Design, fabrication, and characterization of double-sided high-temperature superconducting RF filter.

摘要

This dissertation reports the design, fabrication, and characterization of double-sided high-T_c superconducting (HTS) resonator-based RF filter. This filter operates in HF range (3–30 MHz) of electromagnetic spectrum, demonstrating the center frequency of about 18 MHz, and the 3-dB bandwidth of 5%.; The main feature of the proposed device is the double-sided structure that not only reduces the size of a HF filter, but also provides a much higher quality factor, Q, and extremely low insertion loss between the input and output of the filter. Such ideal characteristics have become possible because of the inherently low surface impedance of the superconductors, and the strong magnetic coupling between the input/output ports of the filter. The latter is accomplished because of the unique device configuration, which provides the maximum magnetic flux shared between the different elements of the filter.; The heart of the new device is the multi-turn HTS spiral resonator structure. Three of such resonators are utilized to form a three-pole filter. The resonant frequencies of these resonators are chosen to be the same in order to provide the maximum coupling and transfer of energy between them. Also due to such coupling, the energy transfer between the input and output of the filter is maximized, indicating a very low insertion loss.; In addition to the resonators, two single-turn coils are employed as the input and output structures. Each loop is concentric with one of the resonators to share the maximum magnetic flux, which in turn translates to stronger magnetic coupling between the different filter elements.; A variety of device configurations have been designed, fabricated, and characterized. The three-pole frequency responses for different filter configurations, including a single-input/three-output channelizer structure, have been analyzed, and the results will be provided in this work. One of the structures for a single-input/single-output three-pole filter demonstrates the insertion loss of smaller than −0.4 dB at the center frequency of about 18 MHz. All the test/characterizations are conducted in a liquid nitrogen bath at 77 K.; In addition, the complete fabrication processes and parameters, including the process of photolithography and device packaging will be discussed in this dissertation.; One chapter of the dissertation is devoted to the new HTS filter theory and analyses. Another chapter discusses HTS parameters and reported data that are conventionally employed in designing the HTS RIF components. By analyzing the above two chapters, as well as reviewing the test results of the filter, it will be proven that the double-sided HTS filter will reduce the non-linearities due to intermodulation, and will eliminate the higher order harmonies.; As the final remarks, it must be mentioned that a similar filter structure can be designed and fabricated to operate in much higher frequencies (as high as GHz range). Such future possibilities make this new approach in HTS RF filter theory and analysis even more attractive.