Analysis and experiment of substrate integrated waveguide cavity of four sidewalls of cylinders and solid top and bottom walls

Given in this paper are the equivalence formulas to convert the substrate integrated rectangular waveguide (SIW) resonant cavity of cylinder sidewalls (and solid top- and bottom-walls) to its equivalent rectangular wavguide cavity of solid sidewalls. The equivalence is analytical, therefore it should be excellent as long as the radius of the cylinders and their separation are small in terms of wavelength. Two prototypes are fabricated to demonstrate the validity of the equivalence formula. Excellent agreement of the measured and analytical resonant frequencies of TE₁₀₁ mode has been observed in the substrate integrated rectangular waveguide resonant cavity, indicating the accuracy of the proposed equivalence theory. Such equivalences are convenient for the design of small waveguides, of millimeter wave, in a multilayer circuit structure, such as the LTCC.     

Analysis of the coupling of two non-parallel dielectric rod waveguides

In this paper the coupling between two closely spaced single mode dielectric rod waveguides is investigated when the corresponding propagation axes are not in the same plane. An approximate analysis is presented by assuming only first order interaction between the guided waves. For a given incident HE₁₁ mode (in one of the rod waveguides) the coupled wave amplitudes are computed in the other waveguide for both propagation directions. Numerical results are presented for several coupling geometries.     

Approximate 3D model of electromagnetic modes in waveguide cross-shaped junctions with dielectric filling

Athree-dimensional electrodynamic model of hybrid electromagnetic modes in a waveguide junction of cylindrical and rectangular waveguides with dielectric filling of a cylindrical waveguide is proposed in this study. To solve the vector problem, the mode matching technique (MMT) is applied with the separation of the common waveguide junction region and the representation of the field in this region in the form of superposition of the fields of the partial eigenwaves of waveguides. Classification of eigenmodes is carried out: intrinsic resonances of junction based on transcendental modes and resonances of a waveguide-dielectric type. The investigated structure can be used for measuring the electrical parameters of dielectric samples of both cylindrical and rectangular cross-section shape. Since the spectral characteristics of the junction are determined mainly by the size of the central coupling region of the waveguides and the electrical parameters of the dielectric in the junction, the measurements are of a local nature.     

Analysis of propagation characteristics of whispering gallery modes in a dielectric disk or a curved rectangular dielectric waveguide

The finite-element method is applied to the analysis of whispering gallery modes in curved optical waveguides. Numerical examples for whispering gallery modes in a dielectric disk with rough boundaries are given. It is demonstrated that the whispering gallery modes and the normal guided modes in a curved rectangular dielectric waveguide are analyzed consistently with this approach, and that the normal guided mode approaches the whispering gallery mode with the increase of waveguide width. The minimum width of the rectangular waveguide needed to support a whispering gallery mode is evaluated.<>     

太赫兹矩形波导与共面波导耦合结构设计

太赫兹（THz）波位于微波与红外光波之间,现有微波和光波段波导技术应用正在向THz波段拓展。但是,由于水汽对THz波的强吸收及制造工艺等原因,THz器件主要是平面结构,而THz源及其传输需要用矩形波导。因此,矩形波导与共面波导之间的转换结构成为决定元件和系统性能的关键部分。该设计利用脊波导进行阻抗匹配及电磁场模式转换,实现THz波矩形波导到共面波导的高效率耦合。结果表明,在0.2~0.4 THz频段内,该转换结构的传输系数(S₂₁)高于?3 dB,可以对THz电磁场进行高效率转换。该结果可用于太赫兹分子探测、太赫兹通信等领域,为0.2 THz以上太赫兹的模式转换提供了一种可行方案。     

Field analysis of rectangular waveguide open junction

The problem of a rectangular waveguide open junction is investigated using field theory and the relevant model of two normally intersected, infinite parallel-planes waveguides. Evanescent waveguide modes generated by waveguide wall edges and/or the discontinuity in dielectric are taken into account; an infinite set of equations is derived, where the mode coupling is given by the dielectric slab modes. Proper pole handling is discussed, and a solution for the system is given. Expressions are derived for the reflected, transmitted, and radiated power, which are shown to be sufficiently reliable in the domain of practical interest, regarding the width and the dielectric loading of the gap. The analysis shows that a substantial fraction of the microwave power leaks from the dielectric gap, confirming the absolute necessity of using a choke-flange at the waveguide junction     

MDM光波导激发高阶SPP模的传输特性

研究了金属-介质-金属(MDM)型表面等离子体激元(SPP)光波导的电磁特性。理论计算结果表明,对于633nm的TM偏振入射光,当介质膜层厚度小于85nm时,波导中只能激发产生一阶SPP模(基模),其余高阶模全部截止。随着介质膜厚度增加,高阶SPP模逐渐被激发产生。当介质膜层厚度较小时,SPP模的有效折射率的实部随阶数的增加而减小,而虚部则随阶数的增加而增加,SPP基模具有最大传输距离。然而,当MDM波导中的介质层厚度超过0.555μm时,由于三阶SPP模的电磁场主要集中在离金属层相对较远的介质层中,其有效折射率的虚部具有最小值,具有最大的传输距离,而非基模。当入射光波长为633nm介质层厚度为0.9μm时,Ag/SiO2/Ag光波导中三阶SPP模的传输距离达到约150μm。     

Modification of Marcatili's method for the calculation ofanisotropic rectangular dielectric waveguides

Mareatili's method for the calculation of rectangular dielectric rod waveguides has been modified for uniaxial anisotropic dielectric materials. The averaging method without guessing the field distribution has been used to derive the equations. Experimental results for an anisotropic sapphire waveguide show a good agreement with those calculated using the approach developed here     

Reducing losses in dielectric waveguide discontinuities

Rectangular dielectric waveguides are used in millimeter-wave applications. They have low loss and wide bandwidth at high frequencies. Another major advantage to dielectric waveguides is that they are inexpensive to design and manufacture. However, a major disadvantage to the dielectric waveguide is that they experience relatively high losses at bends and T-junctions. This paper looks at a novel approach in reducing the insertion loss in dielectric waveguide bends and T-junctions. A high dielectric material is inserted at the discontinuity, causing the electromagnetic energy to be coupled and launched toward the output. The dielectric constant of the material, position of the material, and shape of the material are instrumental in reducing the insertion loss. A transition discontinuity in the form of a 45° bend has also been found to reduce insertion loss when properly designed. The size, shape, and location of the discontinuity and the high dielectric material are optimized and compared to the results without a high dielectric material. The 90°- and 45°-bend simulations were verified by building test structures and comparing predictions of the insertion loss to measurements     

Eigen Q-factor of electromagnetic oscillations of E-type in waveguide junction of plane waveguides with anisotropic dielectric

The electrodynamic and numerical analysis of eigen Q-factor of electromagnetic modes of E-type in waveguide junction of plain waveguides, fulfilled with anisotropic dielectric in depending on a permittivity tensor components and dielectric loss have been carried out in the paper. The recommendations on using of waveguide junctions for measurement of dielectric losses of the materials are given.     

Reflection and transmission at an abrupt change in cross-section of a rectangular waveguide in the E and H plane

For a symmetric cross-sectional enlargement of a rectangular waveguide, the reflection and transmission coefficients of the H10 mode are calculated. At low frequencies, they agree well with the values for the H11 mode at an axial-symmetric junction of two circular waveguides. An axial offset of the two rectangular waveguides has a small influence on these coefficients.     

Excitation of a parallel-plate dielectric waveguide using a coaxialprobe-basic characteristics and experiments

In this paper, we study the basic characteristics of a probe excitation to a parallel-plate dielectric waveguide (PPDW), and present design data and experimental results. A coaxial probe has been used in microstrip lines and rectangular waveguides. The present study shows that it is also an effective method to excite/couple a PPDW, thus facilitating the introduction of a new class of PPDW technology in microwave/millimeter-wave integrated circuits. We use here a spectral-domain analysis for analytical modeling of the probe transition, where the probe is approximated by a current strip of an equivalent width. Applying the method of image, the structure is transformed to an infinite-long thin strip inside a dielectric slab, which reduces the transition analysis into a simpler planar geometry. Basic characteristics of the probe excitation, and a complete design data for the radiation loss, excitation efficiency, and input impedance for various transition parameters are computed. Prototype design experiments were conducted, which show that quite efficient excitation can be achieved using; the probe, with insertion loss as low as 0.1 dB. This is contrary to some misconceptions that a probe transition to the fundamental PPDW mode is quite inefficient due to parallel-plate mode radiation     

太赫兹波导发展现状与展望

太赫兹波具有良好的穿透性、低能性和宽带性,在高速空间通信、环境监测、外差探测、医学探测、无损检测和国防安全等领域具有重要的应用前景.波导传输技术和功能器件是太赫兹系统不可或缺的重要组成部分,太赫兹波导的性能决定了太赫兹系统的信号传输效率和集成度,引起人们的研究兴趣.近年来,太赫兹波导的发展取得了长足的进步,从普通的金属...     

Admittances characterizing a partially filled rectangular waveguide with holes in its side face

Admittances characterizing a partially filled rectangular waveguide with holes in its side face have been determined. Sections of such waveguides are elements of complex waveguide connections that are used to construct microwave digital telecommunications circuits built on rectangular waveguides partially filled with dielectric. Such admittances include transformation ratios that were determined in this study by two different techniques: by way of expanding the Mathieu functions into a series in terms of trigonometric functions and by way of expanding the Mathieu functions into a series in terms of Bessel functions. The results obtained in this study can be used in calculations of six-pole and eight-pole networks and can form the basis for engineering design of microwave channels built on such waveguides and designed for different radiophysical systems.     

Theoretical and experimental analysis of waveguide containing transversally magnetized strongly gyrotropic dissipative semiconductor layer

In this paper we present the Maxwell equations' solution method enabling to electrodynamically rigorously compute opened and screened waveguides containing transversally magnetized gyrotropic material. There have been theoretically and experimentally analysed a rectangular metal waveguide having along the narrow wall a gyrotropic dissipative layer ofn-InSb. There has been found the resonant waveguide losses' dependence on the magnitude of the biasing magnetic field. The correspondence of computed and experimental data is fairly good.     

Loss reduction in curved dielectric optical slab waveguide

Formulas of the pure bending loss and the transition loss valid for TM modes in dielectric optical slab waveguides are presented. The characteristic of the total transmission loss of a step-index slab waveguide containing a circular bend having an asymmetric waveguide structure are analysed numerically by applying derived loss formulas. It is found that the features of the total transmission loss of TM modes are closely analogous to those of TE modes except for small discrepancies in the numerical values.     

Low-loss sapphire waveguides for 75-110 GHz frequency range

Low-loss dielectric waveguides are promising for use instead of metal ones, but problems in transitions have to be overcome. A simple and effective structure made of a monocrystalline sapphire waveguide has been designed. Experimental results at 75-110 GHz indicate good matching with metal waveguides (VSWR ⩽1.13) and low insertion loss (0.05-0.35 dB for 47 mm dielectric section)     

Network analysis of eigenvalue problem for multilayer dielectric waveguide consisting of arbitrary number of layers

In this paper, the eigenvalue problem of a multilayer dielectric waveguide consisting of arbitrary number of layers is solved by the microwave network method. A general program with the function of computer graphics has been developed for analyzing the dispersion characteristics and the electromagnetic field distributions of an N layer dielectric waveguide. As examples of practical applications of the program, first, the dispersions and field patterns for the planar waveguides with refractive index of parabolic and exponential profiles are analyzed. Secondly, the procedure of mode conversion and mode separation in dielectric branching waveguides is vividly demonstrated through analyzing the field distributions of asymmetric multilayer dielectric structures and the general rules of mode conversion are discussed. The examples show that the present method possesses the advantages of versatility, rapidity, simplicity and accuracy.     

NETWORK ANALYSIS OF EIGENVALUE PROBLEM FOR MULTILAYER DIELECTRIC WAVEGUIDE CONSISTING OF ARBITRARY NUMBER OF LAYERS

In this paper,the eigenvalue problem of a multilayer dielectric waveguide consisting of arbitrarynumber of layers is solved by the microwave network method.A general program with the function of com-puter graphics has been developed for analyzing the dispersion characteristics and the electromagnetic fielddistributions of an N layer dielectric waveguide.As an example of practical applications,the procedure ofmode conversion and mode separation in dielectric branching waveguides is vividly demonstrated throughanalyzing the field distributions of asymmetric multilayer dielectric structures and the general rules of modeconversion are discussed.     

Polarization dependent loss in polymeric rib channel waveguide

Large polarization dependent loss (PDL) as high as 15 dB was observed in the rib-type channel waveguide fabricated using a birefringent polymer. The PDL mechanism was explained by the mode-mode coupling between the TM mode of a rib and the TE mode of a slab waveguides. This TM-TE mode conversion is due to nonuniform off-diagonal component of the dielectric susceptibility tensor which is generated by a thermal stress during the curing process.