrange-
3 ment shown in Figure l as taken along line 2-2;
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1 Figure 3 is a front view of a paraboloid of revolution illustrating the portion of the paraboloid of revolution used in the antenna system of Figure l;
Figure 4 is a front elevation drawing illus-trating a general placement o:f two of the reflectors in Figure 1 relative to each other;
Figure S is a sketch illustrating the operation .
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I of a first pair of reflectors ln the antenna system shown in Figure l;
Fig~lre ~ is a sketch i:Llustrating a portion of a few of the vertical elements in one reflector and a vector diagram of the copolarized wave applied to these elements.
Figure 7 is a sketch illustrating a portion of a few of the horizontal elements in one reflector and a vector diagram of the copolarized wave applied to these elements; and Figure 8 is a sketch illustrating the operation of another pair of overlapping reflectors and associated feeds in the antenna system shown in Figure 1.
Referring to Figure 1, a satellite antenna system 10 is shown mounted to satellite structure 11.
The antenna system 10 includes reflectors 12, 13, 15 and 17 and waveguide feed horns l9a, l9b, l9c and l9d.
The reflectors lZ, 13, 15 and 17 are mounted to satellite structure 11 by the support posts 12a, 13a, 13b, 15a, 17a and 17b. Support posts 13b and 17b are hidden from view by horns l9b and l9d in Figure 1. Referring to the side elevation view of reflectors 15 and 17 in Figure 2, it is seen that reflector 15 is supported by post 15a extending through reflector 15 and by fixing the end 16 of reflector 15 to one end of posts 17a and 17b. The reflector 15 is fixed to the posts 15a, 17a and 17b by suitable bonding. The reflector 17 is supported by the two posts 17a and 17b extending through the reflector 17 and by fixing the end 16a to posts 15a at a point just slightly rearward of the reflector 15. The post 17b 3 extends only through an edge portion of reflector 17.
. ~ ~, -. ' ' :
RCA 67,698 10398~2 1 The reflector 17 is fixed to the posts 15a, 17a and 17b by suitable bonding. Posts 12a, 13a and 13b similarly mount reflector 12 forward of refll_ctor 13 and mount reflector 13 re~rward of reflector 12. One suitable material for such support posts in space is a low thermal expansion material known as "GFEC" which letters stand for graphite fiber epoxy composite.
The reflectors 12, 13, 15 and 17 are each portions of a paraboloid of revolution. The portion 21 of the paraboloid of revolution illustrated in Figure 3 is used for reflector 15. The portion 21a is used for reflector 17. The reflectors 12 and 13 use similar but symmetrical portions of a paraboloid of revolution as shown by dashed lines. The long edge of each of the portions intersects $he vertex of the paraboloid. The portion 21 overlaps over half of portion 21a. The vertex V is along the long edge of the portions 21 and 21a, The vertex V is midway along the long edge of portion 21a and about one third up from the end of portion 21. The portion selected is near the center of the parabolcid of revolution to permi-t more closely spaced overlapping of the reflectors and to minimize excitation of cross-polarized fields.
Referri~g to Yigure 1, it is seen that the reflectors 12 and 13 overlap each other and the reflectors 15 and 17 overlap each other. The reflector 12 overlaps about one half of reflector 13. Similarly, reflector 15 overlaps about one half of reflector 17. The reflectors are overlapped so that the long edge of the forward 3 reflector overlaps the long edge of the associated rearward -RCA 67,698 1C~398~Z
reflector. Referring to Figure ~, for example, reflector 15 overlaps reflector 17 with the long edge overlapped.
The vertex point 23 for reflector 15 as shown in Figure 4 is aligned and spaced from the vertex point 25 of reflector 17. The reflectors 15 and 17 overlap at their more flat ends near the vertex of each with essentially even symmetry. In other words, if one were to place a mirror at the middle of the overlap and cover the upper half, the mirror would reflect from the lower half what would substantially be at the covered upper half. The same is true with respect to the placement of reflectors 12 and 13, with reflector 12 forward or extending further away from structure 11 than reflector 13. The vertex `
point 23a for reflector 12 is aligned and spaced from the vertex point 25a of reflector 13.
The reflectors 12, 13, 15 and 17 are formed of parallel conductive elements as represented in part by the parallel lines in Figures 1 and 4. The parallel elements of reflectors 12 and 17 are represented by vertically oriented parallel lines 27 and 29, respectively. The ~
parallel elements of reflectors 13 and 15 are represented ~-by the horizontally oriented parallel lines 31 and 33, respectively. The elements that make up the reflectors 13 and 15 are oriented orthogonal to the elements that make up the reflectors 12 and 17. The parallel elements forming the reflectors may be provided by a plurality of closely spaced parallel wires embedded in a low dielectric plastic base. The wires are laid in such a manner that viewed from a great distance along the axis of the generating paraboloid they appear everywhere parallel to :. - - , . ' :, -RC~ ~7,698 ~0398g2 I themselves ancl to an electric field generated by an associated copolarized f eed.
The feed horn 19a is designed to couple signals over a given wide frequency band and is polarized to S communicate vertically polarized waves This feed horn l9a is mounted by support 51 extending from satellite structure 11 to the horn l9a as shown in Figure 1. The feed horn l9a is positioned with the aperture of the horn l9a at the focus point of the copolarized reflector 12.
The feed horn l9a is further oriented to optimize the illumination of reflector 12.
The f eed horn l9b is designed to couple signals over the same frequency band as feed horn l9a but is polarized to communicate horizontally polarized waves.
This feed horn l9b is mounted by support 53 extending ` ``
from satellite structure 11 to the horn l9b to position the aperture of the horn l9b at the focus point of copolarized reflector 13. The feed horn l9b is further oriented to optimize the illumination of reflector 13.
The feed hor~s l9c and l9d are polarized to communicate horizon-tally and vertically polarized waves, respectively. The horns l9c and l9d are designed to couple signals over the same frequency band. This frequency band may be the same as the given frequency band or may be another frequency band. In the preferred embodiment horns :L9a, l9b, l9c and l9d are designed to communicate signals over the same frequency band The sub-frequency bands or channels within this wide frequency band communicated by horns l9a and l9b in this preferred arrangement differ from that communicated by horns l9c RCA 67,698 103984~Z
I and l9d. The horns l9a and l9b communicate the odd numbered channels for example and horns 19c and l9d communicate the even numbered channels. This minimizes the problems associated with multiplexing these signals.
Similarly the horn l9c is mounted by support 55 at the focus point of copolarized (horizontal) reflector 15, and the horn l9d is mounted by support 57 at the focus pOillt of copolarized (vertical) reflector 17. Figure 2 illustrates more clearly how the supports 55 and 57 are mounted between the horns l9c and l9d and structure 11.
The feed horns l9a, l9b, l9c and l9d are coupled to the transmitter and receiver circuitry located within the structure 11 by waveguides such as waveguides 59 and 61 illustrated in Figure 2 extending between feed horns l9c and l9d, respectively, and structure 11. The feed horns l9c and l9d are further oriented to optimize illumination of reflectors 15 and 17, respectively. The vertically oriented elements of reflectors 12 and 17 pass horizontally polarized vaves and reflect the vertically polarized waves.
The horizontally oriented elements of reflectors 13 and 15 pass vertically polarized waves and reflect the horizontally polarized waves. In the overlapping region 18 and 20 in Figure 1, both horizontally and vertically polarized waves are reflect~ed.
Referring to the illustrative sketch of Figure 5, operation of the antenna system is considered in the case of transmitted vertically polarized waves toward reflector 12. These waves radiated toward the reflector 12 by horn l9a located at the focus fl of reflector 12, are represented in Figure 5 by dashed lines 26. The waves are intercepted - . , RCA 67,698 10;~98~Z
I by reflector 12 having vertical elements and are directed in phase to the antenna aperture (collimated) whereupon a radiated beam in a given direction of arrow 28 is provided. The vertex 23a of the reElector 12 is along one edge 12d of reflector 12 as shown in Figure 1. Since the horn l9a is located at the focus of reflector 12 and in line and forward of the vertex 23a, the horn l9a provides low blockage of the vertically polarized waves.
The reciprocal operation takes place with respect to the received in phase waves at the antenna aperture. These in phase waves at the aperture are reflected to horn l9a.
In the case of horizontally polarized waves transmitted to the reflector 13 by horn l9b located at the focus f2 of reflector 13, these waves represented by dashed lines 36 in Figure 5 are intercepted by horizontally polarized reflector 13 and are directed in phase at the antenna aperture (collimated) whereupon in the illustrated example a radiated beam in the same given direction of arrow 28 is provided. Since the vertex 25a of the reflector 13 is along one edge of reflector 13 and the horn l9b is at the focus f2 in line with the vertex, the horn l9b provides low blockage of the horizontally polarized waves.
As explained below, portions of the vertically polarized waves represented by dashed lines 26 may pass 2S through (instead of being reflected from) the reflector 12.
At the common region 18, those passed portions have a cross (horizontally) polarized field 26h (as observed at the reflector 12). The last-named field passes on to reflector 13. Consequently, the reflected portions are reflected by 13. See Figure 5. Although considerable g _ -.
RCA 67, 698 1~3~984Z
1 skill may be extended in an effort to achieve perfectly parallel vertical elements in reflector 12 represented by lines 27 in Figure 1, some . .
RCA 67,698 ~0398~2 1 degree of cro~s thorl~ontally) polarized field 1~ generated by reflector 12 when intercepting the ~ertically polarized waves. This may be explained in part by a slight mis-al~gnment of the parallel elements relative to th~
polarization of the waves near the edge 22 furthest from the long edge 12d intersecting the vertex 23a Figure 6 is an enlarged Vi8W of a portion of a few elements 27 represented by lines located near edge 22 of reflector 12 and an exaggeræted vector diagram of the copolarized wave 27a applied to these elements and the associated vector components. The misalignment of wave vector 27a relative to the lines 27 is greatly exaggerated for purposes of illustration. With the misalignment of the reflector elements 27 relative to the polarization of the incident wave along vector 27a, there is a horizontal vector component 27b o~ the wave in addition to a vertical vector component 27c. This misalignment of the applied field is due in part to a polarization change in the incident wave as the wave makes a greater angle with respect to the focal axis (increases as the wave is off the focal axis). The result is that wlth an applied field to these reflectors a cross (horizontal) field is produced. This is repre-sented ln Figure 5 by dashed lines 26h.
The reflectors 12 and 13 are overlapped near the vertex of each to lessen this misalignment effect at the overlapped region and therefore minimize this effect.
In addition, by displacing the focal points fl and f2 f the two reflectors 12 and 13 a sufficient distance D, as shown in Figure 5, the cross-polarized field 26h at the horizontally polarized reflector 13 (associated with the RCA 67,698 Canada ~039842 1 generated cross-polarized fiel~ 26h~ is squinted away from the beam 28 associated with the vertically polarized reflector and at the same time is partially de-collimated.
In like manner, a vertically polarized field generated at the horizontally polarized conducting wires 31 in reflector 13 and indicated as 36V in figures 5 is scattered at reflector 12 away from the horizontally ~-polarized beam. Although considerable effect may be taken to achieve perfectly, parallel, horizontal elements in reflector 13 represented by wires or lines 31 in Figure 1, some degree of cross (vertically) polarized field (repre-sented in Figure 5 by dashed lines 36V) is generated at reflector 13 when intercepting the horizontally polarized waves from -feed horn l~b. This is due to a slight mis-alignment of the reflector elements relative to the polarization of the wave as viewed by the waves near the edge 22a in ~igure 1. Figure 7 is an enlarged view of a portion of a few of the elements represented by lines 31 located near the edge 22a of reflector 13 and an exaggerated vector diagram of the copolarized wave applied to these reflector elements 31. It is to be noted that with the mis-alignment of the reflector elements 31 relative to the polarization of the incident wave along vector 31a, there is a vertical vector 31b in addition to a horizontal vector 31c.
This misalignment is due in part to polarization change in the incident wave as the wave makes a greater angle with respect to the focal axis. The result is that a cross ~vertical) field 36V is produced. By the displacement of the focal points fl and f2 of the two reflectors 12 and 13 the sufficient distance D as discussed previously and . -11- , .
~- RCA 67,~98 ~989tZ
illustrated in ~i~ure 5, t~lis c:ross-polarized field 36v at reflector 13 is squintecl away from the main hori:zontally ., polarized beam in the direction 28. In the case OI received horizontally polarized waves generating cross (vertical~
polarized ~vaves at reflector 13, these cross (vertical) polarized waves are squinted away at reflector 13 from either of the horns l9a or l9b.
In the previously described arrangement with the focus fl spaced from focus f2 by ten inches and with the vertex 23a spaced from vertex 25a so that the focal axis of reflector 12 is parallel to the focal axis of reflector 13, the unwanted cross-polarized wave is scattered 20 degrees from the desired direction of the communication signal (direction 28 in Figure ~). Rlith this antenna system lS in a satellite orbit such a scattering of 20 degrees is sufficient to direct the squinted wave away from earth.
Referring to the sketch of Figure 8 and considering the case of horizontally polarized waves transmitted to reflector 15 by horn l9c located at the focus f3 of reflector 15, these waves 46 intercepted by reflector 15 are colli-mated and directed as a beam in for example the same direction - -28 as the waves reflected by reflectors 12 and 13. In the case of vertically oriented waves communicated to reflector 17 by horn l9d located at the focus f4 of reflector 17, these waves 56 intercepted by reflector 17 are collimated and directed as a beam in for example the same direction 28 as the waves reflected by reflectors 12, 13 and 15. The vertex of each of the rbflectors 15 and 17 is located on one edge of these reflectors as shown in Figure 1. The feed horn l9c is located at the focus f3 of the reflector 15 and the . - , .
`~ RCA 67,698 Canada 39t34Z
1 feed horn 19d is located at the focus f4 of reflector 17.
Since the vertex is along one edge of each of the reflectors low blocka~e of the received or reflected waves occurs.
The vertically oriented waves 56 from horn l9d passing through the common regions 20 shown in Figure 1 pass through the reflector 15 to reflector 17 whereupon they are reflected. As discussed above, some degree of `
cross (horizontally) polarized waves indicated by dashed lines 56h are excited and they are squinted away as discussed previously due to the sufficient separation D
of the focus points f3 and f4 of the two reflectors 15 and 17. In the case of horizontally polarized waves 46 falling on the reflector 15 at the common region 20 they generate cross (vertically) polarized fields 46V which are passed on to reflector 17. As mentioned previously, these cross-polarized fields are s~uinted away due to the sufficient separation of the focus points f3 and f4 of the two reflectors. The reciprocity theory of antennas applies in the operation of the antenna structure described -~
herein. Therefore whatever happens in the transmission mode described previously applies in reverse in the ~
reception,rmode . , .:
The above described arrangement illustrates how the present invention provides a communication system which has advantageous reflection properties and further is compact, particularly with respect to the dimension taken parallel to the direction 2g of the beam.
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RCA 67,6~8 1~39~4;~:
1 Figure 3 is a front view of a paraboloid of revolution illustrating the portion of the paraboloid of revolution used in the antenna system of Figure l;
Figure 4 is a front elevation drawing illus-trating a general placement o:f two of the reflectors in Figure 1 relative to each other;
Figure S is a sketch illustrating the operation .
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.
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RCA 67,698 1039~34Z
I of a first pair of reflectors ln the antenna system shown in Figure l;
Fig~lre ~ is a sketch i:Llustrating a portion of a few of the vertical elements in one reflector and a vector diagram of the copolarized wave applied to these elements.
Figure 7 is a sketch illustrating a portion of a few of the horizontal elements in one reflector and a vector diagram of the copolarized wave applied to these elements; and Figure 8 is a sketch illustrating the operation of another pair of overlapping reflectors and associated feeds in the antenna system shown in Figure 1.
Referring to Figure 1, a satellite antenna system 10 is shown mounted to satellite structure 11.
The antenna system 10 includes reflectors 12, 13, 15 and 17 and waveguide feed horns l9a, l9b, l9c and l9d.
The reflectors lZ, 13, 15 and 17 are mounted to satellite structure 11 by the support posts 12a, 13a, 13b, 15a, 17a and 17b. Support posts 13b and 17b are hidden from view by horns l9b and l9d in Figure 1. Referring to the side elevation view of reflectors 15 and 17 in Figure 2, it is seen that reflector 15 is supported by post 15a extending through reflector 15 and by fixing the end 16 of reflector 15 to one end of posts 17a and 17b. The reflector 15 is fixed to the posts 15a, 17a and 17b by suitable bonding. The reflector 17 is supported by the two posts 17a and 17b extending through the reflector 17 and by fixing the end 16a to posts 15a at a point just slightly rearward of the reflector 15. The post 17b 3 extends only through an edge portion of reflector 17.
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RCA 67,698 10398~2 1 The reflector 17 is fixed to the posts 15a, 17a and 17b by suitable bonding. Posts 12a, 13a and 13b similarly mount reflector 12 forward of refll_ctor 13 and mount reflector 13 re~rward of reflector 12. One suitable material for such support posts in space is a low thermal expansion material known as "GFEC" which letters stand for graphite fiber epoxy composite.
The reflectors 12, 13, 15 and 17 are each portions of a paraboloid of revolution. The portion 21 of the paraboloid of revolution illustrated in Figure 3 is used for reflector 15. The portion 21a is used for reflector 17. The reflectors 12 and 13 use similar but symmetrical portions of a paraboloid of revolution as shown by dashed lines. The long edge of each of the portions intersects $he vertex of the paraboloid. The portion 21 overlaps over half of portion 21a. The vertex V is along the long edge of the portions 21 and 21a, The vertex V is midway along the long edge of portion 21a and about one third up from the end of portion 21. The portion selected is near the center of the parabolcid of revolution to permi-t more closely spaced overlapping of the reflectors and to minimize excitation of cross-polarized fields.
Referri~g to Yigure 1, it is seen that the reflectors 12 and 13 overlap each other and the reflectors 15 and 17 overlap each other. The reflector 12 overlaps about one half of reflector 13. Similarly, reflector 15 overlaps about one half of reflector 17. The reflectors are overlapped so that the long edge of the forward 3 reflector overlaps the long edge of the associated rearward -RCA 67,698 1C~398~Z
reflector. Referring to Figure ~, for example, reflector 15 overlaps reflector 17 with the long edge overlapped.
The vertex point 23 for reflector 15 as shown in Figure 4 is aligned and spaced from the vertex point 25 of reflector 17. The reflectors 15 and 17 overlap at their more flat ends near the vertex of each with essentially even symmetry. In other words, if one were to place a mirror at the middle of the overlap and cover the upper half, the mirror would reflect from the lower half what would substantially be at the covered upper half. The same is true with respect to the placement of reflectors 12 and 13, with reflector 12 forward or extending further away from structure 11 than reflector 13. The vertex `
point 23a for reflector 12 is aligned and spaced from the vertex point 25a of reflector 13.
The reflectors 12, 13, 15 and 17 are formed of parallel conductive elements as represented in part by the parallel lines in Figures 1 and 4. The parallel elements of reflectors 12 and 17 are represented by vertically oriented parallel lines 27 and 29, respectively. The ~
parallel elements of reflectors 13 and 15 are represented ~-by the horizontally oriented parallel lines 31 and 33, respectively. The elements that make up the reflectors 13 and 15 are oriented orthogonal to the elements that make up the reflectors 12 and 17. The parallel elements forming the reflectors may be provided by a plurality of closely spaced parallel wires embedded in a low dielectric plastic base. The wires are laid in such a manner that viewed from a great distance along the axis of the generating paraboloid they appear everywhere parallel to :. - - , . ' :, -RC~ ~7,698 ~0398g2 I themselves ancl to an electric field generated by an associated copolarized f eed.
The feed horn 19a is designed to couple signals over a given wide frequency band and is polarized to S communicate vertically polarized waves This feed horn l9a is mounted by support 51 extending from satellite structure 11 to the horn l9a as shown in Figure 1. The feed horn l9a is positioned with the aperture of the horn l9a at the focus point of the copolarized reflector 12.
The feed horn l9a is further oriented to optimize the illumination of reflector 12.
The f eed horn l9b is designed to couple signals over the same frequency band as feed horn l9a but is polarized to communicate horizontally polarized waves.
This feed horn l9b is mounted by support 53 extending ` ``
from satellite structure 11 to the horn l9b to position the aperture of the horn l9b at the focus point of copolarized reflector 13. The feed horn l9b is further oriented to optimize the illumination of reflector 13.
The feed hor~s l9c and l9d are polarized to communicate horizon-tally and vertically polarized waves, respectively. The horns l9c and l9d are designed to couple signals over the same frequency band. This frequency band may be the same as the given frequency band or may be another frequency band. In the preferred embodiment horns :L9a, l9b, l9c and l9d are designed to communicate signals over the same frequency band The sub-frequency bands or channels within this wide frequency band communicated by horns l9a and l9b in this preferred arrangement differ from that communicated by horns l9c RCA 67,698 103984~Z
I and l9d. The horns l9a and l9b communicate the odd numbered channels for example and horns 19c and l9d communicate the even numbered channels. This minimizes the problems associated with multiplexing these signals.
Similarly the horn l9c is mounted by support 55 at the focus point of copolarized (horizontal) reflector 15, and the horn l9d is mounted by support 57 at the focus pOillt of copolarized (vertical) reflector 17. Figure 2 illustrates more clearly how the supports 55 and 57 are mounted between the horns l9c and l9d and structure 11.
The feed horns l9a, l9b, l9c and l9d are coupled to the transmitter and receiver circuitry located within the structure 11 by waveguides such as waveguides 59 and 61 illustrated in Figure 2 extending between feed horns l9c and l9d, respectively, and structure 11. The feed horns l9c and l9d are further oriented to optimize illumination of reflectors 15 and 17, respectively. The vertically oriented elements of reflectors 12 and 17 pass horizontally polarized vaves and reflect the vertically polarized waves.
The horizontally oriented elements of reflectors 13 and 15 pass vertically polarized waves and reflect the horizontally polarized waves. In the overlapping region 18 and 20 in Figure 1, both horizontally and vertically polarized waves are reflect~ed.
Referring to the illustrative sketch of Figure 5, operation of the antenna system is considered in the case of transmitted vertically polarized waves toward reflector 12. These waves radiated toward the reflector 12 by horn l9a located at the focus fl of reflector 12, are represented in Figure 5 by dashed lines 26. The waves are intercepted - . , RCA 67,698 10;~98~Z
I by reflector 12 having vertical elements and are directed in phase to the antenna aperture (collimated) whereupon a radiated beam in a given direction of arrow 28 is provided. The vertex 23a of the reElector 12 is along one edge 12d of reflector 12 as shown in Figure 1. Since the horn l9a is located at the focus of reflector 12 and in line and forward of the vertex 23a, the horn l9a provides low blockage of the vertically polarized waves.
The reciprocal operation takes place with respect to the received in phase waves at the antenna aperture. These in phase waves at the aperture are reflected to horn l9a.
In the case of horizontally polarized waves transmitted to the reflector 13 by horn l9b located at the focus f2 of reflector 13, these waves represented by dashed lines 36 in Figure 5 are intercepted by horizontally polarized reflector 13 and are directed in phase at the antenna aperture (collimated) whereupon in the illustrated example a radiated beam in the same given direction of arrow 28 is provided. Since the vertex 25a of the reflector 13 is along one edge of reflector 13 and the horn l9b is at the focus f2 in line with the vertex, the horn l9b provides low blockage of the horizontally polarized waves.
As explained below, portions of the vertically polarized waves represented by dashed lines 26 may pass 2S through (instead of being reflected from) the reflector 12.
At the common region 18, those passed portions have a cross (horizontally) polarized field 26h (as observed at the reflector 12). The last-named field passes on to reflector 13. Consequently, the reflected portions are reflected by 13. See Figure 5. Although considerable g _ -.
RCA 67, 698 1~3~984Z
1 skill may be extended in an effort to achieve perfectly parallel vertical elements in reflector 12 represented by lines 27 in Figure 1, some . .
RCA 67,698 ~0398~2 1 degree of cro~s thorl~ontally) polarized field 1~ generated by reflector 12 when intercepting the ~ertically polarized waves. This may be explained in part by a slight mis-al~gnment of the parallel elements relative to th~
polarization of the waves near the edge 22 furthest from the long edge 12d intersecting the vertex 23a Figure 6 is an enlarged Vi8W of a portion of a few elements 27 represented by lines located near edge 22 of reflector 12 and an exaggeræted vector diagram of the copolarized wave 27a applied to these elements and the associated vector components. The misalignment of wave vector 27a relative to the lines 27 is greatly exaggerated for purposes of illustration. With the misalignment of the reflector elements 27 relative to the polarization of the incident wave along vector 27a, there is a horizontal vector component 27b o~ the wave in addition to a vertical vector component 27c. This misalignment of the applied field is due in part to a polarization change in the incident wave as the wave makes a greater angle with respect to the focal axis (increases as the wave is off the focal axis). The result is that wlth an applied field to these reflectors a cross (horizontal) field is produced. This is repre-sented ln Figure 5 by dashed lines 26h.
The reflectors 12 and 13 are overlapped near the vertex of each to lessen this misalignment effect at the overlapped region and therefore minimize this effect.
In addition, by displacing the focal points fl and f2 f the two reflectors 12 and 13 a sufficient distance D, as shown in Figure 5, the cross-polarized field 26h at the horizontally polarized reflector 13 (associated with the RCA 67,698 Canada ~039842 1 generated cross-polarized fiel~ 26h~ is squinted away from the beam 28 associated with the vertically polarized reflector and at the same time is partially de-collimated.
In like manner, a vertically polarized field generated at the horizontally polarized conducting wires 31 in reflector 13 and indicated as 36V in figures 5 is scattered at reflector 12 away from the horizontally ~-polarized beam. Although considerable effect may be taken to achieve perfectly, parallel, horizontal elements in reflector 13 represented by wires or lines 31 in Figure 1, some degree of cross (vertically) polarized field (repre-sented in Figure 5 by dashed lines 36V) is generated at reflector 13 when intercepting the horizontally polarized waves from -feed horn l~b. This is due to a slight mis-alignment of the reflector elements relative to the polarization of the wave as viewed by the waves near the edge 22a in ~igure 1. Figure 7 is an enlarged view of a portion of a few of the elements represented by lines 31 located near the edge 22a of reflector 13 and an exaggerated vector diagram of the copolarized wave applied to these reflector elements 31. It is to be noted that with the mis-alignment of the reflector elements 31 relative to the polarization of the incident wave along vector 31a, there is a vertical vector 31b in addition to a horizontal vector 31c.
This misalignment is due in part to polarization change in the incident wave as the wave makes a greater angle with respect to the focal axis. The result is that a cross ~vertical) field 36V is produced. By the displacement of the focal points fl and f2 of the two reflectors 12 and 13 the sufficient distance D as discussed previously and . -11- , .
~- RCA 67,~98 ~989tZ
illustrated in ~i~ure 5, t~lis c:ross-polarized field 36v at reflector 13 is squintecl away from the main hori:zontally ., polarized beam in the direction 28. In the case OI received horizontally polarized waves generating cross (vertical~
polarized ~vaves at reflector 13, these cross (vertical) polarized waves are squinted away at reflector 13 from either of the horns l9a or l9b.
In the previously described arrangement with the focus fl spaced from focus f2 by ten inches and with the vertex 23a spaced from vertex 25a so that the focal axis of reflector 12 is parallel to the focal axis of reflector 13, the unwanted cross-polarized wave is scattered 20 degrees from the desired direction of the communication signal (direction 28 in Figure ~). Rlith this antenna system lS in a satellite orbit such a scattering of 20 degrees is sufficient to direct the squinted wave away from earth.
Referring to the sketch of Figure 8 and considering the case of horizontally polarized waves transmitted to reflector 15 by horn l9c located at the focus f3 of reflector 15, these waves 46 intercepted by reflector 15 are colli-mated and directed as a beam in for example the same direction - -28 as the waves reflected by reflectors 12 and 13. In the case of vertically oriented waves communicated to reflector 17 by horn l9d located at the focus f4 of reflector 17, these waves 56 intercepted by reflector 17 are collimated and directed as a beam in for example the same direction 28 as the waves reflected by reflectors 12, 13 and 15. The vertex of each of the rbflectors 15 and 17 is located on one edge of these reflectors as shown in Figure 1. The feed horn l9c is located at the focus f3 of the reflector 15 and the . - , .
`~ RCA 67,698 Canada 39t34Z
1 feed horn 19d is located at the focus f4 of reflector 17.
Since the vertex is along one edge of each of the reflectors low blocka~e of the received or reflected waves occurs.
The vertically oriented waves 56 from horn l9d passing through the common regions 20 shown in Figure 1 pass through the reflector 15 to reflector 17 whereupon they are reflected. As discussed above, some degree of `
cross (horizontally) polarized waves indicated by dashed lines 56h are excited and they are squinted away as discussed previously due to the sufficient separation D
of the focus points f3 and f4 of the two reflectors 15 and 17. In the case of horizontally polarized waves 46 falling on the reflector 15 at the common region 20 they generate cross (vertically) polarized fields 46V which are passed on to reflector 17. As mentioned previously, these cross-polarized fields are s~uinted away due to the sufficient separation of the focus points f3 and f4 of the two reflectors. The reciprocity theory of antennas applies in the operation of the antenna structure described -~
herein. Therefore whatever happens in the transmission mode described previously applies in reverse in the ~
reception,rmode . , .:
The above described arrangement illustrates how the present invention provides a communication system which has advantageous reflection properties and further is compact, particularly with respect to the dimension taken parallel to the direction 2g of the beam.
Claims (4)
- Claim 1 continued.
the reflectors overlap near the vertices of their respective paraboloids and are essentially symmetrical with respect to the given direction; and the separation between the focal axes of the respective reflectors and the separation between the vertices of the respective reflectors is sufficient to cause cross polarized waves which are generated at either the first or the second reflector in response to the communication therewith of waves from the second or first feed, respectively, to be scattered away from the directions of the copolarized beams and from the given direction. - 2. The antenna set forth in Claim 1, wherein the vertex of the paraboloid of each reflector is disposed on the long edge thereof.
- 3. The combination of Claim 1, wherein one of the reflectors overlaps substantially half of the other reflector.
- 4. The combination of Claim 1, wherein each of the reflectors is formed of parallel metal wires embedded in dielectric.
1. A compact antenna arrangement for communicating electromagnetic waves with a first and second polarization separated by 90 degrees from one another comprising: first and second electromagnetic wave reflectors; each of the reflectors comprising a portion of a paraboloid and having a resultant focus point, and a focal axis; each of the re-flectors having a plurality of parallel electromagnetic wave reflecting elements providing reflection of waves, the elements of one reflector being perpendicular to the elements of the other reflector; a first feed means located at the focus point of the first reflector and adapted to communicate electromagnetic waves polarized parallel to the reflecting elements of the first reflector to produce a copolarized beam in a direction parallel to the focal axis of the first reflector; a second feed means located at the focus point of the second reflector and adapted to communicate electro-magnetic waves parallel to the reflecting elements of the second reflector to produce a copolarized beam in a direction parallel to the focal axis of the second reflector; the reflectors being disposed one behind the other, with the focus points of the first and second reflectors separated from one another, and with the focal axes parallel to each other; so that waves generated at the first and second reflectors are communicated parallel to a given,common direction;
wherein:
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US439871A US3898667A (en) | 1974-02-06 | 1974-02-06 | Compact frequency reuse antenna |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1039842A true CA1039842A (en) | 1978-10-03 |
Family
ID=23746476
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA218,547A Expired CA1039842A (en) | 1974-02-06 | 1975-01-23 | Compact frequency reuse antenna |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US3898667A (en) |
| JP (2) | JPS5729882B2 (en) |
| BE (1) | BE825218A (en) |
| CA (1) | CA1039842A (en) |
| DE (1) | DE2502531C3 (en) |
| FR (1) | FR2260197B1 (en) |
| GB (1) | GB1484102A (en) |
| IT (1) | IT1028386B (en) |
| NL (1) | NL7501367A (en) |
Families Citing this family (36)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3898667A (en) * | 1974-02-06 | 1975-08-05 | Rca Corp | Compact frequency reuse antenna |
| JPS5829205A (en) * | 1981-08-13 | 1983-02-21 | Nippon Telegr & Teleph Corp <Ntt> | Multibeam antenna device |
| GB2110003B (en) * | 1981-11-19 | 1985-03-13 | Marconi Co Ltd | Antenna assemblies |
| JPS58205308A (en) * | 1982-05-25 | 1983-11-30 | Nippon Telegr & Teleph Corp <Ntt> | Multibeam antenna device |
| JPS58205307A (en) * | 1982-05-25 | 1983-11-30 | Nippon Telegr & Teleph Corp <Ntt> | Multibeam antenna device |
| US4575726A (en) * | 1982-08-16 | 1986-03-11 | Rca Corporation | Antenna construction including two superimposed polarized parabolic reflectors |
| US4550319A (en) * | 1982-09-22 | 1985-10-29 | Rca Corporation | Reflector antenna mounted in thermal distortion isolation |
| DE3337049A1 (en) * | 1983-10-12 | 1985-05-09 | Gesellschaft für Schwerionenforschung mbH, 6100 Darmstadt | SOLID WITH SPECIAL ELECTRICAL PROPERTIES AND METHOD FOR PRODUCING SUCH A SOLID |
| DE3402659A1 (en) * | 1984-01-26 | 1985-08-01 | Messerschmitt-Bölkow-Blohm GmbH, 8012 Ottobrunn | REFLECTOR ANTENNA FOR OPERATION IN MULTIPLE FREQUENCY RANGES |
| FR2568062B1 (en) * | 1984-07-17 | 1986-11-07 | Thomson Alcatel Espace | BIFREQUENCY ANTENNA WITH SAME CROSS-POLARIZATION ZONE COVERAGE FOR TELECOMMUNICATIONS SATELLITES |
| JPS6168526A (en) * | 1984-09-12 | 1986-04-08 | Omron Tateisi Electronics Co | Oscillation type temperature measuring circuit |
| JPS6168527A (en) * | 1984-09-12 | 1986-04-08 | Omron Tateisi Electronics Co | Oscillation type temperature measuring circuit |
| US4625214A (en) * | 1984-10-15 | 1986-11-25 | Rca Corporation | Dual gridded reflector structure |
| US4647938A (en) * | 1984-10-29 | 1987-03-03 | Agence Spatiale Europeenne | Double grid reflector antenna |
| CA1258707A (en) * | 1984-12-26 | 1989-08-22 | Tomozo Ohta | Antenna system |
| DE3609084A1 (en) * | 1985-07-26 | 1987-02-05 | Messerschmitt Boelkow Blohm | Reflector arrangement |
| DE3609078A1 (en) * | 1985-07-26 | 1987-02-05 | Messerschmitt Boelkow Blohm | Reflector arrangement |
| JPS6246238A (en) * | 1985-08-23 | 1987-02-28 | Omron Tateisi Electronics Co | Bio-chemical measuring apparatus |
| JPS6256887A (en) * | 1985-09-05 | 1987-03-12 | Zenkichi Kishimoto | Timepiece equipped with thermometer |
| CA1263180A (en) * | 1985-11-12 | 1989-11-21 | Rca Corporation | Linearly polarized grid reflector antenna systems with improved cross-polarization performance |
| USRE34410E (en) * | 1986-08-14 | 1993-10-19 | Hughes Aircraft Company | Antenna system for hybrid communication satellite |
| US4792813A (en) * | 1986-08-14 | 1988-12-20 | Hughes Aircraft Company | Antenna system for hybrid communications satellite |
| DE3629315A1 (en) * | 1986-08-28 | 1988-03-10 | Messerschmitt Boelkow Blohm | Reflector arrangement for a geostationary satellite |
| US5136294A (en) * | 1987-01-12 | 1992-08-04 | Nec Corporation | Multibeam antenna |
| US4845510A (en) * | 1987-08-10 | 1989-07-04 | Hughes Aircraft Company | Reflector surface adjustment structure |
| US4823143A (en) * | 1988-04-22 | 1989-04-18 | Hughes Aircraft Company | Intersecting shared aperture antenna reflectors |
| GB2264006B (en) * | 1992-02-01 | 1995-09-27 | British Aerospace Space And Co | A reflector antenna assembly for dual linear polarisation |
| CA2105745C (en) * | 1992-09-21 | 1997-12-16 | Parthasarathy Ramanujam | Identical surface shaped reflectors in semi-tandem arrangement |
| US6137451A (en) * | 1997-10-30 | 2000-10-24 | Space Systems/Loral, Inc. | Multiple beam by shaped reflector antenna |
| US5949370A (en) * | 1997-11-07 | 1999-09-07 | Space Systems/Loral, Inc. | Positionable satellite antenna with reconfigurable beam |
| US6049312A (en) * | 1998-02-11 | 2000-04-11 | Space Systems/Loral, Inc. | Antenna system with plural reflectors |
| US5977926A (en) * | 1998-09-10 | 1999-11-02 | Trw Inc. | Multi-focus reflector antenna |
| US6225964B1 (en) * | 1999-06-09 | 2001-05-01 | Hughes Electronics Corporation | Dual gridded reflector antenna system |
| US6621461B1 (en) * | 2000-08-09 | 2003-09-16 | Hughes Electronics Corporation | Gridded reflector antenna |
| WO2006110308A2 (en) * | 2005-03-28 | 2006-10-19 | Radiolink Networks, Inc. | Aligned duplex antennae with high isolation |
| FR3068522B1 (en) | 2017-06-30 | 2019-08-16 | Airbus Safran Launchers Sas | MODULAR INTERFACE SYSTEM FOR AN ANTENNA REFLECTOR, ESPECIALLY AN ANTENNA OF A SPATIAL DEVICE SUCH AS A SATELLITE IN PARTICULAR |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE551006A (en) * | 1955-10-03 | |||
| US3096519A (en) * | 1958-04-14 | 1963-07-02 | Sperry Rand Corp | Composite reflector for two independent orthogonally polarized beams |
| FR1214296A (en) * | 1958-10-29 | 1960-04-07 | Thomson Houston Comp Francaise | New antenna for ultra-short waves |
| NL246679A (en) * | 1958-12-23 | |||
| US3049708A (en) * | 1959-11-20 | 1962-08-14 | Sperry Rand Corp | Polarization sensitive antenna system |
| US3267472A (en) * | 1960-07-20 | 1966-08-16 | Litton Systems Inc | Variable aperture antenna system |
| US3898667A (en) * | 1974-02-06 | 1975-08-05 | Rca Corp | Compact frequency reuse antenna |
-
1974
- 1974-02-06 US US439871A patent/US3898667A/en not_active Expired - Lifetime
-
1975
- 1975-01-15 IT IT19295/75A patent/IT1028386B/en active
- 1975-01-22 DE DE2502531A patent/DE2502531C3/en not_active Expired
- 1975-01-23 CA CA218,547A patent/CA1039842A/en not_active Expired
- 1975-01-29 GB GB3956/75A patent/GB1484102A/en not_active Expired
- 1975-02-05 NL NL7501367A patent/NL7501367A/en not_active Application Discontinuation
- 1975-02-05 BE BE153092A patent/BE825218A/en not_active IP Right Cessation
- 1975-02-06 JP JP1614775A patent/JPS5729882B2/ja not_active Expired
- 1975-02-06 FR FR7503741A patent/FR2260197B1/fr not_active Expired
-
1980
- 1980-11-07 JP JP55157555A patent/JPS5816801B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US3898667A (en) | 1975-08-05 |
| DE2502531C3 (en) | 1981-10-15 |
| NL7501367A (en) | 1975-08-08 |
| JPS5678204A (en) | 1981-06-27 |
| BE825218A (en) | 1975-05-29 |
| DE2502531A1 (en) | 1975-08-28 |
| IT1028386B (en) | 1979-01-30 |
| FR2260197B1 (en) | 1980-09-12 |
| JPS50110751A (en) | 1975-09-01 |
| JPS5816801B2 (en) | 1983-04-02 |
| JPS5729882B2 (en) | 1982-06-25 |
| GB1484102A (en) | 1977-08-24 |
| DE2502531B2 (en) | 1981-01-22 |
| FR2260197A1 (en) | 1975-08-29 |
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