Ybco Thin Films, Microwave Power Of Nonlinear Test Study

The power-handing capability of High Temperature Superconductor (HTS) microwave devices is limited by the microwave power nonlinear effects of HTS, so it is difficult to fabricate large power microwave devices with HTS thin films. As the key problem of HTS technique, there is no unified view about HTS microwave power nonlinearity all over the word. Considering the mysteries, the microwave nonlinearity of HTS is studied in this paper. The main work in this paper includes:1. The model of Micro-bridge Resonator has been determined through Full-wave Moment method and used to study the microwave nonlinearity effect of YBCO thin film. At the same time, the formula for designing Micro-bridge resonator has also been given. The Micro-bridge structure facilitates high power measurement and the related research. Through equivalent circuit analysis of Micro-bridge resonator, the equivalent lumped parameters have been linked together with physical parameters and external testing parameters. This gives a good chance for the calculation of Micro-bridge resonator's RF current and RF magnetic filed.2. In order to reduce the influence parameters in the measurement and calculation, and to simplify the testing system and calculation for microwave nonlinearity, one port micro-bridge resonator test method has been used. And the vector network analyzer and software have been combined to determine the detuning reference surface to deal with the test data accurately.3. Through calculation, the value of S parameter that is associated with the largest stored energy in the resonator has been obtained. Basing on ADS Moment Method, Micro-bridge Micro strip Resonator structures have been designed out which has maximum energy storage capability. Then the masker, shielding box, packaging and testing have been completed one by one.4. The microwave nonlinearities tests have been completed, including (1) frequency response test; (2) microwave nonlinear impedance test; (3) power compression test; (4) memory effect test, which is like Hysteric's effect. Every test phenomenon has been described in detail, and followed by a preliminary discussion and analysis. According to the relationship among various parameters given in Chapter 2, the calculation of Micro-bridge resonator's RF current and RF magnetic filed have been completed. And the microwave nonlinear power-dependence characters have been obtained. After the comparisons, power dependence of parameters has been divided into three zones: low input power linear region I; nonlinear mixing region II; high power nonlinear break region III. Through power compression tests, the critical current density value on the impact of non-linear microwave has been ruled out.