Parabolic reflector antennas that support low side lobe radiation patterns
Parabolic reflector antennas advantageously support low side lobe radiation patterns for ETSI class 4 performance, by utilizing: (i) metal choke plates adjacent a distal end of a dielectric cone within a sub-reflector assembly, (ii) “lossy” material feed boom waveguide sleeves and/or (iii) extended length cylindrical shields lined with radiation absorbing materials. Relatively shallow and large diameter parabolic reflectors having an F/D ratio of greater than about 0.25 may be provided with one or more of the identified (i)-(iii) enhancements.
1. A parabolic reflector antenna, comprising:
a dish reflector having a focal length-to-diameter (F/D) ratio greater than 0.25;
a cylindrically-shaped shield coupled to a periphery of said dish reflector;
a feed boom waveguide having a promixal end coupled to said dish reflector;
a radiation absorbing sleeve wrapped around at least a majority of a length of said feed boom waveguide; and
a sub-reflector assembly comprising a dielectric block coupled to a distal end of said feed boom waveguide and a sub-reflector adjacent a distal end of the dielectric block;
wherein said sub-reflector assembly is configured to redirect a feed signal transmitted along said feed boom waveguide into an RF transmission signal, which is directed from the sub-reflector to said dish reflector with a maximum signal intensity at an angle in a range between about 35 degrees and about 60 degrees, as measured between a longitudinal axis of said feed boom waveguide and a line extending from a focal point of said dish reflector and said dish reflector.
2. The antenna of claim 1 , wherein the RF transmission signal is directed from the sub-reflector to said dish reflector with a 3 dB beamwidth in a range between about 25 degrees and about 35 degrees.
3. The antenna of claim 2 , wherein the F/D ratio is in a range from about 0.36 to about 0.44; and wherein the RF transmission signal is directed from the sub-reflector to said dish reflector with a 10 dB beamwidth in a range between about 35 and about 45 degrees.
4. The antenna of claim 1 , wherein said sub-reflector assembly further comprises a choke plate coupled to the distal end of the dielectric block, said choke plate having a maximum diameter equal to or greater than an outer diameter of the sub-reflector.
5. The antenna of claim 4 , wherein said choke plate has at least one annular-shaped groove therein, which is spaced longitudinally relative to the distal end of the dielectric block.
6. The antenna of claim 4 , wherein the dielectric block has an annular-shaped groove therein at a first radius relative to a longitudinal axis of said feed boom waveguide; and wherein said choke plate has an annular-shaped groove therein at a second radius relative to the longitudinal axis of said feed boom waveguide, which is greater than the first radius.
7. The antenna of claim 6 , wherein said choke plate has a plurality of annular-shaped grooves therein, which are spaced radially relative to the longitudinal axis of the dielectric block.
8. The antenna of claim 4 , wherein said choke plate and the sub-reflector comprise different materials; and wherein said choke plate comprises a metal.
9. The antenna of claim 1 , further comprising a radiation absorbing liner on at least a portion of an interior surface of said cylindrically-shaped shield.
10. A parabolic reflector antenna, comprising:
a dish reflector;
a feed boom waveguide having a promixal end coupled to said dish reflector; and
a sub-reflector assembly comprising a dielectric block, which is coupled to a distal end of said feed boom waveguide, a sub-reflector on a distal end of the dielectric block and a choke plate adjacent the sub-reflector, said choke plate having a maximum diameter equal to or greater than an outer diameter of the sub-reflector;
wherein the dielectric block has a plurality of annular-shaped grooves therein that are spaced along a length of the dielectric block; and wherein said choke plate has a plurality of annular-shaped grooves therein, which are spaced radially relative to a longitudinal axis of the dielectric block.
11. The antenna of claim 10 , wherein said choke plate has at least one annular-shaped groove therein, which is spaced longitudinally relative to the distal end of the dielectric block.
12. The antenna of claim 10 , wherein said choke plate and the sub-reflector comprise different materials.
13. The antenna of claim 12 , wherein said choke plate comprises a metal.
14. The antenna of claim 10 , further comprising a radiation absorbing sleeve wrapped around at least a majority of a length of said feed boom waveguide.
15. The antenna of claim 14 , wherein said radiation absorbing sleeve comprises a material selected from a group consisting of foam, rubber, plastics and liquid-filled mediums.
16. A parabolic reflector antenna, comprising:
a dish reflector;
a feed boom waveguide having a promixal end coupled to said dish reflector; and
a sub-reflector assembly comprising a dielectric block, which is coupled to a distal end of said feed boom waveguide, a sub-reflector on a distal end of the dielectric block and a choke plate adjacent the sub-reflector, said choke plate having a maximum diameter equal to or greater than an outer diameter of the sub-reflector;
wherein the dielectric block has a plurality of annular-shaped grooves therein that are spaced along a longitudinal axis of the dielectric block; and wherein said choke plate has a plurality of annular-shaped grooves therein, which are spaced radially relative to the longitudinal axis of the dielectric block, and an annular-shaped groove that is spaced along the longitudinal axis of the dielectric block relative to the annular-shaped grooves in the dielectric block.