A Microwave Liquid Crystal Tunable Waveguide Filter Tuned by a Static Magnetic Field

This letter presents the development of a tunable waveguide filter utilizing liquid crystal (LC) material integrated within quartz glass tubes where the LC material is actuated by a static magnetic field. The proposed filter demonstrates a 7% tuning range with a minimal bandwidth variation. Experimental results are presented for a 7.5 GHz filter with a bandwidth of 2.5%, confirming the viability of the concept. The filter incorporates a single tuning element employing only one pair of magnets to reduce tuning complexity and improve reliability.