Cassinian和SN波导的大功率传输特性

介绍了Cassinian和SN波导的基本理论,分别给出了用于描述这两种波导的曲线方程,通过求解这两种波导的曲线方程并利用HFSS三维场仿真软件设计了工作在X频段的两种特殊形状的波导,实际测试了这两种波导的色散特性、衰减常数、传输功率容量和波阻抗,并对测试结果进行了详细的分析与讨论,初步论证了Cassinian和SN波导用于大功率微波能量传输的可能性,为这两种波导的实际应用打下了良好的基础.     

Wave Propagation and Attenuation in the General Class of Circular Hollow Waveguides with Uniform Curvature

A general method has been developed to evaluate the propagation constant in oversized circular hollow-core waveguides characterized by a surface impedance and admittance due to a uniform bend. Completely different formulas are obtained for the attenuation constants of the modes in metallic or dielectric hollow waveguides from those obtained by Marcatili and Schmeltzer. Electric-field lines are also presented for several lower order modes in bent waveguides.     

A General Power Loss Method for Attenuation of Cavities and Waveguides

The usual power loss method of evaluating the damping constant and Q of cavities and the attenuation constant of waveguides, as caused by finite wall conductivity, breaks down in the case of degenerate modes and fails to predict the coupling between degenerate modes. By means of variational formulations for the lossy case it is shown how the usual power loss method maybe generalized to treat the case when there are degenerate modes present. The generalized method turns out to be a particularly simple extension of the usual procedure.     

Coupling of Modes in Uniform, Composite Waveguides

The principle of coupling of modes is used to compute the phase constant in a uniform waveguide Iilled with two ditferent dielectric materials. The natural modes of two hypothetical waveguides filled with the different dielectrics are computed. The propagation of the combined system is computed by considering the coupling between the two sets of modes. Comparison is made between the approximate theory and an exact theory.     

Transmission Distortion in Multimode Random Waveguides

We consider the coupled line equations for two-mode random media in which both modes travel in the same (forward) direction as a model for multimode millimeter waveguides and optical fibers, in which mode conversion at imperfections occurs primarily in the forward direction. Some exact general properties satisfied by the transfer function and the impulse response of such a system are given for an arbitrary coupling coefficient. A random stationary coupling coefficient with statistically independent successive values, and consequently a white spectrum (e.g., a white Gaussian or a Poisson noise), permits exact determination of transmission statistics; we obtain first- and second-order statistics in the time and frequency domains. No perturbation or other approximations are made in any of the above results, which are obtained directly from the coupled line equations. These results are used to study signal distortion in long guides. By straightforward extension of this work more complicated calculations can treat more forward modes, but not backward modes or nonwhite coupling coefficient spectra. In this paper the coupling coefficient is assumed frequency independent, and under certain conditions the signal distortion decreases as the mode conversion increases. In practical cases the coupling coefficients are frequency dependent and the above behavior is modified; the present work is extended to this important case in a companion paper.     

太赫兹传输波导器件研究进展

随着太赫兹技术的发展,太赫兹传输波导器件的研究成为待解决的重要问题之一。太赫兹波位于微波与红外光之间,寻找高效的传输、耦合器件一直是研究人员的目标。主要介绍了太赫兹传输波导研究现状,并总结了各类型太赫兹波导的优势与不足。根据材料与结构分别对金属波导、介质波导的研究进展进行了分析。其中金属波导包括裸金属线波导、微结构波导、空芯波导以及平板波导,介质波导包括介质空芯波导、多孔芯波导以及微结构波导。最后分别对太赫兹传输波导未来需要解决的研究方向进行了展望。     

Electromagnetic Wave Propagating in Uniform Waveguides Containing Inhomogeneous Dielectric

Uniform waveguides filled with inhomogeneous dielectric whose permittivity varies along one dimension are studied. Emphasis is given to the modes of propagation and to the calculation of the propagation constants. Exact solutions are given for some special cases. In some of these only asymptotic or polynomial solutions have been available previously. No restriction is placed on the waveguide dimensions so that results developed here apply to the transmission of optical frequency waves as well as to microwaves and millimeter waves. In the waveguide problems of this paper, results obtained cannot be directly found in the existing literature and have been worked out from fundamental theory of differential equations. The theory of the confluent hypergeometric function has been of great help in our treatment of these problems.     

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.     

交叉多模光波导传输特性分析

针对交叉多模光波导结构,基于光束传输法(Beam Propagation Method,BPM)对其传输特性进行了分析,通过对方形多模光波导模式Ep,qx的分析发现,对于相同的模式序数p,随着传输模式阶数q的增加,交叉光波导的传输特性基本保持不变;随着模式序数p的增加,小的交叉角度更易引起交叉光波导的相互干扰。     

Symmetry-Induced Modal Characteristics of Uniform Waveguides --- II: Theory

The application of symmetry analysis to uniform waveguides is discussed. Symmetry analysis provides exact information concerning mode classification, mode degeneracy, modal electromagnetic- field symmetries, and the minimum waveguide sectors which completely determine the modes in each mode class. This paper provides a summary of the development. that leads to the results concerning symmetry-induced modal characteristics of uniform waveguides discussed in the previous paper. Some of the concepts of group theory are introduced, including the irreducible representations of symmetry groups. The use of the irreducible representations to determine the mode classes and their degeneracies is described. The projection operators belonging to the irreducible representations are introduced and their application to determining the azimuthal symmetry of the modal fields is explained. The minimum waveguide sectors for the mode classes are obtained from the azimuthal symmetry of the modal fields.     

Uniform Waveguides with Arbitrary Cross-Section Considered by the Point-Matching Method

The point-matching method applies to the problem of wave propagation in many uniform waveguides of very general cross-sections. The boundary conditions are satisfied at a finite number of points on the guide wall only. This method applies when the contour of the cross section of the guide is a closed curve, the function of which is single-valued. The validity of the point-matching method is demonstrated qualitatively. Examples show that accurate values of cutoff wave numbers can be achieved easily.     

Uniform Asymptotic Technique for Analyzing Wave Propagation in Inhomogeneous Slab Waveguides

The guided modes of inhomogeneous dielectric slab waveguides are analyzed by a uniform asymptotic technique based on the related equation method. This technique gives highly accurate solutions in the sense of asymptotic expansion. The algorithm for calculating the guided modes of slab waveguides with an even polynomial refractive-index medium is presented. As an example, we calculate the third-order approximate solutions for the guided modes in an analytic form. The results show that the WKB solutions for higher order modes are more accurate than for the lower order modes and the correction to the WKB solutions is significant for the lower order modes. The numerical result for eigenvalues and modal fields confirms that the third-order asymptotic solution is accurate for all the guided modes of the near-parabolic profile waveguides and for higher order modes in the case of the quasi-Gaussian profile.     

Calculation of Duobinary Transmission Systems with Optical Waveguides

A calculation and optimization method for optical waveguide transmission systems using the principle of digital duobinary transmission is presented. Then, systems with duobinary reception and systems with raised-cosine reception, which also need an equalizer at the receiving end, are compared with regard to the energy per single signal required for a tolerable bit error probability. Other criteria of comparison, such as susceptibility to jitter, additional duobinary system hardware, and error detection facilities, are considered, too. The results of the calculations show that in an optical waveguide transmission system where the duration of the signal at the optical waveguide output exceeds a defined value, the performance of the duobinary system is better than that of the raisedcosine system when the attainable repeater section lengths are compared.     

有均匀芯区场三层任意幂次非线性平板光波导

研究了芯区和包层的非线性介电常数具有相同形式ε∝|E|^δ的光波导,其中E为本地电场强度,δ可以为任意正数。结果表明,在适当的光强下有5种结构芯区电场分布可以变为均匀场,而且强非线性的介质有利于在较低光功率下产生均匀的芯区场。δ＝2时（Kerr型介质,其结构与我们的前期工作一致。     

红外电解质包层金属空芯波导的制备

介绍了用液相化学法制作红外电解质包层金属空芯波导的工作及传输原理。我们制备了在10．6μm透过率每0．5m达到79．95％的红外电解质包层金属空芯波导。对制作中出现的现象及测量结果进行分析。     

Symmetry-Induced Modal Characteristics of Uniform Waveguides --- I: Summary of Results

The application of symmetry analysis to uniform waveguides is discussed. Symmetry analysis provides exact information concerning mode classification, mode degeneracy, modal electromagnetic-field symmetries, and the minimum waveguide sectors which completely determine the modes in each mode class. Tables are presented which list the possible mode classes and their degeneracies for the two general symmetry families, C/sub n/ and C/sub nv/, of uniform waveguides. Tables showing the azimuthal dependence of the longitudinal components of the electric and magnetic fields for each mode class are given. Based on this azimuthal dependence, figures showing the minimum waveguide sectors which are necessary and sufficient to completely determine the modes of the various mode classes are presented. The application of symmetry analysis is illustrated by considering uniform waveguides with C/sub 4/ and C/sub 6v/ symmetry.     

Bidirectionality of Reciprocal, Lossy or Lossless, Uniform or Periodic Waveguides

Using the scattering-matrix equations for two antennas placed in the fields of a waveguide, it is proven that all reciprocal, lossy or lossless, uniform or periodic waveguides are bidirectional. Since Maxwell's equations imply directly that propagation constants on a lossless reciprocal waveguide come in pairs (beta,-beta*), "complex waves" on a lossless reciprocal, uniform or periodic waveguide come in quadruplets with propagation constants (beta,-beta, beta*,-beta*).     

Transmission Modes of Closed Elliptic-Groove Waveguides for Millimeter Waves

In this paper, a new type of horizontal-flat and vertical-flat closed elliptic-groove guides is firstly presented. The field components and characteristic equations for some main transmission modes of the closed elliptic-groove guides are derived by with the help of the mode-matching method and Mathieu function. The variations of the cut-off wavelengths along with eccentricities, widths and lengths of the parallel plates for a number of lower order transmission modes of the closed elliptic-groove guides are also analysed in detail. The calculated results in good agreement with ones in the relevant references are of very important values in theoretical researches and actual applications of closed elliptic-groove guides for millimeter and submillimeter waves.