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Photonic true-time-delays based on multiplexed substrate-guided wave propagation for phased array antenna applications

A compact and affordable photonic true-time-delay (TTD) beam steering device for phased array antenna applications using multiplexed substrate-guided wave propagation is presented. The TTD design uses holographic input and output couplers to change the direction of beam propagation as well as optical fanout. Optical delays of various delay lines can be adjusted easily through the substrate thickness and the total internal reflection angle inside the substrate material. Broadband microwave signals for feeding the radiating elements are generated through optical heterodyne technique and they are detected by metal-semiconductor-metal detector arrays. The physical aspects of phase-shifters and true-time-delays are first introduced. Then design issues on the photonic TTD architecture and practical constraints on making holographic grating couplers are discussed, especially concerning with recording gratings on DuPont photopolymer materials. Finally, the generation and detection of high frequency microwave signals up to 25 GHz by optical heterodyne techniques are illustrated.