In this paper, an interdigital-type resonator with strong electric coupling is proposed for the wideband high-frequency (> 10 GHz) filter design. The proposed microstrip resonator consists of an H-shaped main line part with its both ends installed with interdigital finger parts. Strong electric coupling is achieved between adjacent resonators. A six-pole high-temperature superconducting filter at Ku-band using this resonator is designed and fabricated. The filter has a center frequency of 15.11 GHz with a fractional bandwidth of 30%. The insertion loss of the passband is less than 0.3 dB, and the return loss is greater than 14 dB without any tuning. (c) 2017 Elsevier B.V. All rights reserved.

This paper proposes a modified spiral resonator with a tight three-turn spiral and inner/outer tails. The resonator has good spurious response because the mutual inductances between the three turns at the fundamental mode are positive and thus reduce the fundamental resonant frequency f 0 , whereas those at the first spurious mode are negative and increase the first spurious resonant frequency fS . By further optimizing the lengths of the spiral and inner/outer tails of the proposed resonator, a spurious resonant frequency fS up to 3.4 f 0 is obtained. Moreover, the couplings between such resonators at spurious modes are much weaker than that at the fundamental mode, which is helpful to suppress the spurious response of bandpass filters consisting of such resonators. Furthermore, three dissimilar types of resonators with the same fundamental frequency but with different spurious resonant frequencies are used to compose a bandpass filter and further suppress the spurious response in the stopband. With these methods, a ten-pole superconducting filter at 360 MHz with a 15-MHz bandwidth is successfully designed and fabricated on a LaAlO 3 substrate. The overall measurements show a high performance and agree very well with the simulations. The maximum insertion loss is 0.15 dB, the return loss is greater than 19 dB, and the rectangle coefficient (the ratio between the 40-dB bandwidth and the 3-dB bandwidth) is 1.35. Moreover, the out-of-band rejection is higher than 76 dB up to 2030 MHz, which is 5.64 f 0 . The ten-pole filter occupies a compact area of 33 mm × 15 mm, which amounts to only 0.15 λ g 0 × 0.07 λ g 0, where λ g 0 is the guided wavelength of the 50-Ω line on the substrate at f 0 .

A superconducting resonator, consisting of a microstrip spiral and a 2 b interdigital capacitor array, is proposed. The resonator has a measured unloaded Q over 51 000 in all four states. A two-pole reconfigurable superconducting filter at P-band with a fractional bandwidth of 1% is designed with this resonator and fabricated. The measurements show that the tuning range of the center frequency is from 499.4 to 484.9 MHz with insertion losses of less than 0.1 dB in all four states, and are in good agreement with the simulations.

This paper presents the modeling and optimization of a manifold-coupled superconducting quadruplexer at VHF-band. The quadruplexer consists of four individually designed channel filters with a bandwidth of 400 kHz centered at 216, 224, 232, and 240 MHz, respectively, connected to a common manifold. The complex interactions between the channel filters make the design and optimization of the quadruplexer difficult and even impossible. An equivalent circuit for the manifold and the capacitive external couplings of the four channel filters in the quadruplexer is presented. The parameters of the equivalent circuit are accurately extracted from electromagnetic simulations. Afterward, the equivalent circuit is optimized to compensate for the interactions between the channel filters and obtain a good common-port return loss and channel transfer characteristics. Thereafter, the design of the individual channel filters is improved according to the optimized parameters of the equivalent circuit. The superconducting quadruplexer is successfully designed and fabricated. The measurements show high performance and match well with the simulations. The experimental insertion losses of the four channels are less than 0.45 dB, the center frequency discrepancies of the four channels are less than 40 kHz, the common-port return loss is greater than 16.3 dB, and the out-of-band rejection is higher than 90 dB. Moreover, a high isolation greater than 75 dB between the channels is achieved.

This article presents a 10-pole high-temperature superconducting (HTS) wideband microstrip bandpass filter with a novel configuration and compact size.The filter at 10 GHz with a fractional bandwidth of 40% is designed and fabricated on a 32.6 mm x 6.7 mm x 0.5 mm MgO substrate with double-sided YBCO films. The internal couplings between quarter-wavelength resonators are realized by parallel-coupled microstrip line (PCML) structure and capacitive open-ended stubs. The strong external couplings required by wideband filter are realized by impedance steps and capacitive stubs. The measured results at 55 K, without any tuning, show a high performance. The insertion loss is less than 0.31 dB, the return loss is better than 14 dB, and the out-of-band rejection is higher than 70 dB. The overall measurements are in good agreement with the simulations. (c) 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:10271029, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27485

This letter presents the design, fabrication, and measurements of a high-temperature superconducting (HTS) filter at 16 GHz with a 100-MHz bandwidth. The main aspects of achieving high performance narrowband filter at such high frequency are analyzed and addressed. Simple rectangular resonators and end-coupled structure are used in the design to achieve high quality factor (Q), weak coupling, and good parasitic response. The measurements of the seven-pole HTS filter, without any tuning, exhibit a high performance. The insertion loss is less than 1.1 dB, equivalent of a resonator Q about 6100. The return loss is better than -15 dB, and the out-of-band rejection is over 70 dB up to 29.3 GHz. (C) 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:15141516, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26816

A new Interdigital resonator(IDR) used for designing low frequency and broad stopband high temperature superconducting(HTS) filters is introduced.IDR has the excellent character of compact,strong adjucent coupling and good spurious suppression.The design and fabrication of a 12-pole HTS filter centered at 360 MHz with a 4% bandwidth using IDRs are presented in this paper.The measurements show that the out-of-band rejection from fundamental passband to 1.27GHz is better than 80dB.The ratio between first spurious passband and fundamental frequency is over 3.5.The measured results are in good agreement with the simulated one.

为了解决超高频高温超导滤波器的设计难题，本文分析了超导滤波器的三种损耗来源，分别是导体损耗、介质损耗与微波辐射损耗。针对这三种损耗提出了设计上的基本原则，尤其是提出了超高频谐振器设计中的宽线条、无弯折原则。在此基础上设计、制作了一个中心频率为16 GHz的高温超导超高频滤波器。经过测试，该滤波器的响应结果很好的符合了仿真结果。

为了实现超高频宽带滤波器,本文采用了一种新型的带有插指端口的谐振器结构，实现了相邻谐振器之间的强耦合，设计并制作了中心频率为16 GHz，-3dB带宽4.5 GHz（相对带宽为30%）的6节超高频宽带滤波器。滤波器无需调谐，即获得了带内插损小于0.15 dB，反射损耗约为11 dB的良好性能。仿真与测试结果表明，基于端口插指耦合的方法提升了超高频宽带超导滤波器设计的灵活性。