Search

A high-temperature superconductor (HTS) bandpass filter with special asymmetric cul-de-sac units (SACUs) is introduced and a compact low-radiating microstrip resonator is suggested for the filter realization. Such a filter is capable of providing better selectivity and higher out-of-band rejection and hence a decrease in adjacent-channel interference, which is of critical importance for mobile communication. This improvement of the filter characteristics results from an increase in the number of pairs of transmission zeros (TZs) on the imaginary axis on the complex plane when using the filter composed of the introduced SACUs, each providing a pair of TZs. An 11-pole filter consisting of two SACUs was fabricated using MgO substrate of 0.5 mm thickness with double-sided YBCO HTS film. Characterization of the filter at 77 K gave a central frequency of 2345 MHz, insertion loss 0.19 dB, an overall in-band return loss better than 15 dB, and an ultra-high band-edge steepness as a consequence of the two pairs of TZs. The measured characteristics are in good accord with those obtained by electromagnetic simulation. [ABSTRACT FROM AUTHOR]

A miniaturized eight-order quasi-elliptic function filter configuration with controllable transmission zeros (TZs) is proposed. Without changing the overall layout of the filter, two pairs of TZs are introduced by adopting two cascaded quadruplet (CQ) units to improve the suppression of the filter. At the same time, a cross capacitance coupling is introduced to combine the two CQ units to realize the synchronous adjustment of these two pairs of TZs. Through using this configuration, it not only helps realize the miniaturization of the filter, but also reduces the complexity of adjusting the two CQ units individually. Finally, an eight-order high-temperature superconducting filter with two pairs of TZs is designed on a double-sided YBCO/MgO/YBCO thin film with a size of 15.95 mm × 7.91 mm, a thickness of 0.5 mm, and a dielectric constant of 9.8. At 77 K, the measured central frequency of the filter is 2000 MHz, the bandwidth is 35 MHz, the out-of-band rejection is greater than 60 dB/MHz, the insertion loss is less than 0.22 dB, the return loss is better than 15.8 dB, and the test results are in good agreement with the simulated ones. [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]

A high-performance miniaturized multi-mode ultra-wide band (UWB) filter is proposed in this paper. The simple compact quintuple-mode resonator is constructed by loading three sets of open stubs on a modified conventional triple-mode resonator. Even and odd mode analytical methods are applied to analyze it. In addition, the function of each part of the filter is studied in cases of weak/strong coupling. In order to further improve the insertion loss, selectivity and out-of-band suppression, the designed filter is finally fabricated on double-sided YBCO/MgO/YBCO high-temperature superconducting (HTS) film. The test results show that the HTS UWB filter has excellent performance, and the simulation results are in good agreement with the test ones. The 3-dB bandwidth covers 3.6 ~ 13.2 GHz. The maximum insertion loss in the band was only 0.32 dB, and the reflection was better than –15.1 dB. The band-edge roll-off rate was 56 dB/GHz and the upper stopband with 20 dB rejection extended to 20.7 GHz. [ABSTRACT FROM AUTHOR]