- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Design of High Temperature Superconducting Dual-Band Filter with Multiple Transmission Zeros
摘要： A multi-order dual-band high temperature superconducting (HTS) bandpass filter (BPF) with multiple transmission zeros (TZs) is designed in this paper. The theoretical characteristics of the introduction of TZs by the electric and magnetic mixed coupling, and the cascade quadruplet (CQ) cross-coupling structures are analyzed, respectively. These two methods can be applied to the design of the multi-mode compact dual-band HTS BPF with controllable central frequency, bandwidth and TZs. For demonstration, a Y-shape tunable resonator structure which can simultaneously implement the internal electric and magnetic mixed coupling, and the external cross coupling is constructed to achieve the proposed dual-band BPF. The external quality factors required by the two passbands and the feasibility of independently adjusting the coupling strength between adjacent resonators are analyzed. Finally, a 6-order dual-band HTS BPF with the center frequencies of 1490MHz (bandwidth of 40 MHz) and 2340MHz (bandwidth of 80 MHz) is designed and fabricated on the double-sided YBCO/MgO/YBCO HTS thin films with the size of 17.2mm×14.7mm (0.20λg × 0.17λg), and there are multiple of TZs located outside the two passbands, respectively. The out-of-band rejections are greatly improved to 70dB and 80dB due to these TZs, which fully exhibits the advantages of the proposed dual-band BPF. The measured results are in good agreement with the simulated ones.
关键词： high temperature superconducting (HTS),Dual-band,passband filter,transmission zero (TZ),cascade quadruplet (CQ)
更新于2025-09-23 15:23:52
-
Band gap analysis of periodic structures based on cell experimental frequency response functions (FRFs)
摘要： An approach is proposed to estimate the transfer function of the periodic structure, which is known as an absorber due to its repetitive cells leading to the band gap phenomenon. The band gap is a frequency range in which vibration will be inhibited. A transfer function is usually performed to gain band gap. Previous scholars regard estimation of the transfer function as a forward problem assuming known cell mass and stiffness matrices. However, the estimation of band gap for irregular or complicated cells is hardly accurate because it is difficult to model the cell exactly. Therefore, we treat the estimation as an inverse problem by employing modal identification and curve fitting. A transfer matrix is then established by parameters identified through modal analysis. Both simulations and experiments have been performed. Some interesting conclusions about the relationship between modal parameters and band gap have been achieved.
关键词： Band gap,Periodic structure,Transfer matrix,Parameter identification,Modal analysis
更新于2025-09-23 15:23:52
-
[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - High Resolution Measurements and Characterization of Urban, Suburban and Country Clutter at X-Band and Related Radar Calibration
摘要： At Tor Vergata University we are working on measurements and phenomenological characterization of urban, suburban and country radar clutter at X-band (3 cm wavelength, range resolution 8 to 10 m, azimuth resolution @ 1 km about 23.5 m) and on the related radar calibration problems. Measurements are 'high resolution' when compared to most surveillance radars, and the related applications are in the frame of clutter maps for cognitive radar, drones detection, radar ornithology, and more. After calibration, done using opportunity targets with known radar cross section and a clutter fence, we carry on an analysis and a comparison of land clutter, considering different weather conditions: dry and wet soil, as well as the rare event of snow. Using fixed opportunity targets, such as lamppost and/or a large cylindrical steel tanker, we describe the attenuation effects due to the natural clutter fence (in this case due to cane thicket near to the target position) and its mitigation when the natural fence is gradually removed. Finally, but importantly, we analyze the multipath phenomenon due to reflection/scattering on ground, and propose a procedure to estimate the multipath factor and to correct for it.
关键词： urban clutter,radar calibration,high resolution radar,multipath,X-band
更新于2025-09-23 15:23:52
-
Full wave analysis of plane wave diffraction by a finite sinusoidal grating: E-polarization case
摘要： Plane wave diffraction studies of a finite sinusoidal grating have previously assumed that the grating length is large in wavelengths and the depth of its corrugations is small compared to a wavelength. This paper introduces a rigorous technique, the Method of Analytical Regularization (MAR), which removes these restrictions. The solution obtained by this method is free from limitations on the parameters of sinusoidal grating and possesses the capability to achieve predetermined accuracy of computations uniformly in a wide frequency band. The results of previous studies, which employed the Wiener-Hopf technique combined with a perturbation method, are compared with those obtained by the MAR; excellent concordance of results in the common parameter regimes of applicability of both methods is found. The different regimes of applicability of each approach are identified; within these, the MAR provides effective and efficient solutions to benchmark problems for testing other approximate techniques.
关键词： efficient computational algorithm in wide frequency band,scattering of E-polarized plane wave,method of analytical regularization,Floquet modes for finite grating,finite sinusoidal grating,Wiener-Hopf technique combined with perturbation method
更新于2025-09-23 15:23:52
-
studied with angle-resolved photoemission spectroscopy
摘要： We study the band structure of twinned and detwinned BaFe2As2 using angle-resolved photoemission spectroscopy. The combination of measurements in the ordered and normal states along four high-symmetry momentum directions (Γ/Z-X/Y) enables us to identify the complex reconstructed band structure in the ordered state in great detail. We clearly observe the nematic splitting of the dxz and dyz orbitals as well as folding due to magnetic order with a wave vector of (π, π, π). We are able to assign all observed bands. In particular we suggest an assignment of the electron bands different from previous reports. The high-quality spectra allow us to achieve a comprehensive understanding of the band structure of BaFe2As2.
关键词： band structure,BaFe2As2,angle-resolved photoemission spectroscopy,magnetic order,nematic splitting
更新于2025-09-23 15:23:52
-
Blind Noisy Image Quality Assessment Using Sub-Band Kurtosis
摘要： Noise that afflicts natural images, regardless of the source, generally disturbs the perception of image quality by introducing a high-frequency random element that, when severe, can mask image content. Except at very low levels, where it may play a purpose, it is annoying. There exist significant statistical differences between distortion-free natural images and noisy images that become evident upon comparing the empirical probability distribution histograms of their discrete wavelet transform (DWT) coefficients. The DWT coefficients of low- or no-noise natural images have leptokurtic, peaky distributions with heavy tails; while noisy images tend to be platykurtic with less peaky distributions and shallower tails. The sample kurtosis is a natural measure of the peakedness and tail weight of the distributions of random variables. Here, we study the efficacy of the sample kurtosis of image wavelet coefficients as a feature driving an extreme learning machine which learns to map kurtosis values into perceptual quality scores. The model is trained and tested on five types of noisy images, including additive white Gaussian noise, additive Gaussian color noise, impulse noise, masked noise, and high-frequency noise from the LIVE, CSIQ, TID2008, and TID2013 image quality databases. The experimental results show that the trained model has better quality evaluation performance on noisy images than existing blind noise assessment models, while also outperforming general-purpose blind and full-reference image quality assessment methods.
关键词： sub-band,discrete wavelet transform (DWT),extreme learning machine (ELM),kurtosis,Blind noisy image quality assessment
更新于2025-09-23 15:23:52
-
A 200 Mb/s～3.2 Gb/s referenceless clock and data recovery circuit with bidirectional frequency detector
摘要： This paper presents a 200-Mb/s to 3.2-Gb/s half-rate referenceless clock and data recovery (CDR) circuit in 180 nm CMOS process. A bidirectional frequency detector (FD) is proposed to eliminate the harmonic locking and reduce the frequency acquisition time. A frequency band selector for wide-range the voltage-control oscillator (VCO) is also presented to select an exact frequency band of the VCO. The simulation shows the CDR achieves 11-ps peak-to-peak jitter at 3 Gb/s and the frequency acquisition time of 11.8 μs.
关键词： wide-band VCO,bidirectional frequency detector,referenceless,clock and data recovery
更新于2025-09-23 15:23:52
-
Effects of Ge substrate on the structural and optical conductivity parameters of Bi2O3 thin films
摘要： In this article the structural, optical and dielectric properties of a 200 nm thick Bi2O3 thin films which are deposited onto amorphous germanium substrate are reported. Both of the Ge and Bi2O3 thin films are prepared by the thermal evaporation technique under vacuum pressure of 10^-5 mbar. Bi2O3 thin films are found to prefer the monoclinic nature of structure with larger values of microstrain, dislocation density, stacking faults and smaller grain sizes upon replacement of the glass substrate by germanium. Optically, significant redshift in the energy band gap is observed when the films are grown onto Ge. The Ge/Bi2O3 heterojunctions exhibit a conduction and valence band offsets of value of 0.81 and 1.38 eV, respectively. In addition to the enhancement in the dielectric constant near the IR region, the Drude-Lorentz modeling of the Ge/Bi2O3 heterojunctions has shown remarkable effect of the Ge substrate on the optical conductivity parameters of Bi2O3. Particularly, the drift mobility increased by about one order of magnitude, the free hole density decreased by ~24 times and the plasmon frequency ranges extended from 5.21 to 11.0 GHz to 2.59–12.80 GHz when germanium substrate is used. The optical features of the heterojunction nominate it for visible light communication technology.
关键词： Ge/Bi2O3,Band offsets,X-ray,Heterojunction,Plasmon,Dielectric
更新于2025-09-23 15:23:52
-
Effect of Hydration Procedure of Fumed Silica Precursor on the Formation of Luminescent Carbon Centers in SiO <sub/>2</sub> :C Nanocomposites
摘要： The effect of hydration procedure of fumed silica precursor on photoluminescent properties of carbonized silica (SiO2:C) nanocomposite after chemo/thermal treatments is studied. Main structural effect is the formation of chemical bonding of phenyl groups to silica surface via multiple C─Si─O bonding bridges. Synthesized samples demonstrate very broad photoluminescence (PL) bands in near ultraviolet and visible ranges with maximum intensity dependent on temperature of thermal annealing. Two main trends in luminescence properties are: 1) hydration-induced blue shift of PL in comparison with PL of unhydrated series; 2) red shift of PL bands with increasing synthesis temperature regardless hydration procedure. Temperature dependent evolution of light emission bands is discussed in terms of surface carbon nanoclusters formation and aggregation processes. It is assumed that blue shift of PL bands in the hydrated series is associated with the decreased surface mobility of carbon atoms and clusters as a result of increased chemical bonding with silica surface that slows down carbon thermally stimulated clusterization/aggregation processes.
关键词： carbonized nanocomposite material,carbonized fumed silica,phenyltrimethoxysilane,wide-band visible photoluminescence,carbon clusters
更新于2025-09-23 15:23:52
-
Extended analysis of FTIR high resolution spectra of HD32S and HD34S in the region of the ν2 band: Positions and strengths of individual lines
摘要： The high resolution infrared spectra of deuterated hydrogen sulfide HDS were recorded with a Bruker IFS125HR Fourier transform infrared spectrometer (Zurich prototype ZP2001) and analyzed in the ν2 fundamental band region, 690–1510 cm?1. 2684 transitions with maximum values of the quantum numbers Jmax.=25 and Kmax.a=17 were assigned in the experimental spectra to the ν2 band (compared to Jmax.=22 and Kmax.a=10 in the preceding analogous studies) of HD32S. On this basis, 415 upper ro–vibrational energies were obtained, which were used then in the weighted fit of the Watson Hamiltonian parameters. 33 parameters obtained from the fit reproduce the 415 initial energy values with a root mean square deviation drms=1.1×10?? cm?1. An analysis of 418 experimental ro–vibrational line intensities of the ν2 band of HD32S was made using the Hartmann–Tran profile of individual lines, and results were applied in the fit of parameters of the effective dipole moment operator. Isotopic relations for the dipole moment parameters were derived and used for the fit procedure. The obtained 'model' parameters reproduce the initial line strengths with the drms=4.7%. A list of 2684 experimental transitions of HDS is generated together with the presentation of their individual line strengths predicted on the basis of the obtained effective dipole moment parameters. An analogous analysis was fulfilled for the ν2 band of the HD3?S isotopologue.
关键词： HD32S,isotopic substitution,FTIR,ν2 band,line positions,HD34S,high resolution spectra,line strengths,spectroscopic parameters
更新于2025-09-23 15:23:52