Measurement Of The Surface Impedance Of The High Temperature Superconducting Thin Films With Coplanar Transmission Line

Nowadays, high-temperature superconductor thin film is more and more widely used because of its lower surface resistance and power losses. Especially with the continuous improvement of high-temperature superconducting thin film technology, it has an optimistic prospect of being widely used in the communication and electronic information field. However, it appears much nonlinear responses in microwave field, which limits possible devices applications. High-temperature superconducting thin films' microwave surface impedance is an important parameter in judging nonlinearities of the film. Therefore, the method used to measure high-temperature superconductor thin films' microwave surface impedance plays an important role in nonlinearities research. At present, researches in this respect are carried on in many countries in the world.This dissertation particularly presents the principle of measuring high-temperature superconductor thin films' microwave surface impedance with coplanar transmission line, builds the model of the testing cavity, simulates and analyzes this model. The resonator is simulated and analyzed in the experiment, and then S₂₁ coefficient graphs are compared and optimized. Finally the ideal size and the optimum inserted depth of the probe are found. According to this optimized result, the testing cavities are designed and made.Since the project was established, this method has been continuously experimented through simulation for many times. It solves the difficult problem of coupling, which successfully making the resonator produce a resonant effect. It makes the resonant frequency of the resonators lower to 4.5GHz. A reasonable agreement for the simulation results and experimental results has been observed, which approves the feasibility of measuring high temperature superconducting thin films on microwave vector network analyzer with low frequency.