Increasing the efficiency of a piezoelectric aluminum nitride microstrip resonator by utilizing high temperature superconductors

摘要

High temperature superconductors have potential applications in the field of microwave devices and circuits. To utilize these materials in such a way as to increase the efficiency of these microwave devices would be beneficial for high efficiency/low noise applications. This dissertation accomplishes the following goals: (1) The design and fabrication of an initial device that increases the quality factor, Q, and therefore the efficiency of a high frequency thin film resonator which uses superconducting metal as the device\u27s electrode, (2) the measurement and characterization of this device, (3) the theoretical calculation and predicted performance of this device, and (4) the comparison of the measured response of this device with the measured response of a similar device made by the standard method using metals in place of the superconductor. Using a modified transmission line analysis approach, a theoretical microwave model of a superconducting metal electrode has been developed. These high temperature superconductor characteristics were modeled electrically by the two-fluid model using the modified transmission line model, and acoustically by using an extension of the Mason model for piezoelectric bulk acoustic wave resonators;Experimental test setups were designed to measure the direct current and microwave characteristics of the high temperature superconductors and devices. A high temperature superconducting microwave resonator structure was fabricated and compared with a similar non-superconducting resonator structure. All results were compared with the aforementioned theoretical results, and conclusions were drawn on the feasibility of the overall project;Aluminum electroded bulk acoustic wave resonators performed well at liquid nitrogen temperature as well as at room temperature. The high temperature superconductor bottom electroded bulk acoustic wave resonators with aluminum as the top electrode showed signs of acoustic activity of the aluminum nitride, but the results were not directly comparable to the aluminum electroded structures. More research will need to be performed on the acoustic properties of these high temperature superconductors to further understand and utilize these materials as electrodes on a thin film resonator.