Impulse signal propagation in open dielectric circular waveguide

The dispersion characteristics of a circular dielectric waveguide with periodic metallic strips are analyzed by the Galerkin's method. After obtaining the rigorous dispersion equation, the dispersion curves for both TE01 and TM01 modes are calculated by the improved Newton's method. The variations of the normalized center frequency, width and maximum attenuation constant of the stopband with the normalized width of the metallic strips are given. The convergence properties of numerical solutions are also discussed. On the basis of the analysis, some useful guidelines for filter design are thereby suggested.

A variational method based on the telegraphist's equations is used to calculate the dispersion characteristics of cylindrical dielectric waveguides. These waveguides are enclosed by perfectly conducting walls with a rectangular cross section. In order to show the possibility of these structures to work as power-dividers and filters, multiple disconitinuities in circular dielectric waveguides were analyzed. For this, a procedure which combines the variational method with the modal matching technique has been implemented. Theoretical and experimental results are given.

A new ray representation of electromagnetic field inside a quasi-optical structure in the form of a circular hollow dielectric waveguide (HDW) is suggested, which permits, among other things, estimating the dimensions of the measurement area for the free-space scattering characteristics of an object that can be measured in the millimeter- and submillimeter-wave regions by putting the object into a circular HDW.

A new universal and efficient algorithm is developed for solution of the problem of wave diffraction by a body of revolution located inside a circular dielectric waveguide. The coordinate dependences of the field and the dependences of the mode reflection and transmission coefficients on the dimensions of the body are obtained for various geometries of the body.

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Sections of circular open dielectric waveguides are used as irradiators of radio interferometers of fast processes operating in the millimeter wavelength range. For correct diagnostics of the obtained results, it is necessary to have a radiation field from the end of the waveguide (wave beam) with a given distribution over transverse coordinates. The possibility of forming an axial radiation field from the end of a circular open dielectric waveguide with a given radial distribution has been theoretically shown, implying the use of a spatial filter in the form of a thin dielectric plate made of a material with an absorption coefficient changing according to a radial law, placed on the end of a conically expanding waveguide. The results of the work can be used in the construction of irradiators of UHF radio interferometers.

The finite-element method is applied to the modal analysis of unbounded, arbitrarily shaped, and arbitrarily inhomogeneous dielectric waveguides with the use of new infinite elements incorporating several radially decaying exponential trial functions. The outer optimization loop required by methods that use a single decaying trial function is eliminated, and all modes corresponding to a given phase constant are calculated in one pass of the solver. The method is tested for examples involving slab, circular, and square dielectric waveguides. >

In this paper, a novel circular cross-coupled dielectric waveguide filter is designed based on 45-degree sectoral waveguide resonators. The filter is composed of eight identical resonators with a tuning blind hole arranged above each resonator. The positive coupling is realized by the combination of a partition wall and shallow blind hole, and the negative coupling is realized by the combination of a partition wall and a deep blind hole. The filter finally realizes an excellent performance with a center frequency of 3.5GHz, a passband bandwidth of 260MHz, an in-band return loss of more than 19dB, two steep transmission zeros at 3.31GHz, and 3.7GHz respectively, and a remote suppression of more than 40dB. In this design, the dielectric waveguide is used to successfully realize the miniaturization of the filter. The designed filter can be applied to the base station in 5G band.

New boundary integral equation method which was previously proposed have been examined in detail and extended to the computer‐aided design (CAD) of asymmetrical dielectric slab waveguide bends. Many numerical results of symmetric waveguide discontinuities and asymmetric waveguide bends confirm the validity of the new method. They show that all numerical results satisfy the energy conservation law within an accuracy of 1% and indicate that the new integral equation method is very suitable for the basic theory or a solver of CAD software for various open dielectric waveguide circuits.

At mm- and sub-mm-wave frequencies dielectric waveguides (DWGs) are an interesting alternative to commonly used metallic waveguides. DWGs have lower losses, lower weight and increased flexibility. In addition, dielectric waveguides can be designed for minimal waveguide dispersion over a wide frequency range. For instance, a short section of a metallic waveguide might be more dispersive than several meters of a dispersion-minimized dielectric waveguide. To replace metallic waveguides by DWGs a transition between both waveguide types is needed. In order to benefit from the low dispersion and low losses of DWGs, in this paper a low-dispersive, low-loss transition from circular metallic waveguide to circular dielectric waveguide is presented. The circular feeding waveguide allows dual or circular polarized wave propagation along the DWG.

We present here the solution of the eigenvalue problems for the open metamaterial square and circular rod waveguides. The Maxwell's equations for the electrodynamical analysis of the open waveguides were solved by the Singular Integral Equations' (SIE) method and partial area method. Our SIE method is pretty universal and let us rigorously analyze open waveguides electrodynamically with any arbitrary cross-sections taking into account of the edge condition. The false roots did not occur applying the SIE method. The waveguide media can be of strongly lossy materials. The signs of the complex permittivity and permeability can be positive or negative in difierent combinations. We used our computer algorithms based on the two mentioned methods with 3D graphical visualization in the MATLAB language. We present here our numerical calculations of the metamaterial square waveguide with sides equal to 5 ¢ 10 i3 m and the metamaterial circular waveguide with the diameter equal to 5¢10 i3 m. We present dependences of phase constant and attenuation constant of metamaterial waveguides at the frequency range from 75GHz till 115GHz. We have compared the three dimension (3D) electric fleld distributions of the main mode and the flrst higher mode propagating in the square and circular metamaterial waveguides. The calculations of the electric flelds were fulfllled at approximately 10000 points in every cross-section. We discovered that the electric fleld is concentrated at the waveguide boundary. The distribution of the electric fleld along the perimeter of the waveguide is not uniform. There are two areas on the perimeter of the square and circular waveguides

The eigenequation of a circular chiral ferrite dielectric waveguide is derived. The effects of chiralities in the core and cladding on the cutoff, the dispersion characteristics, and the field distributions are investigated. The results show that, not only the cutoff frequencies, but also the dispersion curves of HE and EH modes with the same mode number separate, and the chiralities in the core and cladding have different effects on the cutoff and dispersion characteristics. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 143–146, 2001.

Electromagnetic waves in loaded cylindrical structures : a radial transmission line approach

We have developed flexible circular dielectric waveguide for millimeter-wave and terahertz frequency applications. In the millimeter and terahertz frequency range, over 70 GHz, metallic waveguide transmission line is generally used. However, it is hard to build-up the system due to noflexibility of metallic waveguide lines. High density polytetrafluoroethylene, i.e. PTFE, is used for developed dielectric waveguide lines. The PTFE has dielectric permittivity constant of approximately 2.0 with low loss, tanδ <; 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> . In the developed dielectric waveguide, the electromagnetic wave can transmit with single mode over 60 GHz and multimode over 90 GHz. The proposed dielectric waveguide has also demonstrated the on-wafer measurements for verification devices compared to on-wafer measurement built up by conventional 1.0 mm coaxial cable system. As the comparison results, the proposed dielectric waveguide can potentially be applied to on-wafer measurement at millimeter-wave frequency and above.

[EN] The general goal of this thesis is the development of a basic tool for the analysis of passive microwave and millimetre-wave devices used in the new generation of communication systems. In particular, the work is focused on the development of a tool for an efficient and accurate modal characterization of passive devices composed of waveguides with arbitrary cross section.&#13;\nIn order to achieve this goal, a method recently arisen and called BI-RME (Boundary Integral - Resonant Mode Expansion) is extended. This method has been revealed as one of the most appropriate, for its high computational efficiency, to characterize waveguides with arbitrary cross section. Regarding the original BI-RME method, this one will improve the precision and the efficiency of the modal solution in presence of circular and elliptic perturbations in the arbitrary waveguide contour.&#13;\nThen, the first work consists on extending the original BI-RME method theory to circular and elliptic geometries including the possibility to connect these two new types of segments (circular and elliptic) with the straight segments used until now in the practical implementation of the method.&#13;\nIn order to validate the new developed theory, a set of parameters as the cut-off frequencies, the cut-off wavelengths or the electromagnetic fields of canonical waveguides and arbitrarily shaped waveguides of great practical interest, are calculated. These results are compared with analytical well-known solutions or results published in the literature.&#13;\nOnce the electromagnetic modal chart of different arbitrarily shaped waveguides is obtained, the following step is the computation of the coupling integrals between these modes and the ones of the rectangular waveguide that completely surrounds the arbitrary contour. Such integrals are essential for the modal analysis of microwave passive structures involving waveguides with arbitrary cross section.&#13;\nFor this purpose, the new extended BI-RME method is included into a software package tool based on the integral equation method, which allows to characterize efficiently waveguide discontinuities by means of inmitance matrices (admittance or impedance). This efficient full-wave analysis method requires the knowledge of the modal chart related to all the waveguides included in the devices under consideration, as well as the coupling integrals between the modes of the two waveguides composing the discontinuity. In the rectangular waveguides case this modal information can be easily obtained in an analytical way. However, when a waveguide or both have arbitrary cross section, the accurate and efficient modal analysis can be obtained by means of the BI-RME method.&#13;\nThe use of the integral equation method based on admittance or impedance matrices to characterize devices composed of cascading waveguides is specially advantageous because it leads to a linear system of equations. The coefficients matrix of this linear system presents a banded structure that can be appropriately exploited to increase the computational efficiency associated to the resolution of the aforementioned system, and to reduce considerably the computational cost associated to the analysis of complex devices.&#13;\nNext step is the demonstration that in waveguides with arbitrary cross section and with one or two symmetry axes you can generate, also by means of the BI-RME method, the whole family of waveguide modes, so that they verify a certain fictitious boundary condition of electric or magnetic walls in the symmetry plane, and the advantages regarding the computation of the modes are discussed. Furthermore, those different symmetry families of waveguide modes propagate in an independent way along the structures constituted by a connection of uniform waveguides. This situation can also be exploited to increase in a remarkable way the efficiency of the Computer-Aided-Design (CAD) electromagnetic software packages.&#13;\nOnce verified with success the efficiency and precision of the new CAD tool developed by means of the analysis of transitions published in the related technical bibliography, the analysis of really complex passive waveguide devices is performed. Some passive waveguide devices analyzed are for instance a filter with inductive coupling windows and tuning screws, a filter with rounded corners, dual mode filters in circular waveguide with elliptic irises or in elliptic waveguides, an evanescent filter, a low bandpass filter in coaxial waveguide, and finally a new 90º twist component for space applications. The simulated results are totally validated by means of comparison with other data published in the related technical bibliography, or by means of measurements of manufactured prototypes.&#13;\nFinally, the conclusions of this work are extracted and future research lines are outlined. Publications in journal and congress presentations in the framework of this thesis are also indicated.