On the Electric Field Lines of the Dominant Mode in Millimetric V-Groove Guide by Finite Element Method

In this paper, the electric field lines of the dominant mode in a closed V-groove guide as well as an open one are analysed by finite element method. The results show that the electric field lines are not parallel to the parallel plate region, but perpendicular to them. Since the attenuation increase with increasing frequency when the electric field lines are perpendicular to the mental walls, the V-groove is not suitable to be used in millimeter and submillimeter wavebands, and it is can't be regarded as low-loss wave guiding structures.     

Transmission characteristics of several kinds of closed groove waveguides for millimeter waves

An advantage of closed groove guide over open groove guide is attended. In this paper, the several kinds of closed groove guides including the trapezoidal-, elliptic- and parabolic-groove guides as new types of millimeter wave transmission lines are presented. Their dispersion and cut-off characteristics of the dominant mode are analysed and compared with ones of the closed V-and circular- groove guides by using the equivalent network method. The obtained results have important meaning in theoretical studies and actual applications of groove waveguides.     

Field Patterns in Asymmetrical Double Groove Guide by Finite Element Method

The electromagnetic power coupling in asymmetrical double-groove guide is analyzed by finite element method (FEM) in this paper. The electrical field patterns of the dominant mode and the first higher-order TE mode have been presented. The electromagnetic field of the dominant mode is distributed with a concentration of energy in the wide groove region, while the electromagnetic field of the first higher-order TE mode is distributed with a concentration of energy in the narrow groove region. The results in this paper have important values in design of groove guide power coupler for millimeter wave applications.     

Finite Element Analysis of Field Pattern in Multiple Groove Guide

Rectangular groove guide with multiple grooves has been analyzed by finite element method (FEM) in this paper. The electrical field patterns of the dominant mode and the first higher-order TE mode have been presented for groove guide with single-, double-, triple-, and quadruple-rectangular grooves. The electromagnetic field of the dominant mode is distributed with a concentration in the groove regions, while the electromagnetic field of the first higher-order TE mode is mainly distributed in regions between grooves. The low loss characteristic has been found not only in single-groove guide, but also in multiple groove guide.     

Finite Element Analysis of the Field Patterns of Higher-Order TE and TM Modes in Rectangular-Groove Guide

The field patterns of the different TE and TM modes in a rectangular-groove guide are analysed by finite element method. The electric field, magnetic field and energy distributions in the groove guide for the dominant TE mode, the lowest TM mode and the 1st, 2nd, and 3rd higher-order TE,TM modes are presented. The results show that the low-loss characteristic of rectangular-groove guide seems unreliable. The results in this paper will be of benefit for us to understand the transmission characteristics of rectangular-groove guide, and will be of practical significance in designing groove guide components.     

Dominant mode characteristics of circular groove guide

Circular groove guide is a kind of waveguide for millimeter waves with low loss, large dimensions, and low dispersion. In this paper, the dominant mode characteristics of it is analysed. The technique that mode macthing method combines with point matching method is used to derive the Nth-order characteristic equation of the guide. The 1st order, 2nd order and 3rd order approximate curves that the normalized cutoff wavelength of circular groove guide varies with c/a are given. The attenuation curves are given at 1mm, 1.5mm and 3mm wavelength. The numerical results are in well agreement with the experimental results published.Supported by National Science Foundation of P. R. China     

The dominant mode in closed circular groove guide

The structure of closed circular groove guide is similar to that of open circular groove guide, but it can prevent energy from leaking out of the guide. In this paper, the dominant mode in closed circular groove guide is considered. The characteristic equation is derived and solved and the results are discussed.The Project Supported by National Natural Science Foundation of P. R. China and National Key Laboratory of Millimeter Waves Foundation of P. R. China     

Analysis for a Novel Cocoon-Shaped Groove Guide with Method of Lines

An arbitrarily cross-sectional groove guide is analyzed by using the method of lines and its characteristic equations are gives for TE and TM modes. Some numerical results show that correctness of the method of lines compared with the relevant results in the references is verified, and it is convenient to solve groove guide with arbitrary shape in practical application problems. A novel cocoon-shaped groove guide is firstly presented and its transmission characteristics are analyzed and discussed. The new type of cocoon-shaped groove guide has the good performances. The obtained results are of important application values in theoretical studies and practical applications of groove guides for millimeter waves.     

The Analysis of Post-Mount in W-Band Circular Groove Guide

Finite-difference time-domain (FDTD) method is used to calculate the driving-point impedance of the circular groove guide diode mount. A simple way is proposed to approximate the curvilinear metal boundary of circular groove guide. Discrete equations are obtained from the Ampere's law and Faraday's law. Perfectly matched layer (PML) is applied on the open boundary of circular groove guide. At last program is made to obtain the field components. The driving-point impedance can be achieved from the ratio of the Fourier transform of the voltage and the Fourier transform of the current. The cutoff frequency and field pattern of the dominant mode are also obtained with well agreement with the theoretical results, this verifies the validity of the FDTD program.     

ANALYSIS OF ARBITRARILY TRAPEZOIDAL-GROOVE GUIDE WITH THE CONFORMAL MAPPING METHOD

The arbitrarily open trapezoidal-groove guide is analyzed with the conformal mapping technique. A new formula is given for the evaluation of one fundamental parameter associated with the technique. The relationship between the cut-off wavelength for the dominant mode and the geometry of the guide structure is studied; dispersion characteristic of the groove guide is also given. Some numerical results are shown to be in good agreement with both experimental data and the results of the finite element method (FEM). Moreover, it is testified that dispersion of the trapezoidal-groove guide is low. The obtained results are significant for the design and application of the open trapezoidal-groove guide for millimeter waves.     

An improved solution to the dominant mode properties of groove guides of general cross section

An improved solution to the dominant mode properties of groove guides of general cross section is presented in this paper. A novel differential equation is formulated and solved by numerical integration technique. Numerical results for single V-groove guide show good agreement with available measured values. Calculated results for the cutoff wavelengths of semicircular-groove and trapezoidal-groove guides are presented.     

Analysis of groove NRD waveguide bend using the coupled-mode theory

In this paper, the propagation characteristics of the dominant mode in GNRD guide bend are analysed employing the coupled-mode theory. The curves of bending loss vs. The groove depth or width, radius of curvature and frequency are given, which caused by the mode conversion of the operatingLSM ₁₁ ^x mode to the parasiticLSE ₁₁ ^x mode. It is found that the groove depth has a great influence upon the bending loss than the other parameters. According to the theoretical results, appropriate sizes of groove and radius of curvature should be chosen in designing a GNRD bend structure.     

On the Main Mode of Trapezoidal-Groove Guide By Finite Element Method

In this paper, the propagation properties such as the dispersion characteristics, cut-off wavelength, guide wavelength and field distribution for the main mode of trapezoidal-groove guide are analysed by using the finite element method. The dispersion is very low, and the field distribution in a trapezoidal-groove guide is similar to that of rectangular one. The results have important values in design, manufacture, and application of groove guides.     

Field Patterns in Double Circular-Groove Guide by Finite Element Method

The electromagnetic power coupling in symmetrical and asymmetrical double circular-groove guides have been analyzed by finite element method (FEM) in this paper. The electrical field patterns of the dominant mode and the first higher-order TE mode have been presented. The electromagnetic field of the dominant mode distributes with a concentration in the two grooves and the region between grooves as well for symmetrical double circular-groove guide, while it distributes with a concentration in the groove with larger radius for the asymmetrical double circular-groove guide. The electrical field patterns of the first higher-order TE mode in symmetrical and asymmetrical double circular-groove guide are also presented. The figures in this paper have important values in design of circular-groove guide power coupler for millimeter wave applications.     

展向凹槽及泄流孔对高超声速平板边界层转捩影响的试验研究

针对展向凹槽和泄流孔对高超声速钝平板边界层转捩的影响,在中国空气动力研究与发展中心F2 m激波风洞(FD-14A)开展了试验及初步的计算与理论研究.试验的来流马赫数为6、单位雷诺数为3.3×107/m,平板的前缘半径为1 mm,攻角为–4°.在距平板前缘110 mm处布置三组不同的二维展向凹槽,凹槽的宽度与深度分别为凹槽1(2.5 mm,1 mm)、凹槽2(3.75 mm,1.5 mm)、凹槽3(5 mm,2 mm),同时凹槽1的两端可以打开泄流孔,记为凹槽4,不含凹槽时的光滑平板情况记为凹槽5或平板.采用热流传感器测量了不同情况下平板中心线的热流分布,测量结果显示,光滑平板情况在x≈340 mm处开始转捩,在x≈425 mm处转捩接近完成.凹槽导致平板边界层的转捩位置提前,且随着凹槽宽度及深度的增加,对转捩的促进作用增强,转捩位置向上游移动.凹槽1增加泄流孔后(凹槽4)其热流分布及转捩位置与光滑平板情况基本一致.边界层流动完全转捩为湍流后,各情况下的热流差别较小,表明不同规格的凹槽只影响转捩过程中的热流分布,对转捩完成后的湍流壁面热流影响较小.数值计算(CFD)结果显示,泄流孔导致了被动抽吸,试验结果显示凹槽两端的泄流孔抽吸效应抵消了凹槽对平板中心线边界层转捩的促进作用.采用线性稳定性理论(LST)及最优扰动方法分析了光滑钝平板情况的流动失稳机制.LST结果显示,本文平板流动不存在Mack第一模态、第二模态失稳,因此传统的模态失稳机制无法解释试验中观测到的转捩现象.最优扰动计算显示,平板流动存在较强的非模态失稳,可以定性解释观测到的转捩现象.     

Network analyses for transmission characteristics of several kinds of curve-shaped groove waveguides

In this paper, the several kinds of the novel curve-shaped groove guides including the whole elliptic-, whole cosine- and hyperbolic-groove guides as the new millimeter wave transmission lines are presented. The dispersion, cut-off and band characteristics of the dominant mode for the several kinds of the curve-shaped groove guides are analysed by using the equivalent network method with transverse resonance. The obtained results have important values in their theoretical studies and actual applications of the curve-shaped groove waveguides.     

Leaky Characteristics of Modified NRD Guide with Finite Parallel Plate Length

Leaky wave characteristics of modified NRD (Nonradiative Dielectric) guide with parallel plate length are systemically investigated. A technique is used to investigate the leaky property of the guide structure, whichis formulated by effectively combining the multimode network theory with the mode-matching method. In the paper, two phenomena are carefully studied: First, the asymmetric position of the dielectric rod generates a leaky hybrid mode that could produce cross talk between components of the circuit. Second, when the length of metallic plate is finite, another type of leaky mode creates which influences and even couples to the normal leaky guide mode under appropriate circumstances.     

FREE VIBRATION ANALYSIS OF CANTILEVER PLATES WITH STEP DISCONTINUITIES IN PROPERTIES BY THE METHOD OF SUPERPOSITION

Utilizing the superposition method, an analytical type solution is obtained for the free vibration eigenvalues and mode shapes of a cantilever plate with step discontinuities in plate properties. Property discontinuity lines run parallel to the clamped edge of the plate. Verification tests are performed for limiting cases by comparing computed eigenvalues with known eigenvalues for plates with uniform properties. Very good agreement is also obtained when computed results are compared with those obtained experimentally utilizing a test plate with discontinuities in thickness. Computed eigenvalues and mode shapes are presented for the benefit of other researchers. Besides the general interest, the problem has an application in the modelling of certain multi-story buildings during seismic studies.     

The characteristic equations of higher-order modes in circular groove guide

The characteristic equations of higher-order modes, including TE mode and TM mode, are derived in this paper. These equations are very useful for us to understand the mode distribution in circular groove guide.The Project Supported by National Natural Science Foundation of P.R.China