Optical true time-delay feeder for phased array antennas using fiber Bragg gratings and metal film reflectors

We propose a novel optical true time-delay (TTD) feeder for phased array antennas (PAAs) using a fiber Bragg gratings (FBGs) prism and Cr/Au film reflectors directly deposited on cleaved fiber ends. This structure requires less number of FBGs than the previously proposed FBG-only TTD feeders and also provides the flexibility in wavelength selection due to the uniform reflectance of the metal film in a broad wavelength range. A TTD feeder with two delay lines for 10 GHz linear PAAs capable of steering beams in three directions at 0° and ±30° has been built. Experimental results on time delays are in good agreement with those calculated at all the steering angles.