Low sidelobe reflector antenna with shield
View Patent ↗A front feed reflector antenna with a dish reflector has a wave guide is coupled to a proximal end of the dish reflector, projecting into the dish reflector along a longitudinal axis. A dielectric block may be coupled to a distal end of the waveguide and a sub-reflector coupled to a distal end of the dielectric block. A shield is coupled to the periphery of the dish reflector. A subtended angle between the longitudinal axis and a line between the focal point and a distal periphery of the shield is 50 degrees or less.
1. A front feed reflector antenna, comprising:
a dish reflector with a focal point;
a wave guide coupled to a proximal end of the dish reflector, projecting into the dish reflector along a longitudinal axis;
a dielectric block coupled to a distal end of the waveguide;
a sub-reflector coupled to a distal end of the dielectric block proximate the focal point; and
a generally cylindrical shield coupled to a periphery of the dish reflector;
wherein a subtended angle between the longitudinal axis and a line between the focal point and a distal periphery of the shield is 50 degrees or less.
2. The antenna of claim 1 , wherein the dish reflector has a reflector focal length to reflector diameter ratio of 0.163 or less.
3. The antenna of claim 1 , wherein the dish reflector has a reflector focal length to reflector diameter ratio of 0.25 or less.
4. The antenna of claim 1 , wherein the dish reflector has a reflector focal length to reflector diameter ratio of 0.298 or less.
5. The antenna of claim 1 , wherein the subtended angle is 40 degrees or less.
6. The antenna of claim 1 , wherein a diameter of the sub-reflector is dimensioned to be 2.5 wavelengths or more of a desired operating frequency.
7. The antenna of claim 1 , wherein the dielectric block is a unitary dielectric block provided with a waveguide transition portion and a dielectric radiator portion;
the dielectric block coupled to the waveguide at the waveguide transition portion;
the dielectric radiator portion situated between the waveguide transition portion and the sub-reflector; an outer diameter of the dielectric radiator portion provided with a plurality of radial inward grooves; a minimum diameter of the dielectric radiator portion greater than ⅗ of the sub-reflector diameter.
8. The antenna of claim 7 , wherein the plurality of grooves is two grooves.
9. The antenna of claim 7 , wherein a bottom width of the plurality of grooves decreases towards the distal end.
10. The antenna of claim 7 , further including a sub-reflector support portion between the dielectric radiator portion and the sub-reflector; the sub-reflector support portion extending from a distal groove of the dielectric radiator portion as an angled distal sidewall of the distal groove.
11. The antenna of claim 10 , wherein the angled distal sidewall is generally parallel to a longitudinally adjacent portion of the distal end.
12. The antenna of claim 1 , wherein the distal end of the dielectric block is provided with a proximal conical surface which transitions to a distal conical surface;
the distal conical surface provided with a lower angle with respect to the longitudinal axis than the proximal conical surface.
13. The antenna of claim 1 , wherein the shield is tapered inward.
14. The antenna of claim 13 , wherein the shield is tapered inward at an angle greater than zero and up to 10 degrees with respect to the longitudinal axis.
15. The antenna of claim 1 , wherein a length of the shield is 1 to 3 times a reflector focal length to reflector diameter ratio of the dish reflector.
16. The antenna of claim 1 , wherein the waveguide transition portion is dimensioned for insertion into the end of the waveguide until the end of the waveguide abuts a shoulder of the waveguide transition portion.
17. A method for manufacturing a front feed reflector antenna, comprising the steps of:
coupling a wave guide to a proximal end of a dish reflector;
coupling a dielectric block to a distal end of the waveguide, a sub-reflector coupled to a distal end of the dielectric block; and
coupling a generally cylindrical shield coupled to the periphery of the dish reflector;
wherein a subtended angle, along the longitudinal axis, between the focal point and a distal periphery of the shield is 50 degrees or less .
18. The method of claim 17 , wherein a diameter of the sub-reflector with a diameter is dimensioned to be 2.5 wavelengths or more of a desired operating frequency.
19. A front feed reflector antenna, comprising:
a dish reflector with a focal point;
a generally cylindrical shield coupled to a periphery of the dish reflector;
wherein a subtended angle between the longitudinal axis and a line between the focal point and a distal periphery of the shield is 50 degrees or less.
20. The reflector antenna of claim 19 , wherein the reflector antenna has a radiation pattern envelope less than a European Telecommunications Standards Institute Class 4 radiation pattern envelope.