Integrated antenna and RF payload for low-cost inter-satellite links using super-elliptical antenna aperture with single axis gimbal

Patent metadata

Field	Value
Publication number	US-9590299-B2
Application number	US-201514739540-A
Country	US
Kind code	B2
Filing date	Jun 15, 2015
Priority date	Jun 15, 2015
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

A dual-reflector inter-satellite link (ISL) subsystem, for a communications satellite in a constellation of satellites in low earth orbit or medium earth orbit. The ISL subsystem includes a main antenna reflector which uses a single-axis gimbal to steer the main reflector only in the elevation plane. An antenna subreflector, a horn and RF feed circuitry are stationary with respect to the host satellite. The main reflector has a super-elliptical design which provides a beam shape which requires no steering in the azimuth plane, while meeting ISL signal strength requirements. By steering the main reflector only, and only in the elevation plane, the disclosed ISL subsystem delivers significantly lower size, mass, complexity and cost, and significantly greater reliability, than traditional ISL systems.

First claim

What is claimed is:

1. An inter-satellite link (ISL) subsystem for a communications satellite, said ISL subsystem comprising:
a main reflector having a super-elliptical shape and an elongated central opening;
a mounting plate fixed to a back side of the main reflector, said mounting plate also having an elongated central opening;
a single axis gimbal motor including a motor mount which mounts the motor to a chassis of the communications satellite;
a pivot arm attached at a first end to an output shaft of the motor, said pivot arm being attached at a second end to the mounting plate such that a rotation of the output shaft of the motor causes the main reflector to tilt;
a radio frequency (RF) feed circuit contained in an electronics housing, where said electronics housing is mounted to the chassis;
a feed cone mounted to the electronics housing, said feed cone having a generally tubular shape and positioned where it passes through the central openings of the main reflector and the mounting plate;
a horn in communication with the RF feed circuit, said horn sending and receiving RF signals to and from a remote satellite, where the horn is positioned inside the feed cone; and
a subreflector mounted via a plurality of struts to the feed cone and centered on an axis of the feed cone,
where the RF signals radiate from the horn to the subreflector to the main reflector to the remote satellite, and vice versa, and a beam of the RF signals is steered in an elevation plane only via tilting of the main reflector by the motor.

2. The ISL subsystem of claim 1 wherein the chassis is a main body of the communications satellite.

3. The ISL subsystem of claim 1 wherein the chassis is an ISL module which is deployed on a boom which is mounted to the main body of the communications satellite.

4. The ISL subsystem of claim 1 wherein the main reflector has a shape which provides a beam resulting in less than 1.0 dB of signal strength loss in a condition of a 0.5° pointing error in an azimuth plane.

5. The ISL subsystem of claim 4 wherein the main reflector has a height in the elevation plane of 30 centimeters (cm), a width in the azimuth plane of 15 cm, and a shape defining a super-ellipse with an exponent value of 4.

6. The ISL subsystem of claim 1 wherein the main reflector is steerable by ±6° in the elevation plane and is steered to eliminate misalignment in the elevation plane with the remote satellite.

7. The ISL subsystem of claim 1 wherein the RF feed circuit includes a polarizer in communication with the horn and one or more multiplexers, where a single transmit channel and a plurality of receive channels pass through the one or more multiplexers.

8. The ISL subsystem of claim 7 wherein the single transmit channel and the plurality of receive channels occupy separate frequency bands in an overall frequency range of 55-75 gigahertz (GHz).

9. The ISL subsystem of claim 1 wherein the communications satellite includes a first ISL subsystem in communication with a leading remote satellite and a second ISL subsystem in communication with a trailing remote satellite.

10. The ISL subsystem of claim 1 wherein the communications satellite and the remote satellite are part of a constellation of communications satellites in low earth orbit or medium earth orbit.

11. A satellite module comprising:
a chassis;
two inter-satellite link (ISL) subsystems, each of the ISL subsystems comprising;
a main reflector having a super-elliptical shape and an elongated central opening;
a mounting plate fixed to a back side of the main reflector, said mounting plate also having an elongated central opening;
a motor including a motor mount which mounts the motor to the chassis;
a pivot arm attached at a first end to an output shaft of the motor, said pivot arm being attached at a second end to the mounting plate such that a rotation of the output shaft of the motor causes the main reflector to tilt;
a radio frequency (RF) feed circuit contained in an electronics housing, where said electronics housing is mounted to the chassis;
a feed cone mounted to the electronics housing, said feed cone having a generally tubular shape and positioned where it passes through the central openings of the main reflector and the mounting plate;
a horn in communication with the RF feed circuit, said horn sending and receiving RF signals to and from a remote satellite, where the horn is positioned inside the feed cone; and
a subreflector mounted via a plurality of struts to the feed cone and centered on an axis of the feed cone,
where the RF signals radiate from the horn to the subreflector to the main reflector to the remote satellite, and vice versa, and the main reflector is steered in an elevation plane only via tilting by the motor.

12. The satellite module of claim 11 wherein the chassis is a main body of a communications satellite, the ISL subsystems communicate with a leading satellite and a trailing satellite, and the communications satellite, the leading satellite and the trailing satellite are part of a constellation of communications satellites in low earth orbit or medium earth orbit.

13. The satellite module of claim 11 wherein the chassis is an ISL module which is deployed on a boom which is mounted to a main body of a communications satellite, the ISL subsystems communicate with a leading satellite and a trailing satellite, and the communications satellite, the leading satellite and the trailing satellite are part of a constellation of communications satellites in low earth orbit or medium earth orbit.

14. The ISL subsystem of claim 11 wherein each of the main reflectors has a height in the elevation plane of 30 centimeters (cm), a width in an azimuth plane of 15 cm, and a shape defining a super-ellipse with an exponent value of 4, and each of the main reflectors provides a beam resulting in less than 1.0 dB of signal strength loss in a condition of a 0.5° pointing error in the azimuth plane.

15. An inter-satellite link (ISL) subsystem for a communications satellite, said ISL subsystem comprising:
a main reflector having a super-elliptical shape;
a motor mounted to a chassis of the communications satellite, said motor being coupled to the main reflector such that a rotation of an output shaft of the motor causes the main reflector to tilt;
a horn in communication with a radio frequency (RF) feed circuit, said horn sending and receiving RF signals to and from a remote satellite, where the horn is mounted in a fixed location on the chassis; and
a subreflector mounted via a plurality of struts in a fixed location on the chassis, where the RF signals radiate from the horn to the subreflector to the main reflector to the remote satellite, and vice versa, and the main reflector is steered in an elevation plane only via tilting by the motor.

16. The ISL subsystem of claim 15 wherein the chassis is a main body of a communications satellite, and the ISL subsystem communicates with the remote satellite which, along with the communications satellite, is part of a constellation of communications satellites in low earth orbit or medium earth orbit.

17. The ISL subsystem of claim 15 wherein the chassis is an ISL module which is deployed on a boom which is mounted to a main body of a communications satellite, and the ISL subsystem communicates with the remote satellite which, along with the communications satellite, is part of a constellation of communications satellites in low earth orbit or medium earth orbit.

18. The ISL subsystem of claim 15 wherein the main reflector has a height

Assignees

• Northrop Grumman Systems Corp

Inventors

• Rao Sudhakar K
• Roper Daniel H
• Taft Alan M
• Chun Sebong
• Brown Christopher S
• Siddique Mansoor K

Classifications

• H01Q19/134

  Rear-feeds; Splash plate feeds · CPC title

• H01Q3/20 Primary

  wherein the primary active element is fixed and the reflecting device is movable · CPC title

• H01Q19/193

  with feed supported subreflector (splash plate feeds H01Q19/134) · CPC title

• H01Q3/06

  over a restricted angle · CPC title

• H01Q1/288

  Satellite antennas · CPC title