Hybrid Analogue-Digital Beamforming for Non Terrestrial Networks

The paper describes active array antennas and beamforming networks (BFN) exploiting a two-level analogue-digital beamforming scheme to reduce the complexity of conventional active arrays based on a fully analogue or a fully digital beamforming. Fully digital BFNs offer clear advantages for meeting the challenging reconfigurability requirements of satellite operators, however the key drawback of these solutions is related to the complexity of the digital BFN implementation, requiring often unaffordable mass and power consumption/dissipation resources. In order to combine the advantages of both analogue and digital beamforming schemes, hybrid active antennas have been introduced. Direct radiating arrays with hybrid beamforming adopt two or more levels of beamforming: one being analogue and the other one digital. While active antennas based on hybrid beamforming schemes have been significantly used for ground systems, only recently they have been considered for satellite systems.