Photonic True-Time Delay Beamforming Based on Superstructured Fiber Bragg Gratings With Linearly Increasing Equivalent Chirps

A photonic true-time delay beamforming system for phased array antennas based on superstructured fiber Bragg gratings (SFBGs) with linearly increasing equivalent chirps is proposed and demonstrated. The theory behind SFBGs with equivalent chirps is detailed and a closed-form equation for the equivalent dispersion is presented for the first time. Array factors, calculated based on the experimentally measured time delays are shown for different wavelengths of the photonic beamformer. An analysis of the errors present in the group delay responses of the fabricated SFBGs is also presented.