Design And Research Of Mult-band Hts Filter Aimed At High Speed Wireless Communication System

Superconducting films have low surface resistance at certain temperature, and the filters based on HTS films are characterized by high selectivity, low insertion loss and steep out-of-band rejection. And with the rapid development of communication industry, it is always needed to compatible with all kinds of spectrum signal, to improve the system integration and reduce cost. As the key device for RF front end, the multiband high-temperature superconducting(HTS) filter has become a research focus in microwave communication field. In this paper, a systematic study of multiband HTS filter is done based on research project in master work. The main researches as follows:(1) A compact triple-band high temperature superconducting(HTS) filter using coupled-line stepped-impedance-resonator(C-SIR) has been proposed in this paper. And this C-SIR can be analyzed by even-odd theory. In order to enhance the selectivity of the proposed filter, an inter-digital structure between the C-SIR and feed-line has been utilized, which introduces several transmission zeros. Then so as to achieve better coupling of two order resonator and miniaturization, spiral lines are applied to the high impedance transmission line section. Meanwhile, a deep discussion for filtering performance is introduced in different temperature. Finally, studying the miniaturization of a transmission line theory, and analyzing the equivalent circuit of miniaturization of transmission line model. Then it provided theoretical guidance for the superconducting circuit miniaturization.(2). Here, we show that achieving a filter with triple-band and wide stopband properties is obtained by using multi-mode stepped-impedance split ring resonator(SI-SRR). Also, properties and equivalent circuit models of the multi-mode SI-SRR are investigated by evenand odd-mode analysis. A concrete analytical relationship between resonators resonant frequency between impedance ratio and electrical length ratios is shown. To verify this design methodology, a triple-band high-temperature superconducting(HTS) filter is designed and fabricated for TD-SCDMA, Wi-MAX, and WLAN with a compact size. Meanwhile, a deep study for external and internal coupling is introduced.(3) Based on the previous researches of stub-loaded resonator, a further expansion is made, and a novel stub-loaded multimode resonator with ring perturbation is proposed. The resonant characteristics of the multi-mode resonator are investigated by even- and odd- mode analysis. A dual-band microstrip filter with compact size and working at WiMAX is designed by using this novel stub-loaded multimode resonator. Meanwhile, a futher research for this novel resonator and an in-depth research about the performance of HTS are also made. And a HTS filter is designed and fabricated based on this novel resonator. It provides theoretical guidance for the coupling of superconducting circuits.