| Summary: | 碩士 === 國立中央大學 === 電機工程研究所 === 99 === In the thesis, the proposed structure, stepped-impedance stub-loaded resonator(SISLR), is utilized in the bandpass filter featuring wide stopband. To begin with, use characteristics of SISLR to control spurious passband and transmission zeros by adjusting impedance ratio and electrical length ratio. Afterward, the results are applied to design filters. The spurious passband is suppressed by the circuit itself instead of adding extra circuit. Consequently, the size of the circuit is minimized. We will take advantage of the proposed structure to fabricate two 2nd-order dual-band bandpass filters with different fundamental frequencies. One is that two fundamental frequencies of the passband are near band, and the other is based on the above filter to develop high-order filters, including one 3rd-order and two 4th order dual-band bandpass filters. Transmission zeros near two sides of the passband result from cross coupling or asymmetric feed line; therefore, the selectivity is enhanced. As mentioned above, all of these dual-band bandpass filters possess wide stopband. Eventually, the proposed resonators can be integrated with the interdigital coupled feed line to attain wide stopband.
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