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This letter proposes a wide-range reconfigurable bandpass filter (WRBPF) based on the cross-shape triple-mode resonator. Varactor diodes and switching diodes are utilized at the ends of the resonator and the positions of external coupling, which combines the two working modes of the low-frequency band and high-frequency band, greatly broaden the tunable range of the center frequency ($f_{0}$). When the 3-dB bandwidth of WRBPF is 180 MHz, $f_{0}$ can be adjusted from 0.78 to 1.93 GHz, and the relative adjustment range is 84.9%. When $f_{0}$ is 1.355 GHz, the absolute bandwidth can be adjusted from 110 to 950 MHz, and the relative bandwidth adjustment range is 8.1%–70.1%. Moreover, the circuit size of WRBPF is only $0.29\,\,\lambda g\,\,\times 0.22\,\,\lambda g$. The experimental results show that WRBPF has not only a simple structure but also an excellent performance. [ABSTRACT FROM AUTHOR]

A novel multimode dual-ring ultrawideband (UWB) bandpass filter is proposed in this article, which is constructed by loading open stubs in the horizontal and vertical directions of the dual-ring resonator. Five modes are evenly distributed in the passband, and a pair of transmission zeros are introduced to the left and right transition bands to enhance selectivity. Parallel-coupled lines ensure external coupling strength for realizing the UWB, and a cross junction suppresses spurious in high frequencies to expand the upper stopband. For demonstration, a quintuple-mode high-temperature superconducting UWB bandpass filter is designed on the 0.5 mm thick MgO substrate with double-sided YBa2Cu3O7 (YBCO) films. The test results show that the 3-dB bandwidth covers 2.56 to 11.15 GHz, the in-band return loss greater than 15 dB. [ABSTRACT FROM AUTHOR]

A new method is proposed to produce even finite transmission zeros without any cross-coupling between the resonators of filter, by loading the second-order extracted-pole unit (EPU) composed of two mutual coupled resonators at the input or output port of the filter. An arbitrary distribution of finite transmission zeros on the imaginary axis can be achieved by adjusting the resonant frequencies of resonators in the EPUs and the coupling strength between them. The finite transmission zeros can be symmetrically or asymmetrically distributed about the center frequency of the filter, even all on the same side outside the passband of the filter. And the topological structures of these filters are given in this paper. Besides, Cauchy method is adopted to analyze the proposed EPU configuration filter as well. This paper not only discusses how to implement a pair and two pairs of finite transmission zeros, and how to control the distribution of finite transmission zeros, but also gives multiple sets of computer-aided synthesized normalized coupling matrices. Based on this, an eighth-order quasi-elliptic function high-temperature superconducting filter with two pairs of finite transmission zeros was designed on a double-sided YBCO/LaAlO3/YBCO films to verify the feasibility of this new structure. [ABSTRACT FROM AUTHOR]

In this paper, a novel trapezoidal meander-line resonator (TMLR) is proposed to design compact high-order high-temperature superconducting (HTS) linear phase bandpass filters with cascaded quadruplet (CQ) structures. By changing the conventional rectangle half-wavelength meander-line microstrip resonator into a trapezoidal resonator, unnecessary cross coupling between nonadjacent resonators in the CQ units can be avoided. And using the proposed TMLR to design the CQ unit, electric field cross coupling or magnetic field cross coupling can be easily achieved and tuned without the cross-coupling line. To further demonstrate the feasibility of using this configuration for miniaturized circuit design, an 8-order HTS linear phase filter with one pair of transmission zeros was designed. The measured responses agree very well with the simulated results. The physical HTS filter has a center frequency of 1935 MHz and bandwidth of 70 MHz. The out-of-band rejection is greater than 50 dB, and the effective bandwidth of group delay fluctuation less than ±3 ns takes up more than 65% in the whole passband. [ABSTRACT FROM AUTHOR]