Three types of impedance-matching structures for diplexer design are analyzed and calculated in this paper. Calculations show that different matching structures should be selected for size reduction, depending on the input impedance of the channel filters in the diplexer. Two channel filters in the superconducting microstrip diplexer at the P-band are designed with spiral resonators and capacitively coupled feedlines. The diplexer is then constructed with an impedance-matching structure of spiral short-circuited stubs. The compact diplexer has a size of 22.9 mm x 21.7 mm on an MgO substrate, which amounts to only 0.101 lambda(g0) x 0.096 lambda(g0), where lambda(g0) is the guided wavelength of the 50-Omega line on the substrate at the midband frequency. The fabricated device exhibits high performance, and its measurements match the simulations well. The experimental insertion loss of both channels is less than 0.13 dB. The common-port return loss is greater than 18.9 dB, and the isolation between the two channels is greater than 60 dB.

A novel defected ground structure (DGS) resonator with improved power handling capability is proposed in this paper. The current density distribution of the DGS resonator is simulated and compared with that of the complete ground structure (CGS) resonator. Simulation shows that the maximum current density of the DGS resonator is lower than that of the CGS resonator. Two four-pole bandpass high-temperature superconducting filters centered at 2.9 GHz with a fractional bandwidth of nearly 1.5% are designed and fabricated using the DGS and CGS resonators, respectively. The measured maximum handling power is 37.3 dBm for the DGS filter at 77 K, which is higher than that of 34.1 dBm for the CGS filter.

This article presents a four-pole continuously tunable high-temperature superconducting combline filter at L band on MgO substrate. Gallium Arsenide varactors are used as tuning elements in the filter. Additional varactors are used to tune the external quality factor of the input and output couplings. A shorted U-shape secondary coupling line is introduced to match the desired couplings so as to maintain a good return loss in the entire tuning range. The four-pole filter achieves a tuning range of 11.5% from 983.85 to 1103.6 MHz. The insertion loss is 0.46 dB at 1103.6 MHz with the bias of 9 V. The unloaded quality factor of the resonators in the four-pole filter is estimated to be 710 at 1077.6 MHz. (c) 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:775-777, 2014

In this article, a modified sliced-line resonator for high temperature superconducting (HTS) filters with high power handling capability is proposed. The resonator consists of 18 equal length lines in parallel with 3 unequal length lines on both outsides. The maximum current density of this kind of resonator is investigated and compared with the conventional microstrip line resonator and the sliced-line resonator. The simulations show that the resonator enables an increase of 76% power handling capability compared with the sliced-line resonator. A four-pole HTS filter with a centre frequency of 3.65 GHz and a bandwidth of 0.7% was designed and fabricated based on the proposed resonator. The measurements of the filter show a power handling capability more than 10 W. (C) 2014 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 paper presents a simple and efficient method for the design of a microstrip contiguous diplexer comprising doubly terminated filters. The equivalent circuit for the channel filters is presented, which can accurately represent both the in-band and out-of-band characteristics of the channel filters. By analyzing and properly adjusting the input impedance of the channel filters, the equivalent circuit of the diplexer can be easily optimized. A high-temperature superconducting diplexer at S-band is successfully designed with this method and fabricated on a MgO substrate with a compact size of 32.6 mm × 18 mm. The measured results show high performance and agree well with the simulations.

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

Based on the established bath of electroless Ni-Fe-Co-P plating,cerium nitrate was added to the bath,and a Ni-Fe-Co-P-Ce alloy coating was prepared on polyester fibers.The effects of the mass concentration of cerium nitrate on the deposition rate,surface morphology,composition,corrosion resistance of the coating were discussed,obtaining an optimal mass concentration as 0.4 g/L.

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.