Ka波段宽带TE01d-TE10W多孔定向耦合器的设计

利用小孔耦合理论,设计了一种应用于Ka波段回旋放大管输出功率和频谱测量的TEd01-TEW10多孔阵列定向耦合器。根据正向叠加和反向相消原则确定圆波导半径及相邻耦合孔间距,用MATLAB编写程序对耦合度及定向性随耦合器尺寸相关参数的变化做了数值分析。数值计算表明:增加耦合孔数目、扩大孔半径及减小孔厚度均可提高耦合度,而耦合孔数目的增加在工作频带内还可提高定向性。给出了16孔定向耦合器尺寸优化设计参数,并利用CST电磁软件对其进行了仿真验证,仿真结果与数值模拟近似一致,其耦合度为-35±0.9 dB,定向性高于24 dB,带宽高达6 GHz。冷测实验表明所设计定向耦合器满足设计要求。     

基于硅基定向耦合器的单纤三向器设计

设计了基于硅基二氧化硅定向耦合器的光纤到户单纤三向器。通过定向耦合器耦合系数对波长的信赖性,在相同的耦合长度下实现单纤三向器三个波长(1310nm,1490nm和1550nm)的全周期耦合或半周期耦合,使三个波长信号从不同的耦合臂输出,完成三向器粗分波功能。有限差分束传播法(FD-BPM)模拟结果表明三向器损耗小于0.5dB,三个响应波长的1dB带宽即可满足ITU.984带宽要求,最优串扰为-14dB。     

功率方程概念用于确定喇叭天线的输入功率

本文介绍了一种用级联定向耦合器扩展小功率标推的量程的方法。在处理功率传输系统中的失配问题时,应用了功率方程概念,使由于失配所引起的误差大大减小。应用该技术,在5cm频段波导系统内测量了标准喇叭天线的输入功率,估计总的不确定度约为±1.8％。     

CO2激光传输用锥形波导耦合器的设计、制备及其性能研究

针对CO2激光传输用空芯波导的特点，设计、制各了锥形空芯波导耦合器系统。对此耦合系统的传输性能测试表明，使用该锥形空芯波导耦合器能够显著提高空芯波导的激光传输性能。     

非均匀线耦合系数的计算

定向耦合器的模拟试验通常需使用专用的计算机程序，而由民用的计算机辅助工程设计程序来处理耦合器是较为困难的。对于那些乐意自己研制耦合器模型的工程师来说，本文所提出的新方法将有助于对称锥形定向耦合器的设计，新理论所给出的近似方法改善了等波纹耦合响应的定向耦合器的性能，体现了宽频带小的体积尺寸。     

微波功率放大器的性能以及增益的测量

介绍一种微波功率放大器增益的测量方法。经校准件进行TRL校准,校准后分别对所用的两只定向耦合器进行耦合衰减、方向性系数、主线插损和输入口驻波比的频率反应进行测量,同时对终端负载的输入驻波比进行测量。最后由安捷伦矢量网络分析仪组建网络参数测试系统对微波功率放大器的增益进行测量。     

基于超表面的紧耦合阵列天线设计

设计了一种应用于WiMAX的紧耦合阵列天线。基于超表面解耦原理,设计了一种具有负介电常数和正磁导率的耶路撒冷十字超表面单元。在二单元紧耦合贴片天线上方加载5×6的超表面以减小单元间互耦,矩形贴片上刻蚀一个U形缝隙改善天线的阻抗匹配。阵列天线的尺寸仅为55 mm×74 mm×8.2 mm(0.64λ₀×0.86λ₀×0.10λ₀,λ₀为3.5 GHz时自由空间的波长),天线单元的间距(边到边的距离)为1.3 mm(0.015λ₀)。测量结果表明,阵列天线能够工作在WiMAX的3.5 GHz频段,-10 dB阻抗带宽为13.83%(3.23 GHz～3.71 GHz),-18 dB解耦带宽为10.34%(3.3 GHz～3.66 GHz),天线具有良好的辐射特性。     

球隙棱镜—波导耦合器(理论分析)

一、序棱镜-波导耦合器是集成光学中很重要的一种耦合器。它不仅能以很高的耦合效率将光耦合入光学波导,而且还是研究光学波导的重要工具。用来测量薄膜的光学特性,(通常称作m谱线法)能简单而准确地同时测得薄膜的折射率和厚度,其精度可以与椭圆仪相比拟。改进这种方法,能测量薄膜各点的特性,并适于吸收薄膜。田中敬     

用于Triplexer Monitor的波长不敏感耦合器

为了提高Triplexer Monitor的光信号采样性能和集成度,提出一种基于非对称锥形波导结构的波长不敏感耦合器.该耦合器采用SiO2-on-Si掩埋型光波导结构,位于中心部位的锥形波导构成耦合区,与之衔接的S型弯曲波导实现信号光的输入和输出.采用传输矩阵法分析了光监测端口输出的归一化的耦合光功率,分析时将耦合区的中心部位作为非对称矩形波导而外侧作为对称矩形波导.利用光束有限差分传播法(FDBPM)和MATLAB数值仿真得出:当耦合区中心非对称矩形波导宽度分别为5.50μrn和3.35 μm时,对于1 300 nm到1 600 nm的输入光波长范围,可实现光监测端口4％～8％的归一化耦合光功率.特别的,在1310nm、1490 nm和1550 nm输入光波条件下,耦合器在输出端的分光比分别为:92∶8、96∶4和93∶7,同时TE模和TM模的分光比变化保持在5％以内.所设计的波长不敏感耦合器具有体积小、可靠性高等优点,适合与PLC型的Triplexer实现单片集成.     

定向耦合器在微波传输系统中的应用

简述了定向耦合器的工作原理 ,分析介绍了实际工作中在微波传输系统方面定向耦合器的几种主要应用。     

Design of a high-efficiency grating coupler based on a silicon nitride overlay for silicon-on-insulator waveguides

A waveguide grating coupler based on a silicon nitride overlay at 1.55 μm for TE polarization is designed with no experimental demonstration. Its coupling efficiency for a fiber is 76%, the 1 dB bandwidth is 75 nm, and the coupling angle is 10°. The effects of different device parameters on the coupling performance for the grating coupler are discussed. The coupling efficiency of our grating coupler is almost equal, yet the 1 dB spectral bandwidth is around 25 nm broader, as compared with the grating coupler design based on a poly-silicon overlay. The coupling performance of our coupling device could still be further improved. The grating coupler presented in this paper is applicable to the optical coupling in nanophotonic integrated circuits.     

Calibration and Use of a Reference Standard Directional Coupler for Measurement of Large Coupling Factors

Fixed frequency, point-by-point calibration is outlined for a reference standard directional coupler to be used in steppedfrequency measurement of 40-dB, or greater, coupling factors of directional couplers. If a reference directional coupler has a 40-dB coupling factor, a main-line waveguide output, and a sexless coaxial side-arm output, the best accuracy obtainable in measurement of its coupling factor is estimated to be ±0.03 dB.     

Characterization of tunable photonic crystal fiber directional couplers

We present a tunable photonic crystal fiber (PCF) directional coupler fabricated by a side-polishing method. The PCF directional coupler was modeled as a typical single-mode fiber-based directional coupler and analyzed using the improved effective-index method (IEIM). The characteristics of the PCF directional coupler such as the coupling coefficient and the coupling ratio were measured and found to be in good agreement with those predicted by the theoretical model. The PCF directional coupler exhibited an insertion loss of approximately 2 dB for a 3 dB coupler and was able to tune the coupling ratio between 0% and 100% by tilting the angle of the top side-polished quartz block against the fixed-bottom quartz block.     

Optical switching in a symmetric three-waveguide nonlinear directional coupler

In this paper we study optical switching in a system of a three-waveguide nonlinear directional coupler. We consider a waveguide structure with three parallel waveguides in a linear, symmetric coupling configuration. We work in the case that the (absolute value of the) difference of the propagation constants of the outer and centre waveguides is much larger than the linear coupling constants. When one of the outer waveguides is initially excited, we show that for small values of the initial power the system behaves as a two-waveguide nonlinear directional coupler where only the two outer waveguides are involved in the switching. For larger values of the initial power, transfer of light between the initially excited waveguide and the centre waveguide is observed.     

Controlling the polarization dependence of dual-channel directional couplers formed by silicon-on-insulator slot waveguides

The polarization dependence of directional couplers (DC) formed by silicon-on-insulator (SOI) slot waveguides was studied, and its applications as highly efficient polarization beam splitters (PBSs) and polarization-independent directional couplers (PIDCs) were investigated. The coupling lengths for the quasi-TE and quasi-TM modes may vary with the waveguide geometry due to structural birefringence; thus numerical simulations of the coupling effects in the directional couplers with different aspect ratios and waveguide spacing were conducted to obtain the optimal design parameters for high efficiency as well as compact device size. The lengths of the coupling regions of the designed PBS and PIDC are 47.61 and 23.13 μm, respectively, and they delivered good performance, with an extinction ratio greater than 20 and 1 dB bandwidth larger than 100 nm. The tolerance of fabrication error in the practical device is also discussed.     

Design of compact narrowband optical filter on SOI using asymmetric directional coupler

A narrowband optical filter on Silicon-on-Insulator based on a directional coupler of continuous and periodic segmented waveguide is theoretically investigated. The study shows that the filtering action is better when a slot waveguide is considered as the continuous waveguide instead of a photonic nano-wire waveguide. A filter of extremely narrow bandwidth at any desired wavelength can be designed by optimizing the feature size of the different components of the device. Comparison of the footprint shows that the proposed filter is much more compact than other available filter. Typical value of proposed filter bandwidth can be as low as 2.5 pm with a footprint of 0.44 mm² which is much less than many available filters of similar bandwidth. In this study, the transfer matrix method has been used to find the effective refractive index and hence the propagation constant.     

Ka波段TE01模回旋行波管宽带输入耦合器的设计

Ka波段TE01模回旋行波管的输入耦合器将矩形波导中输入的TE10模转化为圆波导中TE01模的行波场,以实现对回旋电子注角向速度的调制。本文首先对Ka波段TE01模回旋行波管的输入耦合器进行了解析分析和数值计算。通过数值计算得到输入耦合器的初步结构和尺寸,然后利用三维高频分析软件HFSS进行精确的模拟和修正。通过优化设计在Ka波段获得了3 dB带宽约为3 GHz,1 dB带宽大于2GHz的高性能TE1□0-TE4◎11-TE0○1输入耦合器和3 dB带宽约为3.5 GHz,1 dB带宽约为3 GHz的高性能TE1□0-TE5◎11-TE0○1输入耦合器。冷测实验研究表明优化设计结果与冷测结果相吻合。     

Millimetre-wave monopulse antenna incorporating substrate integrated waveguide phase shifter

A compact planar E-plane monopulse antenna is proposed and realised at 36.5 GHz for millimetre-wave radar or direction-finding system application, which is built on the substrate integrated waveguide (SIW) technology. A phase shifter having a non-uniform SIW width configuration is self-consistently made of a periodically embedded via array and it can achieve good performances over a relative broad bandwidth. A 180deg directional coupler incorporating this proposed phase shifter structure is developed in the design of an integrated feeding network for the monopulse antenna. Four elements array based on the configuration of antipodal linearly tapered slot antenna is designed as radiator, offering a pair of 'sum' and 'difference' beams along the long direction of the substrate. Measured gain of the 'sum' beam is higher than 16 dBi, whereas the zero depth of the 'difference' beam is lower than -38 dB. This type of monopulse antenna presents an excellent candidate in the development of intelligent millimetre-wave directional- finding system.     

Optimized design of polarization-independent and temperature-insensitive broadband optical waveguide coupler by use of fluorinated polyimide

A statistically optimized design method suitable for a polariation-independent and temperature-insensitive broadband waveguide coupler is proposed. By use of this method, a fluorinated polyimide waveguide 3-dB waveguide coupler for 1490 to approximately 1610 nm application is designed by optimizing polarization and temperature fluctuation. The validity of the design is verified through simulation based on the three-dimensional beam propagation method (3D-BPM), which revealed a coupling ratio of 50 +/- 0.8% in a 120-nm bandwidth in the temperature range -10 to 40 degrees C for both orthogonal polarizations.     

Low-loss coupler between fiber and waveguide based on silicon-on-insulator slot waveguides

We propose a novel optical fiber-to-waveguide coupler for integrated optical circuits. The proper materials and structural parameters of the coupler, which is based on a slot waveguide, are carefully analyzed using a full-vectorial three-dimensional mode solver. Because the effective refractive index of the mode in a silicon-on-insulator-based slot waveguide can be extremely close to that of the fiber, a highly efficient fiber-to-waveguide coupling application can be realized. For a TE-like mode, the calculated minimum mismatch loss is approximately 1.8 dB at 1550 nm, and the mode conversion loss can be less than 0.5 dB. The discussion of the present state of the art is also involved. The proposed coupler can be used in chip-to-chip communication.