Waveguide Junction Research Articles

Coupling enhancement of waveguide‐fed dielectric resonator antenna

AbstractIn this article, a novel method is presented to improve the coupling of dielectric resonator antenna (DRA) excited by a waveguide slot at the shorted end.A rectangular DRA is excited by a thick ground plane slot, which is fed by a capacitive waveguide junction (CWJ)‐coupled waveguide end. The objective of using a CWJ is to substantially increase the power coupling to the DRA. Measurements were carried out to verify the design, and a reasonable agreement between them is obtained. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:769–770, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25819

ANALYSIS AND DESIGN OF CRUCIFORM WAVEGUIDE JUNCTION WITH A CONDUCTING DIAPHRAGM AND A DIELECTRIC LAYER IN THE MAIN ARM

This paper proposes a rigorous theory of the H-plane four- port (cruciform) waveguide junction with a conducting diaphragm and a dielectric layer in the main (input) waveguide arm. This theory is based on the mode matching method in conjunction with Fourier transform technique and including the edge conditions in vicinity of the diaphragm edges. The numerical analysis of the cruciform waveguide junction is done, and optimal parameters of inclusions are predicted based on the minima of voltage standing wave ratio (VSWR) in the main arm.

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.

Three-dimensional waveguide junctions inside glass

Three-dimensional waveguide junctions inside glass

Three-dimensional waveguide junctions inside glass

Three-dimensional waveguide junctions inside glass

Plain Models of Very Simple Waveguide Junctions Without Any Solution for Very Rich Sets of Excitations

Almost trivial waveguide junctions involving standard media and metamaterials modelled by effective constitutive parameters are investigated. It is shown that, when some dielectric configurations are present, no solution can be found for these models, for some excitations on the ports which are very regular, are not at all pathological and allow simple modal expansions. The set of excitations for which no solution exists is very rich and contains excitations almost indistinguishable from those for which the solution exists. This lack of solution does not originate, as usual in electromagnetics, from the excitation of a resonance of an ideal cavity. It rather arises from a mechanism similar to the one that causes ill posedness of inverse problems. What is new and unexpected is to find this kind of ill posedness in a direct problem. The well known modal technique is exploited heavily but, quite unusually, to prove the non-existence of solutions rather than to find them. Finally, the importance of results on the a priori well posedness of models is pointed out.

Resonance phenomena in a junction of cylindrical and rectangular waveguides

The electrodynamic and numerical analyses of resonance phenomena in a junction of cylindrical and rectangular waveguides with a magnetodielectric are performed. The applicability of such a junction for nondestructive measurements of the parameters of magnetodielectric specimens of cylindrical and rectangular cross sections is demonstrated.

Eigenoscillations in waveguide junctions filled with an anisotropic dielectric

An electrodynamic model for calculation of the characteristics of waveguide junctions with an anisotropic filling is developed. Several dependences reflecting the relation between the resonance wavelengths of different oscillations and the geometric dimensions of the junction and the components of the filling permittivity tensor are found. These dependences can be used for measurements of the electric characteristics of anisotropic materials. The physics of resonance phenomena is studied.

Nanoengineering Structures on Graphene with Adsorbed Hydrogen “Lines”

It is shown that the lines of adsorbed hydrogen pair atoms divide a graphene sheet into electronically independent strips and form an electron waveguide or 2H-line graphene-based superlattice (2HG-SL). We investigated the electronic properties of such structures in detail. The electronic spectra of a “zigzag” (n,0)-2HG-SL are similar to those of armchair graphene ribbons and have similar oscillation of the band gap with the width between adjacent 2H-lines (number n). The induced strain with the direction perpendicular to the hydrogen pair “lines” significantly changes the electronic properties of the investigated structures. For example, in the case of the 2HG-SL (3n,0) (n > 2) we observed the semiconductor−metal transition. Superlattices of the (n,n) type with a “staircase” of adsorbed pairs of H atoms are semiconductors with nearly linear decreasing of the band gap with increasing n. We found that the configuration with the opposite spin (antiferromagnetic) orientation between ferromagnetically ordered edge states of the (n,n) 2HG-SL is energy favorable. We also suggested an experimental way of fabricating these superlattices. Finally, we discussed properties of possible hydrogen lined waveguide junctions.

Plasmon flow control at gap waveguide junctions using square ring resonators

A compact add-drop coupler with square ring resonator (SRR) in gap plasmon waveguide is studied. It is shown that there exist both travelling-wave and standing-wave resonant modes in the resonator due to the influence of the four corners in the square ring. Based on SRR, a new type of two-dimensional plasmonic L-shaped bend is proposed. The compact geometry and high add-drop efficiency of the proposed structure enable the realization of flexible flow control at waveguide junctions, e.g. T-splitter and waveguide cross intersections, in nano scale. The optical field propagation patterns in the gap waveguide junctions equipped with SRRs are investigated by the finite-difference time-domain method.

METHOD OF MODE MATCHING IN TIME DOMAIN

A new method is presented for analysis of transient electromagnetic flelds in regular structures with abrupt discontinuities. The method is based on mode expansion of the flelds in the Time Domain. The modes propagate independently in the regular parts of the structure and are coupled at the discontinuity. The main idea consists in solving 1D FDTD equations for each independent mode channel in the regular waveguides and using mode-matching at the junction cross-section in order to relate the mode amplitudes in all the channels at the same time instant via imposing boundary conditions. As examples the problems of pulse signal difiraction at a step discontinuity in a parallel-plate waveguide, difiraction at a junction of circular and coaxial waveguides, and pulse radiation of a bi-conical antenna are considered. The latter problem is treated as a junction of two conical lines (one of which is the free space) that are regular in spherical coordinates.

Wideband modelling of cascaded H-plane waveguide junctions using the generalised impedance matrix representation

A strong interest in H-plane waveguide components composed of a large number of cascaded planar junctions is recently renewed. Therefore, the more efficient development of full-wave analysis tools of such devices is again receiving consideration, specially for its potential use within modern design tools. A novel technique for providing the wideband generalised impedance matrix representation of the inductive devices in the form of pole expansions, thus extracting the most expensive computations from the frequency loop is proposed. For such purpose, the whole device is first decomposed into simpler building blocks, i.e. planar junctions and uniform waveguides, which are modelled in terms of the proposed wideband matrices. Then, a novel iterative algorithm for the efficient combination of such matrices is followed. The complete technique has been successfully applied to the full-wave analysis of several inductive waveguide filters of great practical interest.

Low loss optical waveguide crossing based on octagonal resonant cavity coupling

A waveguide crossing utilizing a high index contrast material system is presented. The structure is based on coupling with an octagonal resonant cavity inserted at the waveguide junction. It also employs four identical square metal strips placed at the four corners of the waveguide crossing. The spectral response of the structure calculated using the method of line numerical technique, in general, shows a high power transmission in the forward arm with sufficiently low crosstalk and fraction of radiated power.

Modal analysis and coupling in metal-insulator-metal waveguides

This paper shows how to analyze plasmonic metal-insulator-metal waveguides using the full modal structure of these guides. The analysis applies to all frequencies, particularly including the near infrared and visible spectrum, and to a wide range of sizes, including nanometallic structures. We use the approach here specifically to analyze waveguide junctions. We show that the full modal structure of the metal-insulator-metal MIM waveguides—which consists of real and complex discrete eigenvalue spectra, as well as the continuous spectrum—forms a complete basis set. We provide the derivation of these modes using the techniques developed for Sturm-Liouville and generalized eigenvalue equations. We demonstrate the need to include all parts of the spectrum to have a complete set of basis vectors to describe scattering within MIM waveguides with the mode-matching technique. We numerically compare the mode-matching formulation with finite-difference frequency-domain analysis and find very good agreement between the two for modal scattering at symmetric MIM waveguide junctions. We touch upon the similarities between the underlying mathematical structure of the MIM waveguide and the PT symmetric quantum-mechanical pseudo-Hermitian Hamiltonians. The rich set of modes that the MIM waveguide supports forms a canonical example against which other more complicated geometries can be compared. Our work here encompasses the microwave results but extends also to waveguides with real metals even at infrared and optical frequencies.

FIELD ANALYSIS OF DIELECTRIC WAVEGUIDE DEVICES BASED ON COUPLED TRANSVERSE-MODE INTEGRAL EQUATION-NUMERICAL INVESTIGATION

This is a numerical investigation of a recently proposed for- mulation called coupled transverse-mode integral equation (CTMIE) for analyzing EM fleld properties in general 2-D dielectric waveguide devices. The device is flrst approximated by stack of piece-wise 1-D horizontally layered structures. Transverse fleld components on the in- terface between waveguide slices are unknown functions, which are gov- erned by a coupled integral equation. When unknowns are expanded as a linear combination of given functions, CTMIE is converted to a coupled block matrix equation. We study three waveguide devices, in detail, to understand the relation between modeling parameters and accuracy and convergent rate of the solutions. Examples include a step waveguide junction, a multi-mode interferometer power cross coupler and a linearly tapered waveguide. All results are verifled with inde- pendent calculations using other proven methods.

Electrodynamics of waveguide junctions with anisotropic loading

An electrodynamic model for the calculation of waveguide junctions with anisotropic loading has been built in this study. A wave equation for longitudinal components of hybrid electromagnetic field and a system of linear algebraic equations (SLAE) were obtained. The conditions were found under which the SLAE for HEmnp-oscillations (indexes indicate the number of variations of the field in terms of coordinates x, y, z, respectively) disintegrated into two independent systems corresponding to Hmno — and Eklo-oscillations. The developed algorithm and the software programs were used to carry out numerical analysis for these modes of oscillations that are of practical interest. The recommendations are given on the use of waveguide junctions for measuring components of the dielectric permittivity tensor of anisotropic crystals.

Modeling and Analysis of Round End Slots in Rectangular Waveguides

Modeling and analysis of rectangular waveguide fed round end slots with two different sets of curvatures at the ends are presented in this paper. Performance characteristics of a waveguide slot radiator with transverse wall round end radiating slot and a 2-port waveguide junction with a round end coupling slot in the common cross-section of the rectangular waveguide are evaluated by the method of moments for three different slot models considered – namely, the rectangular end slot, round end slots of Type 1 and Type 2 curvatures. The analysis and formulations have been carried out by considering the thick radiating/coupling slot as a stub waveguide. Entire sinusoidal basis functions and Galerkin’s type of inner product are implemented. The variation of the performance characteristics obtained for the different slot models are compared with experimental results for transverse wall slot radiators and slot coupled junctions.

Design of Circular Corrugated Waveguides to Transmit Millimeter Waves at ITER

Low-loss circular waveguides will be needed for a large number of millimeter-wave transmission lines on ITER, including those transmitting electron cyclotron power and diagnostic signals. In order to provide low-loss transmission, the waveguides need to be several wavelengths in diameter. Corrugating the walls reduces the loss further not only in straight runs but also at bends, and makes the waveguide robust against small deformations. We present results of theoretical calculations showing that these properties can be maintained over very wide bandwidths suitable for ITER applications. The computer code used to make these calculations is based on a space-harmonic analysis of the fields. Measurements on waveguides are described that validate the theory for corrugated waveguides semiquantitatively. Tolerances on the corrugation geometry, waveguide bore, waveguide junctions, input Gaussian beam alignment, and waveguide support alignment are discussed. It is shown that the low-loss properties of corrugated waveguide are insensitive to many variations in geometry and deviations from ideality. Finally, some fabrication considerations are presented. In order to provide more complete coverage of the waveguides themselves, only brief mention is made of the losses due to input coupling and components such as bends. Some review material and some level of technical detail are both presented.

The theory of a plane transverse junction of open waveguides

A rigorous analytic approach to solution of the problem of wave propagation through a plane transverse junction of two open waveguides is proposed. According to the method developed, the problem is reduced to a system of integral equations of the second kind, which is solved with the help of iterations. The use of the method is exemplified by its application to the problem for a coaxial junction of two circular metal/dielectric waveguides.

Transmission Line and Equivalent Circuit Models for Plasmonic Waveguide Components

Modeling of waveguide junctions using transmission lines and lumped circuit elements is common practice in microwave networks. By the help of the scattering matrix formalism, it is possible to describe junction effects in a very concise way. Such a representation is crucial for the design of complex systems containing many interacting parts. Using scattering matrices, we characterize symmetric junctions between 2-D metal--insulator--metal (MIM) waveguides with optical signals at infrared frequencies (1550 nm) propagating in them. We verify our characterization by perfectly matching a wavelength-sized MIM waveguide to a subwavelength-sized one using a Smith chart. We then map the scattering matrix description to an equivalent lumped circuit representation and discuss the physical significance of its elements. We show that the simplified characteristic impedance model is appropriate for the deep subwavelength regime. The scattering matrix model for the MIM junctions leads to simplified analysis that can be integrated into circuit modeling software packages, such as SPICE.