High-Performance Beamforming Network Based on Si-Photonics Phase Shifters for Wideband Communications and Radar Applications

The evolution of microwave and mm-wave systems for communication and remote sensing is heading towards a massive deployment of phased-array antennas with beamforming capabilities. 5G wireless access networks are expected to employ beamforming to optimize resources allocation, whereas radars will benefit from precise and fast-scanning antennas. Moreover, in the next future, those systems are expected to widely employ photonic technologies for signal generation, acquisition, and distribution. In this scenario, photonics can allow for the development of high-performance beamforming networks, which can easily be integrated in photonics-assisted RF systems, combining broad operational bandwidth, low signal distortion, and high pointing precision with unprecedented flexibility. In this paper, a phase shift-based beamforming network for microwave applications is presented and its performance analyzed. The Si-photonics integrated phase shifters exhibit large phase shift (>360°) and limited amplitude fluctuations (~2.5 dB). The packaged beamforming network elements show extremely low signal distortion, low steering error (<; 3°), and fast switching time (<; 5 ns), demonstrated by the transmission with beam-steering of a 2-Gb/s communication signal and of a 1-GHz chirped radar waveform. A comparison with commercial RF devices shows that the photonics-assisted beamforming network is well-suited for high bit-rate 5G communications and for wideband radar applications.