绝热式方向性耦合器修正型汉明权重函数之适当波导长度与结构影响

研究绝热式方向性偶合器修正型汉明权重函数之适当波导长度与结构影响.传统的光方向耦合器之理论是由绝热条件下所获得之结果,因此在波导耦合长度不夠长时则变得可疑,有鑑于此需要依靠光束模拟软件.文中主要的指标为修正型汉明权重函数之低串扰、宽频宽和较短的耦合器长度.最后由结果得知我们所提出使用的修正型汉明权重函数在此架构下能获得较佳的设计结果.     

田口稳健设计优化之绝热式光方向完全耦合器

本研究利用田口实验优化法配合光束传播法设计优化光方向完全耦合器 sin-square 函数,能夠达到低串扰与短耦合器长度的目标,在田口实验优化法中我们选择直交表 L9 做为我们的实验平台.研究结果显示,使用 BPM 辅助设计方式配合田口方法可有效的减少设计优化光方向完全耦合器的实验数.在实验过程中我们尝试去找出并设定符合低串扰与短耦合器长度的绝热式光方向耦合器 sin-square 函数的结构参数范围,并且在田口实验优化法中的确认实验可以达到95%的信心指数.在这份研究中,我们证实利用田口实验优化法配合 BPM 辅助设计优化光方向完全耦合器 sin-square 函数是确实可行的.     

Adiabatic 3-dB couplers, filters, and multiplexers made with silicawaveguides on silicon

The performance of adiabatic 3-dB couplers and V-branches is reported. These devices are broadband and divide power equally. They have no observable polarization dependence. Typical excess losses relative to a straight waveguide is 0.1-0.2 dB for the 3-dB couplers and about 0.4 dB for the V-branches. Fiber to fiber insertion loss of 0.31 dB was measured for a 2.5-cm straight waveguide. The devices were used to fabricate transmission filters peaked at 1.55 μm and power combiners having two channels at 1.48 and 1.55 μm. The device fabrication was improved by use of a flowable top cladding layer containing boron and phosphorous which easily filled-in between closely spaced waveguides     

Mode Converters for Coupling to High Aspect Ratio Silicon-on-Insulator Channel Waveguides

The design, simulation, and experimental performance of mode converters for coupling from single-mode silicon-on-insulator ridge waveguides to high aspect ratio channel waveguides are described. The converters consist of a two-level adiabatic taper structure. The final channel waveguide is 1.5 mum high by 0.8 mum wide. Simulations predict that for total coupler lengths longer than 20 mum, the coupling loss from the fundamental ridge mode to the slit mode is better than -0.2 dB. The couplers and waveguides were fabricated using a two-step self-aligned process. The measured coupling loss for fabricated mode converters is -0.4 dB     

Three-dimensional method for simulation of multimode interferencecouplers

A three-dimensional (3-D) method for modeling multimode interference devices based on a finite element formulation is presented as an alternative to models having one-dimensional cross-sections only. The method is tested for couplers with two different strongly confined waveguides structures. The results show that full treatment of two-dimensional cross-section is of special importance for design and simulation of waveguide devices for which the effective index approximation is no longer valid. For deep rib waveguide geometries, excess loss greater than 15 dB can be obtained if the 3-D method is not used in the design of the couplers     

Analysis and Synthesis of Waveguide Multiaperture Directional Couplers

A precise method of analysis of multiaperture waveguide directional couplers has been developed and used to investigate the performance of couplers designed both by conventional theories and by a new synthesis technique. The analysis is based on the equivalent four-port network of the coupler, the apertures being represented by lumped reactances in series and/or shunt with dispersive transmission lines, representing the waveguides. The effects of finite aperture dimensions and common wall thickness are taken into account. Many couplers designed on the usual basis of a first-order loose-coupling approximation have good directivity, even for tight (3 dB) coupling, but previous theories do not give the predicted directivity and are often far from optimum in design. A new synthesis technique based on the distributed low-pass prototype filter has been devised, and shown to give results close to the predicted performance. It has led to the construction of compact multiaperture directional couplers having directivity greater than 43 dB over complete waveguide operating bands.     

Design of high-performance all-fiber spectral filter with weightedcoupling

Narrow-band and low-sidelobe all-fiber spectral filters are achievable with directional couplers constructed with W-index and step-index fibers. The sidelobe levels can be reduced significantly by properly weighting the coupling strength along the device. We provide numerical simulations in which the different weighting functions are obtained via a variable intercore separation. With a Gaussian function weighting, -38 dB transfer response sidelobes have been obtained, which is more than 29 dB reduction over the uniform coupling case. Some design rules for obtaining filters with desired bandwidths and coupling lengths are also given. These results can be very useful in the design of high-performance all-fiber filters for wavelength multiplexing     

A new class of nonuniform, broadband, nonsymmetrical rectangular coaxial-to-microstrip directional couplers for high power applications

An innovative class of coaxial-to-microstrip broad-band high power directional couplers is studied. The new devices overcome the drawbacks of both stripline and coaxial couplers and allow simple and low cost mechanical construction. In this letter, we present the design, realization and characterization of a set of broad-band (900 MHz to 5.5 GHz) low coupling (-30 dB, -40 dB) directional couplers with directivity of more than 10 dB over the whole band, demonstrating good agreement between predicted and obtained performances.     

Nonuniform transmission line codirectional couplers for hybridMIMIC and superconductive applications

A new design approach for thin-film codirectional quadrature couplers and their applications is described. An in-depth analysis and semi-empirical design curves are presented for these couplers. Forward-wave coupling is achieved by making use of the difference between even- and odd-mode phase velocities. Modified nonuniform codirectional couplers with a dummy channel for continuously decreasing or increasing taper and employing wiggly, serpentined and smooth coupled edges have been designed and tested. It is found that a wiggly coupler can achieve a 50% length reduction compared to a smooth-edge coupler. A further 60% length reduction compared to a wiggly coupler is achieved by a serpentine coupler. Coupler performance for wiggly and serpentined configurations is computed by choosing a realizable phase velocity function for a given coupler length. Either constant 90° or -90° phase shift is possible with these couplers giving significant design flexibility in some applications. The results for a K_u-band Σ-Δ magic-T circuit employing a 0 dB wiggly coupler and a -3 dB smooth-edge coupler are also presented in the paper     

Slot-coupled directional couplers between double-sided substratemicrostrip lines and their applications

A slot-coupled microstrip directional coupler and its application to a planar multiport directional coupler (MDC) are described. This coupler can be applied to both loose coupling (e.g. 10 dB) and tight coupling (e.g. 3 dB). A four-port planar MDC fabricated by combining these couplers is described. Measured and calculated results are in agreement for both couplers     

Field Theory Design of Rectangular Waveguide Broad-Wall Metal-Insert Slot Coulplers for Millimeter-Wave Applications

A design theory for broad-wall metal-insert slot couplers suitable for an inexpensive and very accurate metal-etching manufacturing technique is described. The method of field expansion into suitable eigenmodes used considers the effects of finite insert thickness and higher order mode interaction at the step discontinuities. Computer-optimized design data for -3-dB couplers in the Ka- and W-bands are given. The data of the Ka -band design are transferable into the U- and V-bands by suitable frequency scaling calculation. Since the metal-etching technique is also advantageously applicable for couplers in the centimeter wavelength range, optimized design data for E-plane slot couplers in the often used Ku- and R120-waveguide-bands are included in the tables given. A Ku-band metal-etched four-slot coupler prototype achieves a +-1dB bandwidth of the -3-dB coupling of about 2 GHz, together with -36-dB isolation. The measurements show good agreement with theory.     

A design of wideband 3-dB coupler with N-section microstrip tandem structure

New design equations and a 3-dB microstrip coupler example for N-section tandem connected structure with wide bandwidth are presented. The proposed four-port S-parameters and equations are obtained from a port reduction method. The designed microstrip 3-dB coupler not only does not need high impedance lines, but also uses tight coupling gaps differently from conventional couplers such as Lange couplers, parallel coupled line couplers, etc. The measured data agrees well with the expected data, which show a wide bandwidth of 42%, an amplitude imbalance of /spl plusmn/0.5 dB, a phase unbalance of 1.0/spl deg/, and isolation characteristics of 15 dB at the band of 3.6 to 5.5 GHz.     

Optimum field theory design of broad-band E-plane branchguide phase shifters and 180° couplers

Optimum rectangular waveguide E-plane branch guide phase shifters and 180° branch guide couplers are designed with the rigorous method of field expansion into normalized eigenmodes. The design includes both the higher order mode interaction between the step discontinuities and the finite step and branch heights. The phase shifter design applies the Schiffman principle to branch guide couplers where two ports are short-circuited. The 180° coupler design combines the advantage of the broadband potential of multiple-branch couplers with the low-insertion-loss qualities of E-plane stub-loaded phase shifters. A computer-optimized phase shifter prototype for the waveguide Ku-band (12-18 GHz) shows a 90°±1° differential phase shift with reference to an empty waveguide within about 23% bandwidth. Five-branch three-stub coupler prototypes, designed for 3±0.2 dB coupling, for the waveguide Ku- and Ka-bands (26-40 GHz) achieve a 180°±1° differential phase shift at the output ports within about 19% bandwidth, as well as more than 30 dB isolation and return loss. The theory is verified by measured results     

Coplanar Waveguide Short-Gap Resonator for Medical Applications

A coplanar waveguide short-gap resonator as an electromagnetic energy coupler for medical applications is described. The principles and design formulas are given and the experimental results for a pair of the couplers designed to operate at 915 MHz are provided. From the data obtained on a phantom, it can be shown that the coupling efficiency of this coupler is at least 3 dB better, compared with the other kinds of coplanar waveguide couplers.     

玻璃基离子交换型宽带22 3dB耦合器研究

为满足2N光功率分配器的制作和应用的需求,对宽带集成化22 3dB耦合器进行了深入的理论和实验研究。采用3-D光束传播法,对传统的非对称X结进行了模拟改进,设计了低损耗且具有较宽工作带宽的22 3dB耦合器。采用Ag+-Na+离子交换技术在玻璃基上成功制作了非对称X结结构的宽带22 3dB耦合器。通过对1260nm~1360nm和1460nm~1600nm两个波段宽带光源的光谱测试,得到在宽带范围内小于4.0dB的插入损耗,光谱谱线相对平坦,波长依赖性较小,均匀性小于0.5dB。结果表明,采用这种非对称X结并结合离子交换工艺,可以在玻璃基上制作出宽带的22 3dB耦合器,这为进一步优化器件性能,研制成功具有应用价值的器件奠定了基础。     

Zolotarev Branch-Guide Couplers

A new theory for the design of branch-guide couplers, which enables the designer to optimize the internal impedance level, is presented. This overcomes previous difficulties associated with design of branch-guide couplers for tight-coupling values. Results are demonstrated for couplings as tight as 1.5 dB and give exact agreement between computer predictions and measured results. The theory was used to design a complex matched power divider employing many branch-guide couplers of 14 different coupling values and gave practical results in close agreement with theory.     

Image guide couplers with dielectric coupling elements and radiation reduction

Directional couplers in image guide technique for millimeter-wave circuits are discussed, and steps to improve their properties are demonstrated. The simple two-line-9 dB coupler with periodical coupling is compared to a design with an intermediate dielectric coupling element to reduce the frequency dependence. Radiation from the waveguide bends can be reduced significantly by inserting absorber materials at critical points. Experimental results for a-3 dB coupler are also given.     

Novel microstrip multifunction directional couplers and filters formicrowave and millimeter-wave applications

The design of a particular class of microstrip couplers and filters is presented. The synthesis functions obtained from the solution of first-order nonlinear differential equation of nonuniform lines with a loose coupling assumption are modified and validated for higher coupling values. The design employs a nonuniform coupled line configuration along which a realizable continuous coupling coefficient is obtained by modifying the reflection coefficient distribution function. This modification results in a frequency-selective coupling which minimizes the out-of-band coupling in the specified frequency range. As a result, it is possible to realize -3 dB directional couplers using double-coupled lines without the need for tandem connections or extreme photolithographic techniques. Experimental results for microwave band-pass and periodic couplers are presented together with the computed results. Potential applications of these components are discussed, and the work is extended to include millimeter-wave realization     

Electrooptic polymeric digital optical switches (DOSs) with adiabatic couplers

Electrooptic polymeric digital optical switches with an adiabatic coupler is proposed and demonstrated. The tip portion of the Y-branch is replaced by a full 1 /spl times/ 2 adiabatic coupler. By having this design, the switching voltage can be lowered and the devices are easier to fabricate. The fabricated switches show a characteristic step-like response to the driving voltage. The switching voltage is 5.9 /spl sim/ 6.4 V for dual-arm driving and the extinction ratio is higher than 20 dB. With the improvement of the bias voltage, this nonresonant optical switch design can be driven in a push-pull configuration without bias.     

光方向耦合器汉明函数之波导结构影响

在本文章中研究光方向耦合器汉明函数之波导结构影响.传统的光方向耦合器之理论是由绝热的条件下所获得之结果,因此在波道耦合长度不夠长时则变得可疑,有鑑于此需要依靠光束模拟软体.在文章中有两个主要的指标:第一个为理论所适用的范围,第二个为最佳化低串扰、宽频宽和较短的耦合器长度.最后由结果得知我们所提出使用的汉明权重函数在此架构下能获得较佳的设计结果.