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1. (WO2007002235) STEPPED-REFLECTOR ANTENNA FOR SATELLITE COMMUNICATION PAYLOADS
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WHAT IS CLAIMED IS:

1. A reflector for being illuminated by at least one feed, the reflector comprising:
a central region; and
at least one annular region surrounding the central region, axially stepped a height h above or below the central region.

2. The reflector of claim 1, wherein h is approximately equal to



where m is a positive odd integer,
Φ is a desired amount of phase shift of an outer region of a phase front for reflecting off of the reflector,
φ is a feed phase contribution for an angle θ, and
Θo is an angle formed between an axis of the at least one feed and a line connecting a phase center of the at least one feed and an inner edge of the at least one annular region.

3. The reflector of claim 2, wherein the feed phase contribution φ for an angle θ is equal to kd(l - cos θ) , where k is a circular wavenumber corresponding to a wavelength of the phase front and d is an axial distance between a focal plane of the reflector and a phase center of the at least one feed corresponding to the wavelength of the phase front.

4. The reflector of claim 1, wherein h is approximately equal to an odd multiple of one fourth of a wavelength of an incident wavefront.

5. A reflector for being illuminated by at least one feed, the reflector comprising:
a central region; and
a first annular region with an annular width of W1 surrounding the central region, the first annular region axially stepped a height A1 above the central region,
wherein A1 is approximately equal to

χ [φ1 ± (φ(® = 0)-φ(® = ®0))]><-Ξ-χ±x ^ where m, is a positive odd integer,
O1 is a desired amount of phase shift of an outer region of a phase front for reflecting off of the reflector,
φ is a feed phase contribution for an angle θ, and
Θo is an angle formed between an axis of the at least one feed and a line connecting a phase center of the at least one feed and an inner edge of the first annular region.

6. The reflector of claim 5, wherein the at least one feed is a multiple-band antenna.

7. The reflector of claim 5, wherein Φj is equal to 180°.

8. The reflector of claim 5, wherein the feed phase contribution φ for an angle θ is equal to kd(i - cos θ) , where k is a circular wavenumber corresponding to a wavelength of the phase front and d is an axial distance between a focal plane of the reflector and a phase center of the at least one feed corresponding to the wavelength of the phase front.

9. The reflector of claim 5, wherein a diameter of the central region is between about 60 inches and about 120 inches.

10. The reflector of claim 5, wherein W1 is between 5% and 15% of a diameter of the central region.

11. The reflector of claim 5, wherein a first discontinuity region disposed between the first annular region and the central region is an abrupt discontinuity region with an annular width wtø.

12. The reflector of claim 5, wherein a first discontinuity region disposed between the first annular region and the central region is a smooth discontinuity region with an annular width w</.

13. The reflector of claim 5, wherein a first discontinuity region disposed between the first annular region and the central region has an annular width with an annular width w</ of less than 0.5 inches.

14. The reflector of claim 5, wherein the central region of the reflector has a circular or elliptical shape.

15. The reflector of claim 5, wherein the central region of the reflector has a polygonal shape.

16. The reflector of claim 5, wherein the central region of the reflector has a parabolic curvature.

17. The reflector of claim 5, wherein the central region of the reflector has regions of non-parabolic curvature.

18. The reflector of claim 5, wherein the first annular region of the reflector has a parabolic curvature.

19. The reflector of claim 5, wherein the first annular region of the reflector has regions of non-parabolic curvature.

20. The reflector of claim 5, wherein the reflector further includes a second annular region with an annular width W2 , the second annular region axially stepped a height Zz2 above or below the first annular region and surrounding the first annular region,
wherein h2 is approximately equal to
m2 x[Φ2 +W© = Θ0)-φ = Θ1))]x-|-χAxIj
l oO LK 1
where m2 is a positive odd integer,
Φ2 is a desired amount of phase shift of an outer region of a phase front for reflecting off of the reflector, and
Θj is an angle formed between an axis of the at least one feed and a line connecting a phase center of the at least one feed and an inner edge of the first annular region.

21. The reflector of claim 20, wherein a second discontinuity region disposed between the second annular region and the first annular region has an abrupt discontinuity.

22. The reflector of claim 20, wherein a second discontinuity region disposed between the second annular region and the first annular region has a smooth discontinuity.

23. The reflector of claim 20, wherein a second discontinuity region disposed between the second annular region and the first annular region has an annular width less than 0.5 inches.

24. A multiple-beam antenna system, comprising:
a reflector having a central region and a first annular region, the first annular region having an annular width W1 surrounding the central region, the first annular region axially stepped a height A1 above or below the central region; and
at least one multiple-band feed for illuminating the reflector,
wherein the at least one multiple-band feed is configured for providing transmission and reception of signals over respective transmission and reception frequency bands, and
wherein A1 is approximately equal to

mι x [φι ± (φ(® = 6)- φ(® = ®a))]x — x — X - ,

where mx is a positive odd integer,
O1 is a desired amount of phase shift of an outer region of a phase front for reflecting off of the reflector,
φ is a feed phase contribution for an angle θ, and
Θo is an angle formed between an axis of the at least one feed and a line connecting a phase center of the at least one feed and an inner edge of the first annular region.

25. The multiple-beam antenna system of claim 24, wherein the at least one multiple-band feed is a multiple-band high efficiency horn antenna.

26. The multiple-beam antenna system of claim 25, wherein the multiple-band high efficiency horn antenna includes a substantially conical wall having an internal surface with a variable slope.

27. The multiple-beam antenna system of claim 24, wherein multiple contoured beams are generated by a single multiple-band feed illuminating the reflector.