This letter presents a compact dual-mode tri-band bandpass filter by using a short-circuited stub-loaded stepped-impedance resonator (SIR) and a short-circuited stub-loaded uniform impedance resonator. Also, a hairpin SIR geometry is introduced to miniature the size of this filter while maintaining excellent performance. The use of a short-circuited stub at the central point of the hairpin SIR can generate two resonant modes in two passbands. Its equivalent circuit structure is analyzed by using the even-odd mode theory. For demonstration purposes, a tri-band filter for the applications of the Global Positioning System at 1.57 GHz, Worldwide Interoperability for Microwave Access at 3.5 GHz, and wireless local area networks at 5.2 GHz is designed, fabricated, and measured.

A compact triple-band high-temperature superconducting (HTS) YBa2Cu3Oy microstrip bandpass filter using multimode split ring resonator (SRR) is presented in this letter. Also, its properties and equivalent circuit models are investigated by even- and odd-mode analysis. Moreover, design method of the proposed triple-band HTS filter for the applications of global positioning system at 1.57 GHz, worldwide interoperability for microwave access at 3.5 GHz, and wireless local area networks at 5.8 GHz is discussed. The centre frequencies and the bandwidths of the three passbands can be allocated properly choosing the dimension parameters of the multimode SRR. In addition, four transmission zeros are produced to improve the selectivity of this filter.

A compact elliptic‐function‐response bandpass filter using slotline resonators and stubs is designed in this letter. This slotline resonator is composed by one loop resonator with four corner‐patch perturbation and stubs. The nature of coupling between the degenerate modes is investigated with respect to the perturbation size. Also, slotline stubs are applied to miniature the filter's size by keeping excellent performance. Results verify that the central frequency and the fractional bandwidth of the proposed filter are 5.23 GHz and 7.45%, respectively. A good agreement between simulation and measurement verifies the validity of this design methodology. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:641–644, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26603

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