Attitude-Based User Terminal Beam Pointing Using Downlink Data Bursts From Broadband Satellites

In satellite communications, beam pointing is fundamental for the user terminal to perform stable communications with passing satellites. The traditional energy-based user terminal beam pointing method tracks the energy of received signals, which requires the received signal to have a good enough signal-to-noise ratio (SNR) to search for the energy peak. In this work, an antenna attitude-based beam pointing method using downlink data bursts from broadband satellites is proposed. The proposed method consists of two stages: in the acquisition stage, the user terminal achieves rough beam alignment using a 9-axis inertial measurement unit (IMU) as the conventional method; and in the tracking stage, super-resolution time difference of arrival (TDOA) measurements are obtained from a phased array antenna with multiple subarrays by receiving data bursts from the passing satellite. The TDOA measurements are fused with the triaxial gyroscope and triaxial magnetometer outputs through the proposed factor graph optimization-based fine attitude estimation algorithm to achieve fine attitude estimation results, from which the optimal beam pointing direction is derived. The simulation results show that the proposed method achieves 0.2° beam pointing estimation precision when a 1 ms, 100 MHz 5G non-terrestrial network (NTN) downlink orthogonal frequency division multiplexing (OFDM) signal is available per second.