A true-time delay beamforming system incorporating a wavelength tunable optical phase-lock loop

Abstract

This thesis presents the study of a frequency-discriminator-aided optical phase-lock loop (OPLL) and its application to a fiber-Bragg-grating-based true-time delay (TTD) module for the purpose of phased-array antenna (PAA) beamforming. The TTD module uses uniform fiber Bragg gratings (FBGs) to form the delay lines of an FBG prism. The wavelengths from two external cavity laser diodes are phase-locked by the OPLL and applied to the FBG prism to achieve tunable time delays. The performance of the system is evaluated using a time-delay measurement experiment. The experimental time delays generated are compared with the theoretically designed values and are found to be in close agreement. Simulations of the radiation patterns generated from the measured time delays are found to closely match the steering angle designed for the system. To the best of our knowledge, this is the first time an OPLL has been used in conjunction with an FBG-based TTD beamforming module.