CA2125602A1 - Broadband omnidirectional microwave antenna - Google Patents
Broadband omnidirectional microwave antennaInfo
- Publication number
- CA2125602A1 CA2125602A1 CA 2125602 CA2125602A CA2125602A1 CA 2125602 A1 CA2125602 A1 CA 2125602A1 CA 2125602 CA2125602 CA 2125602 CA 2125602 A CA2125602 A CA 2125602A CA 2125602 A1 CA2125602 A1 CA 2125602A1
- Authority
- CA
- Canada
- Prior art keywords
- axis
- cone
- antenna
- parabolic curve
- feed device
- 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.)
- Abandoned
Links
- 230000005855 radiation Effects 0.000 claims description 5
- 230000010287 polarization Effects 0.000 description 5
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000001902 propagating effect Effects 0.000 description 2
- 238000003491 array Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
Classifications
-
- 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
- H01Q19/13—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 being a single radiating element, e.g. a dipole, a slot, a waveguide termination
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
- H01Q17/001—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems for modifying the directional characteristic of an aerial
-
- 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
- H01Q19/18—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 having two or more spaced reflecting surfaces
- H01Q19/19—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 having two or more spaced reflecting surfaces comprising one main concave reflecting surface associated with an auxiliary reflecting surface
Landscapes
- Aerials With Secondary Devices (AREA)
Abstract
ABSTRACT
An omnidirectional microwave antenna comprising a conical reflector with a surface of revolution defined by a segment of a parabolic curve rotated around the axis of the cone, and a feed device located on the axis of the cone and spaced away from the apex of the cone.
An omnidirectional microwave antenna comprising a conical reflector with a surface of revolution defined by a segment of a parabolic curve rotated around the axis of the cone, and a feed device located on the axis of the cone and spaced away from the apex of the cone.
Description
~ . 2125~2 BROADBANI) OMNIDIRECTIONAL M[ICROWA~E ANT~A
Field ()f The Invention The present invention relates to ornnidirectional microwave antennas and, more particularly, to omnidirectional microwave antennas which are capable of operating over relatively broad frequency bands and at relatively high power levels S and at high frequencies.
Background Of The Invention There are a number of new microwave distribution systems under development using fre~uencies above 10000 MHz. Multi-channel or interactive television would use the 27500 29500 MHz frequency range, while some wireless cable operators are opting for the 12 GHz CARS band. This activity has prompted a strong interest in base station antennas (similar to the broadcast television ~mtennas).
The antennas need to operate over a fairly wide bandwidth with a moderate to high power input. The azimuth coverage requirement, in most cases, is omnidirectional.
The polanzation may be either horizontal or vertical.
Omnidirectional antennas are traditionally arrays of basic radiating elements such as slots or dipoles. However the requirement for broad band operation is not compatible with linear array technology. The problem is further complicated by the relatively high power requirements (up to 2 Kw) at these high fre~uencies.
Summary Of The Invention It is a primary object of the present invention to provide an improved omnidirectional antenna which is a reflector-type antenna capable of operating ~ver a wide frequency band, at relatively high power levels, and at high frequencies.
Specifically, it is an object of this invention to provide such an antenna whlch is capable of operating at frequencies above 10 GHz, including the 7.5 to 29.5 &Hz band, and at power levels as high as 2 Kw.
It is another object of this invention to provide such an improved omnidirectional antenna which can transmit and receive signals having either horizontal or vertical polarization.
A still further object of this invention is to provide such an improved omnidirectional antenna which permits field-adjustable beam tilt by simply moving the feed along the axis of the antenna.
2125~2 A further object of this invention is to provide such an improved omnidirectional antenna which produces a pattern shape that remains stable as the frequency changes.
Yet another object of this invention is to provide such an improved -omnidirectional antenna which facilitates the achievement of a shaped elevation beam, which is stable with frequency, and requires only a slight change in the reflector shape.
Other objects and advantages of the invention will be apparent from the ~ollowing detailed description and the accompanying drawingsO
In accordance with the present invention, the foregoing objectives are realized by providing an omnidirectional microwave antenna comprising a conical reflectorhaving a surface of revolution defined by a segment of a parabolic curve rota~edaround the axis of the cone, and a feed device located on the axis of the cone and spaced away from the apex of the cone. The feed device may be either a feed hornor a subreflector facing the apex of the cone and located approximately at the focal point of the parabolic curve.
Brief Description Of The Drawin~s is FIG. 1 a diagrammatic vertical section taken across a diameter of th reflector of an antenna embodying the present invention; and FIG. 2 is a vertical section taken through a diameter of the reflector of a modified embodiment of the invention.
Detailed DescriptioD (;3f The Preferred Embodiments While the invention is susceptible to various modifications and altemative forms, a specific embodiment thereof has been shown by way of example in the drawings and will be descAbed in detail herein. It should be understood, however, ~hat it is not intended to limit the invention to the par~icular form described9 but, on the contrary, the intention is to cover all modifications, equivalents, and alte~natives falling within the spirit and scope of the invention as defined by the appended claims.
Turning now to the drawings and referring first to FIG. 1, a feed horn 10 3û feeds mierowave energy to a conical rsflector 11. The feed hom 10 has a circular transverse cross section, and is dimensioned to radiate energy in either the 1~01 mode or the ll~ol mode. The horn is located on ~he vertical axis 12 of the conical ~ 2 1 2 5 fi .~ 2 reflector 11 and radiates microwave energy upwardly so that it illuminates the conical reflecting surface and is reflected horizontally therefrom in an omnidirectional pattern (extending 360 degrees around the axis of the reflector). (The term ~feed" as used herein, although having an apparent implication of use in a transmitting mode, will be S understood to encompass use in a receiving mode as well, as is conventional in the art.) The conical refleeting surface 11 defines a surface of revolution formed by rotating a segment A-B of a parabolic curve P around an axis Z which (1) is perpendicular to the axis X of the parabolic curve P, and (2) passes through the focal point ~7 of the parabolic curve P. The axis of the feed horn 10 is coincident with the axis Z of the conical reflecting surface 11, and the phase center of the feed horn is coincident with the focal point F of the parabolic curve P. The segment A-B of the parabolic curve P that defines the reflecting surface 11 is the segment between (1) the point A at which the feed horn axis Z intersects the parabolic cuNe P, and (2) the point B at which the outer edge of the radiation pattern produced by the horn 11intersects the parabolic curve P.
The axis X exeends through the vertex and the foc~l point of the parabolic curve P. As is well known, any microwaves originating at the focal point of such a parabolic surface will be re~lected by the parabolic surface in planar waYefronts~ ~ :
perpendicular to the axis, i.e., in the horizontal direction in FIG. 1. ~ -With the geometry described above, the conical reflecting surface 11 serves as both a 90 omnidirectional reflector and a phase corrector for the diverging sphencal wave radiated by the feed horn 10. The spherical wave propagates vertically fromthe feed horn 10 and is reflected off the surface 11 as a planar wave propagating in a horizontal direction. This planar wave is propagated omnidirectionally, i.e., the pattern that extends completely around (360) the axis Z. At any given azimuthallocation, ~he parabolic shape of the reflecting surface 11 provides th~ desired phase correction. The height H of the parabolic segment A-B deterrnines the directivi~ of the antenna in the "elevation" plane.
The mode of the radiation from the feed horn 10 determines the polarization of the antenna's omnidirectional pattem. Specifically, if the horn 10 radiates ~Mol-mode energy) the polarization is vertical; and if the horn radiates TE0l-mode energy, ~, , 212~fi~2 the polarization is horizontal. Thus, by merely changing the feed bvrn to launchsignals in either the TMol mode or the TEol mode, the same antenna may be used to transmit or receive either polarization.
FIG. 2 llustrates a modified embodiment of the invention in which the feed 5 device for a conical reflecting surface 20 comprises a primary feed horn 21 connected to and supporte~ by a circular waveguide 22 extending along the axis of the reflector 209 and a subreflec~or 23. The conical reflecting surface 20 is still a surface of revolution formed by a segment A-B of a parabolic curve, but in this case the ape~ of ~ -the cone is at the top and is truncated to accommodate the feed horn 21. In the 10 transmitting mode, the feed horn 21 receives microwave signals via the circular waveguide 22 and launches those signals onto the subreflector 23. The spherical wave launched upwardly from the feed horn 21 is reflected ~rom the subreflector 23 as a downwardly propagating spherical wave which impinges on the conical reflector 20. The reflector 20 then reflects the wave horizontally as a planar wave, in an -15 omnidirectional pattern extending 360 around the axis Z.
The subreflector 23, which may be supported on a radome 24, preferably has a convex hyperbolic shape and is positioned so that ;ts virtual focal point is coincident with the phase center of the feed horn and its real focal point is coincident with the virtua} ~ocal point of the parabolic curve that defines the shape of the 20 segment A-B of the main reflector. Ihe subreflector 23 is positioned and dimensioned to intercept a large portion of the radiation launched from the feed horn 21 in the transmitting mode, and an equally large portion of the incoming radiation reflected by the main reflector 20 in the receiving mode. Other surfaces of revolution of conic sections that can be employed are ellipsoids and paraboloids, and 25 conc~Ye as well as conve~ subreflectors may be employed. If desired, the subreflector may even include two or more different geometrics in concentric regions of the subreflector.
Field ()f The Invention The present invention relates to ornnidirectional microwave antennas and, more particularly, to omnidirectional microwave antennas which are capable of operating over relatively broad frequency bands and at relatively high power levels S and at high frequencies.
Background Of The Invention There are a number of new microwave distribution systems under development using fre~uencies above 10000 MHz. Multi-channel or interactive television would use the 27500 29500 MHz frequency range, while some wireless cable operators are opting for the 12 GHz CARS band. This activity has prompted a strong interest in base station antennas (similar to the broadcast television ~mtennas).
The antennas need to operate over a fairly wide bandwidth with a moderate to high power input. The azimuth coverage requirement, in most cases, is omnidirectional.
The polanzation may be either horizontal or vertical.
Omnidirectional antennas are traditionally arrays of basic radiating elements such as slots or dipoles. However the requirement for broad band operation is not compatible with linear array technology. The problem is further complicated by the relatively high power requirements (up to 2 Kw) at these high fre~uencies.
Summary Of The Invention It is a primary object of the present invention to provide an improved omnidirectional antenna which is a reflector-type antenna capable of operating ~ver a wide frequency band, at relatively high power levels, and at high frequencies.
Specifically, it is an object of this invention to provide such an antenna whlch is capable of operating at frequencies above 10 GHz, including the 7.5 to 29.5 &Hz band, and at power levels as high as 2 Kw.
It is another object of this invention to provide such an improved omnidirectional antenna which can transmit and receive signals having either horizontal or vertical polarization.
A still further object of this invention is to provide such an improved omnidirectional antenna which permits field-adjustable beam tilt by simply moving the feed along the axis of the antenna.
2125~2 A further object of this invention is to provide such an improved omnidirectional antenna which produces a pattern shape that remains stable as the frequency changes.
Yet another object of this invention is to provide such an improved -omnidirectional antenna which facilitates the achievement of a shaped elevation beam, which is stable with frequency, and requires only a slight change in the reflector shape.
Other objects and advantages of the invention will be apparent from the ~ollowing detailed description and the accompanying drawingsO
In accordance with the present invention, the foregoing objectives are realized by providing an omnidirectional microwave antenna comprising a conical reflectorhaving a surface of revolution defined by a segment of a parabolic curve rota~edaround the axis of the cone, and a feed device located on the axis of the cone and spaced away from the apex of the cone. The feed device may be either a feed hornor a subreflector facing the apex of the cone and located approximately at the focal point of the parabolic curve.
Brief Description Of The Drawin~s is FIG. 1 a diagrammatic vertical section taken across a diameter of th reflector of an antenna embodying the present invention; and FIG. 2 is a vertical section taken through a diameter of the reflector of a modified embodiment of the invention.
Detailed DescriptioD (;3f The Preferred Embodiments While the invention is susceptible to various modifications and altemative forms, a specific embodiment thereof has been shown by way of example in the drawings and will be descAbed in detail herein. It should be understood, however, ~hat it is not intended to limit the invention to the par~icular form described9 but, on the contrary, the intention is to cover all modifications, equivalents, and alte~natives falling within the spirit and scope of the invention as defined by the appended claims.
Turning now to the drawings and referring first to FIG. 1, a feed horn 10 3û feeds mierowave energy to a conical rsflector 11. The feed hom 10 has a circular transverse cross section, and is dimensioned to radiate energy in either the 1~01 mode or the ll~ol mode. The horn is located on ~he vertical axis 12 of the conical ~ 2 1 2 5 fi .~ 2 reflector 11 and radiates microwave energy upwardly so that it illuminates the conical reflecting surface and is reflected horizontally therefrom in an omnidirectional pattern (extending 360 degrees around the axis of the reflector). (The term ~feed" as used herein, although having an apparent implication of use in a transmitting mode, will be S understood to encompass use in a receiving mode as well, as is conventional in the art.) The conical refleeting surface 11 defines a surface of revolution formed by rotating a segment A-B of a parabolic curve P around an axis Z which (1) is perpendicular to the axis X of the parabolic curve P, and (2) passes through the focal point ~7 of the parabolic curve P. The axis of the feed horn 10 is coincident with the axis Z of the conical reflecting surface 11, and the phase center of the feed horn is coincident with the focal point F of the parabolic curve P. The segment A-B of the parabolic curve P that defines the reflecting surface 11 is the segment between (1) the point A at which the feed horn axis Z intersects the parabolic cuNe P, and (2) the point B at which the outer edge of the radiation pattern produced by the horn 11intersects the parabolic curve P.
The axis X exeends through the vertex and the foc~l point of the parabolic curve P. As is well known, any microwaves originating at the focal point of such a parabolic surface will be re~lected by the parabolic surface in planar waYefronts~ ~ :
perpendicular to the axis, i.e., in the horizontal direction in FIG. 1. ~ -With the geometry described above, the conical reflecting surface 11 serves as both a 90 omnidirectional reflector and a phase corrector for the diverging sphencal wave radiated by the feed horn 10. The spherical wave propagates vertically fromthe feed horn 10 and is reflected off the surface 11 as a planar wave propagating in a horizontal direction. This planar wave is propagated omnidirectionally, i.e., the pattern that extends completely around (360) the axis Z. At any given azimuthallocation, ~he parabolic shape of the reflecting surface 11 provides th~ desired phase correction. The height H of the parabolic segment A-B deterrnines the directivi~ of the antenna in the "elevation" plane.
The mode of the radiation from the feed horn 10 determines the polarization of the antenna's omnidirectional pattem. Specifically, if the horn 10 radiates ~Mol-mode energy) the polarization is vertical; and if the horn radiates TE0l-mode energy, ~, , 212~fi~2 the polarization is horizontal. Thus, by merely changing the feed bvrn to launchsignals in either the TMol mode or the TEol mode, the same antenna may be used to transmit or receive either polarization.
FIG. 2 llustrates a modified embodiment of the invention in which the feed 5 device for a conical reflecting surface 20 comprises a primary feed horn 21 connected to and supporte~ by a circular waveguide 22 extending along the axis of the reflector 209 and a subreflec~or 23. The conical reflecting surface 20 is still a surface of revolution formed by a segment A-B of a parabolic curve, but in this case the ape~ of ~ -the cone is at the top and is truncated to accommodate the feed horn 21. In the 10 transmitting mode, the feed horn 21 receives microwave signals via the circular waveguide 22 and launches those signals onto the subreflector 23. The spherical wave launched upwardly from the feed horn 21 is reflected ~rom the subreflector 23 as a downwardly propagating spherical wave which impinges on the conical reflector 20. The reflector 20 then reflects the wave horizontally as a planar wave, in an -15 omnidirectional pattern extending 360 around the axis Z.
The subreflector 23, which may be supported on a radome 24, preferably has a convex hyperbolic shape and is positioned so that ;ts virtual focal point is coincident with the phase center of the feed horn and its real focal point is coincident with the virtua} ~ocal point of the parabolic curve that defines the shape of the 20 segment A-B of the main reflector. Ihe subreflector 23 is positioned and dimensioned to intercept a large portion of the radiation launched from the feed horn 21 in the transmitting mode, and an equally large portion of the incoming radiation reflected by the main reflector 20 in the receiving mode. Other surfaces of revolution of conic sections that can be employed are ellipsoids and paraboloids, and 25 conc~Ye as well as conve~ subreflectors may be employed. If desired, the subreflector may even include two or more different geometrics in concentric regions of the subreflector.
Claims (13)
1. An omnidirectional microwave antenna comprising a conical reflector having a surface of revolution defined by a segment of a parabolic curve rotated around the axis of said cone, and a feed device located on the axis of said cone and spaced away from the apex of said cone.
2. The antenna of claim 1 wherein the center of said feed device is positioned at the focal point of said parabolic curve, and the axis of said feed device is perpendicular to the axis of said parabolic curve.
3. The antenna of claim 1 wherein said feed device is a feed horn, and the center of the aperture of said feed horn is at the focal point of said parabolic curve.
4. The antenna of claim 1 wherein said segment of said parabolic curve is the segment between the axis of said feed device and the outer edge of the radiation pattern from said feed device.
5. The antenna of claim 1 wherein said feed device is a subreflector facing the apex of said cone, and the center of the reflecting surface of said subreflector is at the focal point of said parabolic curve.
6. The antenna of claim 5 wherein the axis of said cone is substantially vertical.
7. The antenna of claim 6 wherein said cone is inverted, and said feed device is a feed horn located below the apex of said cone and on the axis of said cone.
8. The antenna of claim 5 which includes a feed horn located within said conical reflector on the axis thereof.
9. The antenna of claim 8 wherein the axis of said cone is vertical with the apex of the cone at the top of said conical reflector, and said subreflector is positioned above said conical reflector.
10. An omnidirectional microwave antenna comprising a conical reflector having a reflecting surface defined by a cone having an axisand a surface of revolution around said axis, the line of intersection between said surface of revolution and a plane passing through said axis and said surface of revolution is a segment of a parabolic curve, and a feed device for feeding microwave energy to said conical reflector from a location on said axis and spaced from said conical reflector on the apex side of said cone.
11. A method of transmitting microwave signals comprising feeding said microwave signals to the reflecting surface of a conical reflector,said reflecting surface defining a surface of revolution formed by rotating a segment of a parabolic curve around an axis.
12. The antenna of claim 11 wherein said microwave signals are fed to said reflector in either the TM01 mode or the TE01 mode.
13. A reflector for use in a microwave antenna, said reflector forming a reflecting surface defining a surface of revolution formed by rotating a segment of a parabolic curve around an axis.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US11059093A | 1993-08-23 | 1993-08-23 | |
| US08/110,590 | 1993-08-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2125602A1 true CA2125602A1 (en) | 1995-02-24 |
Family
ID=22333859
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2125602 Abandoned CA2125602A1 (en) | 1993-08-23 | 1994-06-10 | Broadband omnidirectional microwave antenna |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2125602A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015047458A1 (en) * | 2013-09-24 | 2015-04-02 | Northrop Grumman Systems Corporation | Antenna for multiple frequency bands |
-
1994
- 1994-06-10 CA CA 2125602 patent/CA2125602A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015047458A1 (en) * | 2013-09-24 | 2015-04-02 | Northrop Grumman Systems Corporation | Antenna for multiple frequency bands |
| US9246234B2 (en) | 2013-09-24 | 2016-01-26 | Northrop Grumman Systems Corporation | Antenna for multiple frequency bands |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |