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Optical single sideband modulation based on superstructure grating for a remotely controlled phased array antenna system

A single sideband (SSB) modulation scheme using a superstructure fiber Bragg grating (FBG) for a remotely controlled photonic true time-delay (TTD) beamforming system is presented in this paper. Photonic true time-delay (TTD) is considered a promising technique for wideband phased array antennas, as it allows beam steering of the antenna without the beam squint problem. For remotely controlled phased array antennas, the dispersive properties of a single mode fiber induce a power penalty at discrete RF frequencies when a double sideband (DSB) modulation scheme is used. The SSB modulation scheme is an effective way to eliminate this power penalty as only one sideband is transmitted and thus no beating is possible upon the recovery of the electrical signal by a photodetector. This paper presents for the first time a theoretical model as well as experimental results of a SSB modulation scheme based on a superstructure grating with two phase shifts. The true-time delay system considered utilizes a discrete uniform Bragg prism which allows discrete beam steering capabilities for the phased array antenna.