Antenna feed horn with near-constant phase center with subreflector tracking in the z-axis

1. A dual reflector earth station antenna (ESA) system for transmitting uplink in a first frequency band and receiving downlink in a second frequency band, the ESA system comprising:

a reflector;

a reflector tracking assembly coupled to the reflector and configured to control the direction of the reflector;

a feed horn coupled to the reflector and optimized for a near-constant phase center for both the first frequency band and the second frequency band;

a subreflector tracking assembly including a subreflector, configured for tracking in the X, Y and Z-axes and supported proximate a focal point of the reflector; and

a control system in communication with the subreflector tracking assembly and comprising at least one processor configured to:

adjust the subreflector of the subreflector tracking assembly along X, Y and Z axes of the reflector until a signal gain of the reflector antenna is maximized for the second frequency band; and

wherein a signal gain of the reflector antenna is also simultaneously maximized for the first frequency band due to the optimization of the feed horn for a near-constant phase center for both the first frequency band and the second frequency band.

2. The system of claim 1 further comprising at least one feedback sensor arranged to monitor the position of the subreflector tracking assembly at least in the X and Y axes.

3. The system of claim 2 wherein the control system is further configured to adjust the subreflector tracking assembly via the reflector tracking assembly if the at least one feedback sensor indicates that an X or Y-axis travel limit of the subreflector tracking assembly mount has been reached.

4. The system of claim 1 wherein the feed horn has an optimized varying flare angle for near-constant phase center over a range of predetermined frequencies.

5. The system of claim 4 wherein the predetermined frequencies are 17.7-31 GHz.

6. The system of claim 1 wherein the feed horn is a corrugated feed horn with varying flare angle.

7. The system of claim 1 wherein the feed horn has a linear taper and very narrow flare angle of 6 degrees or less, at an aperture of the feed horn.

8. The system of claim 1 wherein the feed horn has a half-cosine taper to provide a narrow flare angle at an aperture of the feed horn.

9. The system of claim 1 wherein the control system is further configured to adjust the subreflector tracking assembly at a periodic interval.

10. A method for reflector tracking with a dual reflector earth station antenna (ESA) system for transmitting uplink in a first frequency band and receiving downlink in a second frequency band, the ESA system including a feed horn optimized for a near-constant phase center for both the first frequency band and the second frequency band and a subreflector tracking assembly supported proximate a focal point of a reflector and capable of tracking in the X, Y and Z-axes, the method comprising:

adjusting the subreflector tracking assembly along X, Y and Z axes of the reflector until a signal gain of the reflector is maximized in the second frequency band; and

whereby a signal gain of the reflector is also simultaneously maximized for the first frequency band due to the optimization of the feed horn for a near-constant phase center for both the first frequency band and the second frequency band.

11. The method of claim 10 , wherein the adjusting of the subreflector tracking assembly is repeated at a periodic interval.

12. The method of claim 10 , wherein the adjusting of the subreflector tracking assembly is initiated responsive to a change in temperature.

13. The method of claim 10 , wherein the adjusting of the subreflector tracking assembly is initiated responsive to a preset time.

14. The method of claim 10 , wherein a range of adjustment along the z-axis is less than 0.5 inches.

15. The method of claim 10 , wherein the adjustment is enabled by a change in the signal gain.

16. The method of claim 10 , further including the step of adjusting the subreflector tracking assembly with respect to a recorded position of the highest signal gain within a defined period: and resetting the recorded position if the adjusting of the subreflector tracking assembly results in a higher signal gain.

17. The method of claim 10 , wherein the adjustment to the subreflector tracking assembly is performed via actuation of a linear actuator for each of the X, Y and Z-axis.

18. The method of claim 10 further comprising adjusting the subreflector tracking assembly via a reflector tracking assembly if at least one feedback sensor indicates that an X or Y-axis travel limit of the subreflector tracking assembly has been reached.