A Two-Dimensional Optical True Time-Delay Beamformer Consisting of a Fiber Bragg Grating Prism and Switch-Based Fiber-Optic Delay Lines

A two-dimensional optical true time-delay (TTD) beamforming system for a planar phased array antenna (PAA) is proposed and demonstrated. The optical beamforming system consists of a fiber-Bragg-grating-prism-based wavelength-dependent TTD (WD-TTD) unit for azimuth beam steering and a microelectromechanical-system-switch-based wavelength-independent TTD (WI-TTD) unit for elevation beam steering. The time delays generated by the WD-TTD and WI-TTD are measured. The results show that the proposed system can achieve the required time delays with the time-delay errors for the WD-TTD and the WI-TTD at 1 GHz less than 11.8 and 3.6 ps, which correspond to radiation direction errors of less than 1.5deg and 0.4deg for a planar PAA with the adjacent array elements spaced by a half radio-frequency wavelength.