Reflector antenna with a self-supported feed

• US 6,137,449 A
• Filed: 08/19/1998
• Issued: 10/24/2000
• Est. Priority Date: 09/26/1996
• Status: Expired due to Term

• Current Assignee: Per-Simon Kildal
• Original Assignee: Per-Simon Kildal
• Inventors: Kildal, Per-Simon
• Primary Examiner(s): Ho, Tan
• Application Number:
  US09/136,332
• Time in Patent Office: 797 Days
• Field of Search: 343/781 CA, 343/781 R, 343/781 P, 343/785, 343/840, 343/786, 343/912, 343/771, 343/837, 343/872
• US Class Current: 343/781.00P
• CPC Class Codes: H01Q 1/42 Housings not intimately mechanically associated with radiating elements, e.g. radome
• CPC Class Codes: H01Q 15/147 provided with means for controlling or monitoring the shape of the reflecting surface for scanning H01Q3/01; aerials or aerial systems providing multiple beamwidths H01Q25/002
• CPC Class Codes: H01Q 19/134 Rear-feeds; Splash plate feeds
• CPC Class Codes: H01Q 19/193 with feed supported subreflector splash plate feeds H01Q19/134

Abstract

The invention consists of improvements of reflector antennas with self-supported feeds. The feed consists of a waveguide tube, a dielectric joint and a sub-reflector. The tube is attached to the center of the rotationally symmetric reflector and extends to the focal region of it. The sub-reflector is located in front of the tube, and the surface of this sub-reflector is provided with rotationally symmetric grooves also called corrugations. The improvements of the present invention are (1) a ring focus reflector to improve the gain of the antenna, (2) an elevated central region of the reflector to reduce the return loss, (3) metal screws or cylinders to strongly fasten the sub-reflector to the tube, (4) corrugations or other similar means around the rim or the reflector in order to reduce far-out sidelobes, (5) dual-band operation by means of a coaxial waveguide outside the circular waveguide in the tube, and (6) dielectric filling or covering of the corrugations or of the region between the corrugations and the waveguide tube end, both in order to avoid the gathering of water, dust or other undesired material in this area which could destroy the performance of the antenna.

Claims

1. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, said main reflector having an axis of symmetry, the improvement comprising:

the main reflector which is shaped as a ring focus paraboloid according to the formula ##EQU3## with z the axial coordinate measured along the symmetry axis, ρ

the radius coordinate measured from the axis, F the focal length of the reflector, and ρ

_O the radius of the ring focus, where the ring focus radius is typically between 0.5 times and 1.5 times the radius of said tube, depending on the dimensions of said sub-reflector and said joint, where the main reflector deviates from the ring focus paraboloid formula due to finite tolerances and different design methods by up to an RMS value of about 0.02 wavelengths, and where the reflector is used together with different tubes and sub-reflectors designed for different frequency bands, in which the ring focus paraboloid formula is valid with the above limitations in at least one of the frequency bands.

2. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector, having a ring focus shape a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

an elevated region in the center of said main reflector around said tube, where said elevated region has a constant height over the ring focus main reflector shape, where in the height of the elevated region has a maximum of between 0.1 and 0.25 wavelengths over the ring focus shaped main reflector, and has a diameter of between 1.9 and 7 wavelengths dependent on the frequency and the focal length of the reflector.

3. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector, having a ring focus shape a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

a dielectric plate in said main reflector around said tube, where the plate has a constant height over the ring focus main reflector shape where in the height of the plate has a maximum over the ring focus main reflector shape which provides a phase delay of between 70 and 180 degrees compared to when the dielectric plate is not present, and where the diameter is between 1.9 and 7 wavelengths, depending on the frequency and the focal length of the reflector.

4. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

fastening means for creating a strong metal connection between said sub-reflector and said tube being located in a plane through the center axis of said tube and said sub-reflector and on opposite sides of this axis.

5. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector having a rim around its outer perimeter, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

one or more air-filled or dielectric-filled grooves, located in or around the rim of said main reflector, where the depth of these grooves are between 0.25 and 0.5 wavelengths of the material inside the groove.

6. In an antenna system, as defined in claim 5 wherein the air filled grooves are located in the rim of said main reflector.

7. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector having a rim around its outer perimeter, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

one or more open-ended dielectric rings which are metalized on the outermost side in such a way that they form coaxial layers of dielectric material and metal, located around the rim of said main reflector, where the depth of the open-ended dielectric-filled coaxial waveguides formed by the dielectric layers are typically between 0.5 and 0.75 wavelengths of the dielectric material.

8. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

a cylinder, said cylinder comprising said tube and said waveguide, and having a constant thickness along its length, said cylinder being fastened to the main reflector.

9. The antenna system as defined in claim 8, further including a support plate fastened between the cylinder and the main reflector.

10. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

an inner cylindrical tube located inside said waveguide tube such that a coaxial waveguide is formed between the outer wall of said inner tube and the inner wall of said waveguide tube, and where the dielectric joint contains metal parts which are connected to said inner tube.

11. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

the main reflector has a paraboloidal shape and includes an elevated region in the center of said main reflector around said tube, said elevated region has a constant height above the surface of the main reflector, the elevated region has a maximum height of between 0.1 and 0.25 wavelengths, and has a diameter between 1.9 and 7 wavelengths depending upon the frequency and focal length of the reflector.

12. In antenna system as defined in claim 11, wherein the elevated region is formed by a dielectric plate.

13. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

an elevated region in the center of said main reflector around said tube, said elevated region has a height which tapers off gradually from a maximum near the tube to zero at a radial distance from the tube, and wherein the maximum height of the elevated region is between 0.1 and 0.25 wavelengths and the diameter at the point where the height is reduced to 0.37 of its maximum value is between 1.9 and 7 wavelengths, depending upon the frequency and the focal length of the reflector.

14. In an antenna system as defined in claim 13, wherein the main reflector has a paraboloidal shape.

15. In an antenna system as defined in claim 13, wherein the main reflector has a ring focus shape.

16. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, said main reflector having an axis of symmetry, the improvement comprising:

the main reflector has a paraboloidal shape and includes an elevated region in the center of said main reflector around said tube, said elevated region has a flat planar surface which is perpendicular to the axis of symmetry of the main reflector, the flat elevated region has a maximum height of between 0.1 and 0.25 wavelengths and has a diameter between 1.9 and 7 wavelengths depending upon the frequency and the focal length of the reflector.

17. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, said main reflector having an axis of symmetry, the improvement comprising:

an elevated region in the center of said main reflector around said tube, a dielectric plate forms the elevated region in the center of said main reflector around said tube, said dielectric plate tapers off gradually from a maximum height near the tube to 0 at a radial distance away from the tube, and where the maximum height of the plate provides a phase delay in the associated electromagnetic waves between 70 and 180 degrees compared to when the dielectric plate is not present, and the diameter at the point where the height is reduced to 0.37 of its maximum value is between 1.9 and 7 wavelengths, depending upon the frequency and the focal length of the reflector.

18. In an antenna system as defined in claim 17, wherein the main reflector has a paraboloidal shape.

19. In an antenna system as defined in claim 17, wherein the main reflectors has a ring focus shape.

20. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

an elevated region in the center of said main reflector around said tube, said elevated region has a constant height above the surface of the main reflector, the elevated region having a maximum height of between 0.1 and 0.25 wavelengths and has a diameter between 1.9 and 7 wavelengths depending upon the frequency and the focal length of the reflector.

21. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector having a rim around its outer perimeter, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

one or more dielectric rings are provided having metalized outer and bottom surfaces, said dielectric rings effectively forming a dielectric-filled groove located around the rim of said main reflector, where the depth of these grooves are between 0.25 and 0.5 wavelengths of the material inside the grooves.

22. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector having a rim around its outer perimeter, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

one or more dielectric rings are provided having metalized outer surfaces and being located around the rim of said main reflector, the width of the rings when measured in the axial direction of the reflector are between 0.50 and 0.75 wavelengths of the material inside the grooves.

23. In an antenna system, as defined in claim 22 wherein the dielectric-filled grooves are located in the rim of said main reflector.

24. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector having a rim around its outer perimeter, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

a plurality of dielectric rings having metal film positioned between the rings so as to form coaxial layers of dielectric material and metal, and said dielectric rings are located around the rim of said main reflector.

25. In an antenna system as defined in claim 24 wherein the dielectric rings are located in the rim of said main reflector.

26. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector having a rim around its outer perimeter, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, said main reflector having an axis of symmetry, the improvement comprising:

the main reflector includes an elevated region in the center of said main reflector around said tube, said elevated region has a flat planar surface which is perpendicular to the axis of symmetry of the main reflector, the flat elevated region has a maximum height of between 0.1 and 0.25 wavelengths and has a diameter between 1.9 and 7 wavelengths depending upon the frequency and the focal length of the reflector.

27. In an antenna system as described in claim 26, wherein the main reflector has a ring focus shape.

28. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

an elevated region in the center of said main reflector around said tube, said elevated region being formed by a dielectric plate, said dielectric plate having a constant height above the surface of the main reflector, said dielectric plate having a maximum height of between 0.1 and 0.25 wavelengths and having a diameter between 1.9 and 7 wavelengths depending upon the frequency and the focal length of the reflector.

29. In an antenna system as defined in claim 28, wherein the main reflector has a ring focus shape.

30. In an antenna system as defined in claim 28, wherein the main reflector has a paraboloidal shape.

31. In an antenna system, a reflector and a feed element for radiating or intercepting electromagnetic waves, constructed with a main reflector having a rim around its outer perimeter, a waveguide inside a tube having a first end and a second end, said first end connected to said main reflector, a sub-reflector with circular grooves or corrugations, and a dielectric joint in the space between said sub-reflector and the second end of said waveguide tube, the improvement comprising:

an inner cylindrical tube located inside said waveguide tube such as that a coaxial waveguide is formed between the outer wall of said inner tube and the inner wall of said waveguide tube, and where the dielectric joint contains metal parts which are not connected to said inner tube.