Nonlinear dielectric thin films for active and electrically tunable microwave devices

We have prepared electrically tunable and active microwave devices incorporating (superconducting YBa₂Cu₃O_7-x)/(nonlinear dielectric SrTiO₃) or (normal metal Au)/(nonlinear dielectric Sr_0.5Ba_0.5TiO₃) bilayers. The dielectric layer thickness for these samples varied between 0.5 μm and 2 μm. The top electrode layer for each sample was patterned into a coplanar waveguide device structure. We have configured these devices as voltage-tunable resonators, voltage-tunable phase shifters, voltage-tunable mixers, and voltage-tunable filters. Under dc voltage bias, these prototype devices have exhibited up to 30% resonant frequency modulation, about 1°/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.