Efficient Photonic Beamforming System Incorporating a Unique Featured Tunable Chirped Fiber Bragg Grating for Application Extended to the Ku-Band

This article demonstrates a photonic-based wideband true-time delay (TTD) beamforming network employing a raised cosine apodized linearly chirped fiber Bragg grating (FBG) of varying lengths, such as 50 × 10-3m, 45 × 10-3m, 40 × 10-3m, and 35 × 10-3m, and different chirp parameters 25 × 10-9m, 35 × 10-9m, 6 × 10-8m, and 8 × 10-8m. The proposed scheme can be used as variable TTD lines having a much lower ripple factor compared with the previously studied apodized linearly CFBG for controlling the radiation angle of phased-array antenna (PAA), i.e., the main lobe radiated by the PAA can be steered squint-free from 0° to ±36.8° suitable for continuous beam forming at microwave frequencies 8-12 GHz extended up to Ku-band. To the best of our knowledge, this is the first experimental demonstration that shows the impact of tuning wavelength on delay change due to raised cosine apodized CFBG in the RF signal fed to the respective element of the antenna array. Four sets of 1 × 4 PAAs have been fabricated with the required electrical parameters, such as reflection coefficient (S11), voltage standing wave ratio, gain, far-field radiation pattern, and so on, to show the photonic feed idea. In addition, FBG's having raised cosine apodization function is fabricated in our collaborative laboratory.