射电天文X波段极化网络一体化设计与研究

射电天文望远镜中极化网络一般由极化器、波导同轴转换器、耦合器等几部分组成,为了获取最高限度的系统灵敏度,极化网络在射电天文低温接收机中会置于低温真空杜瓦20 K 温区,使其对接收机噪声温度的贡献降到最低。通过对极化网络的深入研究设计了一种基于隔板结构的X 波段极化器、耦合器和波导同轴转换器一体化结构。该设计既实现了极化器的线圆转换功能又实现了-30 dB 噪声耦合。测试结果表明该设计拥有良好的轴比、耦合度和驻波特性。同时一体化设计进一步减小了无源器件之间的级联,使低温低噪声放大器之前的馈源网络插入损耗进一步降低,提升了射电望远镜的接收灵敏度。     

一种基于过模波导的高功率8 mm微波传输系统

过模波导是一种突破传统单模波导功率容量的波导结构。在高功率微波系统中,基于过模波导的模式过渡器和模式滤波器都是传输系统的关键器件。本文讨论了这些器件的理论设计依据,并设计了一套包括过模波导、模式过渡器、模式滤波器的8 mm 高功率过模波导传输系统,其中,模式滤波器分别通过膜片和窄缝滤除高次模。并用 CST Microwave Studio建模并仿真。仿真结果表明,该过模传输系统能够有效抑制高次模带来的谐振效应,提高微波的传输效率。     

K波段低轴比的隔板式极化器

展示了一种K波段低轴比的隔板式圆极化器的设计、加工和测试过程。该极化器左、右旋输入端口为WR42标准矩形波导,通过T 型节过渡到极化器方波导主体。设计了盖板式机械结构,降低了极化器的加工和装配难度,同时保证了隔板与波导腔体间贴合的紧密性。给出了不同加工精度对极化器性能影响的评估。最终的实测结果表明,极化器在工作频带内具有良好的端口反射系数与隔离度。在20～24 GHz 频带内所激励圆极化信号轴比约为0.3 dB,可作为高频低轴比极化器研制的参考。     

波纹波导极化器的分析

极化器是天线馈电系统中的重要器件,但传统的极化器带宽一般很窄。介绍了一种新型的宽带极化器(波纹波导极化器),其结构是在方波导的两壁加载横槽波纹,使波导中的2个正交模产生了90°的相位差。因而将线极化信号转化成圆极化信号。波纹波导极化器在超过30%的带宽内仍然有很好的相移特性,因此他在宽带反射面天线馈电系统中有着很广阔的应用。     

一种Ka/EHF双频段圆极化器的设计

为了获得更大的通信容量,卫星通信频率将由Ku/Ka向更高的Ka/EHF频段发展,Ka/EHF双频段圆极化器是EHF卫星通信系统中的关键技术之一。设计了一种Ka/EHF双频段波导圆极化器,同时提出了一种新颖的Ka/EHF双频段极化分解器,该圆极化器和极化分解器获得了良好的驻波比和相位特性。借助仿真软件对圆极化器和极化分解器的尺寸和结构进行了优化,并进行了加工和测试。测试结果与仿真结果吻合较好,对所提出圆极化器和极化分解器的性能进行了验证。     

基于喇曼-奈斯衍射的MOEMS加速度计的设计与工艺实验

本文主要设计了一种新型的基于喇曼奈斯声光衍射的微光机电加速度计。它主要由一个声光移频器与一系列光波导构成。文章首先对器件的基础理论与基本原理做了简要的介绍。然后设计了一种基于弯曲板波的延迟线振荡器做为声光移频器,其克莱因-考克参数为0.38。设计了厚度2微米,宽度0.6微米的单模光波导用于光的传输,同时还设计了波导偏振器以保证波导内的光具有相同的偏振方向。接着,基于前文的设计,文中提出了基于硅工艺的器件加工方案与流程,并详细讨论了加工流程中存在的难点与问题。最后针对提出的难点与问题进行了一系列的工艺实验,找到了解决难点和问题并复合设计要求的工艺条件与参数,实验结果表面本文提出的器件的设计与加工是可靠可行的。     

一种宽带四脊波导正交模极化耦合器

坐落于贵州天然喀斯特地形的500 米口径球面射电望远镜(FAST),其低噪声接收机系统需要高性能正交模极化耦合器,对此,提出了一种四脊波导形式宽带正交模极化耦合器快速有效的设计方法:首先分别设计四脊波导正交模极化耦合器的两个关键部分,然后进行整体优化,为了改善带内阻抗匹配性能可以在同轴输出端口的内探针引入阶梯匹配环。使用这种方法研制的FAST L 波段极化器工作带宽达到2 颐1,在整个带宽范围内极化器的反射系数小于-20 dB,极化耦合水平低于-43 dB,带内插入损耗优于0. 15 dB,仿真和实测结果有很好的一致性。提出的设计方法适用于各种频率范围的宽带四脊波导正交模极化耦合器的设计。     

圆波导介质加载锁式铁氧体变极化器的实验研究

在实验基础上,本文给出圆波导锁式铁氧体变极化器的介质加载的研究结果．实验表明,在铁氧体环内适当加载介质,可明显提高器件的相移,而对插入损耗特性影响甚微．这一发现对改进器件性能,具有极大的实用价值     

基于MSC双声路SAW器件的设计仿真平台

利用模块化设计思想,在Matlab编程环境下实现了基于多条耦合器双声路声表面波器件的设计仿真平台。为了提高MSC双声路SAW器件的性能,该平台将多条耦合器、分裂指及假指设计方案融合到器件设计中。多条耦合器不仅实现了两个变迹换能器传递函数的乘积,而且消除了体声波对器件性能的影响。假指消除了通过变迹换能器引起的波前畸变。分裂指可以最小化换能器内部的声波反射问题。通过一个频率为203.559MHz的基于多条耦合器双声路声表面波器件的设计和实际测试结果的对比分析,证明了该设计仿真平台不仅可以进行器件版图结构的设计和模拟,而且设计平台所得到的版图和数据可以用于器件的掩膜版制作和器件封装尺寸参考。另外,该仿真设计平台可以很好地实现对器件的脉冲特性、频率响应特性的模拟和仿真。     

8-18GHz介质板极化器的分析与设计

介质板极化器在天线设计中的应用非常广泛。从介质板波导形成圆极化波的原理出发,推导出差相移与波导传播常数的关系式。因此只需利用数值方法计算波导的传播常数,从而减小了仿真计算量。分析表明在818GHz超宽带范围内,方波导中插入介质板的圆极化轴比理论上只能达到2．03dB。文中提出介质板插入结合波导口径变形的方法使圆极化轴比小于1．53dB,驻波比小于1．23。对介质板波导的关键参数进行误差分析,得到加工误差对圆极化性能的影响小于2．5％。     

声光可调谐滤波器中波导与模分离器的设计

声光可调谐滤波器（AOTF）是一种基于集成光学技术的光学器件,它的性能主要取决于它的各个关键模块,特别是光波导和模分离器的设计．首先采用有效折射率法设计了工作于1．55um处的Ti：LiNbO3单模波导,之后对所设计波导的模场进行了模拟,并对模拟结果进行了分析．在单模光波导设计的基础上,采用光束传播方法（BPM）设计了TE／TM模分离器,并分析了它的消光比．最终得出波导和模分离器的优化设计结果．     

Unidirectional magnetooptic polarization converters

Inclination of the bias magnetization in a magnetooptic waveguide yields both nonreciprocal phase shifts and polarization conversion. This enables the design of unidirectional polarization converters, i.e., waveguides that switch between orthogonal polarizations for one direction of light propagation, but keep the polarization state for light propagating in the opposite direction. Simulations of double layer raised strip waveguides show that these constraints can be met with properly adjusted geometries. The results lead to the proposal of a polarization independent integrated optical circulator based on two unidirectional polarization converters between a front and a back polarization splitter     

A mode-evolution-type integrated-optical beam combiner for coherent receivers

An integrated-optic sum-and-difference optical beam combiner for coherent receivers based on adiabatic mode evolution in an asymmetric waveguide junction is described. The device was packaged as a 2*2 fiber-compatible LiNbO/sub 3/ chip, and operated as a 180 degrees optical hybrid for combining arbitrary input polarization, exhibiting excellent balance and moderate loss. The advantage of this component over previously studied directional coupler beam combiners is the absence of a strict interaction length requirement for obtaining balanced separation. Integration of this component with a passive mode-evolution-type polarization splitter will result in polarization-diversity receivers with broad constraints on processing, design, and wavelength of operation.<>     

Resonant tunneling three-waveguide polarization splitter

A design for a novel and highly efficient all-dielectric, three-waveguide polarization splitter based on the phenomenon of resonant tunneling is proposed. By considering a glass waveguide structure with an intermediate high-index guiding layer (such as silicon), it is shown that extinction ratios better than -33 dB in both the outer waveguides at a particular thickness of the high-index layer can be obtained. The tolerance required with respect to the separation between the middle and outside guides and the thickness of the high-index layer of such a device is estimated. The design should be of interest in the realization of in-line fiber-optic polarization splitters and in integrated optics     

Polarization stabilizer using a polarization splitter and athermooptic polymer waveguide device

For the stabilization of the time-varying light polarization in the optical fiber, we demonstrates a polarization stabilizer by using a fiber-optic polarization splitter, a passive polarization converter, and a power equalizing waveguide device. Because the ratio of the output light power from the polarization splitter is time-varying depending on the input polarization, we adopt a power equalizer consisting of a polymeric thermooptic (TO) phase modulator and an asymmetric X-junction waveguide. A feedback signal is obtained from the difference of the two outputs of the power equalizer. Then it is applied to the TO phase modulator. The output power is stabilized with the TE polarization independent of the time-varying polarization state of the input light     

Terahertz Wave Polarization Beam Splitter Using Asymmetrical Coupler

This study has proposed and numerically demonstrated a compact terahertz wave polarization beam splitter. The splitter is built by using a asymmetrical directional coupler consisting of a bend waveguide and a slot bend waveguides and achieves a high extinction ratio of 24.88 dB and 16.55 dB for cross and through ports. The optimal coupling region length is found to be 26 μm. By using such a polarization beam splitter, the size of the terahertz wave system could be reduced significantly. The simulation results show that the designed polarization beam splitter can split TEand TM-polarized terahertz wave into different propagation directions with high efficiency over the terahertz wave frequency range from 9.40 THz to 9.65 THz. The device obtained is readily used for a polarization diversity terahertz wave integrated circuit field, particularly for platforms with slot waveguide.     

金属修饰的微结构光纤偏振分束器

提出了一种金属修饰的微结构光纤偏振分束器,并且利用全矢量有限元法仿真分析了该偏振分束器的长度与其结构参数的关系,进而得出了该偏振分束器长度随孔间距、占空比变化的一般规律。研究结果表明:当其他结构参数一定时,该偏振分束器长度会随着孔间距的减小而减短;占空比减小,偏振分束器长度也会随之减短。最终综合考虑其性能与金属材料带来的损耗的影响,设计出一种结构简单的微结构光纤偏振分束器。该偏振分束器长度为3.523 mm,在其工作波长1。55 m处消光比高达74.9 dB,消光比高于20 dB的波长范围为1.53~1.57 m之间的40 nm范围,覆盖了整个光通信的C波段范围。并且该偏振分束器有着较好的冗余特性,在偏振分束器长度存在5%的误差时,仍能保持较好的性能。     

Integrated optical polarization-discriminating receiver in glass

We have successfully demonstrated an integrated optical TE-TM mode discriminator using waveguide polarizers and guided-wave photodetectors for use in polarimetric optical sensor and positioning systems. The photonic integrated circuit consists of a Y-branch waveguide splitter formed by potassium-sodium ion exchange in silicate glass. Hydrogenated amorphous silicon claddings were deposited on each branch of the splitter to act as polarizers. One output cladding was trimmed to a thickness which attenuated the TE polarization, while the other cladding was trimmed to attenuate light having TM polarization. The thickness trimming was accomplished using a process of localized plasma etching which allows in situ extinction optimization by monitoring transmitted light. Optical extinction ratios of up to 27 dB were demonstrated on Y-branch waveguides for polarizers with claddings 1.2 mm in length. The integrated receiver was completed with the deposition of metal-semiconductor-metal photodetectors on each of the output waveguide branches following the polarizers. Amorphous silicon claddings were contacted with chrome-gold interdigitated Schottky contacts to form the waveguide detectors     

Analytical and experimental study of waveguide optical polarizationsplitter with Langmuir-Blodgett cladding layer

The waveguide-type optical polarization splitter, which utilizes birefringence of a Langmuir-Blodgett cladding layer, is studied theoretically and experimentally. By means of the beam propagation method based on Galerkin's principle, characteristics of the polarization splitter are analyzed. Results of the numerical calculation predict excellent polarization splitting properties with a crosstalk of -30 dB and an insertion loss of less than 0.1 dB for both TE and TM polarization. Successful operation of the polarization splitter was demonstrated in an experimental device     

超短双芯光子晶体光纤偏光分束器

提出了一种基于椭圆双芯光子晶体光纤的偏振分束器,并利用全矢量有限元法分析了偏振分束器长度与结构参数的关系,由此得出了偏振分束器长度随孔间距、占空比和桥路变化的一般规律。研究表明,当椭圆双芯光子晶体光纤偏振分束器结构参数一定时,孔间距越小,桥路宽度越宽,则分束器长度越短;占空比变化对长度影响不明显,但对消光比的影响较明显。进而,通过结构参数的优化,设计出一种超短的椭圆双芯光子晶体光纤偏振分束器,在工作波长1 550 nm处,该分束器的长度仅为0.775 mm,消光比高达50 dB,消光比大于20 dB的带宽覆盖了从1 535~1 565 nm之间30 nm的波长范围,即通信C波段范围。