汪径尘
,
陈毅东
,
郭旭波
,
张晓平
,
魏斌
,
曹必松
低温物理学报
本文采用插指电容新结构设计了一个Ku波段低温低噪声放大器（LNA）,并通过优化的封装工艺制备了放大器样品,分析了隔离器对LNA性能的影响.在77K温度下测试结果表明,放大器增益约10dB,噪声系数小于2.0dB,反射系数小于-17dB.
关键词:
低温低噪声放大器(LNA)
,
Ku波段
,
隔离器
,
噪声系数
王丽
,
吴希文
,
张晨鼎
,
张通
,
简丽
,
武朝军
,
周涛
稀土
doi:10.3969/j.issn.1004-0277.1999.02.003
采用湿渣法研究了0℃时碘化钇(YI3)-乌洛托品氢碘酸盐(C6H12N4.HI)-水(H2O)的三元体系相平衡,绘制了该体系的等温溶解度相图,相图分析结果表明,该体系中有组成为YI3.C6H12N4.HI.14H2O的配合物生成,对所得配合物进行了化学分析、X-射线粉末衍射、红外光谱、差热-热重分析,测定了其密度、晶体轴性,确定了配合物结构中的配位关系.
关键词:
相平衡
,
碘化钇
,
乌洛托品氢碘酸盐
,
配合物
Carbon
The natural resonance appears at 16 GHz for (Fe, Ni)/C nanocapsules with (Fe, Ni) alloys as cores and graphite as shells. Reflection loss (RL) exceeding -10 dB was obtained in the whole Ku-band (12.4-18 GHz) for an absorber thickness of 2.0 mm, while it exceeds -20 dB over the 13.6-16.6 GHz range. In addition, the bandwidth does not change dramatically for the thicknesses of 1.87-2.1 mm for the RL values exceeding -10 dB. The (Fe, Ni)/C nanocapsules with wide bandwidth absorption can be used as excellent electromagnetic-wave-absorption materials in the whole Ku-band. (C) 2008 Elsevier Ltd. All rights reserved.
关键词:
microwave-absorption properties;carbon-coated iron;complex;permittivity;nanocomposites;permeability;composites
Journal of Materials Research
The complex relative permittivity epsilon(gamma) and permeability mu(gamma) of microcoiled carbon fibers (MCCFs) imbedded in paraffin wax were measured at Ku band frequencies (12.4-18 GHz). Both the real and imaginary parts of the complex relative permittivity of the MCCFs/paraffin wax composite decreased with increase of the frequency. The real part of the complex relative permeability of the composite increases with increase of the frequency, and the imaginary part is nonzero and nearly constant over the measured frequency range. The dielectric loss tangent (tan delta(m)), the magnetic loss tangent (tan delta(m)), and amplitude attenuation factor W were determined as well. On the basis of the experimental results, the MCCFs/paraffin wax composite is mainly a kind of dielectric lossy material with small magnetic loss and diamagnetism in the Ku band.
关键词:
chemical-vapor-deposition;growth-mechanism;fibers;pyrolysis;acetylene;coils;temperature
刘海文
,
孙晓玮
,
盛怀茂
,
钱蓉
,
周旻
,
李征帆
功能材料与器件学报
doi:10.3969/j.issn.1007-4252.2003.01.013
利用微波晶体管的负阻特性,基于 Agilent(R) ADS软件,设计出一种 Ku波段微带结构、变容 管调谐的 MESFET压控振荡器(简称 VCO).对 VCO进行实测, 结果表明, VCO的中心频率为 14.14GHz,调频带宽大于 100MHz,带内输出功率大于 2mW,满足实际应用.
关键词:
负阻特性
,
微带结构
,
S参数法
,
VCO
,
变容管调谐
Journal of Alloys and Compounds
New type of Fe(Mn)/Mn(7)C(3)/graphite nanocapsules was prepared by a modified arc discharge technique in ethanol vapor, with Fe(Mn) solid solution nanoparticles as the core, Mn(7)C(3) as the inner shell, and graphite as the outer shell. The Cole-Cole semicircle approach was adopted to explain the ternary dielectric resonance, due to a cooperative consequence of the core/shell/shell interfaces and the dielectric Mn(7)C(3) and C shells. A remarkable increase in the anisotropy energy led to a shift in the natural resonance frequency to 6.6 GHz. Dielectric losses come from the ternary dielectric resonance while magnetic losses were from the magnetic natural resonance. An optimal reflection loss (RL) of -142.1 dB was observed at 12 GHz for 5.0 mm thickness layer. RL exceeding -10 dB was obtained at 6.6-18 GHz for 1.4 mm thickness, covering the whole X band (8-12 GHz), Ku band (12-18 GHz), and some of C band (6.6-8.0 GHz). RL exceeding -20 dB was found at 6-10.6 GHz for 2.2 mm thickness. (C) 2011 Elsevier B. V. All rights reserved.
关键词:
Carbon;Complex permeability;Complex permittivity;Electromagnetic wave;absorption;Nanocapsules;Reflection loss;nanocomposites;nanoparticles;composites;iron;nanotubes;nanorods
李启荣
,
魏斌
,
张晓平
,
郭旭波
,
应志军
,
冯骋
,
曹必松
低温物理学报
高温超导滤波器已在移动通信、射电天文、雷达探测等多个领域获得了重要应用．当前高温超导滤波器的研究和应用主要集中于10GHz以下的频段，针对超高频段（〉10GHz）高温超导滤波器的研究很少．本文设计优化了具有无载Q值高、耦合强、尺寸短等特点的H型阶跃阻抗谐振器，并讨论了超高频段滤波器端口激发源的电容效应对滤波器响应的影响，最后采用优化的H型谐振器，应用去嵌入（De-Embed）设计方法消除端口效应，设计了中心频率为16GHz，相对带宽12．5％的6节高温超导滤波器．研制的超导滤波器在未经调谐的情况下，测试结果与仿真结果符合得很好，插入损耗小于0．3dB，反射损耗优于-14dB，带外抑制达到了-70dB．
关键词:
高温超导滤波器
,
Ku波段
,
H型谐振器
F.T.Cheng
材料科学技术（英文）
The present communication addresses an interesting problem related to the indeterminacy in hardness of superelastic NiTi reported by Xu et al. The origin of the indeterminacy is attributed to the inadequacy of the conventional Vickers hardness testing measurement which does not record elastic deformation, and thus the indeterminacy may be removed with suitable techniques. Concepts of hardness in relation to deformation are clarified. Recommendations for measuring the hardness of NiTi and other elastic-plastic materials are suggested, together with comments on the advantages and disadvantages of each of these methods.
关键词:
Hardness
,
null
,
null
,
null
,
null
,
null
