210-320 GHz Multi-Hole Directional Coupler Design and Measurement

The design of a 210-320 GHz multi-hole directional coupler is described. The coupler performance is measured with a millimeter vector analyser across the band 205-350 GHz and compared with simulations. The coupler consists of two waveguides whose broad walls are separated by a thin metal sheet with an array of circular holes according to a Chebyshev distribution of couplings. The coupling is 11 dB with a typical variation of ± 2dB across the WR3 band and the isolation is more than 25 dB.     

宽带雷达散射截面减缩人工磁导体复合结构

提出了宽带雷达散射截面(radar cross section, RCS)减缩人工磁导体复合结构, 通过将多个金属方片周期结构相复合, 进一步拓展了其工作带宽. 测试结果表明, 反射率小于-10 dB的频段为7.7—13.1 GHz, 相对带宽为51.9%. 通过全波仿真研究了其在不同频率的散射特性, 随着频率的增加, 在对角象限平分面上的反射峰逐渐向法线方向靠拢, 但其RCS较金属板的后向RCS仍减小-8 dB以上. 该人工磁导体复合结构具有工作带宽大、设计简单和加工容易等优点, 具有重要的应用前景.     

一种高功率微波金属片波导移相器设计与特性分析

设计了一种高功率微波矩形波导移相器,在矩形波导中平行于电场放置金属片,沿波导宽边移动金属片,实现波导内的可变相移。通过优化设计波导和金属片的结构尺寸可实现0~360°相移,通过优化设计金属片过渡匹配结构可实现较低的插损。设计波导内为全金属结构,不存在介质材料,采用真空绝缘可以承受较高的功率传输。设计了中心频率为9.4GHz的金属片波导移相器,移相器最大插损小于0.2dB,功率容量设计达到64 MW。实验测试,移相器最大插损小于0.5dB,相频曲线呈线性关系。     

基于多模干涉耦合器的集成热光开关实验研究

报道了一种基于多模干涉(MMI)耦合器的马赫曾德尔干涉仪(MZI)型2×2集成热光开关的实验研究结果,插损为3.40 dB,偏振相关损耗为0.47 dB,直通和交叉状态消光比分别为32.01 dB和16.42 dB,响应时间小于3 ms,开关功耗为658 mW。针对直通和交叉状态消光比不对称的现象,从理论上做出了解释,因为半导体平面光波电路(PLC)工艺一致性较好,两个多模干涉耦合器的分光比虽然因工艺误差偏离50∶50,但误差量相近,这个特点对光开关直通和交叉状态的消光比产生了不同影响。分析了在波导上制作加热电极对波导有效折射率的影响,估算其增量在2×10-4量级。     

Low-cross-talk polarization-insensitive 10-GHz-spaced 128-channel arrayed-waveguide grating multiplexer-demultiplexer achieved with photosensitive phase adjustment

We successfully fabricated a polarization-insensitive 10-GHz-spaced 128-channel arrayed-waveguide grating whose cross talk ranged from -39 to -36 dB . The optical phases of all arrayed waveguides were adjusted simultaneously by means of a photoinduced refractive-index change under ArF excimer laser irradiation through metal masks.     

圆波导TM_(01)-TE_(11)模式变换器

提出了一种在圆波导中添加金属分割片及半边金属管壳的结构以实现圆波导TM01-TE11模式转换。通过金属分割片将圆波导分成两个半圆区域:其中一个半圆区域为空波导,另一半圆区域为填充一定厚度金属管壳的空波导。在S波段对设计的中心频率为2.8GHz的物理模型进行数值模拟与实验研究,模拟结果表明:在中心频率2.8GHz转换效率为99.56%,反射率低于0.01;在2.716～2.946GHz频带内转换效率大于90%,S11小于-10dB。实验中测试到的S11参数与模拟结果基本一致,证明了该变换器技术方案的可行性和模拟结果的正确性。     

Long range surface plasmon polariton waveguides at 1.31 and 1.55 μm wavelengths

We investigate characteristics of gold metal strip waveguides based on long range surface plasmon polaritons (LRSPPs) along thin metal strips embedded in a polymer for practical applications at the telecommunication wavelengths of 1.31 and 1.55 μm. Guiding properties of the gold strip waveguides are theoretically and experimentally evaluated with the limited thickness and width up to ∼20 nm and ∼10 μm, respectively. The lowest propagation loss of ∼1.4 dB/cm is obtained with a 14.5-nm-thick and 2-μm-wide gold strip at 1.55 μm. With a single-mode fiber, the lowest coupling loss of ∼0.4 dB/facet is achieved with a 14.5-nm-thick and 5-μm-wide gold strip at 1.55 μm. The lowest insertion losses are obtained 8-9 dB with 1.5 cm-long gold strips of a limited thickness and width at both the wavelengths. We demonstrate a 10 Gbps optical signal transmission via the LRSPP waveguide with a 14 nm-thick, 2.5 μm-wide, and 4 cm-long gold strip. These LRSPP waveguides have potential applications for optical interconnects and communications.     

一种具有声低通滤波特性的无源零差光纤水听器

报道了一种新颖的具有抗混叠功能的无源零差迈克耳孙型光纤水听器.它由一个普通的芯轴型光纤水听器和一个圆柱型亥姆霍兹共振器构成.在驻波罐中对其声压相位灵敏度频响进行了测量,结果表明该光纤水听器具有较好的声低通滤波特性,能有效地抑制声信号中的高频成分,从而实现抗混叠滤波.该光纤水听器的低频声压相位灵敏度主要由传感光纤长度和弹性增敏层的物理特性决定,约为-159 dB(0 dB=1 rad/μPa).在1150 Hz附近出现了一个共振峰,这主要由圆柱型亥姆霍兹共振器的声学特性决定.1150～2280 Hz频段内的灵敏度衰减率约为50 dB/倍频程,1500 Hz以后的灵敏度衰减量大于10 dB.这对于提高我国未来声纳系统的抗干扰能力具有十分重要的意义.     

Phase Transition VO2 Thin Films for Optical Switches

This paper presents a method to make vanadium dioxide (VO₂) crystallites on silicon substrates by reactive ion beam sputtering. The thickness of the thin film is about 100nm. The phase transition temperature of VO₂ is 65°C. The transmittance of the semiconducting phase VO₂ is about 50% and it is reduced to as low as 3% in metal phase at the infrared wavelenghth spectrum. The extinction ratio of the optical switches is 12dB. and the insertion loss is of 1-2dB. The switching time is about 1ms.     

某型飞艇平台微波测试环境研究

针对微波试验用某型飞艇升空平台开展试验环境测试研究,给出了中等气象条件下的测试结果。指出定姿飞控模式下的艇体方位角稳定性优于压航迹模式,两种飞控模式下艇体俯仰角和滚转角稳定性相近; 统计分析指出配试用艇载二轴天线稳定平台可有效隔离飞行中艇体三姿±10°以上的晃动,将接收天线主轴稳定指向辐射源,天线主轴方位、俯仰角控制精度优于±1°。研究了相对辐射源20~40 km,迎头、横向两种航线下,艇载4.5°波束宽度天线接收信号的幅度,统计分析指出迎头飞行时天线增益损失小于1 dB,信号稳定性优于±1 dB,横向飞行时天线增益损失约2.3 dB,信号稳定性约±3 dB。研究给出了飞行条件下艇体散射环境和地面散射环境对艇载天线接收信号幅度的影响。     

基于十字形结构的相位梯度超表面设计与雷达散射截面缩减验证

基于十字形结构设计了一种在雷达波低频段极化不敏感的相位梯度超表面, 并通过仿真和实验进行了验证. 不同金属十字周期结构单元复合, 在超表面上形成附加的平行波矢分量, 对反射波波前进行调控, 获得超表面后向雷达散射截面积(RCS)缩减. 在设计波段内, 超表面在法线方向的单站RCS缩减达18.19 dB, 偏离法线-30°–+30°范围的单站RCS 平均缩减达8 dB; 仿真与实验结果符合较好.     

等离子体用于腔体的雷达散射截面减缩的实验研究

 利用荧光灯等离子体管覆盖金属腔体内壁,测量了筒状等离子体覆盖的金属腔体对电磁波的回波衰减。测试结果表明:金属圆筒内壁的等离子体能够有效吸收0.80~1.75 GHz波段的入射波,入射电磁波的回波衰减值为5~25 dB;当入射电磁波频率接近1.75 GHz时,回波衰减最为强烈,在入射角度为10°时,吸收峰值可达26.71 dB,因此选择合适的电磁波入射角度,能够使等离子体对微波的吸收达到峰值。理论分析了影响等离子体对电磁波衰减的主要因素。结果表明：等离子体可有效缩减腔体结构的雷达散射截面面积,因此在进气道等腔体结构的隐身方面具有一定的应用前景。     

基于极化旋转超表面的圆极化天线设计

本文通过设计出一种反射型极化旋转超表面,在8—12 GHz频域内实现高效的极化旋转,并将其加载于微带缝隙天线下方构成新型的极化旋转超表面天线,利用超表面的90°极化旋转效应,成功实现了天线的圆极化辐射调制.仿真与实验结果表明:圆极化天线的中心工作频率为GHz,阻抗带宽为8.3—10 GHz.当微带缝隙天线与极化旋转超表面的间距H=4.5mm时,天线在8.3—8.8 GHz频带内实现了圆极化辐射;当mm时,天线在8.8—9.3 GHz频带内实现了圆极化辐射;当=8mm时,天线在9.3—10 GHz频带内实现了圆极化辐射.实验结果与仿真结果相符,证明了此种设计方法的有效性,也为微带缝隙天线的圆极化设计提供了一种新的途径.     

Subwavelength confinement in an integrated metal slot waveguide on silicon

We demonstrate propagation losses of less than 0.8 dB/microm in a metal slot waveguide on silicon with a predicted confinement substantially below the optical wavelength (approximately 1.55 microm). We also show compact and efficient coupling of the high-confinement metal slot waveguide with a standard silicon dielectric waveguide with a coupling efficiency of approximately 2.5 dB per facet.     

介质/金属结构太赫兹空芯光纤的传输特性

理论分析了金属、介质/金属结构空芯光纤在THz波段的模式结构和传输特性.金属空芯光纤支持TE11模式,介质/金属空芯光纤的介质膜厚在取最优值时支持HE11模式.对于波长为200μm的太赫兹波,内径为1 mm的两种空芯光纤,TE11和HE11模式的损耗分别为8.4 dB/m和2 dB/m.为优化介质/金属结构宅芯光纤的传输性能,分析了金属和介质材料的光学常数对衰减系数的影响.基于几种已发表的金属在太赫兹波段的光学常数,计算结果表明铝是最好的选择;初步测量结果显示,在各种树脂材料中聚乙烯在THz波段吸收较小,并且其折射率接近介质膜的最优值1.41,为太赫兹波空芯光纤中介质膜材料的理想选择.     

A millimeter and sub-millimeter wave frequency selective surface beamsplitter for geostationary orbit microwave radiometers

We report the design of three frequency selective surface(FSS) filters used on the FengYun-4(FY-4) microwave satellite,which separate five-frequency bands in the frequency range of 50-429 GHz with the insertion loss less than 0.4 dB,and separation between adjacent channels more than 20 dB for either TE or TM incidence.Firstly,we briefly introduce the disadvantages of two types of FSS filter:waveguide-array FSS and printed FSS,which are commonly employed in the millimeter and sub-millimeter wave band.In order to meet the insertion loss requirement and specified spectral transmission response,we adopt a filter composed of two closely spaced freestanding metal plates,which contains an array of resonant ring slot elements.Computer simulation technology(CST) is used to optimize the structural dimensions of the resonant unit and interlayer separation.Numerical results show that these FSS filters exhibit transmission loss of less than 0.4 dB and separation between adjacent channels of more than 20 dB.Simulated transmission coefficients are in close agreement with the required specification,and even exceed the performance specifications.     

Noise reduction algorithm of corrosion acoustic emission signal based on short-time fractal dimension enhancement

The general corrosion and local corrosion of Q235 steel were tested by acoustic emission(AE) detecting system under 6%FeCl_3-6H_O solution to effectively detect the corrosion acoustic emission signal from complex background noise.The short-time fractal dimension and discrete fractional cosine transform methods are combined to reduce noise.The input SNR is 0~15 dB while corrosion acoustic emission signals being added with white noise,color noise and pink noise respectively.The results show that the output signal-to-noise ratio is improved by up to 8 dB compared with discrete cosine transform and discrete fractional cosine transform.The above-mentioned noise reduction method is of significance for the identification of corrosion induced acoustic emission signals and the evaluation of the metal remaining life.     

Enhanced microwave absorption performance of MOF-derived hollow Zn-Co/C anchored on reduced graphene oxide

Composite materials assembled by metal/carbon nanoparticles and 2D layered flakes can provide abundant interfaces, which are beneficial for high-performance microwave absorbers. Herein, Zn-Co/C/RGO composites, composed of Zn-Co metal-organic framework-derived Zn-Co/C nanoparticles and reduced graphene oxide (RGO), were obtained through a facile method. The multilayer structure was due to the introduction of hollow Zn-Co/C nanoparticles in the RGO sheets. Zn-Co/C nanoparticles provided abundant polarization and dipole centers on the RGO surface, which enhanced the microwave absorption abilities. Different concentrations of RGO were introduced to optimize impedance matching. The minimum reflection loss (R_L) of Zn-Co/C/RGO with a thickness of 1.5 mm reached -32.56 dB with the bandwidth corresponding to R_L at -10 dB, which can reach 3.92 GHz, while a minimum R_L of -47.15 dB at 11.2 GHz was also obtained at a thickness of 2.0 mm. The electromagnetic data demonstrate that Zn-Co/C/RGO presented excellent absorption performance and has potential for application in the microwave absorption field.     

基于磁/电介质混合型基体的宽带超材料吸波体的设计与制备

本文设计了一种基于磁/电介质混合型基体的宽带超材料吸波体, 吸波体基本单元由电阻膜、磁/电介质混合型基体以及金属背板组成. 采用时域有限差分法对超材料吸波体吸波性能进行了仿真, 使用遗传算法优化了反射率小于-10 dB的带宽. 仿真结果表明, 当超材料吸波体厚度为2.5 mm时, 在7.8–18 GHz频率范围内的反射率小于-10 dB, 具有厚度薄、宽带、极化不敏感等优点. 通过等效电路模型对其工作机理进行了分析与讨论. 最后制备样品进行测试, 测试结果与仿真结果一致.     

A wideband metamaterial absorber based on a magnetic resonator loaded with lumped resistors

<正>A wideband metamaterial absorber（MA） based on a magnetic resonator loaded with lumped resistors is presented. It is composed of a one-dimensional periodic array of double U-shaped structured magnetic resonators loaded with lumped resistors,a dielectric substrate,and a metal plate.We simulated,fabricated,measured,and analyzed the MA. The experimental results show that the reflectance(S₁₁) is below -10 dB at normal incidence in the frequency range of 7.7 GHz-18 GHz,and the peak value is about—20 dB.Simulated power loss density distributions indicate that wideband absorption of the MA is mainly attributable to the lumped resistors in the magnetic resonator.Further investigations indicate that the distance between two unit cells along the magnetic field direction significantly influences the performance of the MA.