Variational expression of the propagation constant for leaky modes

A variational expression of the propagation constant applicable to leaky modes is described, where we consider an eigenvalue problem of a scalar Helmholtz equation. An example is presented to show how the integration involved is carried out.     

Complex modes in lossless shielded microstrip lines

The possible existence of complex modes in lossless shielded microstrip lines was investigated using the singular integral equation method. The method is used for the analysis of three lossless shielded microstrip line structures with different substrate permittivities. To confirm the validity of the method, results are compared with existing data for propagating modes. Complex modes were found in the moderate and high permittivity structures.<>     

Fundamental- and higher-order modes in open microstrip lines

For the first time, an investigation is made into the higher-order discrete modes in open microstrip lines. A complete set of original current-distribution functions is proposed. For the lowest-order mode, the calculated values of phase velocity are in very good agreement with known experimental results.     

Analysis of a slot microstrip antenna

The slot microstrip antenna is used as a folded slot dipole symmetrically fed across a gap by means of a strip line. A theoretical model equivalent to several lossy transmission lines had been described previously to explain the bandwidth and the radiation admittance. The theory is improved when coupling between the two equivalent radiating lines of every slot is taken into account, and explains a fourth resonance near the third one, which had been measured on several models. Theoretical results and experiments are in good agreement. They are radiation admittance in a wide frequency band, current distribution along each slot and radiation patterns.     

Complex modes in shielded suspended coupled microstrip lines

The existence of complex modes in electrically shielded suspended coupled microstrip lines has been studied extensively, and the results are presented. A rigorous full-wave spectral-domain approach (SDA) with a newly proposed and tested set of basis functions can efficiently and accurately determine the propagation characteristics of the dominant, higher-order, and complex modes for planar or quasi-planar transmission lines. These basis functions are validated by comparing the convergence study of field solutions with those obtained by various sets of preconditioned bases and by the unconditioned subdomain ones. Excellent agreement is obtained for the propagation constants and the normalized complex longitudinal and transverse current distributions on conducting strips for the strongly coupled microstrip lines. For all the particular case studies discussed, it is shown that the complex modes may exist in all the shielded suspended coupled microstrip lines, even when the substrate dielectric constant is low. Theoretical results for the fundamental, higher-order, evanescent, and complex modes are presented for suspended coupled microstrip lines     

基于时域BLT方程的插槽对微带线间串扰分析

紧密放在印制电路板上的多条微带线之间会产生串扰,这是电磁干扰领域一个非常重要的问题,而接地插槽则会对微带线间的串扰产生影响,所以研究接地插槽对微带线间的串扰影响也是非常重要的。在本文中,使用时域BLT方程结合FDTD方法分析微带线间的时域串扰,将其结果与仿真结果进行了比较,验证了该方法的准确性,并分别改变槽的宽度和长度来分析微带线之间串扰的影响。分析结果表明:微带线间的串扰随着槽的宽度增大而增加,微带线间串扰的时间范围随着槽的长度增大而增大。     

Spectral domain analysis of coupled microstrip lines on magnetized ferrite substrates

Dispersion characteristics of coupled microstrip lines on ferrimagnetic substrates are presented and their features discussed. The Hertz vector potentials in the spectral domain method are used to calculate the dyadic Green's functions in an impedance matrix form. The behavior of the propagation constants is obtained by using the spectral Galerkin's technique. Numerical results are found as a function of various geometrical parameters and of the externally applied static magnetic field. Nonreciprocal behavior is mainly observed when the static magnetic field is applied in the transverse direction, parallel to the ground plane.     

Analysis of the effects of a resistively coated upper dielectriclayer on the propagation characteristics of hybrid modes in awaveguide-shielded microstrip using the method of lines

In this paper, propagation characteristics of even-symmetric hybrid modes in a waveguide-shielded microstrip in the presence of a resistively coated dielectric layer affixed to the top cover of the housing is analyzed with the method of lines. The resistive boundary condition is employed to model the resistive film. A shielded microstrip line having a unity strip-width-to-substrate-thickness ratio (i.e., w/h ₁=1) placed on top of a 0.635-mm-thick alumina substrate is considered. Based on a 10h₁×7h₁ reference housing, four different housing arrangements are obtained by varying the structural parameters of the resistively coated dielectric layer. Results obtained indicate that the effects of both the housing walls and the resistively coated upper dielectric layer on the dominant (quasi-TEM) mode are insignificant and may be ignored when frequency is above 15 GHz. For the higher order modes, the resistive film appears to be transparent when film resistance is greater than about 1 kΩ, it behaves as a good conductor when film resistance is much smaller than 100 Ω, and in between it results in nonlinear (and even oscillatory) higher order modal behaviors. Apparently, due to the increasing field concentration inside the upper dielectric (as suggested by the increasing ε_reff) for a given mode, both the maximum attenuation and the film resistance needed to achieve it increase with frequency and dielectric constant of the upper dielectric layer     

Rigorous analysis of open microstrip lines, of arbitrary crosssection in bound and leaky regimes

The problem of an open microstrip line of arbitrary cross section is solved by an integral equation technique in conjunction with the method of moments. The approach is general and can handle, as special cases, multiple strips and strips of finite or infinitesimal thickness. It applies to both the fundamental and higher order modes, whether in the bound or the leaky regime. Computed dispersion curves and modal current distributions are presented for several cases of interest and, where possible, are compared with published data     

Millimeter wave propagation in transmission lines with magnetized semiconductor element

Journal of Infrared, Millimeter, and Terahertz Waves - The peculiarities of electromagnetic wave propagation in transmission lines with a gyromagnetic semiconductor element are analysed....     

Analysis and design of feeding structures for microstrip leaky waveantenna

Three arrangements of the feeding structure for the excitation of a microstrip leaky wave antenna are proposed and investigated in this paper. A full-wave spectral domain integral equation method combined with the fundamental mode sampling technique is applied to determine the reflection coefficient of the excitation source. Tabulation technique is used to reduce the computational effort. Dependence on structural parameters such as line width, line spacing and overlap length is fully analyzed to obtain the design criteria for a microstrip leaky wave antenna. Additionally, an experimental setup is used to check the validity of our numerical results and verify the radiation nature of the microstrip line first higher-order mode     

The dispersion characteristics of shielded microstrip lines on magnetized ferrite and anisotropic dielectric substrates

The dispersion characteristics of the dominant mode in shielded microstrip lines on magnetized ferrite and anisotropic dielectric substrates have been obtained. The solution is obtained by applying the transverse equivalent transmission line in the spectral domain and Galerkin's method. Numerical results for the frequency-dependent propagation constants are presented which could be used in designing directional couplers and isolators.     

Analysis of L-shaped slot cut broadband rectangular microstrip antenna

Broadband microstrip antenna (MSA) is realised by cutting the slot at an appropriate position inside the patch. The bandwidth (BW) of the rectangular MSA (RMSA) has been increased by cutting an L-shaped slot inside the patch and it gives a BW of more than 550?MHz (>25%). The reported antenna has a peak gain of 9?dBi which reduces to less than 4?dBi towards the higher frequencies of BW. In this article, an analysis to study the broadband response of the L-shaped slot-cut RMSA is presented. Through the analysis, it was observed that the slot does not introduce any mode but modifies the orthogonal and higher-order TM₁₁ and TM₂₀ mode resonance frequencies of the patch and along with the TM₀₁ mode realises broader BW. Since TM₁₁ mode is dominant towards the higher frequencies of the BW, the cross-polarisation levels increases, which reduces the antenna gain to less than 4?dBi.     

Electromagnetic modes in conical transmission lines withapplication to the linearly tapered slot antenna

A transmission line analysis of the bow-tie antenna and the linearly tapered slot antenna (LTSA) is presented. These structures belong to the class of conical transmission lines defined here in terms of conical coordinates. A complete set of solutions of the Helmholtz equation is obtained exhibiting TE and TM modes. Modal fields are expressed by Lame (1837) and Bessel-Schelkunoff functions. TE and TM eigenmode analysis is particularized to the bow-tie structure. Bow-tie antenna and LTSA are shown to be dual conical transmission lines by the image method and Babinet's principle. The modes of LTSA are calculated on the basis of the results obtained for the bow-tie structure. The radiation pattern of the LTSA is computed as the integral of a closed-form expression of the dyadic Green's function weighted by the modal electric field distribution over the slot aperture. The obtained dominant mode radiation patterns are validated by measurements from the literature. The radiation patterns of the first two-order modes are calculated and compared     

Investigation of integration paths in the spectral-domain analysis of leaky modes on printed circuit lines

The different integration paths that may arise in the spectral-domain analysis of leaky modes on open printed-circuit transmission lines such as microstrip are investigated. There are an infinite number of paths in the complex plane that may be used to construct leaky-mode solutions. Not all of the paths are valid mathematically. Among the mathematically valid ones, a certain subset correspond to paths that yield "physically valid" solutions. When tracking leaky-wave solutions as frequency changes, it is found that the propagation constants of the leaky modes may go through nonphysical "growing" regions where the attenuation constant is negative. These nonphysical regions may appear between physically valid frequency regions, implying that the leaky modes should be tracked in all frequency regions, including the nonphysical growing ones, in order to obtain the complete frequency dispersion behavior of the leaky mode. The migration of the leaky modes into these nonphysical growing regions gives rise to unconventional integration paths never seen before. Such paths must be used if the dispersion behavior of the leaky modes is to be plotted for all frequencies.     

A general analysis of propagation along multiple-layersuperconducting stripline and microstrip transmission lines

A rigorous spectral-domain formulation for a superconducting stripline or microstrip transmission line with a multiple-layer dielectric substrate is presented. The formulation models the strip conductor as a surface current with an equivalent surface impedance, where the surface impedance is approximated in closed form when the strip is either much thinner or much thicker than a penetration depth. In either case the surface impedance is related to the complex conductivity of the material, which is calculated from a two-fluid model. Results are presented to show the slow-wave propagation and attenuation along both microstrip and stripline packages in a realistic multiple-layer configuration, which accounts for the field penetration into the superconducting ground planes     

一种月牙形缝隙多频微带天线分析与设计

提出了一种微带馈电式圆形微带天线设计方案,通过在辐射贴片表面加载月牙型缝隙,改变电流有效路径,实现多频特性。通过HFSS仿真分析缝隙形状对天线性能的影响。结果表明,天线工作的三个频段相对带宽分别为4.1%(2.39~2.49 GHz),3.98%(3.92~4.08 GHz)和3.75%(5.51~5.72 GHz)。其中低频和中频段的最高增益达到6.58d B和5.01 d B。天线尺寸为35 mm×52 mm,具有小体积、高增益、全向性良好的特点,能够应用于无线通信系统中,并且这种结构简单、参数少、多频段的设计方法为天线设计提供了新的途径。     

An FFT-based signal identification approach for obtaining the propagation constants of the leaky modes in layered media

We propose to find the propagation constants of modes in layered media by means of signal identification methods. To this effect we employ Cauchy's theorem, conformal mapping and Fast Fourier Transform (FFT) techniques to generate relevant Hankel moments, afterwards to be processed with selected signal identification algorithms. The method, terminated by a few Newton steps, provides a batch of highly accurate roots in appropriate disks or half-disks.     

Analysis of leaky modes by a modified finite-element method

The finite-element method with integral boundary conditions is used to investigate leaky modes (quasi-eigenmodes) of open dielectric waveguides. Dispersion characteristics and field distributions in double-layer and multilayer circular waveguides are calculated. The influence of uniform deformations of the waveguide cross section on the properties of these modes is studied.     

Analysis and synthesis of tapered microstrip transmission lines

The input voltage reflection coefficient on a tapered microstrip transmission line is analyzed and a new Fourier transform pair is derived which introduces echo time and frequency as variables. Calculations of the input reflection coefficient take into account the frequency dispersion-characteristics of the effective permittivity. An efficient method is proposed for analysis and synthesis of microstrip tapers and numerical results are presented for microstrip exponential tapers and microstrip Chebyshev tapers