Quasioptical Transmission Lines for ECRH at TJ-II Stellarator

Two mirror lines have been used to transmit the microwave power from the powerful microwave generators to the TJ-II plasmas. Both lines have been tested at nominal power level and they are in operation now. This paper deals with the final design of the transmission lines and their testing. Before starting operation at high power level, measurements of the wave beam parameters at low power level were performed. Two horn antennas were designed to simulate the gyrotron output. The results are presented in this paper. A computer code based on Huygens diffraction theory was developed to simulate the propagation of the beam along the mirror lines. A comparison of the theoretical and the experimental results is also shown here.     

Optimum Sectional Shape of Dominant Mode Waveguide

Approximating the cross section of a waveguide by a truncated Fourier series and using the finite element method (FEM), together with the quasi-Newton optimization method, the optimum cross section of the dominant mode waveguide which has minimum conductor loss is obtained. We take the attenuation constant at the cutoff freqnency of the second higher mode as the index of good quality. This index simplifies the computation and gives a unique solution. The obtained optimum cross section is a kind of cigar shape. The Fourier series converges quite quickfy, supporting the reliability of the numerical results. This optimum cross section gives 9.4-percent smaller conductor loss than, and the same frequency bandwidth as, the standard rectangular cross section. The theoretical results are confirmed by measurements.     

Corrugated Horn Antenna for Low-Power Testing of the Quasioptical Transmission Lines at TJ-II Stellerator

This paper presents the design and characterisation of a millimetre-wave corrugated horn antenna to perform low power measurements of the main parameters of the quasioptical transmission lines of the Electron Cyclotron Resonance Heating (ECRH) at TJ-II stellerator experiment working in Madrid (E). The antenna generates a practically pure Gaussian Beam at 53.2 GHz that simulates the stellerator gyrotron output beam. Simulations of the designed corrugated horn, by using a specially developed computer code, are presented. The far field radiation pattern of the constructed prototype was measured at the ESTEC Compact Antenna Test Range (CATR). The measurement results are in excellent agreement with those obtained from simulations.     

一种基于同轴波导的异向传输线

该文提出了一种基于同轴波导的新型异向传输线,与现有基于微带电路的异向传输线相比,这种结构有更高的工作频率、损耗较低和更大的功率容量;与基于同轴波导和矩形波导的异向传输线相比,其结构更简单容易实现。等效电路与有限元仿真的结果均表明这种结构在特定的频段表现出明显的异向特性。     

A Parallel-Plate Waveguide Approach to Microminiaturized, Planar Transmission Lines for Integrated Circuits

The parallel-plate waveguide with a two-layer loading medium, a conducting semiconductor substrate, and a relatively thin dielectric layer approximates the interconnections in many integrated systems if the fringing fields are ignored. The fundamental mode of this structure is an E mode which is a surface wave. Its propagation behavior is analyzed in this paper and the equations are evaluated by highly accurate numerical methods. The semiconducting substrate is characterized by its dielectric constant and conductivity. A critical conductivity /spl sigma//sub min/ exists and is related to the cross sectional and material parameters. If the substrate conductivity is given by /spl sigma//sub min/ then the attenuation constant of the line is a minimum. The same value of conductivity yields minimum phase distortion at maximum bandwidth. If the conductivity is larger than /spl sigma//sub min/ the substrate acts as a poor conductor with associated skin effect; if it is smaller, lossy dielectric behavior results. Analysis shows that it is appropriate to subdivide the frequency range into three intervals. The lowest-frequency interval is characterized by propagation which resembles diffusion. This is caused by the loss in the dielectric layer. The next frequency range extends to some upper frequency which is determined by substrate conductivity and the cross-sectional dimensions. In this interval, the phase velocity of the fundamental mode is controlled by the ratio of dielectric to semiconductor thickness, which, if typical interconnections are considered, implies a very low velocity. This property indicates that the structure can serve as a delay line. Further increases in frequency result in higher phase velocities. Skin effect and dielectric loss behavior describe the propagation in this third interval.     

The E-Plane Taper Junction in Rectangular Waveguide

This paper compares formulas for reflection in rectangular waveguide from an E-plane junction with radial guide. There is a major discrepancy between results for the junction parameters from earlier results of the author and those in the Waveguide Handbook. The two sets of results are discussed; the Handbook result is apparently in error, but the formulas do not seem capable of reconciliation. Limitations and slight improvements on the author's earlier result are given, together with supporting measurements taken at X band.     

非线性渐变圆波导的数值分析

非线性渐变波导在许多微波系统中具有举足轻重的作用,而它应用在回旋管中主要是为了高效率地输出高纯度的微波。本文分别利用耦合波方程数值解法和散射矩阵级联法分析和计算了0.22THz回旋管非线性渐变输出波导的性能,同时用HFSS10.0仿真软件对其仿真计算,三者得到的结果基本一致,从而验证了渐变波导设计理论的正确性;在这之前,为了能够测试两程序的正确性本文还计算了已发表文献中的两个相关的例子。     

非对称共面波导复合左右手传输线的多频天线

设计了一种新型的基于非对称共面波导(ACPW)馈电复合左右手传输线(CLRH-TL)的四频段混合小型化天线。天线由非对称共面波导接地面加载互补开口谐振环缝隙、单极子天线终端加载复合左右手传输线单元组成,将常规单极子天线与超材料结构的零阶谐振器天线双模式混合。实测结果表明：天线回波损耗大于10 dB的阻抗带宽分别为1.55~1.65 GHz,2.4~3.7 GHz,5.15~5.36 GHz,5.71~5.89 GHz,通带内具有良好的辐射特性。天线结构简单紧凑,易于集成,可应用于GPS,WLAN和WiMAX无线通信系统中。     

An Optimum Linear Receiver for Multiple Channel Digital Transmission Systems

An optimum linear receiver for multiple channel digital transmission systems is developed for the minimum Peand for the zero-forcing criterion. A multidimensional Nyquist criterion is defined together with a theorem on the optimality of a finite lenght multiple tapped delay line. Furthermore an algorithm is given to calculate the tap settings of this multiple tapped delay line. This algorithm simplifies in those cases where the noise is so small that it can be neglected. Finally as an example the transmission of binary data over a cable, consisting of four identical wires, symmetrically situated inside a cylindrical shield, is considered.     

An Accurate Calculation of Uniform Microstrip Transmission Lines

An analytical program for calculating the field distribution about a microstrip transmission line bounded by a shielding wall is used to calculate the impedance, velocity, and attenuation parameters. The program input parameters are the dimensions of the strip and shielding wall and the relative dielectric constant of the substrate material. The field distribution about the strip is integrated to find the charge density on the strip and walls with and without the dielectric substrate. From these two calculations, the relative velocity and impedance can be calculated.     

An Analysis of Gap in Microstrip Transmission Lines

Although microstrip transmission lines have been widely used in microwave integrated circuits, the discontinuity structures in the microstrip transmission lines such as a gap, an abruptly ended strip conductor, and so on, have hardly been analyzed. An analytical method and numerical results for a gap capacitance in the microstrip transmission line are described. The equivalent circuit parameters are formulated with three-dimensional Green's functions, based on a variational principle. The numerical results are in good agreement with the published experimental data. The fringing effect of an abruptly ended strip conductor is also investigated.     

Gain-Stabilized Erbium-Doped Waveguide Amplifier for Burst Transmission

We demonstrate an optical gain-clamped waveguide amplifier robust against wavelength-division-multiplexing (WDM) burst transmission transients even with synchronous arrival of all packets. A maximum power excursion of about 0.3 dB is reported for the worst case under repeated burst arrivals. We show that a very small difference in burst periodicity generates completely different transient dynamics that may also self-impact the modulated channel. The impact of cavity design on amplification performance is reported. Nonlinear behavior is observed near system resonances. We observe burst transmission is a critical application, far more demanding than any use in reconfigurable WDM networks where only abrupt channel add-drop or link failure may occur     

An Accurate Calculation of Uniform Microstrip Transmission Lines

An analytical program for calculating the field distribution about a microstrip transmission line bounded by a shielding wall is used to calculate the impedance, velocity, and attenuation parameters. The program input parameters are the dimensions of the strip and shielding wall and the relative dielectric constant of the substrate material. The field distribution about the strip is integrated to find the charge density on the strip and walls with and without the dielectric substrate. From these two calculations, the relative velocity and impedance can be calculated.     

Design of Taper Structure for Highly Efficient Coupling Between 1-D Photonic Crystal Coupled Resonator Optical Waveguide and Straight Waveguide

This paper presents a design method of a taper structure for highly efficient coupling between 1-D photonic crystal coupled resonator optical waveguides (1-D PC-CROWs) and input straight waveguides. We propose a new taper structure where not only air hole radius but also waveguide width are varied linearly in order to adjust the dispersion curves shift. By using the proposed tapered structure, we can connect each waveguide with high transmission over wide bandwidth. Our numerical simulation results show that a transmission of 98% around 1550 nm wavelength in a 6.6 $mu$m long taper can be obtained with a 42 nm bandwidth.      

An MMIC Pulse Generator Using Dual Nonlinear Transmission Lines

We present a novel nonlinear transmission line (NLTL) pulse generator using dual-NLTL, true-time-delay, waveform-alignment technique, realized in Gallium Arsenide (GaAs) monolithic microwave integrated circuit (MMIC) technology. The diodes in these two NLTLs have opposite polarities in layout. Therefore, they are responsible for sharpening the two signals' rising and falling edges separately. A simple, low-cost, wideband combiner is adopted to combine the two fine aligned waveforms without introducing much distortion to the wideband signal. As a result, a sharp pulse is obtained with both edges compressed. With a sinusoidal signal as the input to the fabricated MMIC, a fall time of around 12 ps and rise time of 14 ps were measured at the output. This MMIC is a candidate for pulse or comb generators in many commercial and military applications     

Planar Transmission Lines

This paper derives formulas for the transmission properties--characteristic impedance and attenuation--in the principal mode of a transmission line consisting of one or two long strips of metal foil embedded in a dielectric material between two long metal strips considerably wider than the central ones. The width and spacing of the central strips is arbitrary, and it is also necessary to take account of their thickness in computing the attenuation. A graphical method is given for evaluating the characteristic impedance in general, and analytic approximations are given for a number of special cases. Finally the question of the leakage of power from between the outer strips is considered briefly.     

Optimum Design of a Ridge Waveguide Transformer for MMW Tube's

A ridge waveguide transformer is commonly used in output structure for millimeter wave tubes(such as magnetron and traveling wave tube). It is not satisfied, if a traditional designing method is used in broadband case. The optimum design of a ridge waveguide transformer is given in this paper. The computation results show that the reflect character of the transformer can be met the demands for broad band match.     

Coupled Transmission Lines

An analysis of coupling between a stripline and a rectangular waveguide is presented. Coupling is through small apertures in the form of a circular hole or a narrow rectangular slot. A closed form expression for the normalized field distribution in the stripline, required for the purpose of analysis, is also derived. The theoretical results show good agreement with the experimental results.     

Optimum Design for Broadband Waveguide Type Impedance Transformer in MMW

For traditional design method of waveguide type impedance transformer, even noncontinuous susceptance produced by steps is considered, match character in wide frequency band are not satisfied commonly. In order to resolve this problem, an optimum design method is given in the paper. The computation shows that match character of the optimum designed multisection impedance transformer is better than traditional design method in MMW.     

数据融合技术在输电线网故障诊断中的应用

数据融合作为一门信息综合处理技术起初应用于军事领域，被引入到技术科学领域只有近十的年的历史。本文开始简述了数据融合的定义，接着阐明了将数据融合应用于输电线网故障诊断可行性的理论依据，然后论述了多种数据融合方法，如人工神经网络、专家系统、模糊理论、小波分析等在输电线网故障中的应用。