Adaptive reflector antenna and method of implementing the same

Abstract

An adaptive reflector antenna includes an adaptive reflector and a mechanism for simultaneously effecting feed rotation and shape change for the adaptive reflector so as to maintain antenna performance with large scan angles while simultaneously reducing weight, complexity, and cost.

1. An adaptive reflector antenna, comprising:
 an adaptive reflector; and 
 means for simultaneously effecting feed rotation and shape change for the adaptive reflector. 
 
     
     
       2. The adaptive reflector antenna of  claim 1 , wherein the means for simultaneously effecting feed rotation and shape change includes an illuminating beam scanner configured to adjust a shape of the adaptive reflector in response to an optical figure sensor. 
     
     
       3. The adaptive reflector antenna of  claim 2 , wherein the illuminating beam scanner includes a line feed array. 
     
     
       4. The adaptive reflector antenna of  claim 2 , wherein the illuminating beam scanner includes a slotted waveguide. 
     
     
       5. The adaptive reflector antenna of  claim 2 , wherein the illuminating beam scanner includes a rotatable line feed. 
     
     
       6. The adaptive reflector antenna of  claim 2 , wherein the illuminating beam scanner includes a fixed line feed with a rotatable auxiliary reflector. 
     
     
       7. The adaptive reflector antenna of  claim 6 , wherein the auxiliary reflector rotates mechanically. 
     
     
       8. The adaptive reflector antenna of  claim 6 , wherein the auxiliary reflector rotates piezoelectrically. 
     
     
       9. The adaptive reflector antenna of  claim 2 , wherein the means for simultaneously effecting feed rotation and shape change is configured such that illuminated reflector shape is adjusted as offset angle and tilt are applied so as to appear as on-axis reflector to the feed. 
     
     
       10. The adaptive reflector antenna of  claim 2 , wherein the means for simultaneously effecting feed rotation and shape change is configured such that antenna gain and sidelobe levels remain constant as scan angle is changed. 
     
     
       11. A method for implementing an adaptive reflector antenna, comprising the step of:
 operatively coupling line feed rotation and reflector shaping for an adaptive off-axis reflector of a parabolic cylinder antenna such that each reflector shaping creates an identical on-axis parabolic shape for the portion of the reflector then illuminated by the line feed rotation. 
 
     
     
       12. The method for implementing an adaptive reflector antenna of  claim 11 , wherein the step of operatively coupling line feed rotation and reflector shaping includes co-locating optical figure sensors and electron beam generators of the adaptive reflector antenna. 
     
     
       13. An adaptive reflector antenna, comprising:
 a membrane including a bimorph substrate; 
 a reflector structure formed over the bimorph substrate; 
 an optical figure sensor; and 
 a beam scanning mechanism configured to simultaneously effect rotation of a feed and adaptively actuate in real time a shape of the membrane in response to an output of the optical figure sensor such that the reflector structure being illuminated by the feed always appears to the feed as an on-axis reflector of original shape as scan angle is changed. 
 
     
     
       14. The adaptive reflector antenna of  claim 13 , wherein the membrane is configurable as a parabolic cylinder antenna. 
     
     
       15. The adaptive reflector antenna of  claim 13 , wherein the reflector structure includes a conductive grid on the bimorph substrate. 
     
     
       16. The adaptive reflector antenna of  claim 13 , wherein the reflector includes a plurality of dipoles centrally positioned along portions of the bimorph substrate. 
     
     
       17. The adaptive reflector antenna of  claim 16 , wherein the dipoles are formed from aluminum. 
     
     
       18. The adaptive reflector antenna of  claim 16 , wherein the dipoles have a cross-section which, at X-band, reduces leakage. 
     
     
       19. The adaptive reflector antenna of  claim 16 , wherein the dipoles have a cross-section which, at L-band, reduces leakage. 
     
     
       20. The adaptive reflector antenna of  claim 13 , wherein:
 the bimorph substrate is formed as a grid of strips which are uniform in width; and 
 the beam scanning mechanism is configured to generate an electron beam with a minimum spot size that is a function of the width of the strips. 
 
     
     
       21. An adaptive reflector antenna, comprising:
 a membrane including a bimorph substrate;   a reflector structure formed over the bimorph substrate;   an optical figure sensor; and   a beam scanning mechanism configured to rotate a feed, illuminate the reflector structure and adaptively shape the membrane in response to an output of the optical figure sensor such that the reflector structure appears to the feed as an on-axis reflector of original shape as scan angle is changed.   
     
     
       22. The adaptive reflector antenna of claim 21, wherein the membrane is configurable as a parabolic cylinder antenna. 
     
     
       23. The adaptive reflector antenna of claim 21, wherein the reflector structure includes a conductive grid on the bimorph substrate. 
     
     
       24. The adaptive reflector antenna of claim 21, wherein the reflector includes a plurality of dipoles centrally positioned along portions of the bimorph substrate. 
     
     
       25. The adaptive reflector antenna of claim 24, wherein the dipoles are formed from aluminum. 
     
     
       26. The adaptive reflector antenna of claim 24, wherein the dipoles have a cross-section which, at X-band, reduces leakage. 
     
     
       27. The adaptive reflector antenna of claim 24, wherein the dipoles have a cross-section which, at L-band, reduces leakage. 
     
     
       28. The adaptive reflector antenna of claim 21, wherein: the bimorph substrate is formed as a grid of strips which are uniform. 
     
     
       29. A method for constructing an adaptive reflector antenna, comprising:
 forming an adaptive reflector structure over a membrane with a bimorph substrate;   locating an optical figure sensor on one side of the reflector structure;   locating an electron beam feed and back potential generator on another side of the reflector structure that is opposite the optical figure sensor;   illuminating and scanning both the reflector structure and optical sensor with the electron beam feed;   providing an output from the optical figure sensor to the electron beam feed and back potential generator; and   adaptively shaping the membrane in response to the output of the optical figure sensor,   wherein the electron beam feed and the optical sensor provide closed loop control that sets and maintains a curvature and original shape of the reflector structure in the presence of disturbances, and   wherein the adaptive reflector structure illuminated by the electron beam feed appears as an on-axis reflector of the original shape as a scan angle is changed.   
     
     
       30. The method of claim 29, wherein the membrane is configurable as a parabolic cylinder antenna. 
     
     
       31. The method of claim 29, wherein the reflector structure includes a conductive grid on the bimorph substrate. 
     
     
       32. The method of claim 29, wherein the reflector includes a plurality of dipoles centrally positioned along portions of the bimorph substrate. 
     
     
       33. The method of claim 32, wherein the dipoles are formed from aluminum. 
     
     
       34. The method of claim 32, wherein the dipoles have a cross-section which, at X-band, reduces leakage. 
     
     
       35. The method of claim 32, wherein the dipoles have a cross-section which, at L-band, reduces leakage. 
     
     
       36. The method of claim 29, wherein the bimorph substrate is formed as a grid of strips which are uniform.