FERROELECTRIC FILM PHASE SHIFTER UNDER ELEVATED MICROWAVE POWER

ABSTRACT Voltage-controlled phase shifters based on fin-lines incorporating barium-strontium titanate (BSTO) films were studied at high microwave power levels (∼37 GHz). The two primary mechanisms responsible for phase variation in the ferroelectric phase shifters under microwave power were experimentally identified and theoretically described: (i) microwave-electric-field induced instantaneous variation of the BSTO film dielectric constant; (ii) a comparatively slow thermal drift of dielectric constant due to microwave power dissipation in the ferroelectric films. It is shown that the power handling capability of these tunable microwave devices is defined by the thermal effects.