A TE/TM modal solution for rectangular hard waveguides
06 Mar 2006-IEEE Transactions on Microwave Theory and Techniques (IEEE)-Vol. 54, Iss: 3, pp 1048-1054
TL;DR: In this article, a TE/TM modal solution for a longitudinally corrugated rectangular waveguide is developed, which can be used to achieve the hard boundary condition resulting in the quasi-TEM wave in a hard waveguide for discrete values of corrugation depth.
Abstract: A TE/TM modal solution for a longitudinally corrugated rectangular waveguide is developed. These longitudinal corrugations can be used to excite a quasi-TEM wave and form a hard waveguide by correctly choosing the impedance at the guide wall. The correctly chosen impedance is referred to as the hard boundary condition. The modal solution developed here solves the problem of longitudinal corrugations filled with a dielectric material by first finding and solving the characteristic equation for a complete TE/TM modal set. It is shown that this TE/TM mode solution can be used to achieve the hard boundary condition resulting in the quasi-TEM wave in a hard waveguide for discrete values of corrugation depth. Beyond each of these depths, a mode becomes a surface wave. The theoretical mode set is amenable to the solution of problems using the mode-matching method. A combination of the mode-matching method and the TE/TM modal solution will allow the solution of larger problems.
Citations
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01 Jan 1996
TL;DR: In this article, the unidirectional current screen was used as an asymptotic strip boundary condition (ASBC) for analysis of field problems containing metal strip grids.
Abstract: We discuss the unidirectional current screen as an asymptotic strip boundary condition (ASBC) for analysis of field problems containing metal strip grids, and we introduce a related asymptotic corrugation boundary condition (ACBC) for analysis of corrugated surfaces. The boundary conditions are asymptotic in the sense that the exact boundary conditions approach the asymptotic ones when the strip and corrugation periods approach zero. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 14: 99–101, 1997.
69 citations
TL;DR: In this paper, the cutoff frequencies of TE and TM waveguides with arbitrary wall impedance were derived for a rectangular waveguide bounded by periodic rectangular corrugations along the direction of mode propagation.
Abstract: The coupled transcendental equations describing cutoff frequencies of TE and TM modes are deduced for a rectangular waveguide with arbitrary wall impedance. In the case of TE modes, their generalization is made to a rectangular guiding structure, which possesses both distributed wall impedance and inhomogeneous dielectric loading. Effective impedance is obtained for imperfectly conducting surface incorporating periodic rectangular corrugations along the direction of mode propagation. Circular waveguide bounded by such corrugated surface and rectangular impedance waveguide are considered as numerical examples. For these waveguides, the computations performed to determine the cutoff frequencies of TE guiding modes are validated against the results of the perturbation theory and the finite-element method.
17 citations
Cites background or methods from "A TE/TM modal solution for rectangu..."
...PDET is FEM-based toolbox, which is capable of solving the eigenvalue problems (1) and (4) for arbitraryshaped waveguide with constant parameters ai and bi on its contour C ....
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...Among them are the field expansion method [15], [16], the finite-element method (FEM) [4], [5], [7], [8] [10], [11], [17], and the finite-difference timedomain method [9], [12], [17], which now find use in various commercial software packages....
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...For example, kx is invariant with ω in the following cases: a1 = a3 = 0 [2]–[4], [6]–[8] (kx = πn/w, n = 0, 1, 2 ....
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...Among them, the best-studied case is that when two opposite walls of the rectangular waveguide possess zero surface impedance [2]–[4], [7], [8]....
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...The numerical results have been validated against those followed from the perturbation theory and the FEM....
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TL;DR: In this article, a continuous transverse stub (CTS) antenna is proposed to achieve circular polarization using a single CTS array and without any polarization converter, where the structure consists of long radiating slots/stubs fed by over-moded parallelplate waveguides.
Abstract: This article presents an efficient analysis method for a novel continuous transverse stub (CTS) antenna. As opposed to state-of-the-art CTS antenna designs, the proposed architecture achieves circular polarization using a single CTS array and without any polarization converter. The structure consists of long radiating slots/stubs fed by over-moded parallel-plate waveguides. More precisely, the transverse electromagnetic (TEM) mode and the first transverse electric (TE1) mode of the feeding waveguides are used to generate a circularly polarized field. The array is analyzed using a spectral mode-matching method. First, the active reflection coefficient of the infinite array is derived in closed form. A windowing approach is then adopted to compute the radiation patterns of finite-size arrays. Numerical results obtained with this method are in excellent agreement with full-wave simulations, carried out with a commercial software. The performance of this class of CTS antennas has been investigated using the developed model. It is theoretically demonstrated that the proposed array can be designed to attain an axial ratio (AR) lower than 3 dB over a 52.9% relative bandwidth at broadside. Furthermore, the active input reflection coefficient is lower than −10 dB over a 40.8% relative bandwidth, when the array steers its main beam at $\theta _{0}=45^\circ $ . This solution is an attractive candidate for next generation satellite communication terminals.
14 citations
Cites background from "A TE/TM modal solution for rectangu..."
...TM1 modes may occur along any eventual discontinuities, a possible solution to cut-off the TM1 mode relies on feeding the slots with longitudinally corrugated PPWs (LCPPWs) [21]–[25]....
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TL;DR: In this article, the problem of determining the eigenmodes of a rectangular waveguide with one hard wall formed by longitudinal corrugations with grooves filled with dielectric is considered.
Abstract: The problem of determining the eigenmodes of a rectangular waveguide with one hard wall formed by longitudinal corrugations with grooves filled with dielectric is considered. The characteristic equation is derived by using the asymptotic boundary conditions for corrugated surfaces. It is shown analytically that if the groove depth is equal to the value 0.25 lambda/(epsilon - 1)(1/2) corresponding to the hard wall condition, the TE eigenmode spectrum of the waveguide contains an infinite set of new non-uniform quasi-TEM modes with different transverse propagation constants in the empty part and identical longitudinal propagation constants equal to the wavenumber k. Analytical solution for the case of excitation of the waveguide by a specified source is given, and an example of forming local quasi-TEM waves is considered and discussed.
9 citations
Cites background from "A TE/TM modal solution for rectangu..."
...Note, that the non-uniform quasi-TEM waves described above represent a new type of the eigenmodes different from the well known uniform quasi-TEM modes existing in the waveguides and horns of rectangular (or square) cross section considered in [9–11]....
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...The concept of artificial electromagnetic hard and soft surfaces or walls [1, 2], that can be realized by corrugations with grooves filled with dielectric or by strips on a grounded dielectric layer, find important applications in design of conical horn antennas [3–8] and pyramidal horn antennas [9–11]....
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Proceedings Article•
23 Mar 2009TL;DR: In this paper, the dispersion equation of a rectangular waveguide with one broad hard wall formed by longitudinal corrugations with grooves filled with dielectric is derived on the basis of using the asymptotic boundary conditions for corrugated surfaces.
Abstract: The problem of determining the eigenmodes of a rectangular waveguide with one broad hard wall formed by longitudinal corrugations with grooves filled with dielectric is considered. The dispersion equation is derived on the basis of using the asymptotic boundary conditions for corrugated surfaces. It is shown analytically that if the groove depth is equal to the value 0.25λ/(e−1)½ corresponding to the hard wall condition, the TE eigenmode spectrum of the waveguide comprises an infinite set of degenerated quasi-TEM modes with different transverse propagation constants and identical longitudinal propagation constants equal to the wavenumber k. Such solutions are important for understanding the local waves appearing along ridges in such waveguides, that has inspired to the invention of new so-called gap waveguides.
6 citations
Cites background from "A TE/TM modal solution for rectangu..."
...Note, that this is a new type of the quasi-TEM modes different from the well-known TEM mode existing in a rectangular waveguide with corrugated hard walls [13], [14]....
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References
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TL;DR: In this paper, a classical-type approach is used to analyze the hard horn antenna and the quasi-TEM mode in the longitudinally corrugated cylindrical waveguide is found by using the homogenized asymptotic boundary conditions.
Abstract: In this paper, a classical-type approach is used to analyze the hard horn antenna. The quasi-TEM mode in the longitudinally corrugated cylindrical waveguide is found by using the homogenized asymptotic boundary conditions. The finite horn length is accounted for by including a phase factor in the waveguide-aperture fields, and the radiation patterns are finally obtained by aperture integration. The bandwidth is found to be much wider than previously anticipated with respect to low cross-polarization. Also, an advanced mode-matching code has been used for verification of the aperture field and the radiation patterns obtained with the much faster classical model.
6 citations
01 Feb 2004
TL;DR: In this paper, a hard horn was proposed to achieve the hard boundary condition by using longitudinal corrugations filled with a low-loss dielectric material along the vertical walls.
Abstract: In recent years, there has been significant interest in the use of corrugated, periodic structures to control the wave impedance of a given surface. It has been shown [1] that a quasi-transverse-electromagnetic (TEM) wave can be excited in a waveguide by correctly choosing the impedance at the guide wall. This correctly chosen impedance is referred to as the hard boundary condition. We have taken advantage of this property of the so-called “hard” guide to attempt to create a spatial power combiner/splitter that couples to an array of microstrip patch antennas feeding a bank of monolithic microwave integrated circuit (MMIC) power amplifiers. The hard horn described here employs longitudinal corrugations filled with a low-loss dielectric material along the vertical walls to achieve the hard boundary condition. We believe the use of dielectric-filled corrugations will improve the insertion loss performance over that of a hard guide using dielectric slabs bonded to the guide wall. Additionally, the horn is tapered to its maximum aperture along a cosine curve in order to improve return loss performance. Included in this article is a discussion of the fabrication process of prototype hard horns, measurements of a hard horn prototype, and preliminary modal analysis results.
3 citations
"A TE/TM modal solution for rectangu..." refers background or methods in this paper
...This leads to a TE/TM mode representation [10] for longitudinally corrugated waveguides, which extends the original quasi-TEM solution of Kildal [4]....
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...For modes satisfying these symmetry conditions [10], we expand the propagating field in the center region and seek their forward and reflected modal coefficients [16]...
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2 citations
TL;DR: In this paper, the scattering matrices representing all possible transformations of modal bases in rectangular waveguide are presented, without requiring the use of a common modal base for the characterization of each element.
Abstract: The excitation of hybrid modes by discontinuities in rectangular waveguide can often be decomposed into separate LSE/LSM or TE/TM mechanisms, so that each component can be analyzed with the most suitable modal base. Correct interfacing, however, is required. We report the scattering matrices representing all the possible transformations of modal bases in rectangular waveguide. Such matrices provide an useful tool to simulate complex circuits made up of components strongly interacting, without requiring the use of a common modal base for the characterization of each element. Since the transformation matrices can easily include pieces of transmission lines, their use does not require any additional computation effort.
2 citations
1 citations
"A TE/TM modal solution for rectangu..." refers result in this paper
...As previously reported [12]–[14], the standard TM modes for a rectangular waveguide satisfy the hard boundary condition for this excitation....
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...Contrary to [12] and postulated previously [13], [14], TE modes can also exist, albeit in a modified form....
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