LEO flexible single axis beamforming
A hybrid system of satellite-based beamforming that includes digitally beamforming in one axis and physically beamforming in an orthogonal axis. Based on the orientation of the satellite, the digital beamforming axis may be the in-track axis, the cross-track axis, or anywhere in between those two axes. In the digitally beamformed axis, the beam pattern can be steered to different positions along the axis and it can be compressed or expanded, as desired.
1. A transmit beamformer, comprising:
a first beamforming unit that receives M different digital signals to each be placed into M beams; and
a second beamforming unit that receives M different digital signals to each be placed into M beams;
wherein each of the first and second beamforming unit includes:
a digital beamformer that receives the M different digital signals to each be placed into a beam, and performs digital beamforming on the M different digital signals to create M different beamformed digital signals;
M digital-to-analog converters to convert the M different beamformed digital signals to M different beamformed analog signals;
M amplifiers to amplify the M different beamformed analog signals; and
M antenna elements to transmit the M different amplified beamformed analog signals to form M different beams oriented along a first axis in space;
wherein the first and second beamforming units that each form M different beams creates an M×2 array of different beams;
wherein each of the beams in the M×2 array of beams is created by digital beamforming; and
wherein the width of the beams in the M×2 array of beams along a second axis orthogonal to the first axis is based on one or more physical characteristics of the antenna elements.
2. The transmit beamformer as defined in claim 1 , wherein the physical characteristics of the antenna elements include an orientation of the antenna elements.
3. A receive beamformer, comprising:
a first beamforming unit that receives M different element signals to each be formed into M beams; and
a second beamforming unit that receives M different element signals to each be formed into M beams;
wherein each of the first and second beamforming unit includes:
M antenna elements to receive the M different analog RF element signals to form M different overlapping element beams oriented along a first axis in space;
M amplifiers to amplify the M element signals;
M Analog to Digital Converters (ADCs) to digitize the amplified element signals; and
a digital beamformer that receives the M different digitized element signals, and performs digital beamforming on the M different digital element signals to create M different digital beam signals;
wherein the first and second beamforming units that each form M different beams create an M×2 array of different beams;
wherein each of the beams in the M×2 array of beams is created by digital beamforming; and
wherein the width of the beams in the M×2 array of beams along a second axis orthogonal to the first axis is based on one or more physical characteristics of the antenna elements.
4. The receive beamformer as defined in claim 3 , wherein the physical characteristics of the antenna elements include an orientation of the antenna elements.
5. A method for forming transmitted beams, comprising:
performing the following operations N times on different sets of digital signals:
receiving, via a plurality of antenna elements, M different digital signals to each be placed into a beam;
performing digital beamforming on the M different digital signals to create M different beamformed digital signals;
converting the M different beamformed digital signals to M different beamformed analog signals;
amplifying the M different beamformed analog signals; and
transmitting the M different amplified beamformed analog signals to form M different beams oriented along a first axis in space;
wherein an M×N array of different beams is formed thereby wherein the M×N array includes N columns of M beams, and wherein a position of each of the M beams in each column is created by digital beamforming, but each column has a width along a second axis orthogonal to the first axis that is determined by an orientation of the antenna elements and is not determined by digital beamforming.
6. A method as defined in claim 5 , wherein each column of M beams has an angular extent.
7. A method as defined in claim 6 , wherein the angular extent can be varied by digital beamforming.
8. A method as defined in claim 7 , wherein the angular extent is reduced.
9. A method as defined in claim 7 , wherein the angular extent is increased.
10. A method as defined in claim 5 , wherein the method is practiced in a satellite orbiting around the Earth, wherein the direction of orbit of the satellite relative to the Earth is an in-track direction and an orthogonal direction is a cross-track direction;
wherein one or more of the M beams is moved relative to the satellite by digital beamforming to move the position of the one or more of the M beams on the Earth.
11. A method as defined in claim 10 , wherein one or more of the M beams is moved in the in-track direction by digital beamforming.
12. A method as defined in claim 10 , wherein one or more of the M beams is moved in the cross-track direction by digital beamforming.
13. A method for forming received beams, comprising:
performing the following operations N times on different sets of analog element signals:
receiving, via a plurality of antenna elements, M different analog element signals;
amplifying the M element signals;
digitizing the M element signals; and
performing digital beamforming on the M different digital element signals to create M different digital beam signals that are oriented along a first axis in space;
wherein an M×N array of different beams is formed thereby, wherein the M×N array includes N columns of M beams, and wherein a position of each of the M beams in each column is created by digital beamforming, but each column has a width along a second axis orthogonal to the first axis that is determined by an orientation of the antenna elements and is not determined by digital beamforming.
14. A method as defined in claim 13 , wherein each column of M beams has an angular extent.
15. A method as defined in claim 14 , wherein the angular extent can be varied by digital beamforming.
16. A method as defined in claim 14 , wherein the angular extent is reduced.
17. A method as defined in claim 14 , wherein the angular extent is increased.
18. A method as defined in claim 13 , wherein the method is practiced in a satellite orbiting around the Earth, wherein the direction of orbit of the satellite relative to the Earth is an in-track direction and an orthogonal direction is a cross-track direction;
wherein one or more of the M beams is moved relative to the satellite by digital beamforming to move the position of the one or more of the M beams on the Earth.
19. A method as defined in claim 18 , wherein one or more of the M beams is moved in the in-track direction by digital beamforming.
20. A method as defined in claim 18 , wherein one or more of the M beams is moved in the cross-track direction by digital beamforming.