Graded-index planar dielectric waveguides

Properties of planar dielectric waveguides having a diffusion-induced index of refraction distribution are investigated. It is found that the spatial distribution of modes, group velocity, and mode spectrum of these guides differed qualitatively from the corresponding properties found in a slab waveguide. These results were experimentally verified by measuring the mode spectrum of a dielectric waveguide having an assumed complimentary error-function distribution of refractive index.     

Wide-angle impedance matching of a planar array antenna by a dielectric sheet

For wide-angle scanning array antennas, the magnitude of the reflection changes substantially with scan angle and wave polarization. Conventional matching techniques in the individual element feed lines cannot compensate for these changes. There is a method of wide-angle impedance matching (WAIM) which utilizes a thin, high-k, dielectric sheet spaced in front of the array. It is capable of equalizing the reflection coefficient forEandHpolarization at any specified scan angle, or for any angle in theEandHscan planes. This technique is applied to an array having element aperture windows flush with a metal face. It is adapted for the procedure of matching in a waveguide simulation of an infinite array.     

Simple relations derived fom a phased-array antenna made of an infinite current sheet

The simplest concept of a phased array is an infinite planar current sheet backed by a reflecting boundary. The electric current sheet, or resistance sheet, is the limiting case of many small electric dipoles, closely spaced, and backed by an open-circuit boundary. If this array is viewed as a receiver, a plane wave incident on the array at some angle (theta) meets a boundary resistance varying in proportion tocos thetafor angles in theHplane, and1/cos thetafor angles in theEplane. If the array is matched at broadside (theta=0), the corresponding reflection coefficient has the magnitude(tan frac{1}{2}theta)^{2}. While the electric current sheet is realizable, the open-circuit boundary is not. However, a magnetic current sheet can be simulated by a conductive sheet with holes utilized as magnetic dipoles, such a sheet providing the backing equivalent to a short-circuit boundary. The latter case is related to the former by electromagnetic inversion or duality. Therefore, an incident plane wave meets a boundary conductance varying in proportion tocos thetafor angles in theEplane, and1/cos thetafor angles in theHplane. The predicted behavior is verified qualitatively by tests of such a model with elements of a practice size. The derivation is based on the principle of dividing the space in front of the array into parallel tubes or waveguides, one for each element cell in the sheet or array. This is one of the principles published by the author in 1948. A related principle enables the simulation of an infinite array by imaging a few elements in the walls of a waveguide. This latter principle is utilized for making tests of the array.     

Reflection and transmission characteristics of an uncoincidentaljunction on rectangular dielectric waveguides

A novel approach to the analysis of an uncoincidental junction in a rectangular dielectric waveguide is presented. The boundary condition equations on the junction plane are presented through the tangential components of guided modes and radiation modes which are excited at the discontinuity. To obtain the reflection and transmission coefficients at the discontinuity, the equations are transformed into the spectral domain by the two-dimensional Fourier transformation. In the spectral domain, the orthogonal relationship between the guided and radiation modes is used to determine the reflection and transmission coefficients approximately. The parameters corresponding to the phase constant of the radiation fields in the spectral domain are defined by using an iterative calculation. The reflection and transmission coefficients are determined exactly. These coefficients are compared with 10-GHz band experiments. The analysis shows good agreement with experimental results     

The grating-lobe series for the impedance variation in a planar phased-array antenna

In an infinite planar array of elements with periodic spacing, the element active impedance varies with phasing for beam steering. This impedance variation may be expressed as the sum of a double Fourier series. This series is identified with the periodic grating-lobe pattern on the "sin thetaplane" which is also the plane of two-dimensional phasing coordinates. An "impedance crater," with contours peculiar to the kind of element, is placed on every grating-lobe center. The inside of the central crater, which coincides with the unit circle of real space on this plane, determines the resistance variation with scan angle of the main lobe. The central crater and the skirts of the surrounding craters overlap in this circle; their sum determines the accompanying reactance variation. All craters together form the "grating-lobe series," which gives a picture of the entire impedance variation with scan angle. In a simple example, the reactance variation associated with half-wave spacing of the elements is found to be nearly equal to the resistance variation associated with the kind of element.     

Coplanar-waveguide-fed slot-coupled rectangular dielectric resonator antenna

A novel coupling scheme to a rectangular dielectric resonator antenna is proposed and investigated. In particular, coupling to the resonator is achieved through a narrow slot at the end of a coplanar waveguide (CPW). The objectives of this design are to maximize the coupling, match the dielectric resonator to the CPW feed line, achieve resonance at the desired frequency, obtain linear polarization with low cross polarization components, and minimize back radiation without using a back conductor. An approximate and quick design approach is given followed by more accurate design and analysis using commercial software. The antenna was fabricated and tested. Measurements match well with simulation results.     

Scattering by an E plane dielectric sheet in rectangular waveguide

A method for the computation of S-parameters associated with a rectangular waveguide with a rectangular dielectric obstacle is presented. The method uses the Method of Lines and discretization of the dielectric permittivity to treat the dielectric discontinuity along the discretization direction. In this way, the Method of Lines can be applied to analyze waveguide discontinuity with dielectric inhomogenousity along the discretization direction. The numerical results have been verified by both theoretical and experimental results.     

Broadband dual-frequency CPW-fed planar monopole antenna with rectangular notch

A rectangular notch is introduced to obtain a broadband dual-frequency operation of a planar monopole antenna fed by a coplanar waveguide (CPW). The antenna is printed on a single metal layer and therefore is easily constructed. Prototypes of the proposed antenna designed for WLAN operations in the 2.4 and 5.2 GHz bands have been constructed and tested. Both theoretical and experimental results for bandwidths and radiation characteristics are presented and discussed.     

Fabrication of planar dielectric waveguides with high optical damage threshold

We realized with a simple inexpensive process planar dielectric waveguides for the visible with the following improved properties: The waveguiding layers are mixed oxide films (∼40 percent TiO2in SiO2). They are hard and durable against mechanical and chemical attack. The losses are low and comparable to other planar waveguide materials. The films withstand high energy densities and intensities for pulsed and CW Laser irradiation, respectively.     

Coupled-mode analysis of anisotropic dielectric planar branching waveguides

We present a theoretical study of mode propagation in anisotropic planar branching waveguides consisting of isotropic and anisotropic layers. The characteristic equation of anisotropic five-layered structure is introduced to calculate the propagation constants and field patterns of the branching-waveguide modes. Coupled-mode analysis shows that the normalized parameter is effective for the evaluation of mode-coupling effects in the anisotropie branching waveguides as well as in the isotropic branching waveguides.     

Coupled mode analysis of dielectric planar branching waveguides

The mode conversion behavior of planar dielectric branching waveguides is studied as a function of branching angle, propagation direction of modes, and thickness ratio of branches. The multimode coupled equation and new step approximation method of branch taper are introduced, which give the accurate analysis of mode behavior in the branching waveguide of a large taper angle.     

Characteristics of TE-modes in rectangular waveguides containing dielectric layers

The eigenequation of TE-modes in rectangular waveguides filled with arbitrary layer dielectrics is presented. As an example, we calculate the characteristics of a rectangular waveguide which is devided three regions by dielectrics. Using a Personal Computer the results can be got in several minutes, and the results agree with that of other authors very well. Some curves are given.     

Mode coupling between dielectric and semiconductor planar waveguides

Computer modeling studies on four-layer silicon-clad planar dielectric waveguides indicate that the attenuation and mode index behave as exponentially damped sinusoids when the silicon thickness is increased. This effect can be explained as a periodic coupling between the guided modes of the lossless structure and the lossy modes supported by the high refractive index silicon. Furthermore, the attenuation and mode index are significantly altered by conductivity changes in the silicon. An amplitude modulator and phase modulator have been proposed using these results. Predicted high attenuations in the device may be reduced significantly with a silicon dioxide buffer layer.     

介质埋藏平面蝶形天线的设计

采用了介质埋藏的形式将平面蝶形天线埋藏于介质中,并设计了渐变的平面微带巴伦给平面蝶形天线馈电,实现了不平衡到平衡的转换;还设计了三角形微带巴伦和微带传输线一起的结构形式,进行阻抗匹配。使用电磁仿真软件Ansoft HFSS对该天线进行了优化设计和仿真实验,与制作的实物天线性能进行对比。仿真和实测结果表明,该天线S11≤-10 dB仿真的相对带宽达到88.7%而实测的相对带宽为79.3%,具有超宽带特性;在工作频率处,仿真增益为6.9 dB,实测增益为5.8 dB。该天线满足某工程项目的需要,可作为探地雷达系统的收发天线。     

SCATTERING ANALYSIS OF E-PLANE UNIFORM DIELECTRIC POSTS IN RECTANGULAR WAVEGUIDES

Based on the polarization current integral equation with the modified Green's Function as ker-nel, the scattering properties of the E-plane. uniform dielectric posts in rectangular waveguide arenumerically analyzed by the moment method. These posts are of arbitrary cross section and post-numberThe calculation accuracy and speed are remarkable improved by segmenting the dielectric region into manysmall rectangular oells and applying local analytic integration. The higher-order modes are considered in cal-culation, improving the computation accuracy and providing the scattering information of all modes excitedas well.     

A MATRIX METHOD FOR SOLVING PLANAR DIELECTRIC OPTICAL WAVEGUIDES

A matrix method used in multilayer stack of dielectric films is applied-to planar dielectric optical waveguides. A simple and applicable method for obtaining characteristic equation is presented.     

Radiation of a rectangular microstrip patch antenna covered with a dielectric layer

The effect of a protecting dielectric superstrate on the radiation pattern of a rectangular microstrip patch antenna is investigated theoretically. The analysis approach is based on the spectral-domain method of moments in conjunction with the stationary phase method. A new concise expression is derived for computing the radiation electric field. The validity of the solution is tested by comparing the computed results with the experimental data. At higher superstrate thicknesses, numerical results indicate that the radiation pattern drastically changes into three lobes. The resonant frequency, on the other hand, increases with the increase of the thickness of the dielectric cover.     

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     

Coupling characteristics of two rectangular dielectric waveguides laid in different layers

The coupling characteristic of rectangular dielectric waveguides which lay in different, parallel layers and one waveguide crossed over the other one are studied. Step-like approximation and the variational method are used for calculating the coupling coefficient which varies with axial distancez. Electromagnetic field expression for the dielectric waveguide mode of rectangular cross section is newly introduced and used. Calculated coupling characteristics are compared with experimental results carried on 50 GHz band. The principle of crossed waveguides leads us to the new design concept of "multilayered integrated circuit."