Multi-pattern antenna having frequency selective or polarization sensitive zones

Information

  • Patent Grant
  • 6169524
  • Patent Number
    6,169,524
  • Date Filed
    Friday, January 15, 1999
    26 years ago
  • Date Issued
    Tuesday, January 2, 2001
    24 years ago
Abstract
A multi-pattern antenna for providing a plurality of antenna patterns at different frequencies or polarizations from a single reflector body eliminates the need for multiple reflector antennas on a single spacecraft. The reflector antenna comprises a reflector body and an illumination source. The illumination source illuminates the reflector with a plurality of RF signals each of a preselected frequency or polarization. The reflector comprises a plurality of zones with each zone reflecting preselected RF signals. A plurality of antenna patterns are generated from the reflected RF signals. Each zone is sized to a preselected shape such that the antenna patterns have a desired shape or beamwidth characteristic.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to the field of reflector antennas, and more particularly, to a reflector antenna which includes frequency selective or polarization sensitive zones to provide a plurality of antenna patterns having different polarizations or frequencies from a single reflector.




2. Description of the Prior Art




Reflector antennas are frequently used on spacecraft to provide multiple uplink and downlink communication links between the spacecraft and the ground. The downlinks operate at one frequency, typically around 20 GHz, and the uplinks operate at a second higher frequency, typically around 30 or 44 GHz. It is typically desirable for a single spacecraft to have multiple uplink and downlink antennas where each antenna provides a separate antenna pattern covering a predetermined coverage zone on the earth. It is also typically desirable to provide both an uplink and downlink antenna pattern having the same beamwidth so that users can both receive and transmit to the same spacecraft. For example, a single spacecraft may have one uplink antenna which provides a 3°×6° antenna beam at 30 GHz for uplink communications from the continental United States (CONUS), and, one downlink antenna at a frequency of 20 GHz which provides a 30°×6° beam for downlink communications to CONUS. The method typically used to provide multiple uplink and downlink antenna patterns from a single spacecraft is to provide separate reflectors for each uplink and downlink antenna. This requires a large amount of space on a spacecraft, is expensive and extracts a weight penalty.




One method attempted to save weight is to couple one uplink and one downlink antenna together in a single reflector body. To do so, an illumination source is configured to illuminate the reflector body with two RF signals, one having a frequency of 20 GHz and the other having a frequency of 30 GHz. The reflector is typically fabricated of a composite or honeycombed material coated with a reflective material, typically aluminum, which is reflective to RF signals of all frequencies. The disadvantage with this system is that it is difficult to provide antenna patterns having predetermined beamwidths at different frequencies from the typical reflector. The beamwidth of an antenna beam is inversely proportional to the size of the reflector and the frequency of illumination. From the same sized reflector, the uplink antenna pattern at 30 GHz would have a smaller beamwidth than the downlink antenna pattern at 20 GHz thereby covering a smaller coverage zone than the downlink antenna pattern. To address this problem, conventional reflector antennas have used specially designed feed horns configured to under illuminate the reflector at 30 GHz, the higher frequency, thereby generating an antenna pattern at 30 GHz having a wider beamwidth. This is inefficient and often difficult to do since feed horns are extremely sensitive to tolerance and bandwidth limitations.




A need exists to have a single reflector which provides a plurality of antenna patterns each having a predetermined beamwidth allowing a single spacecraft to carry the weight and expense of only one reflector while having the ability to provide multiple uplink and downlink antenna patterns.




SUMMARY OF THE INVENTION




The aforementioned need in the prior art is satisfied by this invention, which provides a reflector antenna having frequency selective or polarization sensitive zones to provide a plurality of antenna patterns from a single reflector body. A reflector antenna, in accord with the invention, comprises a single concave reflector body having a plurality of zones with each zone configured as a frequency selective or polarization sensitive zone. The zones can be partially, completely or not overlapping. An illumination source is configured to illuminate the reflector body with a plurality of RF signals with each zone reflecting one or more of the RF signals. The reflector body generates a plurality of antenna patterns from the reflected RF signals with the shape & beamwidth of the antenna patterns being determined by the shape and dimensions of each zone. The shape and dimensions of each zone is thus preselected to provide an antenna pattern having a desired shape and beamwidth.




For the preferred embodiment of the invention, the reflector body has two concentric zones comprised of an inner zone and an outer zone encompassing the inner zone. The two zones are illuminated with the RF signals having frequencies of approximately 20 GHz and 30 GHz. The inner zone is comprised of a material which is reflective to RF signals of all frequencies, and, the outer zone is comprised of a material which reflects RF signals of a 20 GHz frequency and passes RF signals having a frequency of 30 GHz. The 30 GHz signal is reflected only by the inner zone and is not reflected by the second zone. Antenna patterns are generated at 20 and 30 GHz from the 20 and 30 GHz reflected signals respectively with the size and shape of only the inner zone determining the shape and beamwidth of the 30 GHz antenna pattern and the shape and beamwidth of both zones determining the shape and beamwidth of the 20 GHz antenna pattern. The dimensions of the inner and first zone are preselected to generate 20 and 30 GHz antenna patterns having approximately equal shapes and beamwidth.











BRIEF DESCRIPTION OF THE DRAWINGS




Reference is now made to the detailed description of the preferred embodiments illustrated in the accompanying drawings, in which:




FIG.


1




a


is a top plane view of a reflector body in accordance with one embodiment of the invention;




FIG.


1




b


is a side plane view of a reflector antenna having the reflector body shown in FIG.


1




a;






FIG.


1




c


shows antenna patterns generated by the reflector antenna shown in FIG.


1




b;






FIG.


2




a


is a top plane view of a reflector body in accordance with a second embodiment of the invention;




FIG.


2




b


is a side plane view of a reflector antenna having the reflector body shown in FIG.


2




a;






FIG.


2




c


shows antenna patterns generated by the reflector antenna shown in FIG.


2




b;






FIG.


3




a


is a top plane view of circular loop frequency selective elements in accordance with a third embodiment of the invention;




FIGS.


3




b


and


3




c


are top plane views of nested circular loop frequency selective elements in accordance with a fourth embodiment of the invention;




FIG.


4




a


is a top plane view of a reflector body in accordance with a fifth embodiment of the invention;




FIG.


4




b


is a side plane view of a reflector antenna having the reflector body shown in FIG.


4




a;






FIGS.


4




c


and


4




d


show the x and y axis principle plane antenna patterns respectively generated by the reflector antenna shown in FIG.


4




b.






FIG.


5




a


is a top plane view of a reflector body in accordance with a sixth embodiment of the invention;




FIG.


5




b


is a side plane view of a reflector antenna having the reflector body shown in FIG.


5




a;






FIG.


5




c


shows antenna patterns generated by the reflector antenna shown in FIG.


5




b;






FIG.


6




a


is a top plane view of a reflector body in accordance with a seventh embodiment of the invention;




FIG.


6




b


is a side plane view of a reflector antenna having the reflector body shown in FIG.


6




a;






FIG.


6




c


shows antenna patterns generated by the reflector antenna shown in FIG.


6




b;






FIG.


7




a


is a side plane view of a reflector body in accordance with a eighth embodiment of the invention;




FIG.


7




b


is a side plane view of a reflector antenna having the reflector body shown in FIG.


7




a


; and,




FIG.


7




c


shows antenna patterns generated by the reflector antenna shown in FIG.


7




b.













DETAILED DESCRIPTION OF THE INVENTION




Referring to FIGS.


1




a


-


1




c,


a reflector antenna


10


for providing multiple antenna patterns


12


-


16


is illustrated. The reflector antenna


10


can be configured as a prime focus feed reflector, an offset reflector, a cassegrain reflector or the like. The reflector antenna


10


includes a reflector body


18


and an illumination source


20


. The reflector body


18


is comprised of a plurality of zones


22


-


26


with each zone


22


-


26


configured to be a frequency selective or polarization sensitive zone. The illumination source


20


is configured to illuminate the reflector body


18


with a plurality of RF signals depicted by the lines marked


28


-


32


with each RF signal


28


-


32


being of a preselected frequency or polarization. Each zone


22


-


26


is configured to selectively reflect, pass or absorb selected RF signals


28


-


32


having preselected frequencies or polarizations. Antenna patterns


12


-


16


are generated from each reflected RF signal


34


-


38


with the characteristics of each antenna pattern


12


-


16


, including the shape and beamwidth, being determined by the shape and dimensions of the zones


22


-


28


. The size and shape of each zone


22


-


28


is preselected so that antenna patterns


12


-


16


are generated having desired shapes and beamwidths. By configuring a single reflector body


18


to comprise one or more frequency selective or polarization sensitive zones


22


-


26


, a plurality of antenna patterns


12


-


16


, each being of a preselected shape and beamwidth, can be generated from a single reflector antenna


10


.




For one embodiment of the invention shown in FIGS.


2




a


-


2




c,


the reflector body


40


is comprised of three concentric zones


42


-


46


. The first zone


42


is configured to reflect RF signals having frequencies of f


1


-f


3


; the second zone


44


is configured to reflect RF signals having frequencies f


2


and f


3


and pass RF signals having a frequency of f


1


. The third zone


46


is configured to reflect RF signals having frequencies of f


3


and pass RF signals having frequencies of f


1


and f


2


. The illumination source


48


is configured to generate three RF signals depicted by the lines marked


50


-


54


where each RF signal


50


-


54


is of a different frequency f


1


-f


3


respectively.




The first RF signal


50


is incident on the reflector body


40


with the portion of the first RF signal


50


which is incident upon the first zone


42


being reflected by the first zone


42


. However, the portion of the first RF signal


50


which is incident on the second


44


and third


46


zones is not reflected and pass through the second


44


and third


46


zones. Thus, only the first zone


42


reflects the first RF signal


50


to provide a first reflected signal


56


which will form a first antenna pattern


58


having characteristics including shape and beamwidth which are substantially determined by the shape and dimensions of only the first zone


42


. The shape and dimensions of the first zone


42


is thus preselected to provide a first antenna pattern


58


having predetermined pattern characteristics such as shape and beamwidth.




The first zone


42


is preferably formed of a light weight core


60


fabricated from a material such as Graphite, Kevlar™, Nomex™, aluminum honeycomb, or the like which are all commercially available materials with Kevlar™ being fabricated by Hexcel Corporation located in Huntington Beach, Calif. and Nomex™ being fabricated by Hexcel Corporation located in Huntington Beach, Calif. A highly reflective coating


62


such as aluminum is typically applied to the top surface


64


of the light weight core


60


preferably by a vapor deposition or sputtering process to provide a surface which is highly reflective to RF signals


50


-


54


of a plurality of frequencies. A more detailed description of processes such as vapor deposition or sputtering used to apply materials can be found in Microelectronic Processing and Device Design, by Roy A Colclaser, 1980.




The second RF signal


52


is incident on the reflector body


40


with the portion of the second RF signal


52


which is incident upon the first


42


and second


44


zones being reflected


66


by the first


42


and second


44


zones. However, the portion of the second RF signal


52


which is incident on the third


46


zone is not reflected and passes through the third


46


zone. Thus, only the first


42


and second


44


zones reflect the second RF signal


52


to provide a second reflected signal


66


which will form a second antenna pattern


68


having characteristics which are substantially determined by the shape and dimensions of both the first


42


and second


44


zones combined.




The third RF signal


54


is incident on the reflector body


40


and is reflected


70


by the all three zones


50


-


54


. A third antenna pattern


72


is generated from the third reflected RF signal


70


with characteristics associated with the dimensions of all three zones


42


-


46


combined.




Each frequency selective zone


44


&


46


is typically comprised of a patterned metallic top layer


74


or


76


over a dielectric core


78


or


80


respectively. The dielectric cores


78


and


80


are fabricated of materials such as Kevlar™, Nomex™, Ceramic Foam, Rohacell foam™ or the like which are commercially available materials known in the art to pass RF signals with Rohacell foam™ being fabricated by Richmond Corporation located in Norwalk, Calif. For simplicity in manufacturing, all three cores


60


,


78


and


80


are typically fabricated of the same materials. To produce the patterned metallic top layers


74


and


76


, a metallic top layer is first applied to the dielectric cores


78


and


80


using a vapor depositing or sputtering process and portions of the metallic top layer are removed by an etching technique thereby forming the patterned metallic top layers


78


and


80


. A more detailed discussion of vapor depositing, sputtering and etching processes can be found in the reference cited above. Alternatively, the patterned top layers


74


and


76


can be formed on separate sheets of material and then bonded to the cores


78


and


80


respectively. The patterned layers


74


and


76


typically include crosses, squares, circles, “Y's” or the like with the exact design and dimensions of the patterned top layers


74


and


76


being determined by experimental data coupled with design equations and computer analysis tools such as those found in the book Frequency Selective Surface and Grid Array, by T. K. Wu, published by John Wiley and Sons, Inc. The design and dimensions of the first patterned top layer


74


covering the second core


78


is selected to reflect RF signals having frequencies f


2


and f


3


and pass RF signals having a frequency of f


1


, whereas, the patterned top layer


76


covering the third core


80


is selected to reflect RF signals having a frequency of f


3


and pass RF signals having frequencies f


1


& f


2


.




For example, referring to FIGS.


2




a,




2




b,


and


3




a,




3




b


and


3




c,


the first patterned metallic top layer


74


could consist of a plurality of singular circular loops


81


each of which having a diameter of D


1


and a width of W


1


. Alternatively, the first patterned metallic top layer


74


could consist of a plurality of nested circular loops


82


where each nested circular loop


82


is comprised of an inner loop


83


and an outer loop


84


. Each inner loop


83


has a diameter D


2


and a width W


2


, and, each outer loop


84


has a diameter D


3


and width W


3


where D


2


<D


3


and W


2


<W


3


. Both the singular circular loops


81


and the nested circular loops


82


will pass RF signals having a frequency of 44 GHz and reflect RF signals having frequencies of 29 and 30 GHz. Nested circular loops


82


are preferred for embodiments which pass and reflect RF signals which are closely spaced in frequency.




The second metallic top layer


76


could also consist of a plurality of nested circular loops


85


where each nested circular loop


85


is comprised of an inner loop


86


and an outer loop


87


. Each inner loop


86


has a diameter D


4


and a width W


4


, and, each outer loop


87


has a diameter D


5


and width W


5


where D


4


<D


5


and W


4


<W


5


. These nested circular loops


85


will pass RF signals having frequencies of 30 and 44 GHz but will reflect RF signals having a frequency of 20 GHz.




Alternatively, frequency selective zones


44


&


46


can be fabricated from RF absorbing materials which absorb RF signals of preselected frequencies and reflect RF signals of other preselected frequencies. One such material is a carbon loaded urethane material manufactured by The Lockheed-Martin Corporation located in Sunnyvale Calif.




For the embodiment of the invention shown in FIGS.


4




a


-


4




d,


the reflector antenna


86


is comprised of an offset reflector body


88


having four zones


90


-


96


with each zone


90


-


96


configured to pass or reflect RF signals, depicted by the lines marked


98


-


104


of preselected frequencies f


1


-f


4


. The illumination source


106


is comprised of four feed horns


108


-


114


with each feed horn


108


-


114


generating one of the RF signals


98


-


104


respectively. The first zone


90


is configured to be reflective to RF signals of all frequencies such that all four RF signals


98


-


104


are reflected


116


-


122


by the first zone


90


. The second zone


92


is configured to be reflective to RF signals


100


-


104


having frequencies of f


2


-f


4


and pass RF signals


98


having a frequency of f


1


such that the second


100


through fourth


104


RF signals are reflected


118


-


122


by the second zone


92


and the first RF signal


98


passes through the second zone


92


. The third zone


94


is configured to be reflective to RF signals


102


and


104


having frequencies of f


3


& f


4


and pass RF signals


98


and


100


having frequencies of f


1


& f


2


such that the third


102


and fourth


104


RF signals are reflected


120


and


122


by the third zone


94


and the first


98


and second


100


RF signals pass through the third zone


94


. The fourth zone


96


is configured to reflect an RF signal


104


having a frequency of f


4


and pass RF signals


98


-


102


having frequencies of f


1


-f


3


such that the fourth


104


RF signal is reflected


122


by all from zones


90


-


96


.




The dimensions of each zone


90


-


96


determines the characteristics of the antenna patterns


124


-


130


generated therefrom. FIGS.


4




c


and


4




d


shows the principal plane cuts of the antenna patterns generated by the antenna


86


in the x and y planes (FIG.


4




a


) respectively. The first


90


and third


94


zones are configured in elliptical shapes, and, the second


92


and fourth


96


zones are configured in circular shapes. Thus, the antenna patterns


130


and


126


generated from the first


116


and third


120


reflected signals will have elliptical pattern shapes and the antenna patterns


128


and


124


generated from the second


118


and fourth


122


reflected signals will have circular pattern shapes. This embodiment of the invention generates four antenna patterns


124


-


130


from a single reflector antenna


86


with each antenna pattern having a predetermined shape and being of a different frequency f


1


-f


4


respectively.




Referring to FIGS.


5




a


-


5




c,


for a second embodiment of the invention, the first zone


132


reflects all RF signals, the second zone


134


is a polarization sensitive zone; and, the third zone


136


is both a frequency selective and polarization sensitive zone.




Polarization sensitive zones will pass RF signals having one sense of polarization and reflect orthogonally polarized signals. For example, a polarization sensitive zone will either pass horizontally polarized RF signals and reflect vertically polarized RF signals or pass vertically polarized RF signals and reflect horizontally polarized RF signals. Like the frequency selective zones described in the embodiments above, polarization sensitive zone are typically comprised of a patterned metallic top layer over a dielectric core. For horizontally or vertically polarized RF signals, the patterned top layer typically includes metallic parallel lines oriented such that an RF signal having one sense of polarization is passed through and an orthogonally polarized RF signal is reflected. Using polarization sensitive zones enables two oppositely polarized RF signals operating at the same frequency to be coupled in a single reflector with each reflected RF signal providing a separate antenna pattern having a desired shape and beamwidth.




For example, the first zone


132


is configured to reflect all RF signals. The second zone


134


is configured as a polarization sensitive zone


134


designed to reflect all vertically polarized RF signals regardless of the frequency. The third zone


136


is configured to be both a frequency selective and polarization sensitive zone


136


which is designed to reflect only vertically polarized RF signals having a frequency of f


2


.




The reflector


138


is illuminated by three RF signals, depicted by the lines marked


140


-


144


. The first RF signal


140


is at a first frequency f


1


and is horizontally polarized. This RF signal


140


will be reflected


146


by the first zone


132


but will pass through the second


134


and third


136


zones. A horizontally polarized antenna pattern


152


, having a frequency of f


1


, and having characteristics determined by the dimensions of the first zone


132


will be generated from the first reflected signal


146


.




The second RF signal


142


is also at a frequency of f


1


but is vertically polarized. This second RF signal


142


will be reflected


148


by both the first


132


and second


134


zones but will pass through the third zone


136


. A vertically polarized antenna pattern


154


, having a frequency of f


1


, and having characteristics determined by the characteristics of both the first


132


and second


134


zones will be generated from the second reflected signal


148


.




The third RF signal


144


is also vertically polarized but is at a different frequency f


2


. The third zone


136


is both a frequency selective and a polarization sensitive zone


136


configured to pass all horizontally polarized RF signals regardless of frequency but reflect vertically polarized RF signals of a frequency f


2


. The third RF signal


144


will be reflected


150


by all three zones


132


-


136


. A vertically polarized antenna pattern


156


, having a frequency of f


2


, and having characteristics determined by the characteristics of the entire reflector


138


will be generated from the third reflected signal


150


.




For the embodiment of the invention shown in FIGS.


6




a


-


6




c,


the reflector antenna


158


generates two antenna patterns


160


and


162


each having approximately the same shape and beamwidth with the first antenna pattern


160


being at a frequency of approximately 20 GHz and the second antenna pattern


162


being at a frequency of approximately 30 GHz. The reflector antenna


158


includes an illumination source


164


and a reflector body


166


. The illumination source


164


is configured to illuminate the reflector body


166


with two RF signals, depicted by the lines marked


168


and


170


. The first


168


and second


170


RF signals have frequencies of 20 &




30




GHz respectively. The first zone


172


of the reflector body


166


is configured to be reflective to RF signals having frequencies of 20 and 30 GHz and the second zone


174


is a frequency selective zone


174


which is configured to be reflective to RF signals having a frequency of 20 GHz and pass RF signals having a frequency of 30 GHz signal. The first


172


and second


174


zones of the reflector body


166


are dimensioned to generate antenna patterns


160


and


162


having equal beamwidths at frequencies of 20 and 30 GHz respectively. Since the beamwidth of an antenna pattern


160


and


162


is inversely proportional to both the frequency and the diameter d


1


or d


2


of the reflective zones


172


and


174


, generating the antenna pattern


160


and


162


respectively, to generate antenna patterns at both 20 and 30 GHz which have the same beamwidth, the diameter d


1


of the first zone


172


should be approximately two thirds the diameter d


2


of the second zone


174


.




Referring to FIGS.


7




a


-


7




c,


the present invention is not limited to antenna reflectors having concentric zones but may be implemented with a reflector body


176


having a plurality of zones


178


-


184


located within the reflector body


176


, with each zone


178


-


184


being of a preselected shape and dimension. For this embodiment, the illumination source


186


is configured to generate three RF signals, depicted by the lines marked


188


-


192


. The first and second zones


178


and


180


are configured to reflect the first RF signal


188


generating a first antenna pattern


194


therefrom whereas the third


182


and fourth


184


zones are configured to pass the first RF signal


188


. The second


180


and third


182


zones are configured to reflect the second RF signal


190


generating a second antenna pattern


196


therefrom whereas the first


178


and fourth


184


zones are configured to pass the second RF signal


190


. All four zones


178


-


184


are configured to reflect the third RF signal


192


and generate a third antenna pattern


198


therefrom.




The portions of the first


188


and second


190


RF signals which pass through zones


178


-


184


of the reflector body


176


can create problems in other electronic components (not shown) being in a close proximity to the reflector body


176


. RF absorbing material


200


can be attached to the bottom side


202


of the reflector body


176


and absorb the passed through RF signals


188


-


190


.




It is typically desirable for the antenna patterns


196


-


198


generated from a reflector body


176


to have low sidelobe levels


204


-


208


. To do so, a ring of resistive material


210


, such as R-card™ manufactured by Southwall Technologies Corporation located in Palo Alto, Calif. can be coupled to the reflector body


176


. Analysis has shown that the sidelobe levels


204


-


208


of an antenna pattern


194


-


198


generated by a reflector body


176


is decreased when resistive material


210


is coupled to the edge of a reflector body


176


.




The present invention utilizes a preselected plurality of frequency selective and/or polarization sensitive zones to provide multiple antenna patterns from a single reflector antenna. By configuring each zone to a preselected shape and dimension, the present invention generates a plurality of antenna patterns from a single reflector body with each antenna pattern having a desired shape and beamwidth. In this manner, a single reflector can replace multiple reflector antennas saving weight, cost and real estate.




It will be appreciated by persons skilled in the art that the present invention is not limited to what has been shown and described hereinabove. The scope of the invention is limited solely by the claims which follow.



Claims
  • 1. An antenna for providing multiple antenna patterns from a plurality of RF illumination signals having differing electrical characteristics from a single reflector antenna comprising:a concave reflector body formed of a plurality of zones, each of the zones is configured to reflect a portion of one of the RF illumination signals and a first of which is configured to be non-reflective to one of the RF illumination signals having a different electrical characteristic than the electrical characteristic of the RF illumination signal reflected by the first zone, at least one of said zones is both a frequency selective and a polarization sensitive zone; an illumination source configured to illuminate said reflector body with the plurality of RF signals; and absorbing material coupled to said reflector body and operative to absorb a non-reflected portion of one of said RF illumination signals, each of said zones reflecting one of the RF illumination signals, each reflected RF signal generating one of the plurality of antenna patterns.
  • 2. An antenna in accordance with claim 1, wherein said non-reflective zone is formed of a dielectric core coupled to a patterned metallic top layer configured to reflect preselected RF signals and pass other preselected RF signals.
  • 3. An antenna in accordance with claim 1, wherein said absorbing material is coupled to a bottom side of said first zone and is configured to absorb said one non-reflected RF signal having a different electrical characteristic than the electrical characteristic of the RF illumination signal reflected by the first zone.
  • 4. An antenna in accordance with claim 1, wherein each said zone has a predetermined shape and said antenna patterns are generated by one or more zones.
  • 5. An antenna in accordance with claim 1,wherein said plurality of RF signals comprise a first RF signal having a frequency of 20 GHz and a second RF signal having a frequency of 30 GHz,said plurality of zones comprising a first zone configured to reflect signals having frequencies of 20 and 30 GHz and a second zone being of a frequency selective material configured to reflect RF signals having frequencies of 20 GHz and pass RF signals having frequencies of 30 GHz, said second RF signal being reflected from said first zone and passing through said second zone, said first RF signal being reflected by both said first and said second zones, first and second antenna patterns being generated from said first and second reflected RF signals, said first and second zones being concentric and dimensioned such that said first and second antenna patterns have approximately similar shapes and beamwidths.
  • 6. An antenna for providing multiple antenna patterns from a plurality of RF illumination signals having a plurality frequency and polarization characteristics from a single reflector antenna comprising:an illumination source configured to illuminate said reflector body with the plurality of RF signals; a concave reflector body formed of a plurality of zones, each of which is configured to reflect a portion of one of the RF illumination signals, a first of which is configured to be non-reflective to one of the RF illumination signals having a different polarization characteristic than the RF illumination signal reflected by the first zone, a second of which is configured to be non-reflective to one of the RF illumination signals having a different frequency characteristic than the RF illumination signal reflected by the second zone, each reflected RF signal generating one of the plurality of antenna patterns.
  • 7. An antenna in accordance with claim 6, wherein said illumination source is a single feed horn.
  • 8. An antenna in accordance with claim 6, wherein said first zone is a first frequency selective zone configured to pass RF signals of a first frequency and reflect RF signals of a second frequency, one of said RF signals being at said second frequency and one of said RF signals being at said first frequency.
  • 9. An antenna in accordance with claim 8, wherein said second zone is a polarization sensitive zone configured to reflect RF signals having a first sense of polarization and pass RF signals having a second sense of polarization, one of said RF signals having said first sense of polarization, another one of said RF signals having said second sense of polarization.
  • 10. An antenna in accordance with claim 9, wherein said first sense of polarization is approximately orthogonal to said second sense of polarization.
  • 11. An antenna in accordance with claim 6, where said first zone is encompassed by said second zone.
  • 12. An antenna in accordance with claim 6, wherein said plurality of zones are configured concentrically creating an innermost zone and a plurality of successive zones, each said successive zone encompassing a previous zone, said innermost zone being configured to reflect all said RF signals and each successive zone being configured to reflect less RF signals than said innermost zone.
  • 13. An antenna in accordance with claim 12, wherein said innermost zone generates a first antenna pattern and each successive zone together with previous zones generate additional antenna patterns.
  • 14. An antenna in accordance with claim 6, wherein each of said antenna patterns has antenna pattern characteristics comprising beamwidth and shape, each zone being configured to preselected dimensions such that said plurality of antenna patterns are generated having preselected shapes and beamwidths.
  • 15. An antenna in accordance with claim 14, wherein each said zone is configured to preselected dimensions such that said plurality of antenna patterns have approximately equivalent shapes and beamwidths.
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Entry
Lee, et al., “Compound Reflector Antennas,” published in the IEEE Proceedings on Antennas and Propagation, Apr. 1992, pp. 135-138.