Paraelectric thin films for microwave applications

We have designed, fabricated and characterized electrically tunable and adaptive microwave devices incorporating paraelectric thin films of Sr0.5Ba0.5TiO3 (SBTO) and SrTiO3 (STO) on 1 cm x 1 cm x 0.5 mm LaAlO3 substrates. The paraelectric layer thickness for these devices varied between 0.5 mu m and 2 mu m. We used normal metal Au and superconducting YBa2Cu3O7-x top electrodes for SBTO and STO devices, and operated them at room- and cryogenic-temperatures, respectively. The microwave devices included voltage-tunable resonators, voltage-tunable phase shifters, voltage-tunable mixers, and voltage-tunable filters. Under de voltage bias, these compact planar devices exhibited up to 30% resonant frequency modulation, about 1 degrees/mm-GHz phase shift, more than 40 dB change in mixed microwave power, and fine-tunable symmetric filter profile with less than 2% bandwidth and more than 15% adaptive range.