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This paper presents a miniaturized quint-band hightemperature superconducting (HTS) bandpass filter (BPF) based on a single-perturbed multimode resonator (PMMR). By properly adjusting the lengths and the position of the perturbation line in a PMMR, the intrinsic resonance modes can be controlled, which is advantageous for multiband design. The source-load coupling, spurlines, and matching stubs on feedlines are introduced to improve impedance matching and to generate multitransmission zeros, so that enhanced isolation and harmonics suppression can be realized. A low insertion loss (IL) within each band is obtained by using an HTS technology. The filter is fabricated on an MgO substrate with the YBCO thin films, and measured at the temperature of 77 K. The passband measurement is consistent with the simulation, which verifies five passbands located at 0.56, 1.52, 3.8, 4.7, and 5.3 GHz, respectively. A low-measured IL with less than 0.2 dB level is obtained due to the application of a superconducting technology. The proposed HTS BPF owns the great merits of a simple structure, a miniature size (0.008λg 2), an enhanced upper stopband, and a low IL. [ABSTRACT FROM AUTHOR]

A novel short- and open-stub loaded spiral resonator (SOSL-SR) is presented and analysed by the odd- and evenmode method to obtain three controllable resonant modes. Therefore, a triple-mode bandpass filter (BPF) has been designed with good frequency selectivity based on the proposed SOSL-SR. Then, by dividing these three resonant modes into two passbands or stopbands, a dual-band BPF and a dual-band bandstop filter using the proposed SOSL-SR have been demonstrated. Because of the spiral structure, the sizes of these three designed microstrip filters are reduced significantly. Good agreement between simulated and measured results validates the design concept. [ABSTRACT FROM AUTHOR]

A compact seventh-order wideband bandpass filter (BPF) with sharp roll-off skirts using coupled lines and open stubs (OSs)/shorted stubs (SSs) is proposed. Seven transmission poles in the passband and four deep transmission zeros from 0 to 2f0 ( f0 denotes centre frequency of the passband) can be realised with the help of half-wavelength OSs and quarter-wavelength SSs. For demonstration, a wideband BPF prototype is designed, fabricated with a measured 3-dB fractional bandwidth of 78% (1.22-2.77 GHz) and transition band roll-off rates of over 175 dB/GHz. Good agreement between the simulations and measurements validates the design method. [ABSTRACT FROM AUTHOR]