Forward and reverse calibration for ground-based beamforming
View Patent ↗Methods and systems for calibrating the return and forward links of a satellite communication system are provided according to embodiments of the invention. The phase and/or amplitude variations caused by the return and forward links are calculated and/or estimated to aid in beamforming, such as ground-based beamforming. Calibration earth stations, distributed within one or more beam patterns, may be used to transmit calibration codes to the gateway to calibrate the return link. Return links variations may be estimated using a weighted minimum mean square algorithm at the gateway. Forward links may be calibrated with calibration codes transmitted from the gateway through a hybrid matrix to at least one calibration station. Forward calibration links may also calibrate for temperature-dependent signal variations such as diplexer variations at the satellite.
1. A method for estimating the effects of a satellite return link at a gateway, the method comprising:
receiving a signal comprising a plurality of PN codes from a plurality of calibration stations through the satellite, wherein the satellite receives the PN codes from the calibration stations through one or more satellite feeds, the satellite retransmits the PN codes to the gateway, and at least two of the plurality of calibration stations are located within distinct satellite beam coverage areas;
extracting phase information from the received PN codes; and
estimating the phase effects of the satellite return link by applying a weighted minimum mean square algorithm to the extracted phase information.
2. The method according to claim 1 , wherein the weighted minimum mean square algorithm uses at least one matrix of nominal feed excitation levels to estimate the phase effects.
3. The method according to claim 1 further comprising:
receiving an indication of the satellite orbital position from the satellite;
retrieving a matrix of nominal feed excitation levels from memory associated with the satellite orbital position; and
using the retrieved matrix of nominal feed excitation levels to estimate the phase effects.
4. The method according to claim 1 further comprising:
calculating beamforming parameters using the estimated phase effects; and transmitting the beamforming parameters to the satellite.
5. The method according to claim 1 further comprising:
extracting amplitude information from the received PN codes; and
estimating the amplitude effects of the satellite return link by applying a weighted minimum mean square algorithm to the extracted amplitude information.
6. A method for estimating the effects of a satellite return link at a gateway, the method comprising:
receiving a signal comprising a plurality of PN codes from a plurality of calibration stations through the satellite, wherein the satellite receives the PN codes from the calibration stations through one or more satellite feeds, the satellite retransmits the PN codes to the gateway, and at least two of the plurality of calibration stations are located within distinct satellite beam coverage areas;
extracting amplitude information from the received PN codes; and
estimating the amplitude effects of the satellite return link by applying a weighted minimum mean square algorithm to the extracted amplitude information.
7. The method according to claim 6 , wherein the weighted minimum mean square algorithm uses at least one matrix of nominal feed excitation levels to estimate the amplitude effects.
8. The method according to claim 6 further comprising:
receiving an indication of the satellite orbital position from the satellite;
retrieving a matrix of nominal feed excitation levels from memory associated with the satellite orbital position; and
using the retrieved matrix of nominal feed excitation levels to estimate the amplitude effects.
9. The method according to claim 6 further comprising:
calculating beamforming parameters using the estimated amplitude effects; and
transmitting the beamforming parameters to the satellite.
10. The method according to claim 6 further comprising:
extracting phase information from the received PN codes; and
estimating the phase effects of the satellite return link by applying a weighted minimum mean square algorithm to the extracted amplitude information.
11. A method for estimating the effects of a satellite return link at a gateway, the method comprising:
receiving a signal comprising a plurality of PN codes from a plurality of calibration stations through the satellite, wherein the satellite receives the PN codes from the calibration stations through one or more satellite feeds, the satellite retransmits the PN codes to the gateway, and at least two of the plurality of calibration stations are located within distinct satellite beam coverage areas;
extracting phase and amplitude information from the received PN codes;
estimating the amplitude effects of the satellite return link by applying a weighted minimum mean square algorithm to the extracted amplitude information; and
estimating the phase effects of the satellite return link by applying a weighted minimum mean square algorithm to the extracted phase information.
12. A satellite communication system comprising:
a plurality of calibration stations;
a satellite comprising more than one feed, wherein the calibration stations transmit PN signals to the satellite and the PN signals are received at least one of the satellite feeds; and
a gateway configured to receive signals from the satellite, wherein the gateway receives the PN codes from the satellite, and the gateway is further configured to:
extract phase information from the PN codes,
extract amplitude information from the PN codes,
estimate the amplitude effects of a satellite return link using a minimum mean square algorithm; and
estimate the phase effects of a satellite return link using a minimum mean square algorithm.
13. The satellite communication system according to claim 12 , wherein the gateway includes memory that stores a plurality of matrices of nominal feed excitation levels, and the gateway is configured to receive an indication of the satellite orbital position from the satellite, retrieve a matrix of nominal feed excitation levels from memory associated with the satellite orbital position; and use the retrieved matrix of nominal feed excitation levels to estimate the amplitude effects.
14. The satellite communication system according to claim 12 , wherein the gateway is configured to calculate beamforming parameters using the estimated amplitude effects; and transmit the beamforming parameters to the satellite.