Satellite system using optical gateways and onboard processing

1. A ground based subsystem for use in transmitting an optical feeder uplink beam to a satellite that is configured to receive the optical feeder uplink beam and in dependence thereon produce and transmit a plurality of RF service downlink beams within a specified service downlink RF frequency range to service terminals, wherein the satellite comprises a space based forward link subsystem including a channelizer that is configured to operate within an intermediate RF frequency range that is lower than the specified service downlink RF frequency range, the ground based subsystem comprising:

a plurality of lasers, each of the lasers operable to emit an optical signal having a different peak wavelength within a specified optical wavelength range;

a plurality of electro-optical modulators (EOMs), each of the EOMs configured to receive an optical signal from a respective one of the plurality of lasers, receive a different data modulated RF carrier signal that has been modulated to carry data for at least one of the plurality of RF service downlink beams, and output an optical data signal carrying data for at least one of the plurality of RF service downlink beams and having an RF frequency within the same intermediate RF frequency range within which the channelizer of the space based forward link subsystem on the satellite is configured to operate;

a wavelength-division multiplexing (WDM) multiplexer configured to receive the optical data signals output by the plurality of EOMs, and combine the plurality of optical data signals into a wavelength division multiplexed optical signal;

an optical amplifier configured to amplify the wavelength division multiplexed optical signal to thereby produce an optically amplified wavelength division multiplexed optical signal; and

transmitter optics configured to receive the optically amplified wavelength division multiplexed optical signal and transmit an optical feeder uplink beam to the satellite in dependence thereon;

wherein because the RF frequencies of the optical data signals output by the plurality of EOMs are within the same intermediate RF frequency range within which the channelizer of the space based forward link subsystem on the satellite is configured to operate, there is an elimination of any need for the satellite to perform any RF frequency conversions upstream of the channelizer of the space based forward link subsystem on the satellite.

2. The subsystem of claim 1 , wherein:

the specified service downlink RF frequency range within which the satellite is configured to produce and transmit the plurality of RF service downlink beams comprises a downlink portion of the Ka band; and

the intermediate RF frequency range within which the channelizer of the space based forward link subsystem on the satellite is configured to operate is lower than the downlink portion of the Ka band.

3. The subsystem of claim 2 , wherein:

the downlink portion of the Ka band is from 17.7 GHz to 20.2 GHz, and thus, has a bandwidth of 2.5 GHz; or

the downlink portion of the Ka band is from 17.3 GHz to 20.2 GHz, and thus, has a bandwidth of 2.9 GHz.

4. The subsystem of claim 1 , further comprising:

a plurality of RF modulators configured to produce the data modulated RF carrier signals that are received by the plurality of EOMs;

wherein each of the RF modulators receives an RF carrier signal having an RF frequency within the same intermediate RF frequency range within which the channelizer of the space based forward link subsystem on the satellite is configured to operate.

5. The subsystem of claim 4 , further comprising:

one or more oscillators configured to produce the RF carrier signals that are provided to the RF modulators, each of the RF carriers signals having an RF frequency within the same intermediate RF frequency range within which the channelizer of the space based forward link subsystem on the satellite is configured to operate.

6. The subsystem of claim 1 , wherein the specified optical wavelength range is a contiguous or non-contiguous optical wavelength range within an infrared (IR) spectrum.

7. A method for enabling a ground based subsystem to produce and transmit an optical feeder uplink beam to a satellite that is configured to receive the optical feeder uplink beam and in dependence thereon produce and transmit a plurality of RF service downlink beams within a specified service downlink RF frequency range to service terminals, wherein the satellite comprises a space based forward link subsystem including a channelizer that is configured to operate within an intermediate RF frequency range that is lower than the specified service downlink RF frequency range, the method for use by the ground based subsystem comprising:

emitting a plurality of optical signals each having a different peak wavelength that is within a specified optical wavelength range;

electro-optically modulating each of the optical signals with one of a plurality of different data modulated RF carrier signals, each of which has been modulated to carry data for at least one of the plurality of RF service downlink beams, to thereby produce a plurality of optical data signals, each of which carries data for at least one of the plurality of RF service downlink beams and has an RF frequency within the same intermediate RF frequency range within which the channelizer of the space based forward link subsystem on the satellite is configured to operate;

multiplexing the plurality of optical data signals to thereby produce a wavelength division multiplexed optical signal that includes data for the plurality of RF service downlink beams;

producing an optical feeder uplink beam, in dependence on the wavelength division multiplexed optical signal; and

transmitting the optical feeder uplink beam through free-space to the satellite;

wherein because RF frequencies of the optical data signals produced during the electro-optically modulating are within the same intermediate RF frequency range within which the channelizer of the space based forward link subsystem on the satellite is configured to operate, there is an elimination of any need for the satellite to perform any RF frequency conversions upstream of the channelizer of the space based forward link subsystem on the satellite.

8. The method of claim 7 , further comprising:

receiving a plurality of RF carrier signals each of which has a different RF frequency within the same intermediate RF frequency range within which the channelizer of the space based forward link subsystem on the satellite is configured to operate; and

producing the data modulated RF carrier signals, which are electro-optically modulated with the optical signals, in dependence on the plurality of RF carrier signals.

9. The method of claim 7 , wherein:

the specified service downlink RF frequency range within which the satellite is configured to produce and transmit the plurality of RF service downlink beams comprises a downlink portion of the Ka band; and

the intermediate RF frequency range within which the channelizer of the space based forward link subsystem on the satellite is configured to operate is lower than the downlink portion of the Ka band.

10. The method of claim 9 , wherein:

the downlink portion of the Ka band is from 17.7 GHz to 20.2 GHz, and thus, has a bandwidth of 2.5 GHz; or

the downlink portion of the Ka band is from 17.3 GHz to 20.2 GHz, and thus, has a bandwidth of 2.9 GHz.

11. A space based forward link subsystem of a satellite for use in transmitting a plurality of RF service downlink beams within a specified downlink RF frequency range to service terminals, the space based forward link subsystem comprising:

receiver optics configured to receive an optical feeder uplink beam from a ground based subsystem;

an optical amplifier optically coupled to the receiver optics and configured to amplify an optical feeder uplink signal that is output from the receiver optics;

a wavelength-division multiplexing (WDM) demultiplexer optically coupled to the optical amplifier and configured to separate the amplified optical feeder uplink signal, which is output from the optical amplifier, into a plurality of separate optical signals that each have a different peak wavelength; and

a plurality of photodetectors upstream of a channelizer of the space based forward link subsystem;

each of the photodetectors operable to convert a different one of the optical signals that are output from the WDM demultiplexer, to a respective electrical data signal having an RF frequency within the same intermediate RF frequency range within which the channelizer of the space based forward link subsystem is configured operate;

the channelizer of the space based forward link subsystem including a plurality of input ports, a plurality of output ports, and circuitry therebetween configured to operate within an intermediate RF frequency range that is lower than the specified downlink RF frequency range, the input ports receiving the electrical data signals produced by the photodetectors, which are optionally filtered and/or amplified before being provided to the input ports;

frequency upconverters downstream of the output ports of the channelizer of the space based forward link subsystem and configured to convert frequencies of signals output by the channelizer from being within the intermediate RF frequency range to being within the specified downlink RF frequency range; and

RF components and antennas downstream of the frequency upconverters and configured to produce and transmit the plurality of RF service downlink beams within the specified downlink RF frequency range;

wherein because the RF frequencies of the electrical data signals output by the plurality of photodetectors are within the same intermediate RF frequency range within which the channelizer of the space based forward link subsystem is configured to operate, there is an elimination of any need for the space based forward link subsystem to perform any RF frequency conversions upstream of the channelizer of the space based forward link subsystem.

12. The subsystem of claim 11 , wherein:

the specified service downlink RF frequency range within which the satellite is configured to produce and transmit the plurality of RF service downlink beams comprises a downlink portion of the Ka band; and

the intermediate RF frequency range within which the channelizer of the space based forward link subsystem is configured to operate is lower than the downlink portion of the Ka band.

13. The subsystem of claim 12 , wherein:

the downlink portion of the Ka band is from 17.7 GHz to 20.2 GHz, and thus, has a bandwidth of 2.5 GHz; or

the downlink portion of the Ka band is from 17.3 GHz to 20.2 GHz, and thus, has a bandwidth of 2.9 GHz.

14. The subsystem of claim 11 , wherein the specified optical wavelength range is a contiguous or non-contiguous optical wavelength range within an infrared (IR) spectrum.

15. The subsystem of claim 11 , wherein the channelizer of the forward link subsystem of the satellite is configured to digitize RF signals provided to input ports of the channelizer, separate the digitized RF signals into independently routable sub-channels, selectively rearrange and combine the sub-channels, and output at output ports of the channelizer analog RF signals that are used to produce the plurality of RF service downlink beams.

16. A method for enabling a space based forward link subsystem of a satellite to produce and transmit a plurality of RF service downlink beams within a specified service downlink RF frequency range to service terminals, wherein the space based forward link subsystem of the satellite includes a channelizer that is configured to operate within an intermediate RF frequency range that is lower than the specified service downlink RF frequency range, the method for use by the space based forward link subsystem comprising:

receiving an optical feeder uplink beam from a ground based subsystem;

producing, in dependence on the received optical feeder uplink beam, a plurality of separate optical signals that each have a different peak wavelength;

without performing any frequency converting upstream of the channelizer of the space based forward link subsystem of the satellite, converting each of the separate optical signals into a respective electrical data signal having an RF frequency within a same intermediate RF frequency range within which the channelizer of the space based forward link subsystem of the satellite is configured to operate;

providing the electrical data signals to the channelizer of the forward link subsystem of the satellite to thereby enable the channelizer of the forward link subsystem of the satellite to perform one or more of analog to digital conversions, digital signal processing, and digital to analog conversions within the intermediate RF frequency range within which the channelizer of the forward link subsystem of the satellite is configured to operate;

upconverting frequencies of electrical data signals output from the channelizer so that the frequencies of the electrical data signals are within the specified service downlink RF frequency range;

producing, in dependence on the frequency upconverted electrical data signals, the plurality of RF service downlink beams within the specified service downlink RF frequency range; and

transmitting the plurality of RF service downlink beams within the specified service downlink RF frequency range.

17. The method of claim 16 , wherein:

the specified service downlink RF frequency range within which the satellite is configured to produce and transmit the plurality of RF service downlink beams comprises a downlink portion of the Ka band; and

the intermediate RF frequency range within which the channelizer of the space based forward link subsystem of the satellite is configured to operate is lower than the downlink portion of the Ka band.

18. The method of claim 17 , wherein:

the downlink portion of the Ka band is from 17.7 GHz to 20.2 GHz, and thus, has a bandwidth of 2.5 GHz; or

the downlink portion of the Ka band is from 17.3 GHz to 20.2 GHz, and thus, has a bandwidth of 2.9 GHz.

19. The method of claim 16 , wherein the specified optical wavelength range is a contiguous or non-contiguous optical wavelength range within an infrared (IR) spectrum.

20. The method of claim 16 , further comprising using the channelizer of the forward link subsystem of the satellite to digitize RF signals provided to input ports of the channelizer, separate the digitized RF signals into independently routable sub-channels, selectively rearrange and combine the sub-channels, and output at output ports of the channelizer analog RF signals that are used to produce the plurality of RF service downlink beams.