A DBF self-beam steering array antenna for mobile satellite applications using beam-space maximal-ratio combination

This paper proposes a diversity-receiving array antenna scheme achieved by digital beamforming (DBF) for the purpose of self-beam steering toward the unknown direction-of-arrival (DOA) of a modulated signal in a mobile satellite communications environment. This scheme uses a multibeam former with a spatial fast Fourier transform (FFT) for the received baseband signals to coarsely acquire the attenuated signal. It also uses a self-phasing processor (SPP) applied to the multibeam outputs for precise acquisition and tracking. In the SPP, maximal-ratio combining is achieved with simple digital numerical operations in the complex baseband, allowing for rapidity and stability in beamforming. As a result, the array antenna steers its receiving beam toward the DOA automatically without the need for nonlinear optimization methods. Moreover, the beam is steered toward the DOA of multipath signals according to their signal levels, leading to the optimal cophase recombination of all correlated signals, which improves the quality of the total receiving signal. This paper discusses the scheme, and its performance is evaluated by computational simulation and experiments conducted in a radio anechoic chamber.