Energy loss in a planar waveguide caused by a high refracting andabsorbing overlay

An explanation of the mode behavior in dielectric waveguides with an absorbing, high-refractive-index cladding is given. By considering the total waveguiding system as two separate waveguides, it is possible to attribute the behavior of the complex refractive index of the guided modes to the mixing of the modes of both waveguides. For systems with absorption, so-called quasi-leaky waves are observed in the total system for finite thicknesses of the overlay. For absorptionless systems these leaky waves are found only for infinite thicknesses of the overlay. The occurrence and behavior of these quasi-leaky waves versus the increasing overlay thickness are interpreted. A method for calculating the coupling efficiency of modes at the junction unclad waveguide-clad waveguide, taking into consideration waveguides with absorption, is presented. An experimental method for measuring the absorption coefficient for the guided modes in the cladded waveguide and the coupling losses at the unclad-clad waveguide junction was developed. The measured values are in a good agreement with the theoretical calculations     

Equivalent circuit formulation for an array of phased waveguide apertures

An expression for the radiation admittance of an infinite planar array of rectangular waveguide apertures is formulated and a technique for finding the complete equivalent circuit of the waveguide to space junction is given. The formulation includes multiple layers of dielectric above the array ground plane and waveguide elements which are center loaded with dielectric. Experimental verification of the radiation admittance formulation and the equivalent circuit concepts is given.     

Performance of an array of circular waveguides with strip-loadeddielectric hard walls

An infinite planar periodic antenna array of radiating open-ended circular waveguides is considered. The conducting waveguide walls are covered with dielectric layers loaded with longitudinal conducting strips for providing the hard wall boundary condition. Analysis of the array is carried out by the mode-matching method. The waveguide modes involved in the method are calculated by using the asymptotic strip boundary condition. It is shown that they are split into an independent subsystem of TE modes for the whole cross section and two independent subsystems of TM modes: one is for the central region and another is for the layer region. The calculations show that the operation of the hard waveguides in an array with small element spacing is similar to that of the multimode smooth wall waveguides completely filled with dielectric. For large diameters and element spacing, the hard waveguides have significant advantages over the smooth ones. It is shown that unlike an individual hard waveguide, the aperture efficiency of such a waveguide in the array has a nonmonotonic dependence on the waveguide radius. The results characterizing the behavior of the aperture efficiency and cross-polarization level in a frequency band as well as the contribution of certain waveguide modes in the reflected power are presented and discussed. The examples of the element patterns corresponding to minimal cross polarization are also given     

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.     

Full-Wave Analysis of Microstrip Open-End and Gap Discontinuities

A solution is presented for the characteristics of microstrip open-end and gap discontinuities on an infinite dielectric substrate. The exact Green's function of the grounded dielectric slab is used in a moment method procedure, so surface waves as well as space-wave radiation are included. The electric currents on the line are expanded in terms of longitudinal subsectional piecewise sinusoidal modes near the discontinuity, with entire domain traveling-wave modes used to represent incident, reflected, and, for the gap, transmitted waves away from the discontinuity. Results are given for the end admittance of an open-ended line, and the end conductance is compared with measurements. Results are also given for the reflection coefficient magnitude and surface-wave power generation of an open-ended line on substrates with various dielectric constants. Loss to surface and space waves is calculated for a representative gap discontinuity.     

Rigorous Analysis of the Scattering of Surface Waves in an Abruptly Ended Slab Dielectric Waveguide

The reflection and the scattering properties of even TE and TM surface waves incident in an abruptly ended dielectric slab waveguide are analyzed. The discontinuity is regarded as a junction between two open waveguides namely the dielectric slab waveguide and the free space waveguide. The boundary conditions acting together with the orthogonality provide singular coupled integral equations on the discrete and the continuous wave amplitudes at the discontinuity. These singular coupled intergral equations with Cauchy kernels and infinite limits of integration are solved by iteration via the Neuman series. Numerical results are presented for the reflectivity of the even TE/sub 0/ and TM/sub 0/ fundamental modes, together with their mode conversion on even TE/sub 2/ and TM/sub 2/ in a slab where two guided modes can propagate. Reflectivity and mode conversion of higher order excitations are also investigated     

General Field Theory Treatment of H-Plane Waveguide Junction Circulators

In this paper an exact field theory treatment for the waveguide junction circulators is presented. The treatment is general, being dependent on neither the geometrical symmetry of the junction nor the number of ports. The electromagnetic fields in the joining waveguides are written in the form of infinite summation of waveguide modes. The solutions of the wave equations in the ferrite rod and in the surrounding air are obtained in the form of infinite summation of cylindrical modes. The fields at the ferrite air interface and at an imaginary boundary chosen arbitrarily between the air region and the waveguides are then matched. This process leads to an infinite system of nonhomogeneous equations in the field amplitudes. Three types of waveguide junction circulators using this technique are analyzed: the simple ferrite-rod Y junction, the simple ferrite-rod T junction, and the latching Y junction. Point-matching techniques are used to get numerical results for the field distributions and the circulator characteristics. Excellent agreement has been found between the published experimental measurements and the numerical results obtained by this technique.     

Input Admittance of a Circular Waveguide Aperture Covered by a Dielectric Slab

The input admittance of a circular waveguide opening onto an infinite flange with a homogeneous lossy dielectric coating is derived using integral transforms and assuming the dominant TE11mode as the trial field at the aperture. Admittance calculations for low-loss dielectric sheets of various thicknesses are given and compared with measurements obtained using ground planes of varying sizes. Excellent agreement with theory is obtained for the circular waveguide terminated into a square ground plane only1lambdato2lambda. on a side. A quantitative comparison of the surface wave contribution to the total admittance is also given.     

An Exact Calculation for a T-Junction of Rectangular Waveguides Having Arbitrary Cross Sections

An exact method is developed for the calculation of the electrical performance of the rectangular waveguide T-junction. This method is used to find the equivalent circuit of a rectangular waveguide T-junction in which both cross-sectional dimensions of the side waveguide are different from the cross-sectional dimensions of the through waveguide. The theoretical calculations for a particular T-junction of this type are verified by experimental measurements. In this method the electrical performance is analyzed by using equivalent-circuit concepts applied to waveguide modes to calculate an admittance matrix relating propagating and cutoff waveguide modes to each other. Then the cutoff modes are terminated in their characteristic impedance, and an equivalent admittance matrix of the junction is found relating only the propagating modes in each waveguide to each other. The anlysis is valid when any number of modes can propogate in the waveguides forming the junction. The Inversion of an infinite matrix is required; however, any desired accuracy can be obtained by considering a matrix of finite but sufficient size or equivalently by considering a sufficient number of cutoff modes.     

A generalized approach to the analysis of infinite planar array antennas

In this paper a generalized expression for the complex power radiated by an element in an infinite planar array antenna is derived. Since this power formula applies to a large class of phased array antennas where the aperture field distribution can be completely specified (in normal mode form), it proves to be a powerful, unifying principle. The utility of this approach is illustrated by the simplicity with which previously known results can be derived; e.g., an infinite array of slots in a ground plane and an infinite array of flat dipoles with or without a ground plane. Further demonstrations of the usefulness of the power formula are provided by the systematic and straightforward solutions of the less-well-known problems of infinite arrays of crossed-dipole pairs and infinite arrays of open-ended rectangular waveguides. The waveguide array solution is particularly interesting because it reduces to a set of equations which are identical to those one would use to characterize an N-port network on an admittance basis (N is the number of waveguide modes). Since the power formula is derived for a parallelogram element Lattice, the resultant solution for a specific type of element is in its most general form. Expressions for the scan-dependent, dominant mode radiation admittance and the element gain function for a multimode rectangular waveguide radiator are also derived. In addition, various aspects of the waveguide array solution are investigated in the light of previous studies of infinite arrays.     

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.     

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.     

The Excitation of a Dielectric Rod by a Cylindrical Waveguide

This paper is a theoretical analysis of the excitation of the lowest circular symmetric TM surface wave along an infinite circular dielectric rod by a metallic cylindrical waveguide coaxial with the rod. The asymptotic expressions for all the fields are obtained by means of the Wiener-Hopf method. The expressions for the total average power transmitted to the surface wave, the total average power reflected, and the total power radiated, per unit incident power, are derived and computed for epsilon=2.49 for various radii of the dielectric rod.     

Mutual Coupling in Infinite Planar Arrays of Rectangular Waveguide Horns

The radiation admittance and effective power transmission coefficient are derived by a field matching method for arbitrary scan of an infinite array of open rectangular waveguides. Higher order waveguide modes, as well as higher order modes in the free space cell above the array, are included in the field matching problem. The convergence of the solution was studied, and the number of external free space and internal waveguide modes necessary for an adequate answer are given. Numerical results are obtained and compared with previous theory and with experiment for rectangular grids. Comparison is also made with experiment on a triangular grid which exhibited an anomalous notch in the element pattern. The experimental results in both cases seem to substantiate the theory, at least to the extent that could be expected from the small test arrays that were used for the measurements. The comparison indicates that the method of analysis includes all of the necessary features required for the study of mutual coupling effects in infinite arrays of rectangular waveguides having thick walls.     

High-Permittivity Dielectrics in Waveguides and Resonators

Resonators and waveguides containing a region of high dielectric constant are considered. The dielectric constant is first assumed to be infinite, but is later given a high, but finite value. Perturbation formulas are derived for the resulting shift in either the resonant frequency of the resonator or the wavenumber of the waveguide mode.     

An integral equation analysis of an infinite array of rectangulardielectric waveguides

An integral equation analysis is applied to the study of the propagation characteristics of an infinite array of dielectric waveguides. The geometry under study is assumed to be rectangular. To find the Green's function of the structure, the Floquet theorem is applied such that the mutual coupling between dielectric waveguide elements is effectively included in the analysis. The effect of the coupling on the propagation characteristics of a dielectric waveguide is studied by varying the size of the Floquet cell. The validity of this analysis to simulate the case of an open dielectric waveguide is confirmed by a comparison with previous results, this in spite of the fact that radiation and leaky wave modes are not accounted for. The complex modes due to the periodicity of the structure are found and their properties are described. The analysis presented, with minor modification, can deal with the problems of dielectric image lines, or dielectric-loaded metallic waveguides     

Radiation impedance of a dipole printed on periodic dielectric slabs protruding over a ground plane in an infinite phased array

The radiation impedance of a dipole printed on periodic dielectric slabs standing over a ground plane in an infinite phased array is calculated. The calculation is made by means of modal expansions in terms of longitudinal section electric (LSE) and longitudinal section magnetic (LSM) modes. Derivations of these hybrid space modes and development of the modal expansions are presented first. The impedance of the dipole element is then calculated by a method based on the complex power relations with the aid of Poynting's theorem. The results calculated by the present theory in the limiting case of no dielectric slab loading have been compared with the results calculated by the method of ordinary plane wave expansions. A comparison is also made between results calculated by the theory and the experimental data obtained from waveguide simulators or test array. These results are shown to be in good agreement. An outline of steps to formulate the solution of the current distribution on dipole is also given.     

Generalized Coupled Dielectric Waveguide and its Variants for Millimeter-Wave Applications

The characteristic equations of hybrid TM and TE modes for a generalized coupled dielectric waveguide are derived using the mode-matching technique. From the characteristic equations of the generalized coupled dieketric waveguide, the phase constant, wave impedance, and field distribution can be evaluated. A variety of single and coupled dielectric waveguides can be obtained by assigning proper parameter values to the generalized coupled dielectric waveguide.     

Field Analysis of a Metal-Coated Planar Waveguide with Chiral Core

Eigenequations for a metal-coated planar chiral dielectric waveguide and a mirror-conjugate planar chiral dielectric waveguide are derived. The eigenequations are given in simple formulations. The results indicate that the perfect conductive (or magnetic) boundary can produce mirror-conjugate of chiral media and the left-handed and right-handed circularly polarized modes couple with each other due to the conductive boundary. The propagation characteristics of a metal-coated planar waveguide with chiral core are presented. An interesting phenomenon is observed that the field distributions vary with respect to the operating wavelength.     

绝缘介质波导的单模带宽等传输特性的分析

本文研究了绝缘介质波导两类模式的本征方程的不同表达形式对基模Ey11截止特性的影响,指出采用三角函数的表达形式可避免导致Ey11模有非零截止这一不恰当的结论,推导了四个低阶模存在的条件。在此基础上用正交选优法对绝缘介质波导影响传输特性的五个参数进行选优,得到多组单模带宽较宽,导体损耗和介质损耗较小、外场发散也较小的参数,并与镜象波导作了对比。