Directional couplers in trapped image guide configuration

Dispersion characteristics and wave impedance of trapped coupled image guides are computed by using mode matching techniques. Dispersion curves for trapped coupled image guide are plotted for various dielectric materials and dimensional parameters. The hybrid directional couplers in the above configuration have been theoretically designed by computing the normalization propagation constant.     

Effect of metallic side walls on field distribution of generalized,single and coupled dielectric wave guide

The effect of metallic side walls on the field distribution of generalized single and coupled dielectric guide has been theoretically computed for even and odd modes using mode matching technique in E^Ymn configuration. It is concluded that the field E^Ymn is not symmetrical due to presence of side walls.     

Non-radiative phenomenon in couple dielectric guide

The solutions of electromagnetic field equations for non-radiative coupled dielectric guides are derived using mode matching technique. Dispersion curves are plotted for various dielectric materials and dimensional parameters. The non-radiative phenomenon in the coupled dielectric guide has been discussed in detail. The hybrid directional couplers in the above configuration have been theoretically designed by computing the normalized propagation constants. The superiority of such directional couplers is discussed.     

Trapped Coupled Dielectric Overlay Guide Configuration at Millimeter Wave Frequencies

Trapped coupled dielectric overlay guide has several interesting characteristics useful for millimeter wave applications. Dispersion characteristics and wave impedance for even and odd modes are computed by using Effective Dielectric Constant (EDC) method. Dispersion curves realized for Trapped coupled overlay guide for various dielectric materials and dimensional parameters as a function of frequency. Conductor and dielectric loss in the above configuration have also been studied. Polystyrene (µ_r = 2.56) and Stycast (µ_r = 3.4) have been used as dielectric materials.     

Shielded rectangular dielectric wave guides for millimeter wave integrated circuits

The dispersion characteristics of Insulated non-radiative dielectric guides are computed using mode matching technique. From the dispersion characteristics the dielectric loss conductor loss and wave impedances are derived. Effect of metallic walls on trapped insulated image guide are also discussed. The dimensions of Insulated non radiative dielectric guide are same as that of rectangular metallic wave guide at ka band.     

Hallow Image Guide and Overlayed Image Guide Coupler

A dielectric waveguide structure, hollow image guide, is described. This structure has several interesting characteristics useful for millimeter-wave applications. Dispersion characteristics and field distributions are theoretically and experimentally studied. The structure can also be considered as two parallel image guides coupled strongly by a dielectric overlay. Coupling characteristics between two image guide arms are studied numerically and experimentally.     

Variation of wave impedance of shielded suspended dielectric guide

A shielded suspended dielectric guide is a dielectric rectangular slab enclosed by regular metallic side walls from all the sides. This type of structure is used in dual mode phase shifter where the size of the normal rectangular wave guide is reduced at the ends, where a dielectric material is embeded in ferrite core. Hence impedance variation of a phase shifter at its transition may be easily calculated using shielded suspended dielectric guide which is a prime parameter for optimum efficiency of wave launching.     

Wide-Band Directional Couplers in Dielectric Waveguide

In this work, the H guide is proposed as an alternative in designing proximity directional couplers using dielectric guides in order to obtain coupling factors constant with the frequency, thus increasing the bandwidth of these devices. The propagation constants of the even and odd modes of the coupling zones are determined by means of Schelkunoff's method and the effective dielectric constant method (EDCM). Two directional couplers, 10 dB and 3 dB, made of polystyrene and Teflon respectively, were designed and measured to work in the millimetric frequency band (32-40 GHz). The inclusion of metallic walls in the curved zones avoids additional couplings and results in flat coupling. Furthermore, the metallic walls reduce the radiation losses and allow the coupling factor to be finely adjusted. The results obtained show a maximum coupling variation of +-0.5 dB for 20-percent bandwidth.     

A generalized theory for asymmetrical coupled lines

A method that calculates the properties of geometrically or electromagnetically asymmetrical coupled lines is discussed. Analogous to the normally used theory of even and odd modes, the electromagnetic fields on the computer are described in terms of two modes as the basic variables to calculate the coupling behavior. As a criterion for determining the amplitudes of the two modes, the power transported on the two guides is used. An image guide coupler with a ferrite slab theoretically demonstrates the feasibility of this method     

耦合陷波镜象波导的传播常数及耦合特性

本文用等效介电常数法及表面阻抗匹配法分析了耦合陷波镜象波导的奇偶模传播特性,进而分析了耦合陷波镜象线耦合器的理论特性,为实际耦合器的设计提供了理论依据。     

Propagation constants and coupling properties of coupled trapped image waveguide

The odd and even mode propagation constants of uniformly coupled trapped image waveguides are calculated by using the methods of the effective dielectric constant and surface impedance matching. Theoretical characteristics of a coupler made of coupled trapped image waveguides are analyzed and they can be used as a foundation for the design of this kind of coupler.     

The Millimeter Wave Radiation of a Dielectric Leaky-Wave Antenna Coupled with a Diffraction Grating for the Broadside Radiation: Narrow-Face Interaction

A dielectric leaky-wave antenna (DLWA) coupled with a metallic diffraction grating is experimentally investigated in millimeter-waves. The interaction between dielectric line and grating is from the narrow-face of dielectric and it is contactless. Measured patterns are compared with simulated ones. The antenna parameters (HPBW, side lobe levels, etc.) are also obtained. The most significant achievement of this antenna is to obtain broadside radiation without any suppression, which occurs due to the periodicity of grating. This situation is not available for the most of the periodic leaky-wave antennas. This antenna type can be used as a broadside radiator by this property as well as a frequency scanning purposes.     

Limitations on power-transfer efficiency in three-guide optical couplers

The eigenvalue equations for a slab three-guide coupler were solved and the power-transfer efficiency was calculated when the coupler is used as 1) a power divider and 2) to transfer power from one outside guide to another. In the first case, two modes take part in the power transfer, and unless the guides are very tightly coupled, periodic beats with high power transfer are obtained at multiples of the coupling length as in a two-guide coupler. In the second case, three modes take part in the power transfer, and periodic beats and high power-transfer efficiency can only be obtained if the propagation velocities of the three modes are related to each other in a simple way. This condition will occur only if the guides of a three-guide coupler made up of identical guides are much more loosely coupled than guides generally used in a two-guide coupler.     

Analysis of rib dielectric waveguides

An analysis of rib dielectric waveguides based on a mode matching technique is presented. When the constituent slab guides support only one guided mode, it is shown that the cutoff condition for the higher order modes is the same as the result of the effective dielectric constant method. However, when the rib region is thick enough to support two guided slab modes, the cutoff conditions are significantly different. For this case universal design curves are produced and plotted. The results are also compared with another theory that exists to analyze such structures.     

Analysis of leakage properties of periodic dielectric image guides

The leakage properties of dielectric image guides with periodic surface corrugations on their top or side walls are analysed. A finite-element method in conjunction with an improved perturbation technique is employed to calculate numerically the leakage constant of the lowest-order E/sub y//sup 11/ mode.<>     

Analysis of directive radiation from a line source in a metamaterial slab with low permittivity

In this paper an investigation is presented of metamaterial structures excited by a line source aimed at producing narrow directive beams. The structure under consideration is a grounded slab made of a homogeneous metamaterial medium with a plasma-like dispersive permittivity; for low values of the slab permittivity an extremely directive beam pointing at broadside can be obtained. Conditions for the maximization of radiation at broadside are given and the narrow-beam effect is shown to be related to the excitation of a leaky mode supported by the slab, with radiation maximization corresponding to small and equal values of the phase and attenuation constants. The frequency bandwidth and directivity are expressed in a simple closed form in terms of the attenuation constant of the leaky mode. By increasing the slab height for a fixed frequency, the leaky mode is analytically shown to give rise to a beam that is scanned from broadside to the critical angle for plane-wave refraction, thus being confined to a narrow angular region around broadside. Numerical results are given that illustrate these features, and full-wave simulations of a metamaterial structure made of an array of metallic cylinders are presented that confirm the results of the analytical study. The case of a line source inside a semi-infinite metamaterial region is also considered and its radiation characteristics compared with those of the metamaterial slab.     

The Calculation and the Measurement of the Coupling Properties of Dielectric Image Lines of Rectangular Cross Section

In this paper the coupling properties of uniformly coupled dielectric image lines of rectangular cross section are calculated employing an exact method for the determination of the phase constants of the even and the odd mode. The theoretical results are verified experimentally. The results are also applied to the calculation of the coupling characteristics of practical dielectric image line directional couplers.     

Propagation of TE Modes in Dielectric Loaded Waveguides

The propagation of TE/sub no/ modes in rectangular wave-guides that contain two dielectric slabs parallel to the narrow wall and extending over the full height of the guide is investigated. Waveguide and dielectric are assumed to be lossless and infinitely long. Apart from these restrictions, the dielectric slabs may have arbitrary thickness, position, and dielectric constant. The analysis is restricted to TE/sub no/ modes with the E-field parallel to the narrow guidewall. The guide containing only one dielectric slab is covered by this analysis. The even modes n = 2, 4, 6, . . . of the guide with two slabs correspond to the odd modes n' = n/2 = 1, 2, 3, . . . of the guide with one slab half the width of the guide with two slabs. For six relative dielectric constants (/spl epsilon/= 2.25, 4.00, 9.00, 12.25, 16.00, 25.00) the cutoff frequencies for TE 10, 20, 30, 40, 60 modes and the normalized propagation constants for TE 10 and TE 20 modes between their respective cutoff frequencies and a frequency slightly above the second- and fourth-order mode cutoff frequency for the empty guide, respectively, have been computed for a large range of slab thicknesses and slab positions. Selected results are presented graphically. These results are discussed. The parametric dependence of field distributions, of normalized characteristic impedances, of the ratio of cutoff frequencies (fractional bandwidth), and of the ratio of magnetic field components (ellipticity) are illustrated.     

The Microstrip Double-Ring Resonator (Short Papers)

The resonance frequencies and the fields of a microstrip double-ring resonator are discussed. It is shown that no pure even or odd mode can be excited on the resonator. Therefore it is concluded that the rnicrostrip double-ring resonator principally cannot be used to measure the phase velocities of the even and the odd modes on a coupled microstrip line.     

Image guide couplers used in millimeter wave integrated circuits

The dispersion and coupling characteristics of the coupled image guides are studied by using the odd-even mode principle and effective dielectric constant method. The practical design of the image guide directional couplers is presented. The experiments of 3-dB and 10-dB couplers in ka band show several good features which are very useful to millimeter wave integrated circuits with flat coupling, easy design and fabrication, mechanical stability and low losses.