HTS microstrip matching networks and filters

High-temperature superconducting (HTS) YBCO microstrip bandpass filters and microstrip impedance matching networks were fabricated, tested and compared with the predicted performance. Vector corrected measurements of these circuits were performed at cryogenic temperatures. Comparisons of the insertion loss for the HTS and corresponding Au filters are presented, as well as the predicted noise figure for the low-noise amplifiers using HTS and Au matching networks     

HTS coplanar meander-line resonator filters with a suppressed slot-line mode

The design and experimental results of a four-pole coplanar waveguide (CPW) quasi-elliptic filter using high-temperature superconductor (HTS) films are presented. Quarter-wavelength meander-line resonators are used in the filter topology. Although the resonators are aligned in two lines, no bond-wire bridges are required to balance the ground planes in the design and measurement. The slot-line mode of the filter was shifted to be higher than its third harmonic. The filter is highly miniaturized and the performance is significantly improved by the use of superconductors. The main circuit of the filter only has an area of about 6.6 mm /spl times/ 2.4 mm on a magnesium oxide substrate, coated with 600-nm-thick YBCO HTS thin film on single side of the substrate. The 3-dB bandwidth is about 1.6% centered at 2.95 GHz. The performance measured at 30 K, without any tuning, gives an insertion loss of better than 0.4 dB and a return loss of about 12 dB in the passband. The first spurious mode is about triple the center frequency.     

Dielectric multilayer thin-film filters for WDM transmission systems

Dielectric multilayer thin-film (DMF) filters for a wavelength-division-multiplexing (WDM) system are discussed. It was found that a 23-layer 3-cavity bandpass-type DMF-filter made of TiO2and SiO2is most suitable for this type of system. An optical multi/demultiplexer employing this type of bandpass DMF-filter is applicable to a two-way WDM transmission system.     

Compact cross-coupled circular cavity filters using multilayer substrate integrated waveguide

Using standard low-temperature co-fired ceramic technology, a novel fourth-order cross-coupled circular cavity filter is proposed, where multilayer substrate integrated waveguides are implemented. In particular, one slot is introduced on the metal surface of one filter, which can suppress the spurious mode in the filter cavities effectively. Good agreement is obtained between the simulated and measured S-parameters of the proposed new structure.     

An adaptive Gauss-Newton algorithm for training multilayer nonlinear filters that have embedded memory

We describe herein a new means of training dynamic multilayer nonlinear adaptive filters, orneural networks. We restrict our discussion to multilayer dynamic Volterra networks, which are structured so as to restrict their degrees of computational freedom, based on a priori knowledge about the dynamic operation to be emulated. The networks consist of linear dynamic filters together with nonlinear generalized single-layer subnets. We describe how a Newton-like optimization strategy can be applied to these dynamic architectures and detail a newmodified Gauss-Newton optimization technique. The new training algorithm converges faster and to a smaller value of cost than backpropagation-through-time for a wide range of adaptive filtering applications. We apply the algorithm to modeling the inverse of a nonlinear dynamic tracking system. The superior performance of the algorithm over standard techniques is demonstrated.This work was supported by the Stanford Gravity Probe-B project under NASA contract AS 8-36125.     

Numerical analysis of the effects of the magnetic self-field on the transport properties of a multilayer HTS cable

In this paper, the effects of the magnetic self-field on the transport properties of a multilayer high-T/sub c/ superconducting (HTS) cable are investigated by means of two-dimensional finite-element method (FEM) simulations. Analyzed is a three-layer HTS cable, but the developed methods can be used for a different number of layers. The superconductor is described by the nonlinear power-law relation E=E/sub c/(J/J/sub c/)/sup n/, where the parameters J/sub c/ and n depend on the magnetic field experienced by the material. This dependence decreases the global transport capacity of the superconductor, enhancing its AC losses. It is shown that, especially at high transport currents, the AC losses are considerably higher than in the case where the dependence on the magnetic field is neglected. A simple electrical model, considering the cable from macroscopic point of view, has been proposed for finding the optimal winding pitches, leading to a uniform current repartition. The use of this electrical model allows to overcome the difficulties of direct three-dimensional FEM computations. In addition, the rapidity of solutions by the electric model gives the possibility of testing quickly many geometrical configurations in order to find the ones leading to an even current repartition. This optimization process would not be possible with detailed FEM simulations.     

Characteristics Measurements of HTS Tape with Parallel HTS Tapes

Many high temperature superconducting (HTS) tape manufactures make an effort to reduce the transport current loss of HTS tapes. The knowledge of critical current and self-field in an HTS tape is very useful to compute the transport current losses. The spatial distribution and magnitude of self-field are variable due to the neighboring materials. In this paper, the critical currents and the transport current losses of BSCCO and YBCO tapes with paralleled magnetic material (Ni tape) and/or diamagnetic material (BSCCO tape) are experimentally investigated to improve the AC loss properties. The critical currents of HTS tapes with paralleled Ni tape are slightly decreased and the transport current losses are markedly increased. However, the critical currents and transport current losses of HTS tapes with paralleled BSCCO tape have not current carrying are more improved than single HTS tape.     

Concerning the influence of housing dimensions on the response anddesign of microstrip filters with parallel-line couplings [HTS circuits]

In this paper, measured results obtained from a narrow-band microstrip filter are compared with computed responses obtained using two different classes of software for various assumed housing conditions. (Some results from filters with wider bandwidths are also cited.) Housing modes are found to have a potentially significant affect on the bandwidth of microwave filters that involve microstrip coupled lines, even though the housing resonant frequencies are much above the passband of the filter. When analyzing such filters using full-wave three-dimensional (3-D) or 3-D planar field solver programs, it is found to be necessary to accurately model the housing if high accuracy in the computed response is needed. For carrying out filter design by optimization, it is usually convenient to use faster programs that utilize a full-wave two-dimensional (2-D) field solver to obtain line parameters and then use transmission-line analysis for the third dimension. Such programs can introduce housing-mode errors since 2D full-wave analysis implies an infinitely long housing. Ways for getting around this problem are suggested, Physical explanations for the various effects observed are presented and are supported by computer studies of the natural frequencies of a coupled-line microstrip filter structure in the presence of various housing perturbations     

Tunneling in HTS junctions

The effects caused by the layered structure of high-temperature superconductors (HTS) ought to be taken into consideration at the time of constructing different HTS junction devices. The authors demonstrate this by studying tunneling phenomena in HTS. The tunneling current-voltage characteristics of different structures such as “Normal Metal-Insulator-HTS” (NIS-structure) and “HTS-Insulator-HTS” (SIS-structure) are calculated. The real layered structure of HSS is taken into account and corresponding peculiarities on I(V) are obtained. The authors have analyzed different types of contacts which are realized in the NIS- and SIS-junctions. The contributions of the superconducting and normal layers of HTS to the tunneling current of NIS- and SIS-structures are found     

Development of HTS Transformers and a 10 kVA HTS Transformer Prototype Design

With the improvement of high temperature superconductor （HTS） practical performance, research and development concerning the applications of HTS transformers have been progressed actively worldwide. This paper provides a comprehensive summary on various HTS transformers, and studies the design of a single-phase 10 kVA （220V/24V） HTS transformer prototype to verify HTS for practical transformer applications.     

Thin-film HTS planar antennas

The “H” microstrip antenna is suitable for use as an efficient small antenna when it is constructed out of superconducting thin-film materials. An aperture feed and matching network is described which provides a convenient enhancement of the capabilities of the “H” antenna. Methods of prediction of the center frequency are given. In addition, an analytical expression is developed for the far field radiation pattern of the “H” antenna and the efficiency and Q of superconducting and copper antennas are described using this expression. It is likely that superconducting antennas will only have significant application when they are used in arrays. Three arrays are described demonstrating multiband self-diplexing multifrequency-enhanced bandwidth and multifrequency beam forming     

Test results of HTS dipole

Test of HTS dipole with coil wound by Bi-2223 tape was carried out. Volt-current characteristics of the dipole at various temperatures as well as results of magnetic field measurements are presented. A process of transition to normal state for the HTS coil was calculated.     

High-resistance HTS SNS edge junctions

HTS SFQ digital circuit applications require high resistance HTS Josephson junctions. We have investigated the factors affecting the resistance of SNS edge junctions which use Co-doped Y-Ba-Cu-O as the normal metal layer. Several parameters are found to have a surprisingly large effect on device resistance, including edge angle, base electrode material, and deposition conditions of the normal metal and counterelectrode. Controlling these factors has enabled the fabrication of high-quality, high-resistance (≈1 Ω) SNS edge junctions with 1-σ I_c spreads down to 10% and critical currents and I_cR_n products suitable for SFQ digital applications.     

可调圆起偏器

给出一种可调式圆起偏器。调整复合片快轴间的夹角,便能在可见光范围内使用。     

Modeling of HTS Josephson junctions

We discuss recent developments for HTS Josephson junctions: (i) isolated (S/I) and resonantly coupled (S/I/S) Andreev interface states, (ii) d-wave models with resonantly coupled midgap states for ab-plane junctions and (iii) resonant tunneling models for c-axis junctions.     

反射式可调移相器

针对现代通信中线性功率放大器的补偿要求,介绍一种利用反射理论设计可调移相器,实现大范围移相,同时幅度波动很小,并详细讨论了它的工作原理和实验结果。     

高温超导技术在电子装备中的应用探讨

结合现代雷达应用环境和技术发展趋势,分析了高温超导在雷达装备应用的潜在优势及面临的工程和技术问题,并结合具体工程项目给出了近期迫切需要突破的关键技术。     

Development of a Conduction-Cooled HTS SMES

A 35-kJ/7-kW conduction-cooled high-temperature superconductor (HTS) superconducting magnetic energy storage (SMES) is developed. This paper presents the configuration of the HTS SMES and a part of important test results. The magnet of the SMES is a solenoid-type coil made of Bi-2223/Ag tapes, and cooled to about 20 K by conduction-cooled method. The SMES is assembled in the Electric Power System Dynamic Simulation Laboratory, Huazhong University of Science and Technology. A series of tests are successfully carried out to evaluate the performance of the SMES, including the current-carrying ability of the magnet, the active and reactive power exchange capability between the SMES and a simulated power system, as well as the power-compensating effect of the SMES to the simulated power system after short-circuit fault, etc.     

Model for analyzing manufacturing-induced internal stresses in 50-GHz DWDM multilayer thin-film filters and evaluation of their effects on optical performances

The manufacture of a high-quality reliable thin-film filter (TFF) requires a detailed understanding of the stresses created within the device during fabrication. The ability to systematically approximate the internal stress effect on optical performance is of crucial importance to provide fabrication guidance and improve manufacturing yield. This paper analyzes the internal stress distributions in the substrate and thin-film layers of a 50-GHz TFF and examines the relation of these stresses to the filter's optical characteristics. A linear model along the thickness direction is introduced based upon Townsend's theory of multilayer structures. The analytical results for the key optical parameters are in good agreement with measurements on fabricated filters. This model analyzes the effects of process parameters, such as the substrate type, its coefficient of thermal expansion, and the final substrate thickness on the optical performance of the transmission spectrum center wavelength, transmission passband ripple and isolation, the chromatic dispersion, and polarization-mode dispersion.     

Magnetic flux diffusion through HTS shields

Slow field leakage in a polycrystalline superconducting cupshield placed in an external axial field (H_ext) much weaker than H _C1 shows a diffusive time dependence with a time scale of 10 ² s. As the field strength increases but is still less than H _C1, a logarithmic time dependence of 10² s time scale is observed. It is shown that this logarithmic time dependence is a result of flux line diffusion between superconducting grains rather than fluxoid avalanches or flux bundle creep