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), 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, the variable gain amplifier unit configured to amplify input signals to the variable beamwidth antenna in accordance with a gain of the variable gain amplifier unit to provide a variable amplifier instantaneous power output; and
a processing unit coupled to the variable gain amplifier unit, the processing unit configured to
utilize navigational data to determine target station direction data associated with direction of the steerable beam pattern towards a target station,
determine, based upon the target station direction data, a target amplifier instantaneous power output that corresponds to an effective isotropic radiated power (EIRP) spectral density (ESD) limit, and
adjust the gain of the variable gain amplifier unit to the variable amplifier instantaneous power output to the target amplifier instantaneous power output.
2. The ESAA of claim 1 , wherein the target station direction data includes a target scan angle and a target skew angle for the steerable beam pattern to direct the steerable beam pattern towards the target station.
3. The ESAA of claim 1 , wherein a gain of the variable beamwidth antenna changes with changes in the target station direction data, and wherein the processing unit is configured to determine the target amplifier instantaneous power output 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 target station direction data.
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 target station direction data so as to cause the gain of the variable gain amplifier unit to be adjusted to set the variable amplifier instantaneous power output to the target amplifier instantaneous power output.
5. The ESAA of claim 3 , wherein the processing unit is configured to use the target station direction data to determine the ESD limit and the gain of the variable beamwidth antenna that corresponds to the target station direction data 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 the variable amplifier instantaneous power output;
use the measured variable amplifier instantaneous power output to determine a transmitted EIRP associated with the variable beamwidth antenna;
determine whether the transmitted EIRP is less than a maximum transmitted EIRP based upon the ESD limit for the target station direction data; 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 updated target station direction data;
determine, based upon the updated target station direction data, an updated target amplifier instantaneous power output that corresponds to an updated ESD limit; and
adjust the gain of the variable gain amplifier unit to set the variable amplifier instantaneous power output to the updated target amplifier instantaneous power output.
8. A method of adjusting effective isotropic radiated power (EIRP) spectral density (ESD), comprising:
determining, by a processing unit, target station direction data associated with steering of a steerable beam pattern from an earth station aboard aircraft (ESAA) towards a target station based upon navigational data of at least one of an aircraft at which the ESAA is located or the target station;
determining, based upon the target station direction data, a target amplifier instantaneous power output of a variable gain amplifier unit of the ESAA that corresponds to an ESD limit associated with the target station direction data, the variable gain amplifier unit being configured to amplify input signals to a variable beamwidth antenna configured to transmit in accordance with the steerable beam pattern; and
adjusting, by the processing unit, a gain of the variable gain amplifier unit to set a variable amplifier instantaneous power output of the variable gain amplifier unit to the target amplifier instantaneous power output.
9. The method of claim 8 , wherein determining the target station direction data associated with steering of the steerable beam pattern from the ESAA towards the target station comprises determining a target scan angle and a target skew angle for the steerable beam pattern to direct the steerable beam pattern towards the target station.
10. The method of claim 8 , wherein determining the target amplifier instantaneous power output that corresponds to the ESD limit associated with the target station direction data is performed based upon the ESD limit associated with the target station direction data and based upon a gain of the variable beamwidth antenna that corresponds to the target station direction data.
11. The method of claim 10 , comprising determining, by the processing unit based upon the target station direction data, the ESD limit associated with the target station direction data and the gain of the variable beamwidth antenna that corresponds to the target station direction data using an ESD limit lookup table (LUT) and an antenna gain LUT, respectively.
12. The method of claim 8 , further comprising:
using a measurement of the variable amplifier instantaneous power output 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 associated with the target station direction data; 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.
13. The method of claim 8 , further comprising:
utilizing updated navigational data to determine updated target station direction data;
determining, based upon the updated target station direction data, an updated target amplifier instantaneous power output that corresponds to an updated ESD limit; and
causing the gain of the variable gain amplifier unit to be adjusted so that the variable amplifier instantaneous power output is set to the updated target amplifier instantaneous power output.
14. A vehicle, comprising:
an on-board system configured to generate navigational data indicative of changes in at least one of a location of the vehicle or an attitude of the vehicle; and
a station configured to:
transmit signals via a variable beamwidth antenna in accordance with a steerable beam pattern;
utilize the navigational data to determine target station direction data associated with direction of the steerable beam pattern towards a target station;
determine, based upon the target station direction data, a target amplifier instantaneous power output of a variable gain amplifier unit that corresponds to an effective isotropic radiated power (EIRP) spectral density (ESD) limit associated with the target station direction data, the variable gain amplifier unit being configured to amplify input signals to the variable beamwidth antenna; and
adjust a gain of the variable gain amplifier unit to set a variable amplifier instantaneous power output of the variable gain amplifier unit to the target amplifier instantaneous power output.
15. The vehicle of claim 14 , 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 vehicle of claim 14 , wherein the target station direction data includes a target scan angle and a target skew angle for the steerable beam pattern to direct the steerable beam pattern towards the target station.
17. The vehicle of claim 14 , wherein a gain of the variable beamwidth antenna changes with changes in the target station direction data, and wherein the station is configured to determine the target amplifier instantaneous power output that corresponds to the ESD limit associated with the target station direction data based upon the ESD limit associated with the target station direction data and based upon a gain of the variable beamwidth antenna that corresponds to the target station direction data.
18. The vehicle of claim 17 , wherein the station is configured to determine the ESD limit associated with the target station direction data and the gain of the variable beamwidth antenna that corresponds to the target station direction data using an ESD limit lookup table (LUT) and an antenna gain LUT, respectively.
19. The vehicle of claim 14 , wherein the station is further configured to:
use a measurement of the variable amplifier instantaneous power output to determine a transmitted EIRP associated with the variable beamwidth antenna;
determine whether the transmitted EIRP is less than a maximum transmitted EIRP based upon the ESD limit for the target station direction data; and
further adjust the gain of the variable gain amplifier unit when the transmitted EIRP is greater than the maximum transmitted EIRP.
20. The vehicle of claim 14 , wherein the station is further configured to:
determine updated target station direction data based upon a change in the navigational data;
determine, based upon the updated target station direction data, an updated target amplifier instantaneous power output that corresponds to an updated ESD limit; and
further adjust the gain of the variable gain amplifier unit to set the variable amplifier instantaneous power output to the updated target amplifier instantaneous power output.