Scattering at a nonchiral-chiral interface in a coaxial waveguide

A formally exact full-wave solution is presented for the problem of scattering at a nonchiral-chiral interface in a coaxial waveguide. The field components for the axisymmetric modes in a coaxial chirowaveguide are initially obtained. A new orthogonality relation for the modes is then proposed and used to find expansion coefficients for the electromagnetic fields in the coaxial chirowaveguide. The scattering matrix for the nonchiral-chiral dielectric discontinuity in a coaxial waveguide is finally derived by enforcing the continuity conditions of the tangential field components across the interface. Numerical results for the reflection and transmission coefficients at the nonchiral-chiral interface in a coaxial waveguide are presented     

Design of Conical Transmission Line Power Combiners Using Tapered Line Matching Sections

An axially symmetric power combiner, which utilizes a tapered conical impedance matching network to transform ten 50-Omega inputs to a central coaxial line over the X-band, is presented. The use of a conical line allows standard transverse electromagnetic design theory to be used, including tapered impedance matching networks. This, in turn, alleviates the problem of very low impedance levels at the common port of conical line combiners, which normally requires very high-precision manufacturing and assembly. The tapered conical line is joined to a tapered coaxial line for a completely smooth transmission line structure. Very few full-wave analyses are needed in the design process since circuit models are optimized to achieve a wide operating bandwidth. A ten-way prototype was developed at X-band with a 47% bandwidth, very low losses, and excellent agreement between simulated and measured results.     

Coaxially-fed tapered slot antenna

An improved design of the longitudinal tapered slot antenna is presented which incorporates a tapered coaxial line balun. This transformer type offers large bandwidth, allows for the direct connection of coaxial sources and reduces the complexity of the printed circuit. Experimental results for an antenna prototype are presented     

Design of microstrip hyperbolic line to match a complex impedance to a standard coaxial transmission line

Based on the solution of the Riccati equation, a hyperbolically tapered microstrip transmission line for matching a complex load to a standard coaxial cable is designed. An iterative procedure is used to yield the phase constant leading to an accurate design. A numerical example is considered. The result shows that a tremendous reduction in the size of matching components can be achieved if hyperbolic instead of uniform transmission lines are used. This is highly advantageous in the miniaturization of solid state circuits.     

A Variational Expression For The Scattering Matrix Of A Double-Step Discontinuity In A Coaxial Line And Its Application To A Tem Cell

A variational expression for the scattering matrix of a double-step discontinuity in a two-mode coaxial transmission line is obtained and generalized to the case of a multimode coaxial transmission fine. The result is used to analyze the transmission characteristics of a two-mode coaxial TEM cell.     

Tapered coaxial microwave probe sensor

A tapered coaxial cavity probe sensor is introduced to demonstrate progressive improvements in the spatial resolution of metallisation patterns for scanning microwave microscopy (SMM) applications. Two versions of this design are described and experimental results illustrate the advantages of a reduced end area surrounding the projecting probe.     

On Solving TM0n Modal Excitation in a Ka-Band Overmoded Circular Waveguide by the Conservation of Complex Power Technique

To measure the radiation properties of relativistic diffraction generator (RDG) in Ka-band, a TM0n modal excitation model is established, which consists of an overmoded circular waveguide and a coaxial line feeding probe. Using the transverse E-field mode matching and the conservation of complex power technique (CCPT), we deduce the scattering matrix at coaxial line to coaxial line and coaxial line to circular waveguide junctions. Then using the overall cascaded junction scattering matrix, the numerical results for the reflection coefficient of the coaxial line and the power distribution of TM0n multi-modal are presented. The numerical results are in agreement with HFSS simulation results and experimental results. The analysis shows that by choosing the appropriate position of coaxial line probe, the power proportion of the device operating mode excited in circular waveguide could be the largest.     

On Solving TM0n Modal Excitation in a Ka-Band Overmoded Circular Waveguide by the Conservation of Complex Power Technique

To measure the radiation properties of relativistic diffraction generator (RDG) in Ka-band, a TM0n modal excitation model is established, which consists of an overmoded circular waveguide and a coaxial line feeding probe. Using the transverse E-field mode matching and the conservation of complex power technique (CCPT), we deduce the scattering matrix at coaxial line to coaxial line and coaxial line to circular waveguide junctions. Then using the overall cascaded junction scattering matrix, the numerical results for the reflection coefficient of the coaxial line and the power distribution of TM0n multi-modal are presented. The numerical results are in agreement with HFSS simulation results and experimental results. The analysis shows that by choosing the appropriate position of coaxial line probe, the power proportion of the device operating mode excited in circular waveguide could be the largest.     

Effect of Ripple Taper on Coupling Modes in a Coaxial Bragg Structure

Based on the mode-coupling method, numerical analysis is presented to demonstrate the influence of ripple taper on coupling modes on the frequency response in a coaxial Bragg structure. Results show that the interval between the band-gaps of the competing mode and the desired working mode is narrowed by use of a positive taper, but is expanded if a negative taper is employed, and the influence of the negative taper is more obviously advantage than the positive taper. The residual side-lobes of the frequency response on coupling modes can be effectively suppressed by employing the windowing-function technique. These characteristics of a tapered coaxial Bragg structure are favorable to improvement of the performance as a reflector or a filter in its application, also favorable to the mode selectivity and further weaken the excitation of unwanted spurious modes.     

低掠角入射动态分形粗糙海面与船目标的双站散射数值模拟

为快速数值计算动态粗糙分形海面上有船目标时的双站散射，该文将广义前后向迭代法（GFBM）与谱积分加速算法（SAA）结合用于求解磁场积分方程（MFIE）。避免了电场积分方程（EFIE）数值计算的不稳定性。数值模拟了TE锥形波低掠角入射在一维动态分形粗糙导体海面以及船目标存在时的双站散时，讨论了多次散射传播的双疲散射与动态分形海面和船目标特征参数的关系。     

A rigorous analysis of a coaxial to shielded microstrip linetransition

The transition from a coaxial to shielded microstrip line is analyzed by applying a rigorous mode-matching technique. The symmetry axes of the two transmission lines are assumed to be parallel, while the relative position of the coaxial line center conductor with respect to the microstrip line is taken to be arbitrary. The fields inside the shielded microstrip line are expanded in terms of the normal hybrid modes, while in describing the fields inside the coaxial line the transverse electric and magnetic modes are utilized. Both propagating and evanescent modes are taken into account in each transmission line. A modified mode-matching procedure is used on the junction plane of the two transmission lines to formulate the corresponding discontinuity problem. The mode-matching equations are solved by applying projection techniques. Numerical stability and computational efficiency are achieved in determining the scattering parameters of the coaxial to microstrip line transitions. Numerical results are computed and presented for several coaxial-to-microstrip-line transition geometries     

High-speed optoelectronic sampling with semiconductor-laser pulsed coplanar photoconductor

A semiconductor-laser strobed photoconductive sampling gate for the measurement of ultra-high-speed electronic signals on coaxial lines is reported. For the short response (<100 ps) and high responsivity (>0.1 A/W) at the 830 nm laser wavelength the sampling gate uses a miniaturised (8×8×1 ?m) epitaxial GaAs photoconductor on a broadband tapered coplanar 50 ? microwave structure.     

一种改进的V型渐变槽天线

提出了一种新型V型槽天线，与原来的V型天线相比，极大地抑制了天线的色散效应，天线辐射方向的旁瓣电平降低到-10dB以下。对容易混淆的直线渐变式微带槽线和指数渐变式微带槽线的性能进行了系统分析，重点比较了主面极化方向图等。     

舰船尾流共轴激光雷达近场抑制比的计算方法

水下激光雷达在近场就已经发生了激光的多次散射,其共轴光学系统对近场水体的强散射信号将具有一定的抑制能力,可防止接收系统饱和。研究共轴光学系统近场抑制比的计算方法具有重要意义。分析讨论了常规光子返回贡献公式不适于近场计算的原因,提出新的水下近场共轴光学系统的返回贡献公式及基于坐标变换的简单计算方法,结合Monte Carlo仿真计算了水下近场抑制比。分析计算了近场抑制比、抑制时长与激光脉冲宽度的关系,结果表明:该方法完全可满足水下共轴光学系统计算的需要。     

锥形光纤的结构与特性

通过理论分析和仿真试验,研究了锥形光纤的几何形状对锥形光纤的传输损耗和耦合效率的影响.用几何光学的分析方法,说明了光信号在锥形光纤中的传输损耗远低于同类型的圆柱形光纤;仿真试验研究了光源与光纤的相对位置、锥形光纤的尖端半径、锥形光纤的锥角大小对锥形光纤耦合效率的影响.     

Investigation of tapered multiple microstrip lines for VLSIcircuits

The analysis of tapered, coupled microstrip transmission lines is presented. These lines, used as interconnects between integrated circuit devices, are modeled using an iteration-perturbation approach applied in the spatial domain. From this model, a frequency-dependent scattering parameter characterization is determined. A time-domain simulation of pulse propagation through the tapered, coupled microstrip lines is performed. The frequency-domain scattering parameters are inverse Fourier transformed to obtain the time-domain Green's function. The input pulse is convolved with the Green's function, and a Newton-Raphson algorithm is applied to account for nonlinear loads. Some experimental results are shown, and a simulation approximation is proposed     

Moment method analysis of infinite stripline-fed tapered slotantenna arrays with a ground plane

A full-wave method of moments solution for infinite arrays of stripline-fed tapered slot antennas is described. The formulation of the problem is sufficiently general to permit performance evaluation of most of the geometries that have been proposed for stripline-fed antennas as well as of several other types of array antennas. Computed results for some well-known antenna arrays are presented to demonstrate the validity and accuracy of the method. Excellent agreement with published results has been obtained for scattering from corrugated surfaces and grounded dielectric slabs and for the input impedance of dipole and monopole arrays. Catastrophic effects such as scan blindness are accurately predicted. A sample result showing the measured and computed input impedance of a stripline-fed tapered slot antenna array is also presented     

6~20GHz同轴-矩形波导转换器的设计

宽带同轴-矩形波导转换器是高性能天馈系统的重要组件之一。针对现代电子系统对高频宽带特性的迫切需求,采用矩形波导宽壁平行加载金属双脊、同轴探针与脊波导非接触式转接、脊波导-矩形波导渐变转换的结构,设计了一种多过渡段、宽频带的同轴-矩形波导转换器,获得了6～20GHz工作带宽内插入损耗小于1dB、回波损耗小于-18dB的实测结果,可满足一般宽带天馈系统的馈电及测试要求。     

Solution of the problem of diffraction by a grating of bodies of revolution with the use of the modified null field method

The 3D problem of scattering by a grating consisting of coaxial impedance bodies of revolution is solved with the help of the modified null field method. A system of integral equations is derived, and numerical results are obtained for the scalar and vector formulations of the problem.     

Tapered single-mode optical fiber evanescent coupling

We describe the results of a numerical and experimental investigation of how a point source of radiation couples light to the HE ₁₁ mode of a tapered single-mode fiber. Specifically, we have investigated two different geometries of nonadiabatic, tapered single-mode optical fiber. The motivation for this study is the characterization of a single-mode tapered optical fiber biosensor. In such a device light is collected from fluorescent sources located along the cladding surface of the tapered fiber. Taper-to-taper coupling measurements and fiber mode calculations indicate the device sensitivity decreases exponentially as sources are moved away from the tip of the tapered fiber