Non-linear microwave response of HTS thin films: a comparison of intermodulation and conventional measurements

The non-linear microwave response of HTS thin films is a crucial issue for applications of the cuprates in future communications technologies. We repo rt comparisons of nonlinear characterisation measurements made by two diffe rent techniques. The first involves two-tone intermodulation measurements, for which the HTS thin films are incorporated into a high Q resonant struct ure and two spectrally pure tones are injected within the resonator bandwid th. The second consists of a conventional high power steady-state parallel- plate resonator measurement of the non-linear response of Z(s)(H-rf). Two v ery different HTS thin film samples are examined and simple physical models , involving grain boundary effects or film heating, are used to relate the intermodulation and power dependent impedance results to properties of the HTS thin film.