Calculating the Characteristic Impedance of Finlines by Transverse Resonance Method

The characteristic impedance of finlines with up to three slots is calculated by a rigorous hybrid-mode analysis which includes the finite metallization thickness and finite depth of the mounting grooves. The transverse resonance principle utilized reduces considerably the order of the involved matrix eigenvalue problem. The propagation constants for the fundamental HE/sub 1/ mode (and EH/sub 0/ mode at related structures), as well as for the higher order modes (up to HE/sub 7/), and the characteristic impedances for the fundamental modes are computed as a function of frequency for the bilateral and unilateral finline, as well as for the unilateral finline with two coupled slots, and an additional slot on the opposite side of the substrate surface. The finite metallization thickness and mounting groove depth considered show significant influence on the behavior of the characteristic impedance.     

鳍线阻抗不连续性的混合模散射特性

本文用混合模展开鳍线中的本征场,并应用谱域法确定主模和高次模的传播常数和谱域中的本征场,然后结合模匹配法分析鳍线阻抗不连续性的混合模散射特性。文中给出计算的单鳍前30个模,双鳍前20个模的传播常数和阻抗不连续性的主模散射参数,计算结果与文献发表的结果一致。有关数值收敛性问题亦在文中进行了讨论。     

Accurate Hybrid-Mode Finline Configurations Including Analysis of Various Multilayered Dielectrics, Finite Metallization Thickness, and Substrate Holding Grooves

An accurate analysis of various finline configurations is introduced. The method of field expansion into suitable eigenmodes used considers the effects of finite metallization thickness as well as waveguide wall grooves to fix the substrate. Especially for millimeter-wave range applications, the propagation constant of the fundamental mode is found to be lower than by neglecting the finite thickness of metallization. For increasing groove depth in cases of asymmetrical and "isolated finline," higher order mode excitation reduces the monomode bandwidth significantly. In contrast to hitherto known calculations, this parameter only causes negligible influence on a fundamental mode if the groove depth is lower than hall of the waveguide height.     

Analysis of Finline with Finite Metallization Thickness (Short Papers)

In this paper, we present a method for analyzing finline structures with finite metallization thickness. The method is based on a hybrid mode formulation but it by-passes the lengthy process of formulating the determinantal equation for the unknown propagation constant. Some numerical results are presented to show the effect of the metallization thickness for unilateral and bilateral finlines.     

Finlines in rectangular and circular waveguide housings includingsubstrate mounting and bending effects-finite element analysis

The finite-element method is used to derive the dispersion characteristics and field components of dominant and higher order modes in finlines. The method is accurate and covers the metallization thickness, substrate mounting grooves, bending of the substrate, and arbitrary cross sections. Results for structures already obtained with other methods have been found to agree well with available data. As a new contribution, the effect of substrate bending on the propagation constant is studied. The dispersion characteristics for the dominant and higher order modes for bilateral finlines in circular waveguide housing are calculated. The field plots for all the modes are given     

Numerical modeling of generalized millimeter-wave transmission media with finite element and transmission line matrix methods

In this paper, a general finite element method as well as a graded-mesh TLM procedure for determining the dispersion characteristics, field distribution, pseudo-impedance and losses of generalized millimeter-wave transmission media are described. These methods cover arbitrary cross-sections and account for realistic features (finite metallization thickness, substrate mounting grooves etc.) that are often neglected in theoretical analysis. Dispersion characteristics and characteristic impedances obtained for dielectrically loaded ridged wave-guides compare well with the available data. Conductor and dielectric losses are also computed for these structures. A modified finline structure called “ridged finline” is also analysed. The main advantages of this structure are its large monomode bandwidth and reduced dispersion. The cutoff frequencies of bilateral finlines in circular waveguides are also computed.     

Finite element analysis of inductive strips in unilateral finlines

A three-dimensional finite-element method (FEM) is used in conjunction with the boundary-marching algorithm to characterize inductive strips in unilateral finlines. For an idealized finline of zero fin thickness, without mounting groove effect, the results agree with those obtained by the hybrid-mode spectral-domain approach to within a few percent with only 98 elements. Field distributions for the dominant propagation mode in unilateral finlines are generated with the boundary-marching algorithm. The effect of metallization thickness, the influence of the mounting groove, and the effect of substrate bending on the discontinuity parameters are studied in detail     

A Modified Mode-Matching Technique and its Application to a Class of Quasi-Planar Transmission Lines

A rigorous and versatile hybrid-mode analysis is presented to determine the normalized propagation constants in a class of quasi-planar transmission-line structures. The method is accurate and covers the finite metallization thickness, mounting grooves, and an arbitrary number of dielectric subregions. Utilizing a modified mode-matching technique, one can derive discontinuity and transmission-line matrices for each homogeneous subregion. Successively multiplying matrix equations of all subregions leads to the characteristic matrix system. This procedure makes it possible to create a modularized computer program which can be conveniently extended to a wide spectrum of conceivable configurations simply by inserting the matrix equations of additional subregions in the multiplication process. To demonstrate the efficiency of the proposed method, dispersion characteristics of dominant and next higher order hybrid modes in earthed and insulated finlines, suspended microstrips, and coupled striplines with tuning septa, are given as examples.     

The influence of metallization thickness on the characteristics ofcascaded junction discontinuities of shielded coplanar type transmissionline

A full-wave analysis based on the mode-matching technique is applied to analyze cascaded junction discontinuities of coplanar-type transmission lines, coplanar waveguide (CPW) and finline. Results for a CPW-finline transition, a shielded CPW gap and a symmetric notch incorporating the finite metallization thickness effect are presented. The influence of metallization thickness on the coupling effect exhibited by cascaded junction discontinuities is also presented and discussed     

Explicit formulas of propagation characteristics for unilateral finline

In this paper, the unilateral fintine characteristics including finite metallization thickness and depth of mounting grooves are analysed by transverse resonance principle combining moment method. The numerical results are presented, the influence of the finite metallization thickness and depth of grooves on the propagation characteristics are investigated in detail. Finally, a set of explicit formulas for the propagation characteristics of unilateral fintine are developed. To be compared with the rigorous numerical results, the errors are within ±1% for phase constant and ±2% for characteristic impedance respectivelly.     

Characterization of shielded coplanar type transmission linejunction discontinuities incorporating the finite metallizationthickness effect

Frequency-dependent characteristics of shielded junction discontinuities between coplanar type transmission lines, specifically coplanar waveguide (CPW) and finline, are analyzed by the mode-matching technique. The effect of finite metallization thickness is also incorporated in the analysis for the first time. Scattering parameters of finline step discontinuity are compared with existing data to confirm the accuracy of the approach. Numerical results for finline step discontinuity, shielded CPW step discontinuity and CPW-finline transition are presented     

Full-wave analysis of coplanar strips considering the finite stripmetallization thickness

An extensive analysis, based on a full-wave mode-matching technique, is described for coplanar strips (CPS) incorporating the strips' finite metallization thickness. Results for the effective dielectric constant and characteristic impedance are presented to show the effect of the metallization thickness. It is found that the characteristic impedance has a strong dependence on the metallization thickness, which signifies the fact that the finite metallization thickness needs to be considered in designing practical microwave circuits employing CPS. Numerical results of CPS with zero metallization thickness obtained using this method are found to be in good agreement with those published previously. Extensive investigation of the numerical convergence of these results is also described     

On the mode-coupling formation of complex modes in a nonreciprocalfinline

This paper studies and models the mechanism for forming the complex modes commonly found in boxed quasi-planar or planar guided-wave structures. To illustrate the fact that the mode-coupling among the various forms of modes is closely related to the formation of complex modes, the dispersion characteristics of the complex propagation constants (or the so-called mode spectrum) of a nonreciprocal unilateral finline are obtained by the rigorous full-wave SDA (spectral-domain approach). It is found that in the mode spectrum of the nonreciprocal finline, a forward wave and a backward wave interact to produce a pair of complex modes. The interactions between two forward (backward) traveling waves, between a forward wave and a backward wave, and between two complex waves (modes) are modeled by applying the mode-coupling theory. The concept of hypothetical modes is introduced in the model. These hypothetical modes are obtained by applying mode-coupling theory to the mode spectrum previously obtained. The approximate values obtained for the propagation constants of the three types of wave interactions using the model presented in the paper are in close agreement with those given by the full-wave SDA     

Application of a Projection Method to a Mode-Matching Solution for Microstrip Lines with Finite Metallization Thickness (Short Paper)

It will be demonstrated that the convergence behavior of the well-knowm mode-matching technique can be improved significantly by a general projection method. The advantage of this approach becomes obvious in the discussion of the electromagnetic field distribution near metal edges. The implementation is rather simple and will be described below. Numerical results and the validity of this method are discussed for shielded microstrip lines with finite metallization thickness.     

Leakage characteristics of groove guide having a conductor strip

A full-wave characterization of the groove guide having a conductor strip is made based on the mode-matching procedure. All of the constituents of the structure, including a coupling strip, grooves and a radiating open end, are treated in a concise and rigorous way by using the generalized scattering matrix technique. Numerical results show that a set of channel guide leaky modes is also present in this structure in addition to the groove guide leaky mode. The complex propagation behaviors of both the groove guide leaky mode and the channel guide leaky mode are illustrated for various waveguide geometric parameters, and some conclusions regarding the design of leaky wave antennas using this structure are drawn     

Eigenvalue approach to the efficient determination of the hybridand complex spectrum of inhomogeneous, closed waveguide

Many hybrid modes are required in computing the fields scattered from discontinuities in structures such as finline, coplanar waveguide, or microstrip. The authors present a new analytical method based on an eigenvalue formulation of the generalized telegrapher's equations discretized by using the modes at cutoff as an expanding set. This approach produces a compact theoretical model while providing at the same time an effective algorithm for finding the characteristics of many modes, including their below cutoff and complex behaviour. The theoretical approach gives some direct insights about the appearance of complex modes. Due to the explicit formulation of the eigenvalue equation for the complex propagation constant, the proposed method overcomes some of the typical drawbacks of the currently used algorithms, such as the limited numerical accuracy and efficiency, the numerical degeneracy and appearance of spurious solutions, the inability to trace the characteristics of degenerate modes. Numerical results for ordinary and complex propagation in finline show excellent agreement with existing data     

A modified transverse resonance method for the analysis ofmultilayered, multiconductor quasiplanar structures with finiteconductor thickness and mounting grooves

A modified transverse resonance method is presented for analyzing generalized multilayered, multiconductor quasiplanar structures with practical parameters such as finite conductor thickness and mounting grooves. Recurrence relations are obtained by using network theory for obtaining the overall transverse equivalent network. while the discontinuity involving the finite-thickness metal sheet and mounting groove is carried out by a field-theory-based multimodal variational formulation. The frequency behaviors of propagating, evanescent, and complex modes are obtained for several commonly used quasiplanar lines, showing good agreement with published results. Furthermore, a leaky-wave study is carried out for open structures, since the open condition can be included in this formulation without difficulties     

Spectral-domain immittance approach for the propagation constantsof unilateral finlines with magnetized ferrite substrate

The admittances of TM and TE modes in a ferrite substrate are given, and the propagation constants for the forward and backward directions of the dominant mode in unilateral finlines with magnetized ferrite substrates are obtained. The solution is obtained by applying the transverse equivalent transmission line in the spectral domain and Galerkin's method. Numerical results are presented which can be used in designing a finline displacement isolator