Synergistic Design of Practical High-Capacity Satellite Communication: Leveraging FFT-Based Digital Beamforming

The growing demand for high-capacity satellite communications, particularly in Medium Earth Orbit (MEO) and Low Earth Orbit (LEO) constellations, has made digital beamforming essential to enhance system performance by producing simultaneous beams. Among various techniques, Fast Fourier Transform (FFT)-based beamforming is favored for its power efficiency and effectiveness in terms of Signal-to-Interference Ratio (SIR) when the number of antennas matches the number of beams. However, to reduce costs and complexity in the RF-chain, the number of antennas is often reduced relative to the number of beams, compromising beam pattern orthogonality and degrading the SIR. This article investigates the combination of techniques to mitigate this degradation, including regular spaced triangular-lattice beam pattern and antennas, hexagonal subarray lattices, 4-color scheme, and tapering, all working synergistically to enhance the overall SIR. The proposed method employs regular hexagonal sampling grids, enabling the generation of triangular-lattice beam pattern using standard rectangular FFT-routines. By avoiding interpolation, this approach minimizes artifacts in beam pattern generation over wide fields of view and preserves the SIR, making it particularly suitable for satellite applications. The simulation results demonstrate that the proposed strategy, using a 16-point FFT-beamforming approach with only 100 antenna elements, significantly enhances the SIR by nearly 20 dB compared to the regular scenario.