Methods and systems for mitigating interference with a nearby satellite
In one embodiment, an antenna system is described. The antenna system includes a primary antenna on an aircraft. The primary antenna is mechanically steerable and has an asymmetric antenna beam pattern with a narrow beamwidth axis and a wide beamwidth axis at boresight. The antenna system also includes a secondary antenna on the aircraft, the secondary antenna including an array of antenna elements. The antenna system also includes an antenna selection system to control communication of a signal between the aircraft and a target satellite via the primary antenna and the secondary antenna. The antenna selection system switches communication of the signal from the primary antenna to the secondary antenna when an amount of interference with an adjacent satellite reaches a threshold due to the wide beamwidth axis of the asymmetric antenna beam pattern.
1. A method of controlling communication with a target satellite via an antenna system onboard an aircraft, wherein the antenna system has a primary antenna and a secondary antenna, and the method comprises:
determining a geographic location of the aircraft;
switching between the primary antenna and the secondary antenna for transmitting an uplink signal to the target satellite, in dependence on the geographic location of the aircraft in relation to a first acceptable service area where transmission of the uplink signal via the primary antenna satisfies an uplink interference requirement with a non-target satellite, and further in relation to a different second acceptable service area where transmission of the uplink signal via the secondary antenna satisfies the uplink interference requirement with the non-target satellite; and
adjusting one or more transmission parameters of the uplink signal when switching between the primary antenna and the secondary antenna, to account for performance differences between the primary and secondary antennas and thereby maintain a return link operating point at the target satellite with respect to reception of the uplink signal.
2. The method according to claim 1 , wherein, for transmitting the uplink signal from the primary antenna, the method includes controlling a transceiver to enable electronics associated with the primary antenna and disable electronics associated with the secondary antenna, and wherein, for transmitting the uplink signal from the secondary antenna, the method includes controlling the transceiver to enable the electronics associated with the secondary antenna and disable the electronics associated with the primary antenna.
3. The method according to claim 1 , wherein differences between the first and second acceptable coverage areas result from differences in antenna characteristics between the primary and secondary antennas.
4. The method according to claim 1 , wherein a portion of the first acceptable service area overlaps with a portion of the second acceptable service area, thus defining an overlapped area.
5. The method according to claim 4 , wherein switching between the primary antenna and the secondary antenna for transmitting the uplink signal comprises using the primary antenna for transmitting the uplink signal responsive to the geographic location of the aircraft being within the first acceptable service area, including within the overlapped area, and using the secondary antenna for transmitting the uplink signal responsive to the geographic location of the aircraft being within the non-overlapped portion of the second acceptable service area.
6. The method according to claim 1 , wherein adjusting the one or more transmission parameters of the uplink signal comprises adjusting one or more of a power level of the uplink signal and a bandwidth spreading of the uplink signal.
7. The method according to claim 1 , wherein adjusting the one or more transmission parameters of the uplink signal comprises increasing a transmit power of the uplink signal when switching transmission of the uplink signal from the primary antenna to the secondary antenna, to account for a difference in antenna gains between the primary and secondary antennas.
8. The method according to claim 1 , further comprising using the primary antenna for receiving a downlink signal from the satellite, independent of which antenna is used for transmitting the uplink signal.
9. The method according to claim 1 , wherein at least one of the target satellite and the non-target satellite is a non-geostationary satellite.
10. The method according to claim 9 , where the target satellite is a first non-geostationary satellite, and the non-target satellite is a second non-geostationary satellite.
11. The method according to claim 9 , wherein a first one of the target satellite and the non-target satellite is a non-geostationary satellite, and a second one of the target satellite and the non-target satellite is a geostationary satellite.
12. The method according to claim 1 , wherein the target satellite is a first geostationary satellite, and the non-target satellite is a second geostationary satellite.