Reduced Nonlinearity Superconducting Thin Films for Transmit and Receive Applications

Superconductor Technologies Inc. (STI) has deployed more than 5,800 high-performance RF filter systems incorporating high-temperature superconducting (HTS) thin films. The deposition method of reactive coevaporation (RCE) used to produce these HTS films in high volume has also allowed the optimization of their RF properties to the point at which their deleterious nonlinearities have been reduced to their intrinsic limit. A new formulation of the theory of these nonlinearities for d-wave superconductors predicts that they may be further reduced by increasing the thickness of the HTS films. The RCE growth technique provides advantages in fabricating thicker single-layer and multilayer HTS films of optimal composition while maintaining excellent crystallinity. During Phase I of this project, we propose to grow such thick HTS films and measure their RF properties at STI and at Lincoln Laboratory. HTS receive filter systems with reduced nonlinearities, and hence intermodulation distortion, will benefit by being operable in high-interference environments. Increased power handling provided by reduced nonlinearity HTS films also promises to pave the way for the introduction of HTS transmit filters, thereby opening the door to myriad important commercial and Government applications.