Coupling Characteristics of Nonradiative Dielectric Waveguides

An analytical method is presented for predicting coupling characteristics of dielectric strips in the nonradiative dielectric waveguide. Starting with an approximate but very accurate expression for the coupling coefficient between parallel dielectric strips, the scattering coefficients for nonuniform coupling structures are derived in simple closed-form expressions by taking the effect of the field deformation at the curved sections into account. The coupling coefficient of the nonradiative dielectric waveguide is found to be so large compared to those of other dielectric waveguides that complete power transfer can be attained with coupled polystyrene bends having a curvature radius as small as 20 mm at 50 GHz. The theory was verified experimentally for various coupling structures. As an application toward millimeter-wave integrated circuits, 0-dB couplers, quadrature hybrid couplers, and an in-phase power divider were constructed based on the present analysis. A comparison of theory and experimental data of these fabricated coupling circuits suggests that the effect of the nondegenerate modes in the straight and curved guides must be included in the analysis to further improve the theory.     

正交矩形波导复合耦合槽特性分析

两个正交矩形波导公共宽边上偏离中心线的耦合斜槽称为复合耦合槽。考虑波导壁的厚度，根据等效原理和缝隙口面切向磁场的连续条件建立一对耦合积分方程，利用矩量法进行求解，给出复合耦合槽的谐振长度、散射参量随缝隙的倾角、偏离波导中心线距离的关系曲线     

The Calculation and the Measurement of the Coupling Properties of Dielectric Image Lines of Rectangular Cross Section

In this paper the coupling properties of uniformly coupled dielectric image lines of rectangular cross section are calculated employing an exact method for the determination of the phase constants of the even and the odd mode. The theoretical results are verified experimentally. The results are also applied to the calculation of the coupling characteristics of practical dielectric image line directional couplers.     

Scalar Variational Analysis of Single-Mode Waveguides with Rectangular Cross Section (Short Papers)

We use the variational method to analyze single-mode optical waveguides with rectangular cross section. In particular, we propose a new trial field and show that it gives much better results and involves less computational effort as compared to other trial functions.     

Field Profile In A Single-mode Curved Dielectric Waveguide Of Rectangular Cross Section

An approximate and simple method for predicting the field profile in a curved dielectric waveguide of rectangular cross section is described. For a single-mode propagation, it is shown that the transverse field can be approximated inside the dielectric guide by the Airy function of the first kind and that the radial attenuation constant is a function of the bending radius outside the guide. Experimental verification of the theoretical results is included.     

Analysis of Single and Coupled Rectangular Dielectric Waveguides

Single and coupled rectangular dielectric waveguides are analyzed by means of the mode-matching technique. Dispersion characteristics are given for dominant modes of the inverted stripline and rib waveguides. The propagation constant for E/sup y//sub 11/-mode of the inverted strip line is found to become less than the lowest limit for guidance above a certain frequency. Influence of frequency and dielectric constant of the rib on the normalized coupling length of two coupled rib waveguides is investigated.     

Characteristics Of Loaded Rectangular Waveguides

Electromagnetic fields of a rectangular waveguide with an arbitrarily loaded slab are theoretically analyzed. Eigenvalues for the transmission modes are presented in the form of universal eigenvalue charts. Electric field distributions in the loaded waveguide are obtained theoretically, and they are compared with the results of measurements. Power attenuation is also discussed, and attenuation charts that give the lowest limitation for the attenuation are shown. As an example of application the attenuation characteristic of waveguide resistance attenuators are investigated, and a new interpretation is derived for the phenomena where the curves of attenuation characteristic have sharp peak points.     

Suppression of Cross Coupling in Plasmon Waveguides

Suppression of cross coupling between dielectric plasmon waveguides by inserting an additional waveguide between two main waveguides has been demonstrated. It has been found that the cross-sectional dimensions of the system can be less than two microns, i.e., several hundreds of times smaller than the cross-sectional dimensions of a system made with the use of a dielectric fiber. It has been determined that modes propagating in these waveguides are the sum of one of the symmetric modes and one antisymmetric mode of the coupled system, and the cross coupling is suppressed by matching the wave numbers of these modes. Analytical results are confirmed by numerical simulation.     

Scattering by Abrupt Discontinuities on Planar Dielectric Waveguides

Two unifying aspects of the problem of scattering by an abrupt discontinuity on a planar dielectric waveguide are considered. The first aspect is concerned with the numerical solution of the scattering problem through consideration of a corresponding bounded waveguide problem in which perfect electric or magnetic conductor bounds with variable locations are introduced. It is shown that the solutions to the bounded problem, when numerically integrated over a range of bound locations defined within half a wavelength, allow the complete mode spectra of the unbounded waveguide to be accurately accounted for. Scattering solutions for both TE- and TM-modes are presented for a wide range of discontinuities and, in the TE-mode case, are in agreement with results obtained using the method due to Rozzi [5]. The second aspect is concerned with the relationship between scattering and "inter-waveguide mode orthogonality." Based on a simple iterative scheme, a meaningful physical interpretation of the scattering process is developed. This allows the scattering to be classified as being of first or higher order, to be explained in terms of the physical characteristics of the mode fields.     

Nondegenerate Surface-Wave Mode Coupling Between Dielectric Waveguides

A new variational derivation of the coupling coefficient is given for the problem of nondegenerate surface-wave modes on parallel dielectric waveguides. The results coincide with those of a number of different methods in the literature on the degenerate case, but all give distinct results in the nondegenerate case. These differences are examined and compared with the exact solution, whereby the approximations involved can be evaluated for the case of two parallel slab waveguides.     

Modal Characteristics of Crossed Rectangular Waveguides

The modal solution for the crossed rectangular waveguide is presented. Cutoff frequencies and modal fields are determined by formulating an integral eigenvalue equation which can be solved by application of the Ritz-Galerkin method. Field equations are given for both TE and TM modes. The calculated cutoff frequencies of several lower order modes agree very well with the available experimental results in the literature.     

Dispersion Characteristics of Twisted Rectangular Waveguides

Based on the expressions for the dominant hybrid-mode fields in twisted rectangular waveguides, dispersion formulas with two perturbational factors have been derived theoretically. These factors correspond to the two effects of the twist on the dominant wave propagation, respectively. The one expresses a shift in the cutoff frequency while the other expresses the effect of elongation in the transmission path. A set of 20-cm-long waveguides twisted uniformly by various multiples of 90° has been manufactured by the method of electroforming. The resonant frequencies of the respective waveguides have been measured as a transmission cavity in the 10-GHz band to obtain dispersion relations. Experimental results are found to be in good agreement with the theoretically derived formulas. The results of Lewin's theory are also compared with the present ones.     

Toroidal Resonators and Waveguides of Arbitrary Cross Section

After introducing a new method to solve Maxwell's equations using a complex electromagnetic field vector F, a rotational coordinate system xi, Theta, psi is introduced. In this coordinate system, the field vector components F/sub xi/, F/sub Theta/ may be expressed by F/sub psi/. This component can be obtained from a two-dimensional Hehlmholtz equation. Specifying xi, Theta by cylindrical coordinates r, z the complex Maxwell equation curl F= gamma F is solved for the axisymmetric case (/spl part///spl part/psi = 0) and for the nonsymmetric case. The differential equations for magnetic field lines are solved and surfaces on which the normal component of B and the tangential components of E vanish are recognized as metallic walls of toroidal resonators of various arbitrary cross sections. In the Appendix the results of the new method are compared with well known results for circular cylindrical waveguides.     

On Performance Limitations of Aperture Coupling Between Rectangular Waveguides

The conditions for and expressions of the best coupling flatness and optimum directivity obtainable over a given bandwidth from broad-wall aperture coupling between rectangular waveguides are derived. An inequality representing a constraining relationship among coupling flatness, directivity, and bandwidth is established.     

Null-Field Method for Waveguides of Arbitrary Cross Section

It is shown how to obtain accurate numerical values for waveguide characteristics using the null-field method, which is derived using Waterman's extended boundary condition. Computational results are presented for the sector waveguide (for which the field is known in closed form), the cross section of which possesses a sharp re-entrant corner. It is demonstrated that explicitly satisfying the edge conditions at this corner significantly improves the computational accuracy. In agreement with a previous conjecture it is shown, by example using the sector waveguide, that the straightforward point-matching method sometimes gives completely erroneous fields, even when predicting cutoff wavenumbers with moderate accuracy.     

脊形波导大截面理论研究

比较了两种不同的大截面脊形波导单模条件下,分析了由Pogossian等人给出的单模条件及其偏差的产生原因,对这一条件进行了修正,使其偏差大大减小,并在此基础上,对大截面脊形波导中的多模问题进行了研究。     

Slot Coupling Between Uniform Rectangular Waveguides (Letters)

The results of a recent paper, which analyzes the slot-coupled waveguide problem using a 'reaction' method, are shown to be at variance with those of more established theories, for the particular case of a centrally located transverse slot in the common broad wall separating a pair of rectangular waveguides.     

Resonance Absorption in Nonsymmetrical Lossy Dielectric Inserts in Rectangular Waveguides

Features of resonance power absorption in a lossy dielectric resonator shaped as a rectangular trapezium in a rectangular waveguide are studied. It is found that such a resonator can provide strong absorption (or reflection) of the TE₁₀-mode input from the straight (or inclined) interface port. The maximum absorption is observed when the sum of the coupling coefficients equals unity. Simple formulas relating the scattering and absorption coefficients with the coupling coefficients at the resonance frequency are presented. The physical mechanism of resonance absorption is discussed.     

SOI梯形截面光波导的模式分析

采用有效折射率和转移矩阵理论相结合的方法得到了SOI梯形光波导的本征模方程。计算得到的有效折射率与WKB法相比误差不超过10^-5,其垂直方向电场分布与BPM模拟结果基本相符。首次得到了SOI梯形波导的单模曲线和其近似解析表达式,此结果与修正的WKB法一致。     

On Mode Classification in Rectangular Waveguides Partially Filled with Dielectric Slabs

Arguments are given for the designation of the lowest order longitudinal-section magnetic mode in a dlelectrically loaded rectangular waveguide as LSM/sub 01/ rather than LSM/sub 11/.