Ku/Ka波段双通带频率选择表面雷达罩设计研究

为了满足现代通信设备多频带及集成化要求,基于耦合机理和谐振机理,在实心半波壁雷达罩和A 夹层雷达罩等效平板基底上设计了一种由容性表面（内嵌谐振单元）-感性表面-容性表面（内嵌谐振单元）-等效基底级联而成的Ku/Ka波段双通带频率选择表面结构. 根据FSS的物理结构建立了等效电路模型,分析了滤波机理,利用全波分析软件计算了两种FSS雷达罩的传输特性. 该结构基于容性表面与感性表面的耦合作用在Ku波段形成具有微型化特性的第一通带,基于两个容性表面内嵌的方环单元谐振在Ka波段形成第二通带,两通带透过率分别为89%,94.7%（实心半波壁FSS雷达罩）、88.2%/93.7%（A夹层FSS雷达罩）,在0°–45°扫描范围内,两通带传输特性稳定. 在半波壁雷达罩的等效平板上制作了Ku/Ka双通带实验样件,利用自由空间法测试其传输特性,在制作误差允许的范围内,测试结果与仿真结果基本一致. 为研究通带间隔较宽的多频FSS 提供了理论和实验依据. 关键词： 雷达罩 频率选择表面(FSS) 双通带     

Frequency selective surface with a flat topped passband

Two frequency selective surface (FSS) configurations with flat topped passband are presented in this paper.One configuration is single layer FSS with λ/4 thickness dielectric loaded on both sides, and the other is double layers FSS. Based on the modal matching method, the frequency response properties including angle effect and polarization effect of both FSS configurations are analyzed, and the plots of the frequency versus transmission coefficient are obtained for different incident angles and polarizations. It is shown that the structure with the single layer FSS embedded centrally in the λ/2 thickness dielectric has a wider flat top bandwidth of 6.8 GHz than that of the double layers FSS of 3 GHz. In addition, the fabrication of single layer is relatively easier than the double layers FSS.     

双带频率选择表面设计

为了实现频率选择表面(FSS)的双带特性,设计了由矩形栅格和三圆环组合单元FSS。对FSS的谱域求解方法进行了详细的描述。采用谱域法分析了不同角度和极化入射波下FSS的频率响应性能。结果表明,所设计的FSS对于不同入射角度和极化电磁波具有稳定的双带、平顶传输及陡峭下降边缘特性。双带特性大致表现为1.8～5.4GHz的阻带和5.4～20.0GHz的通带。阻带谐振频率稳定在3.1GHz左右,而通带在-4dB的平顶传输带宽达14.3GHz以上。其陡峭下降边缘特性表现为S波段信号强烈反射,而其他波段信号通过,从而实现多波段通讯。该结构FSS可应用于卫星通信、雷达罩及其他相关领域。     

电磁屏蔽用低频比小型化双频带频率选择表面

为满足敏感电子设备对频段密集相邻干扰信号的屏蔽需求,提出了一种低频比双频段带阻频率选择表面（FSS）结构。该结构由介质层和印刷在其两侧并谐振在不同频率的金属导带层构成。通过对两侧金属导带的互补型设计,削弱了两个谐振点间的耦合影响,使该FSS结构具有两个可以独立调节且紧密相邻的阻带,呈现出低频比特点。仿真结果表明,此结构可以实现低至1.16的谐振频率比。基于弯折结构的小型化设计使该FSS的单元尺寸仅为0.071λ,确保所提结构在TE和TM两种极化电磁波照射下,电磁屏蔽效能大于24 dB的入射角度稳定性高达60°。制作了实物并进行测试,实测结果与仿真结果吻合良好,验证了FSS结构设计的可靠性。     

Binary phase filters with a maximally-flat response

We investigate the binary phase filters of finite support that have a Fourier transform magnitude that is the broadest and flattest. We call this behavior maximally flat, after the electrical filters devised by Butterworth. Solutions are obtained by direct algebraic manipulation, and numerical results are given for filters of up to five elements. Their application for increasing depth of focus is described.     

Wideband FSS for electromagnetic architecture in buildings

Interweaving the elements of a frequency selective surface (FSS) is a technique that allows wideband frequency filtering as well as size reduction. FSS structures using this method are well suited to wireless indoor applications where the operating bands are spread over a wide spectrum. Interwoven square loop slots FSS have been designed, fabricated and measured. The FSS structure to be presented offers transparency at the emergency services band at around 400 MHz and suppresses most of the mobile and wireless bands up to 3 GHz. The size of the unit cell developed is around 3% of the corresponding wavelength, significantly smaller than a half wavelength resonant dipole.     

Enhanced transmittance of a dual pass-band metamaterial filter

A broad pass-band metamaterial-based optical filter is experimentally and numerically studied. The designed structure consists of periodically arranged composite metallic arrays and dielectric layer that exhibits transmission responses composed of two flat pass-bands. The coupling of localized surface plasmon (LSP) modes results in the low-frequency pass-band, while the internal surface plasmon polaritons (ISPPs) between the upper and lower metal layers leads to the high-frequency pass-band. Structural parameters (L and R) are experimentally considered from the viewpoint of exploiting their effects on the pass-bands and resonance frequencies. The bandwidths of these pass-bands both can reach to maximums by optimization of these structural parameters. In addition, the two pass-bands can be modulated to be a single pass-band with a bandwidth of 10.7 THz by optimizing L and R simultaneously.     

Micropatterning and transferring of polymeric semiconductor thin films by hot lift-off and polymer bonding lithography in fabrication of organic field effect transistors (OFETs) on flexible substrate

Micropatterning and transferring of polymeric semiconductor thin films by hot lift-off and polymer bonding lithography in fabrication of OFETs with polymeric dielectric on the flexible substrate was proposed. The desired polymeric semiconductor patterns were fabricated on the flat polydimethylsiloxane (PDMS) surface with a selective lift-off method we proposed previously. The isolated and well defined polymeric semiconductor patterns left on the flat PDMS surface can be further transferred to the gate polymeric dielectric surface by polymer bonding lithography due to the low interfacial energy of PDMS. The transistor fabricated with this ‘dry’ process has a higher field-effect mobility compared with that using spin coated semiconductor layer.     

Permalloy-FeMn exchange-biased multilayers grown on flexible substrates for microwave applications

Permalloy-FeMn multilayers deposited onto flexible substrates oriented for wide-band absorber applications were fabricated using RF sputtering deposition. The ferromagnetic resonance (FMR) frequency was tuned by changing the thickness of the Permalloy layers. Plural FMR frequencies appeared in the multilayer film due to the difference in exchange couple energies at their interfaces. A multilayer thin film with varying thickness of Permalloy layers was also fabricated with the properties of a wide-band absorber. Its range of 1-4 GHz (the absorption width where the reflection loss is less than 10 dB) appears promising for future applications.     

LED柔性照明及显示用超弹性柔性荧光膜

柔性LED是近年来照明及显示领域研究的热点之一.本文提出了一种新的基于有机硅胶(PDMS)制备的兼具超弹性和柔性的荧光薄膜,它不仅在-50~230℃这一较宽的温度范围内展现了良好的热稳定性,还保持了原料荧光粉的光学性能.所制备的透明PDMS基质膜和相应的荧光膜具有完全的柔性和超弹性,其最大伸长率分别高达400%与275%.此外,采用所制掺YAG荧光膜和普通商用1 W蓝光芯片简单封装的白光LED灯珠满足日常白光照明的应用要求,呈现出约6925 K的平均色温,约71的平均显色指数,115.7 lm/W左右的平均发光效率.最后,基于所提出荧光膜成膜工艺而制备的三色3×3柔性阵列显示,可以轻易被拉伸、卷曲和折叠,显示了它在柔性照明及显示器件方面具有应用价值和潜力.     

Growth of optical waveguides by pulsed laser deposition

An overview of active and passive waveguiding thin films fabricated by pulsed laser deposition (PLD) is given. The focus is on materials used, deposition conditions, films characterization and on waveguiding properties. Parameters of lasing layers fabricated by PLD are summarized. Summary of potential applications of optical waveguides is presented.     

Gold coated metal nanostructures grown by glancing angle deposition and pulsed electroplating

Nickel based nanostructures are grown by glancing angle deposition (GLAD) on flat and pre-patterned substrates. These fabricated porous thin films were subsequently coated by pulsed electroplating with gold. The morphology and conformity of the gold coating were investigated by scanning electron microscopy and X-ray diffraction. Controlled growth of closed gold layers on the nanostructures could be achieved, while the open-pore structure of the nanosculptured thin films was preserved. Such gold coated nanostructures are a candidate for optical sensing and catalysis applications. The demonstrated method can be applied for numerous material combinations, allowing to provide GLAD thin films with new surface properties.     

界面合金化控制柔性Al/PI薄膜应力的研究

针对航天器用MEMS热控百叶窗存在的柔性薄膜应力问题, 开展界面合金化控制薄膜应力技术研究. 通过给柔性Al/PI薄膜体系添加中间层Sn, 使其合金化, 使晶格产生膨胀畸变, 来引入相反的应力与已经存在的本征压应力相抗衡, 可获得低表观应力的薄膜. 用SEM和EDS剖面分析验证了Sn原子发生了明显的扩散现象, 形成了Al-Sn合金层. 这种方法可作为控制薄膜应力的一种新的技术手段.     

Response of an open curved thin shell to a random pressure field arising from a turbulent boundary layer

A method is presented to predict the root mean square displacement response of an open curved thin shell structure subjected to a turbulent boundary-layer-induced random pressure field. The basic formulation of the dynamic problem is an efficient approach combining classic thin shell theory and the finite element method, in which the finite elements are flat rectangular shell elements with five degrees of freedom per node. The displacement functions are derived from Sanders’ thin shell theory. A numerical approach is proposed to obtain the total root mean square displacements of an open curved thin structure in terms of the cross spectral density of random pressure fields. The cross spectral density of pressure fluctuations in the turbulent pressure field is described using the Corcos formulation. Exact integrations over surface and frequency lead to an expression for the total root mean square displacement response in terms of the characteristics of the structure and flow. An in-house program based on the presented method was developed. The total root mean square displacements of a curved thin blade subjected to turbulent boundary layers were calculated and illustrated as a function of free stream velocity and damping ratio. A numerical implementation for the vibration of a cylinder excited by fully developed turbulent boundary layer flow was presented. The results compared favorably with those obtained using software developed by Lakis and Païdoussis (J. Sound Vib. 25 (1972) 1–27) using cylindrical elements and a hybrid finite element method.     

0.34 THz频率选择表面带通滤波器设计

为满足太赫兹通信的需求,基于薄膜工艺和双层级联的结构,设计了一种0.34THz频率选择表面带通滤波器。利用等效电路模型分析了该滤波器的频率特性,通过仿真研究了入射角对该结构频率特性的影响,显示水平极化条件下其在低于45°入射角范围内具有较好的性能。最终按照所评估的误差容忍度加工了Jerusalem十字单元的频率选择表面样片,并进行了频率传输特性的测试与分析,结果表明:该滤波器具有较好的滤波特性。     

一种适用于雷达罩的频率选择表面新单元研究

从传统的频率选择选择表面(frequency selective surface,简称FSS)Y孔单元出发,提出了一种新单元.经优化设计,给出了Y孔单元和新单元的FSS结构参数,运用谱域Galerkin法对两种单元FSS的传输特性进行了数值计算.采用镀膜和光刻技术制作出相应的等效平板样件,在微波暗室对两种FSS等效平板在8—12GHz频段内的传输特性进行了测试,测试值与计算值基本一致.结果表明：与Y孔单元相比,新单元FSS在电磁波大角度(66°)入射时具有高的透过率,在电磁波大扫描角范围内(0°—66°)新单元FSS中心频率的漂移量更小.因此,所提出的新单元更适合于电磁波大角度入射下的应用,为FSS在曲面雷达罩上的应用提供了一种新单元. 关键词： 频率选择表面 中心频率 雷达罩     

A three-dimensional frequency selective structure based on the modes coupling of spoof surface plasmon and waveguide transmission

A three-dimensional frequency selective structure (3D FSS) was proposed by applying the spoof surface plasmon (SSP) structures into periodic waveguides, which realizes an enhanced broadband transmission in low frequencies, below the cut-off frequency of periodic waveguides. The transmission characteristics of SSP structures and periodic waveguides as well as their coupling modes are investigated by simulation and experiment method. According to our analysis, the pass-band of this 3D FSS can be customized through changing the values of structure parameters and it also has a good angular stability. In addition, this paper also provides a simple assembly plan for sample preparation. This proposal may be useful for improving filtering performances and gives an effective approach for designing 3D FSSs.     

连续离子层吸附反应沉积后硫化法制备柔性铜锌锡硫薄膜太阳电池

在柔性钼箔衬底上采用连续离子层吸附反应法(successive ionic layer absorption and reaction)制备ZnS/Cu2SnSx叠层结构的预制层薄膜,预制层薄膜在蒸发硫气氛、550 C温度条件下进行退火得到Cu2ZnSnS4吸收层.分别采用EDS,XRD,Raman,SEM表征吸收层薄膜的成分、物相和表面形貌.结果表明,退火后薄膜结晶质量良好,表面形貌致密.用在普通钠钙玻璃上采用相同工艺制备的CZTS薄膜表征薄膜的光学和电学性能,表明退火后薄膜带隙宽度为1.49 eV,在可见光区光吸收系数大于104cm 1,载流子浓度与电阻率均满足薄膜太阳电池器件对吸收层的要求.用上述柔性衬底上的吸收层制备Mo foil/CZTS/CdS/i-ZnO/ZnO:Al/Ag结构的薄膜太阳电池得到2.42%的效率,是目前报道柔性CZTS太阳电池最高效率.     

平顶响应薄膜滤波器透射特性的分析研究

对垂直多腔F-P规整膜系进行了结构上的划分,以反射膜系、腔层、耦合层为单位将膜系划分为若干个结构单元,利用史密斯方法将结构分为A、B两个系统。改变内膜系单元参数,得到了两腔F-P结构A、B系统反射率变化规律;改变A、B反射率的曲线交点和相位正弦值零点的位置,分析了透射曲线平顶响应的形成原因,得到了影响平顶响应薄膜滤波器性能参数的因素。得出透射性能良好的三半波膜系结构。其0．5dB带宽为0．52nm,3dB带宽为0．67nm,25dB带宽为1．59nm,矩形度为2．37（小于3）。     

Varactor-tunable frequency selective surface with an embedded bias network

A new technique for designing a varactor-tunable frequency selective surface （FSS） with an embedded bias network is proposed and experimentally verified. The proposed FSS is based on a square-ring slot FSS. The frequency tuning is achieved by inserting varactor diodes between the square mesh and each unattached square patch. The square mesh is divided into two parts for biasing the varactor diodes. Full-wave numerical simulations show that a wide tuning range can be achieved by changing the capacitances of these loaded varactors. Two homo-type samples using fixed lumped capacitors are fabricated and measured using a standard waveguide measurement setup. Excellent agreement between the measured and simulated results is demonstrated.