Stepped-reflector antenna for satellite communication payloads

• US 7,737,903 B1
• Filed: 03/02/2006
• Issued: 06/15/2010
• Est. Priority Date: 06/27/2005
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Rao, Sudhakar K., Tang, Minh
• Primary Examiner(s): Owens; Douglas W
• Assistant Examiner(s): TRAN, CHUC
• Application Number:
  US11/365,487
• Time in Patent Office: 1,566 Days
• Field of Search: 343/753, 343/786, 343/781, 343/840, 343/910, 343/914, 343/912, 343/772, 343/776, 343/909
• US Class Current: 343/786
• CPC Class Codes: H01Q 13/025 Multimode horn antennas; Horns using higher mode of propagation H01Q13/0241 takes precedence; multiple beam H01Q25/04
• CPC Class Codes: H01Q 15/16 curved in two dimensions, e.g. paraboloidal
• CPC Class Codes: H01Q 19/12 wherein the surfaces are concave H01Q19/18 takes precedence
• CPC Class Codes: H01Q 5/55 for horn or waveguide antennas

Abstract

A stepped reflector for being illuminated by at least one multiple-band feed is provided. The reflector includes a central region and a first annular region with an annular width of w. The first annular region is axially stepped a height h above the central region, where h is approximately equal to

$m\times \left[\Phi \pm \left(\varphi \left(\Theta =0\right)-\varphi \left(\Theta ={\Theta }_0\right)\right)\right]\times \frac{\pi }{180}\times \frac{\lambda }{2\pi }\times \frac{1}{2},$
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 Θ₀ 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.

The central region and the annular region of the reflector may be parabolically curved or may alternately be shaped. The reflector may be fed by one or more multiple-band horn antennas.

Claims

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, wherein the height h is selected to create a 180°

phase reversal between radiation reflected from the central region and radiation reflected from the at least one annular region at one of a receive or transmit frequency band,

wherein h is approximately equal to

$m\times <br><br>\left[\mathrm{\Phi <br><br>}\pm <br><br>\left(\mathrm{\varphi <br><br>}<br><br>\left(\mathrm{\Theta <br><br>}=0\right)-\mathrm{\varphi <br><br>}<br><br>\left(\mathrm{\Theta <br><br>}={\mathrm{\Theta <br><br>}}_0\right)\right)\right]\times <br><br>\frac{\mathrm{\pi <br><br>}}{180}\times <br><br>\frac{\mathrm{\lambda <br><br>}}{2<br><br>\mathrm{\pi <br><br>}}\times <br><br>\frac{1}{2},$

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

Θ

₀ 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.

2. The reflector of claim 1, wherein the feed phase contribution φ

for an angle Θ

is equal to kd(1−

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.

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

4. The reflector of claim 1, wherein the one of the receive or transmit frequency band at which a 180°

phase reversal is created is a higher frequency band than the other of the receive or transmit frequency band.

5. The reflector of claim 1, wherein the reflector is used for a dual band multiple-beam antenna system.

6. 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 h₁ above the central region,

wherein h₁ is approximately equal to

$m_1\times <br><br>\left[{\mathrm{\Phi <br><br>}}_1\pm <br><br>\left(\mathrm{\varphi <br><br>}<br><br>\left(\mathrm{\Theta <br><br>}=0\right)-\mathrm{\varphi <br><br>}<br><br>\left(\mathrm{\Theta <br><br>}={\mathrm{\Theta <br><br>}}_0\right)\right)\right]\times <br><br>\frac{\mathrm{\pi <br><br>}}{180}\times <br><br>\frac{\mathrm{\lambda <br><br>}}{2<br><br>\mathrm{\pi <br><br>}}\times <br><br>\frac{1}{2},$

where m₁ is a positive odd integer,

Φ

₁ 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

Θ

₀ 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.

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

8. The reflector of claim 6, wherein Φ

₁ is equal to 180°

.

9. The reflector of claim 6, wherein the feed phase contribution φ

for an angle Θ

is equal to kd(1−

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.

10. The reflector of claim 6, wherein a diameter of the central region is between about 60 inches and about 120 inches.

11. The reflector of claim 6, wherein w₁ is between 5% and 15% of a diameter of the central region.

12. The reflector of claim 6, wherein a first discontinuity region disposed between the first annular region and the central region is an abrupt discontinuity region with an annular width w_d.

13. The reflector of claim 6, 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_d.

14. The reflector of claim 6, wherein a first discontinuity region disposed between the first annular region and the central region has an annular width with an annular width w_d of less than 0.5 inches.

15. The reflector of claim 6, wherein the central region of the reflector has a circular or elliptical shape.

16. The reflector of claim 6, wherein the central region of the reflector has a polygonal shape.

17. The reflector of claim 6, wherein the central region of the reflector has a parabolic curvature.

18. The reflector of claim 6, wherein the central region of the reflector has regions of non-parabolic curvature.

19. The reflector of claim 6, wherein the first annular region of the reflector has a parabolic curvature.

20. The reflector of claim 6, wherein the first annular region of the reflector has regions of non-parabolic curvature.

21. The reflector of claim 6, wherein the reflector further includes a second annular region with an annular width w₂, the second annular region axially stepped a height h₂ above or below the first annular region and surrounding the first annular region,

wherein h₂ is approximately equal to

$m_2\times \; <li></li>\left[{\mathrm{\Phi <br><br>}}_2\pm <br><br>\left(\mathrm{\varphi <br><br>}<br><br>\left(\mathrm{\Theta <br><br>}=0\right)-\mathrm{\varphi <br><br>}<br><br>\left(\mathrm{\Theta <br><br>}={\mathrm{\Theta <br><br>}}_1\right)\right)\right]\times <br><br>\frac{\mathrm{\pi <br><br>}}{180}\times <br><br>\frac{\mathrm{\lambda <br><br>}}{2<br><br>\mathrm{\pi <br><br>}}\times <br><br>\frac{1}{2},$

where m₂ is a positive odd integer,

Φ

₂ is a desired amount of phase shift of an outer region of a phase front for reflecting off of the reflector, and

Θ

₁ 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 outer edge of the first annular region.

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

23. The reflector of claim 21, wherein a second discontinuity region disposed between the second annular region and the first annular region has a smooth discontinuity.

24. The reflector of claim 21, 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.

25. 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 h₁ 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 h₁ is approximately equal to

$m_1\times <br><br>\left[{\mathrm{\Phi <br><br>}}_1\pm <br><br>\left(\mathrm{\varphi <br><br>}<br><br>\left(\mathrm{\Theta <br><br>}=0\right)-\mathrm{\varphi <br><br>}<br><br>\left(\mathrm{\Theta <br><br>}={\mathrm{\Theta <br><br>}}_0\right)\right)\right]\times <br><br>\frac{\mathrm{\pi <br><br>}}{180}\times <br><br>\frac{\mathrm{\lambda <br><br>}}{2<br><br>\mathrm{\pi <br><br>}}\times <br><br>\frac{1}{2},$

where m₁ is a positive odd integer,

Φ

₁ 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

Θ

₀ 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.

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

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

28. The multiple-beam antenna system of claim 25, wherein multiple contoured beams are generated by a single multiple-band feed illuminating the reflector.