Input impedance of an overmoded coaxial line fed coaxial waveguide

A theoretical formulation for the input impedance of an overmoded coaxial probe fed coaxial waveguide has been derived in terms of the geometrical variables, the modal field solutions, and the probe excitation current distribution. The formulation includes higher order mode propagation, a variable probe length, and general coaxial terminations in the secondary waveguide. The model compares well with experimental data derived from a structure supporting three propagating modes.     

微带线匹配负载的FDTD建模

提出了一种有效的微带线端接匹配负载的FDTD模型.该模型将微带线的有效阻抗作为匹配负载电阻,然后按适当的比例分布到端接面的网格中.和传统的FDTD方法相比, 该模型可以有效地减少负载的反射,改善负载的匹配特性,并且通过一次FDTD计算就可以得到电路的S-参数.     

Simple transmission line feed model for microstrip antennas in two-sided structure with coaxial probe coupling

A simple transmission line feed model is presented for microstrip antennas in a two-sided structure coupling through a coaxial probe. The parameters of the model are extracted directly from the feed structure. The validity of the feed model combined with the recently developed transmission line model of microstrip antennas is verified by measurement.<>     

The input impedance of a coaxial line fed probe in a cylindricalwaveguide

Dyadic Green's functions for determining the electric and magnetic fields in a cylindrical waveguide due to a radially directed infinitesimally short electric dipole are derived. The waveguide is shorted at one end and terminated at a perfectly matched load at the other. Both TE and TM modes are considered. Based on these dyadic Green's functions, the input impedance of a coaxial line fed probe in front of the plunger is derived. The formula is expressed in a closed form. Excellent agreement between theoretical results and experimental data for exciting the TE₁₁ mode in the X band for various probe positions is observed     

Analysis of TEM mode on a curved coaxial transmission line

Through the use of a perturbation approach, explicit expressions are derived for the changes in the electromagnetic field structure that occur when a transverse electromagnetic (TEM) mode on a coaxial transmission line enters a bend in the line. All of these changes are evaluated to at least first order in the inverse of the radius of curvature of the first nonvanishing correction term of the propagation constant (which is found to be of second order). Graphical results for the variation of the propagation constant as a function of curvature and other parameters characteristic of the coaxial line are presented     

Impedance transformation using a hyperbolic cosine-squared tapered transmission line

A closed-form equation for the impedance transformation of an arbitrarily complex load, using a hyperbolic cosine-squared tapered transmission line, is presented. Design charts are also given. A numerical example is considered and results indicate a tremendous reduction in size, in comparison to other forms of lines, when hyperbolic cosine-squared lines are employed to match a large complex impedance to a real 50 Ω impedance.     

Decoupling between two conductor microstrip transmission line

A numerical analysis of two-conductor transmission line with a rectangular notch in the dielectric between the strips is presented. Three media integral equations are derived and solved for the charge distributions. The decoupling between such two-conductor coupled microstrip transmission lines is investigated for asymmetric conductors. It is found that the coupling between two conducting lines can be reduced significantly by removing dielectric material between the lines which has a rectangular shape. For best decoupling, the width should be as wide as possible between the conducting lines but the depth should have an optimum somewhere in the base dielectric substrate     

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     

Input impedance of rectangular patch antenna fed by microstrip line

A simple full-wave method for analysing rectangular microstrip antennas is presented. The problem of voltage term calculation is elucidated in the case of the microstripline-fed antenna. A new model for calculating the voltage term is proposed and compared to the other two models taken from the literature.<>     

基于左手传输线的双线极化微带阵列天线

基于左手传输线,提出了一种新型串联馈电的双线极化微带阵列天线结构.通过上层微带线边馈和下层小孔耦合馈电的方式分别实现了天线单元的垂直极化和水平极化的激励,进而使得该天线单元具有高极化隔离度、低交叉极化和宽频带工作等优点.同时由于左手材料具有相位超前的特性,利用传统的右手微带传输线和左手微带传输线的组合以达到零相位延迟,实现了对上述单元构成的微带阵列天线的串联馈电.相对于传统微带阵列天线,该阵列天线结构简单、面积小、插入损耗小、阵列效率高、易于扩展成更大的平面阵列.     

Multisection transmission line with random characteristic impedance

A probabilistic model of a multisection transmission line with a random characteristic impedance is developed. The average value of the voltage at the end of the random line is estimated from an equivalent homogeneous line, which depends on the mean values of the characteristic impedance and admittance distributions     

Analysis of a double step microstrip discontinuity using generalized transmission line equations

In this paper, a new analysis for a double step microstrip discontinuity is presented by using generalized transmission line equations . The new analysis is based on a new concept of a finite-length transmission line integrated with its double step discontinuity so that the double step discontinuity is regarded as a finite-length nonuniform transmission line and the generalized equations could be directly implemented. Since the generalized equation coefficients are determined by dynamic numerical methods and the coefficients are invariant with the line excitation and load, the equations are dynamic rather than TEM. The interested discoveries are that the generalized equations for the whole double step structure or a partial double step structure can give us the same results and the generalized equations have broadband frequency characteristics. For the double step structure used in this paper for the analysis, the S-parameters for a frequency band from 0.5 GHz to 10 GHz can be well calculated by using only two separately generalized equations at frequency of 3 GHz and 8 GHz.     

Input impedance of a short antenna in a warm plasma driven from a coaxial air line

An approximation technique is used to calculate numerically the input impedance of a short antenna immersed in a warm plasma driven from a coaxial air line. The effect of the gap configuration is observed to be significant on the antenna reactance only.     

Linear antennas in a warm plasma driven from a coaxial air-filled transmission line

The Green's function is formed for the warm-plasma region surrounding an antenna driven from a coaxial air-filled transmission line, and hence the current distribution and input admittance of three types of antenna having this feed system are computed. Comparison is made between the antenna characteristics when driven in this fashion and by an idealised delta gap.     

Quadrature hybrid made from transmission line of a single characteristic impedance

A quadrature hybrid is presented which is entirely composed of lengths of transmission line of characteristic impedance equal to that of the system in which it is used. It is useable over a 10% bandwidth centred on its nominal frequency. Its theoretical frequency responses over this band are presented.     

基于CRLH传输线的微带漏波天线的研究与设计

提出了一种基于谐振频率的等效电路参数提取方法,该方法可以精确地描述多节复合左右手传输线结构,并通过仿真软件研究了其物理模型及等效电路模型的一致性,从而验证了这种新的参数提取方法。根据此种新的等效模型设计制作了复合左右手传输线型微带漏波天线,并利用网络分析仪对它的S参数进行了测量。结果表明,所设计的平衡状态下的微带漏波天线波束方向随着频率的变化而变化,并且改变传统漏波天线仅能实现前半空间扫描的局限性,并拓展漏波天线扫描范围至全空间,同时在各个波束方向上的能量也较为均匀,相比于传统漏波天线,尺寸缩小接近50%。     

Spectral analysis considerations relevant to radiation and leakymodes of open-boundary microstrip transmission line

The continuous radiation spectrum of an open microstrip transmission line and its nonspectral leaky modes are conceptualized through a transform-domain integral-operator formulation and relevant spectral analysis. The radiation spectrum is identified with branch cuts in the axial wavenumber plane, which constrain the migration of branch-point singularities in the transverse wavenumber plane. Leaky-wave modes occur only when the branch cuts in the axial wavenumber plane are violated. The relationship among spectral radiation modes, nonspectral leaky-wave modes, and branch cuts in the axial wavenumber plane is discussed. The influence of branch cuts in the axial wavenumber plane upon the location of branch points in the transverse wavenumber plane is detailed, and a rationale is offered for the choice branch cuts in the latter plane. The formulation is applicable to a wide class of open conducting or dielectric waveguides     

A transmission line model for arrays of rectangular microstrip antennas

A very efficient transmission line model for the analysis of arrays of rectangular microstrip antennas is presented. The structure of the model is discussed, and its validity is proved. This is done for the isolated microstrip antenna as well as for the coupling between antennas. Then follows a discussion of the numerical efficiency. And finally a numerical example shows the effect of mutual coupling on the impedance and radiation pattern of a 21 element Chebyshev array at different scanangles.     

End-correction network of a coaxial probe for microstrip patchantennas

A simple end-correction network for the constant current probe model of probe-fed microstrip patch antennas is derived. The parameters of the network are solved asymptotically and verified by the numerical solution of the integral equation formulation. Based on the analysis of a problem concerning a coaxial-fed microstrip patch, it is concluded that: (1) TEM (transverse electromagnetic) aperture field approximation can provide an accurate result to the input admittance, and there is no need to introduce a specific correction network for most applications; and (2) Constant current probe is valid only when both k₁ h≪1 and a/h≪1 are satisfied. An end-correction network consists of a series inductance and a shunt capacitance should be used in other ranges or for higher accuracy     

Propagation characteristics of microstrip transmission line on ananisotropic material ridge

A microstrip transmission line residing on an electrically anisotropic material ridge embedded in a multilayered environment is studied using a coupled set of integral equations (IE's). The full-wave IE formulation easily accommodates arbitrary material anisotropy and inhomogeneity in the finite ridge region using equivalent polarization currents residing in a multilayered isotropic background. New results are presented for uniaxially anisotropic ridge structures which show that the transmission line propagation constant is sensitive to anisotropy for certain ridge structures and insensitive for others, compared to the conventional line on an infinite substrate. Results are also presented for a transmission line printed on a nonreciprocal solid-state magnetoplasma ridge. The current distribution associated with the dominant microstrip mode is investigated, where it is found that the transverse component of current is much larger for the ridge geometry than for the infinite substrate case, although the transverse component is still small compared to the longitudinal component