A unique method for reducing losses of bends in dielectric optical wave guide

The dielectric optical wave guide is finding growing attention at millimeter wave frequencies. However the dielectric optical waveguide radiates at bends and thus transmission loss increases. These radiations are in the outword direction of bends. This output radiation at output bends arises due to change in phase velocities of the propagating wave at the centre of the dielectric guide and the phase velocity at the outer surface of the dielectric guide. A unique methiod is suggested to avoid these radiation losses.Experimental results are also shown at microwave frequencies.     

Matching of a Gaussian beam into hollow oversized circular waveguides

A Gaussian beam entering an hollow oversized circular waveguide of dielectric or low-conductivity wall material is considered: a simple formula giving the optimal beam charac-teristics for the lowest losses in the guide is derived from an optical theory. This optimization depends on the geometry and the wall material of the guide. The formula is valid for small beam diameters at the guide entrance and for low losses inside the guide, which are conditions corresponding to usual cases. Physical interpretations are given. Comparisons with some experimental results show a good agreement with the theory. These results are of interest for waveguides lasers and waveguide transmission lines.     

Transmission Characteristics of Dielectric Tube Leaky Waveguide

Loss formula of the dielectric tube leaky waveguide is derived by using a transverse transmission-line model which carries most of the transmitted power in air inside a dielectric tube. It is shown that low-loss leaky waveguide can be realized in optical through submillimiter wavelengths with moderate guide parameters and the transmission loss does not depend strongly on the material losses. It is also shown that the attenuation constant of this leaky waveguide is smaller than that of the hollow waveguide by several orders of magnitude.     

Measurement of quality factor of the coupled nonradiative dielectric guide

The dispersion characteristics of non radiative coupled dielectric guide have been computed using mode matching technique. From dispersion characteristics the conductor and dielectric losses have been evaluated and thus knowing the total losses, the quality factor of the coupled non radiative dielectric guide is evaluated in Ka band.     

Propagation in a Dielectric-Loaded Parallel Plane Waveguide

A theoretical analysis of wave propagation in a parallel plane waveguide partially filled with a dielectric is performed. This transmission line is a symmetrical three-region structure consisting of two infinite parallel conducting planes with a dielectric slab of rectangular cross section between and contacting each of the planes. It has been found that TEM and TM modes cannot propagate on this structure. This investigation is concerned with TE modes, although hybrid modes can also propagate on this line. The lowest order TE mode, which is the dominant mode, has no cutoff and hence is inherently suited to extremely wide bandwidth operation. Equations have been presented for the field components, guide wavelength, cutoff criteria, power handling capabilities, wall losses, and dielectric losses as a function of the operating wavelength, waveguide dimensions, and material constants. In the case of the dominant mode, design curves covering a large range of wavelengths, dimensions, and dielectric constants are presented. For a loosely bound wave, the losses are comparable or less than those of conventional rectangular waveguide and the power handling capacity is an order of magnitude greater.     

TE Modes of the Dielectric Loaded Trough Line

The properties of TE modes on a dielectric loaded trough waveguide have been investigated. In the case of the dominant mode of this line (TE/sub 20/), families of design curves giving the field distribution, guide wavelength, power handling capability, wall losses, and dielectric losses as a function of operating wavelength, waveguide dimensions and dielectric constant are presented. For a loosely bound wave, the losses are comparable to those of conventional rectangular waveguide and the power handling capability is an order of magnitude greater. The apparatus and procedure used to measure guide wavelength, rate of field decay in the transverse direction, and attenuation are described. The measured performance is in close agreement with the theoretically predicted characteristics.     

Propagation in Dielectric Slab Loaded Rectangular Waveguide

Propagation in dielectric loaded rectangular waveguide is investigated theoretically for varying slab thickness and dielectric constant. The slabs are placed across the center of the waveguide in the E plane. This geometry is found to offer bandwidths in excess of double that of rectangular waveguide for dielectrics having dielectric constants of approximately 18. Power handling capacities which are double or triple that of standard waveguide are achievable using the dielectric loaded waveguide. In addition to the theory, design curves of bandwidth, guide wavelength, cutoff wavelength, impedance, power handling capacity, wall losses, and dielectric losses are presented and compared to experiment where possible.     

Transmission characteristics of dielectric-coated metallic waveguide for infrared transmission: Slab waveguide model

A metallic hollow waveguide with inner dielectric multilayers is proposed for the transmission of infrared light and its basic transmission characteristics are fully analyzed by using a two-dimensional slab waveguide model. The power loss in the waveguide is shown to be extremely reduced by coating dielectric layers properly. Simple loss formulas are also presented which consider absorptions of dielectric materials, and minimum possible losses are theoretically estimated. Finally, relations to bending losses in the waveguide are discussed.     

Propagation properties of ferromagnetic insulator guide

In order to realize new ferrite planar devices for applications at millimeter-wavelength frequencies, the authors have developed nonreciprocal ferrite devices schemes for incorporating ferromagnetic layers in dielectric insulator guide geometries. Their research program involves both the calculation and the measurement of device characteristics. For the calculation, a method of effective permeability, in which the permeability is a tensor, is introduced to characterize the ferrite material. The propagation properties of the insular guide are calculated by using a single-mode approach. The calculated results for dispersion, dielectric, and conductivity losses show resonant behavior with the application of a magnetic bias field for a guide configuration in which the ferrite replaces the insular dielectric. Ferrite phase shifters, filters, isolators, and circulators are potential applications of this guide configuration. For the experimental part of the study, wave dispersion and attenuation were measured in a purely dielectric insular guide from 26.5 to 40GHz. In addition to these experiments wave attenuation was measured as a function of magnetic bias field for the case where a hexagonal ferrite platelet was mounted on the ground plane near the insulator guide. General agreement is found between calculated and measured attenuation     

Dissipation Loss Effects in Isolated and Coupled Transmission Lines

This paper describes a computer-aided analysis of dissipation losses in uniform isolated or coupled transmission lines for microwave and millimeter-wave integrated-circuit applications. The analysis employs a quasi-TEM model for isolated transmission lines and for the even- and odd-mode transmission lines associated with coupled-line structures. The conductor and dielectric losses are then related to equivalent charge density distributions, which are evaluated using a method-of-moments solution. The transmission lines treated by this analysis may contain any number of Iossy conductors and inhomogeneous dielectrics, consisting of any number of different homogeneous dielectric regions. A development is provided to explicitly relate the four-port terminal-electrical performance of directional couplers to evaluated even- and odd- mode loss coefficients. Examples of evaluated losses are presented in graphical form for isolated lines of inverted microstrip and trapped inverted microstrip and edge-coupled microstrip with a dielectric overlay. The analysis accuracy has been confirmed using microstrip and coplanar waveguide configurations. A comparison is made of the total loss characteristics for microstrip, coplanar waveguide, inverted microstrip, and trapped inverted microstrip. Calculations are compared with measurements for the coupled-line structure. Accuracy of the solution and suggested refinements are discussed. Five computer programs are documented.     

介质损耗对频率选择表面传输特性的影响

应用模匹配技术,研究了Y形缝隙平面周期阵列夹嵌于均匀有耗介质层中心的夹心频率选择表面(FSS)结构对平面波的传输特性。讨论了介质层对结构中心谐振频率、传输带宽、以及传输损耗的影响规律。相同介电常数的介质材料在有耗和无耗情况下的模拟分析结果清楚表明介质本身的损耗是影响FSS结构损耗特性的主要因素。     

The impact of CMP and underlying back-end topographical features on losses in deposited dielectric waveguides

The bending losses in rectangular dielectric waveguides deposited on a chemical mechanical polished (CMP) surface above the metal interconnect/interlayer dielectric stack of a processed Si wafer are modeled and estimated. CMP efficiently removes local topography and microroughness, but leaves long-range surface profile undulations due to variations in the metal pattern density. These surface undulations are then transferred to the waveguides deposited on this surface. A beam propagation method (BPM) waveguide simulation program and an equation for bending loss developed by Marcuse have been used to examine the bending losses seen by waveguides deposited on such a surface. In order to simplify the simulation of the bending losses of the waveguides, the undulations are modeled as a series of arcs, which is shown to be a good approximation. It was determined that under typical conditions, the bending losses may be ignored as they are less than 0.1 dB/cm, which is below the range of typical propagation losses for a straight guide.     

矩形介质天线的时域分析

用经典的EDC近似方法分析矩形介质波导的传输特性，由边界条件导出传输常数满足的特征方程，应用代数学中经典的对分法进行求解，从而获得矩形介质杆中波传播的相速度和内外能量分布与介质杆的相对尺寸之间的关系曲线，据此分析矩形介质杆用作时域天线的可行性，并给出介质杆参数选择的依据。还使用FD—TD(时域有限差分法)模拟计算矩形介质杆天线对高斯脉冲的辐射，分析介质杆的横向尺寸、长度及终端渐变方式对天线辐射特性的影响，多次模拟比较，从而确定介质杆天线的材料和尺寸参数。结果表明这种天线适合用作时域天线。     

Circular Bends in Dielectric Frame Beam Waveguides (Short Papers)

An investigation is described on circular bends in beam waveguides constituted by dielectric frames. A uniform bending of the guide axis is obtained by tilting each frame by a small angle; however, due to the phase correction performed by the dielectric frame, the losses introduced by the bending can be made lower than those of an analogously bent iris waveguide. A numerical analysis is performed on the basis of the analogy between beam waveguides and open resonators which permits the assessment, in a number of cases, of the maximum permissible amount of tilting and the corresponding optimum frame dimensions in view of acceptable losses. The losses due to mode conversion are also evaluated when considering the connection between a straight and a curved section of the waveguide.     

An Accurate Determination of Dielectric Loss Effect in Monolithic Microwave Integrated Circuits Including Microstrip and Coupled Microstrip Lines

For the first time, by a rigorous analysis, the performance of MIC planar transmission lines with Iossy substrates can be studied accurately. The generaf structural shape chosen for the analysis includes infinitely thin metallic strips embedded within the layers of homogeneous dielectric substrates. The rigor of the analysis was guaranteed by the assumption of the propagation of an electromagnetic hybrid wave (i.e., TE+TM) along tbe planar transmission lines. An efficient computation was, however, achieved by implementing the spectral domain approach as the basis for the analysis. To test the analysis, phase constants, characteristic impedances, and attenuations, due to dielectric losses, were computed for microstrip and coupled microstrip lines. The results obtained were compared with those given previously by the spectral domain analysis in which dielectric losses were not included directly [1]. The comparison showed an excellent agreement between the two theories for low-loss substrates. However, for Iossy substrates the present method is more accurate.     

High temperature dielectric stability of liquid crystal polymer at mm-wave frequencies

The temperature dependent dielectric stability and transmission line losses of liquid crystal polymer (LCP) are determined from 11-105 GHz. Across this frequency range, LCP's temperature coefficient of dielectric constant, /spl tau//sub /spl epsi/r/, has an average value of -42 ppm//spl deg/C. At 11GHz the /spl tau//sub /spl epsi/r/ is the best (-3 ppm//spl deg/C), but this value degrades slightly with increasing frequency. This /spl tau//sub /spl epsi/r/ average value compares well with the better commercially available microwave substrates. In addition, it includes information for mm-wave frequencies whereas standard values for /spl tau//sub /spl epsi/r/ are usually only given at 10 GHz or below. Transmission line losses on 3- and 5-mil LCP substrates increase by approximately 20% at 75/spl deg/C and 50% or more at 125/spl deg/C. These insertion loss increases can be used as a design guide for LCP circuits expected to be exposed to elevated operating temperatures.     

Analysis of the propagation properties in an inverted strip dielectric guide

In this paper the conditions are derived which the three lowest modes satisfy respectively in an inverted strip dielectric guide (ISDG). The method of optimal design is dealt with for five parameters selected by the Orthogonal Array Table (OAT), which affect the propagation properties including the single-mode bandwidth, the external field divergence, the conductor and the dielectric losses. Many sets of parameters are presented, for which the ISDG s have optimal propagation properties.     

Propagation characteristics of coplanar-type transmission lineswith lossy media

Lossy coplanar-type transmission lines are analyzed based on the hybrid-mode formulation by combining the spectral-domain approach with the perturbation method. Introducing a finite thickness of metallization and choosing the proper basis functions for the thick conductor model prevent the integrals used for calculating the conductor losses from becoming singular when evaluated at the conductor edge. An orthogonality relation is used to reduce the double infinite or semi-infinite integral to a single integral, thus reducing the computation effort drastically. Numerical computations by new basis functions for the thick conductor show convergence rates as fast as those for the zero-thickness cases. Numerical results include the effective dielectric constants, characteristic impedances, and total losses (conductor and dielectric losses) for slot lines and symmetrical and asymmetrical coplanar waveguides     

Modified H Guide for Millimeter and Submillimeter Wavelengths (Short Papers)

A theoretical and experimental investigation is being made of a modified form of H guide as a possible guided wave structure for millimeter and submilliieter wavelengths. The effects of channels in the conducting planes to support a dielectric film has been studied by scaled-up models at 3-cm wavelength. Low losses, even at the shorter wavelengths, are predicted. The channels may be used to filter unwanted higher order modes, and the use of high-permittivity dielectric is suggested to further reduce the guide attenuation.     

周期介质结构传输特性的严格模匹配分析

用严格模匹配与多模网络理论相结合的方法,对几种周期介质结构的传输特性进行了深入的分析．包括两种有限长周期介质镜像波导滤波器;一种有限长变周期无辐射介质波导滤波器;一种无限长周期部分介质填充的矩形波导．实验结果表明该方法是精确有效的．