All-optically Controlled Microwave Analog Phase Shifter with Insertion Losses Balancing

An all-optically driven microwave phase shifter is designed and experimentally demonstrated for 1–10 GHz. The proposed optical addressing is realised in nematic liquid crystals (NLC) mixed with novel mesogenic azobenzene (azo) dyes, allowing a dielectric constant variation from a surface anchoring nematic state to a photo-induced isotropic state when exposed to a laser beam with a wavelength of 465 nm. The phase shifter device is implemented in a compact meandered inverted microstrip with impedance matched by a novel light-intensity-dependent method for insertion loss balancing between tuning states. Prototyped by photolithography, the device is assembled with an azo NLC mixture of GT3-24002 and CPND-7 (10wt%). Measurements report a continuously tunable differential phase shift of 0–184˚ at 10 GHz with a maximum insertion loss of –3.53 dB and negligible insertion loss variations (up to 9%) between phase-shifting states, which eliminates complex phase-biasing networks and amplitude-compensating circuits for the standalone high-resolution phased array beamforming application with reduced distortions