Dynamic effective radiated power (ERP) adjustment
Antennas used aboard aircraft to communicate with satellites or ground stations may have complex antenna patterns, which may vary as the aircraft moves throughout a given coverage area. Techniques are disclosed for dynamically adjusting the instantaneous power fed to an antenna system to ensure that the antenna transmits at the regulatory or coordinated effective isotropic radiated power (EIRP) spectral limit. The antenna may transmit, in accordance with aircraft location and attitude, steerable beam patterns at different scan and skew angle combinations, causing variations in antenna gain and fluctuations in the transmitted EIRP. Using on-board navigational data, an antenna gain and ESD limit may be calculated for a particular scan and skew angle, which may be used to adjust power fed to the antenna such that the antenna transmits substantially at maximum allowable EIRP as the steerable beam pattern is adjusted.
1. An earth station aboard aircraft (ESAA), the ESAA comprising:
a variable beamwidth antenna configured to transmit in accordance with a steerable beam pattern;
a variable gain amplifier unit coupled to the variable beamwidth antenna; and
a processing unit coupled to the variable gain amplifier unit, and configured to
utilize navigational data to determine the steerable beam pattern towards a target station,
determine a gain of the variable gain amplifier based upon the determined steerable beam pattern and an effective isotropic radiated power (EIRP) spectral density (ESD) limit, and
adjust a gain of the variable gain amplifier unit to the determined gain.
2. The ESAA of claim 1 , wherein determining the steerable beam pattern includes determining a target scan angle and a target skew angle.
3. The ESAA of claim 1 , wherein a gain of the variable beamwidth antenna changes with changes in the steerable beam pattern, and wherein the processing unit is configured to determine a target instantaneous power output of the variable gain amplifier that corresponds to the ESD limit based upon the ESD limit and based upon a gain of the variable beamwidth antenna that corresponds to the steerable beam pattern.
4. The ESAA of claim 3 , wherein the variable gain amplifier unit includes a gain trim block and an amplifier block, and wherein the processing unit is configured to adjust a gain trim of the gain trim block based upon the ESD limit and based upon the gain of the variable beamwidth antenna that corresponds to the steerable beam pattern so as to cause the gain of the variable gain amplifier unit to be adjusted to set an instantaneous power output of the variable gain amplifier unit to a target instantaneous power output.
5. The ESAA of claim 3 , wherein the processing unit is configured to use the steerable beam pattern to determine the ESD limit and the gain of the variable beamwidth antenna using an ESD limit lookup table (LUT) and an antenna gain LUT, respectively.
6. The ESAA of claim 1 , wherein the processing unit is further configured to:
measure an instantaneous power output of the variable gain amplifier unit;
use the measured instantaneous power output to determine a transmitted EIRP associated with the variable beamwidth antenna;
determine whether the transmitted EIRP is greater than a maximum transmitted EIRP based upon the ESD limit for the steerable beam pattern; and
cause the gain of the variable gain amplifier unit to be further adjusted when the transmitted EIRP is greater than the maximum transmitted EIRP.
7. The ESAA of claim 1 , wherein the processing unit is further configured to:
utilize updated navigational data to determine an updated steerable beam pattern;
determine, based upon the updated steerable beam pattern and an updated ESD limit, an updated gain of the variable gain amplifier; and
adjust the gain of the variable gain amplifier unit to the updated gain.
8. The ESAA of claim 1 , wherein the ESAA is located in a vehicle, and wherein the navigational data includes at least one of (i) a latitude of the vehicle, (ii) a longitude of the vehicle, (iii) an altitude of the vehicle, (iv) a latitude of the target station, (v) a longitude of the target station, (vi) an altitude of the target station, (vii) a roll orientation of the vehicle, (viii) a pitch orientation of the vehicle, or (ix) a yaw orientation of the vehicle.
9. A method, comprising:
determining, by a processing unit, a steerable beam pattern from an earth station aboard aircraft (ESAA) towards a target station based upon navigational data;
determining, by the processing unit, a gain of a variable gain amplifier coupled to a variable beamwidth antenna of the ESAA based upon the determined steerable beam pattern and an effective isotropic radiated power (EIRP) spectral density (ESD) limit; and
adjusting, by the processing unit, a gain of the variable gain amplifier to the determined gain.
10. The method of claim 9 , further comprising determining, by the processing unit, the steerable beam pattern from the ESAA towards the target station by determining a target scan angle and a target skew angle.
11. The method of claim 10 , further comprising determining a target instantaneous power output that corresponds to the ESD limit based upon a gain of the variable beamwidth antenna that corresponds to the steerable beam pattern.
12. The method of claim 11 , further comprising determining, by the processing unit, the ESD limit and the gain of the variable beamwidth antenna using an ESD limit lookup table (LUT) and an antenna gain LUT, respectively.
13. The method of claim 9 , further comprising:
using a measurement of an instantaneous power output of the variable gain amplifier unit to determine a transmitted EIRP associated with the variable beamwidth antenna;
determining whether the transmitted EIRP is less than a maximum transmitted EIRP based upon the ESD limit for the steerable beam pattern; and
causing the gain of the variable gain amplifier unit to be further adjusted when the transmitted EIRP is greater than the maximum transmitted EIRP.
14. The method of claim 9 , further comprising:
utilizing updated navigational data to determine an updated steerable beam pattern;
determining, based upon the updated steerable beam pattern and an updated ESD limit, an updated gain of the variable gain amplifier; and
adjusting the gain of the variable gain amplifier unit to the updated gain.
15. The method of claim 9 , wherein the ESAA is located in a vehicle, and wherein the navigational data includes at least one of (i) a latitude of the vehicle, (ii) a longitude of the vehicle, (iii) an altitude of the vehicle, (iv) a latitude of the target station, (v) a longitude of the target station, (vi) an altitude of the target station, (vii) a roll orientation of the vehicle, (viii) a pitch orientation of the vehicle, or (ix) a yaw orientation of the vehicle.
16. The method of claim 9 , wherein the steerable beam pattern includes a target scan angle and a target skew angle to direct the steerable beam pattern towards the target station.
17. The method of claim 9 , wherein a gain of the variable beamwidth antenna changes with changes in the steerable beam pattern, and wherein the ESAA is configured to determine a target instantaneous power output that corresponds to the ESD limit associated with the steerable beam pattern based upon a gain of the variable beamwidth antenna that corresponds to the steerable beam pattern.
18. The method of claim 9 , further comprising:
determining a transmitted EIRP associated with the variable beamwidth antenna;
determining whether the transmitted EIRP is greater than a maximum transmitted EIRP based upon the ESD limit for the steerable beam pattern; and
further adjusting the gain of the variable gain amplifier unit when the transmitted EIRP is greater than the maximum transmitted EIRP.
19. The method of claim 9 , further comprising:
determining an updated steerable beam pattern based upon a change in the navigational data;
determining, based upon the updated steerable beam pattern and an updated ESD limit, an updated gain; and
further adjusting the gain of the variable gain amplifier unit to the updated gain.
20. A non-transitory machine-readable medium storing instructions that, when executed by a processor, cause an earth station aboard aircraft (ESAA) to:
utilize navigational data to determine a steerable beam pattern towards a target station;
determine a gain of the variable gain amplifier based upon the determined steerable beam pattern and an effective isotropic radiated power (EIRP) spectral density (ESD) limit;
configure a variable beamwidth antenna to transmit in accordance with the determined steerable beam pattern; and
adjust a gain of the variable gain amplifier unit coupled to a variable beamwidth antenna to the determined gain.