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Y.V.K., A.S., and S.K.I. acknowledge funding of this study by RFBR and DFG according to the research project no. 18-502-12080 and SZ 276/19-1. V.V.K.acknowledges financial support from the Portuguese Foundation for Science and Technology (FCT) under Contract no. UIDB/00618/2020. Y.V.K.and L.T. acknowledge support from the Government of Spain (Severo Ochoa CEX2019-000910-S), Fundació Cellex, Fundació Mir-Puig, Generalitat de Catalunya (CERCA program), and NEPA: PGC2018-097035-B-I00 project funded by MCIN/ AEI /10.13039/501100011033/ FEDER “A way tomake Europe"., Peer Reviewed, Postprint (author's final draft)

This article presents a new, very compact silicon-micromachined two-port waveguide platform that features axial ports but allows to integrate waveguide devices, which is enabled by integrated broadband, back-to-back, stepped E- and H-plane bends. This approach of rotating the waveguide plane in two axes enables devices of complex geometry to be directly mounted between two waveguide flanges. A prototype transition operating at 220-320 GHz has experimentally demonstrated an insertion loss of less than 0.2 dB and a return loss of better than 18.5 dB throughout the entire WM-864 waveguide band, characterized by an integrated on-chip waveguide calibration kit. Two 5th-order waveguide filters have been designed as complex demonstrator devices and co-fabricated with the proposed axial integration platform, demonstrating a direct-coupled filter at 270 GHz and a cross-coupled filter at 300 GHz with three transmission zeros. The filters with 1.85% and 2% fractional bandwidths demonstrate a measured insertion loss of 1.92 and 1.50 dB, respectively, to which the two transitions combined add a total of 0.3 dB, and a return loss of 19 and 15 dB in the passbands, respectively. The unloaded Q -factors for the resonator cavities of the two filters were extracted to 750 and 900, respectively. These results are so far unparalleled for filters of similar complexity in this frequency range. The sensitivity to fabrication tolerances is analyzed., QC 20220921

This paper presents a narrowband silicon-micro machined 4th-order waveguide filter concept at 300 GHz with 2% fractional bandwidth, which is highly compact and has axial port arrangements, so that it can be mounted directly between two standard waveguide flanges without needing any split-block interposers. This filter is composed of four TE101 series resonators arranged in one plane which leads to a very small size in real application direction. Underetching effects on the response of the filter are investigated. Prototype devices are fabricated by deep-silicon etching on silicon-on-insulator wafers with a standard process. The measured passband insertion loss is 1.65 dB. The corresponding extracted unloaded quality factor of the resonators is about 600. The filters demonstrate excellent repeatability of the measured S-parameters on a single chip. The presented filters are extremely compact in terms of size; their footprints have areas of only 2 mm2, and the length reaches 0.6 mm in the practical application direction., Part of proceedings: ISBN 978-1-7281-3517-5QC 20200702

This paper deals with the propagation of electromagnetic waves in cylindrical waveguides with irregularly deformed cross-sections. The general theory of electromagnetic waves is of high interest because of its practical use as a transmission medium. But only in a few special cases, an analytic solution of Maxwell's equations and the appropriate boundary conditions can be found (Spencer 1951). The coupled-mode theory, also known as Schelkunoff's method, is a semi-numerical method for computing electromagnetic waves in hollow and cylindrical waveguides bounded by perfect electric walls (Saad 1985). It allows to calculate the transverse field pattern and the propagation constant. The aim of this paper is to derive the so-called generalized telegraphist's equations for irregular deformed waveguides. Subsequently, the method's application will be used on a circular waveguide as an illustrating example.

Propagation of monochromatic nonlinear symmetric hybrid waves in a cylindrical nonlinear inhomogeneous metal–dielectric waveguide is considered. The physical problem is reduced to solving a transmission eigenvalue problem for a system of ordinary differential equations where spectral parameters are the wave propagation constants. The setting under study is reduced to a new type of nonlinear eigenvalue problem. An analytical method for solving this problem is elaborated. For the numerical solution, a method is proposed based on solving an auxiliary Cauchy problem (a version of the shooting method). As a result of comprehensive numerical modeling, new propagation regimes are discovered.

The propagation of monochromatic electromagnetic waves in a cylindrical anisotropic metal-dielectric waveguide is considered. The physical problem is reduced to solving a transmission eigenvalue problem for a system of ordinary differential equations. Spectral parameters of the problem are propagation constants of the waveguide. Numerical results are found with a projection method., Project Largescale

The propagation of monochromatic electromagnetic waves in a cylindrical anisotropic inhomogeneous waveguide with longitudinal magnetization is considered. The physical problem is reduced to solving a transmission eigenvalue problem for a system of ordinary differential equations. Spectral parameters of the problem are propagation constants of the waveguide. Numerical results are obtained using a modification of the projecting methods. The comparison with known exact solutions (for particular values of parameters) are made. © 2018 Electromagnetics Academy. All rights reserved., Export Date: 4 June 2018; Conference Paper, Project Largescale

We present an analysis on wave propagation in superconducting circular waveguides. In order to account for the presence of quasiparticles in the intragap states of a superconductor, we employ the characteristic equation derived from the extended Mattis-Bardeen theory to compute the values of the complex conductivity. To calculate the attenuation in a circular waveguide, the tangential fields at the boundary of the wall are first matched with the electrical properties (which includes the complex conductivity) of the wall material. The matching of fields with the electrical properties results in a set of transcendental equations which is able to accurately describe the propagation constant of the fields. Our results show that although the attenuation in the superconducting waveguide above cutoff (but below the gap frequency) is finite, it is considerably lower than that in a normal waveguide. Above the gap frequency, however, the attenuation in the superconducting waveguide increases sharply. The attenuation eventually surpasses that in a normal waveguide. As frequency increases above the gap frequency, Cooper pairs break into quasiparticles. Hence, we attribute the sharp rise in attenuation to the increase in random collision of the quasiparticles with the lattice structure.

We present an analysis on wave propagation in superconducting circular waveguides. In order to account for the presence of quasiparticles in the intragap states of a superconductor, we employ the characteristic equation derived from the extended Mattis-Bardeen theory to compute the values of the complex conductivity. To calculate the attenuation in a circular waveguide, the tangential fields at the boundary of the wall are first matched with the electrical properties (which includes the complex conductivity) of the wall material. The matching of fields with the electrical properties results in a set of transcendental equations which is able to accurately describe the propagation constant of the fields. Our results show that although the attenuation in the superconducting waveguide above cutoff (but below the gap frequency) is finite, it is considerably lower than that in a normal waveguide. Above the gap frequency, however, the attenuation in the superconducting waveguide increases sharply. The attenuation eventually surpasses that in a normal waveguide. As frequency increases above the gap frequency, Cooper pairs break into quasiparticles. Hence, we attribute the sharp rise in attenuation to the increase in random collision of the quasiparticles with the lattice structure.

We present an analysis on wave propagation in superconducting circular waveguides. In order to account for the presence of quasiparticles in the intragap states of a superconductor, we employ the characteristic equation derived from the extended Mattis-Bardeen theory to compute the values of the complex conductivity. To calculate the attenuation in a circular waveguide, the tangential fields at the boundary of the wall are first matched with the electrical properties (which includes the complex conductivity) of the wall material. The matching of fields with the electrical properties results in a set of transcendental equations which is able to accurately describe the propagation constant of the fields. Our results show that although the attenuation in the superconducting waveguide above cutoff (but below the gap frequency) is finite, it is considerably lower than that in a normal waveguide. Above the gap frequency, however, the attenuation in the superconducting waveguide increases sharply. The attenuation eventually surpasses that in a normal waveguide. As frequency increases above the gap frequency, Cooper pairs break into quasiparticles. Hence, we attribute the sharp rise in attenuation to the increase in random collision of the quasiparticles with the lattice structure.

In this paper, a new systematic technique to design manifold-coupled multiplexers in waveguide technology is proposed. The new technique uses generalized low-order electromagnetic (EM) distributed models, which constitute a half-way point between the fast, but imprecise, analytical models, and the more accurate, but costly, full-wave EM models. The method can be applied to contiguous and noncontiguous channel multiplexers, in both E-plane or H-plane configurations. This paper covers the complete design procedure for manifold multiplexers, starting from the required specifications and finishing with the physical dimensions. After explaining the general design technique for multiplexers with channel filters based on transmission-line resonators, the method is specialized for the design of classic multiplexers with circular-waveguide dual-mode filters. As a further application example, the same methodology is also used for the design of a nonconventional tuningless wideband multiplexer with a new type of rectangular waveguide filters. This paper is concluded with a comparison between simulation and measurements for the wideband multiplexer. Excellent agreement between measurements and simulations are demonstrated, thereby validating the complete design procedure.

Owing to the recent research a method of estimating transmission coefficients for a waveguide of rectangular cross-section loaded with multi-layered parallel-plane dielectrics is found. Consequently, the analysis of the transmitted and reflected fields in terms of the scattering matrix formalism can be performed explicitly. This article is mainly based on comparisons between real measured and computed transmission coefficients of a waveguide filter. the computation employs analysis of closed-form solutions and numerical multi-parameter optimization. the presented waveguide filter is formed by multi-sectional diaphragms placed in a waveguide of rectangular cross-section. Comparison of the computed and measured transmission coefficients demonstrates that the difference is very low, rather marginal and thus the output of the work is considerably promising.

The vector problem of time-harmonic electromagnetic wave diffraction by a system of non-intersecting solid inhomogeneous bodies, infinitely thin perfectly conducting screens and wire antennas is considered. The original boundary value problem for Maxwell’s equations is reduced to a system of integro-differential equations over the volume domains, the screen surfaces and antennas. To solve the integral equations approximately, the Bubnov-Galerkin method is applied; basis functions on the body, the screens and antennas are introduced as well as formulas for matrix elements in the Galerkin method. To solve the problem of diffraction by obstacles of complex shape, the subhierarchical approach is applied. © 2015 IEEE., Article number: 7297389

In this paper, a new systematic technique to design manifold-coupled multiplexers in waveguide technology is proposed. The new technique uses generalized low-order electromagnetic (EM) distributed models, which constitute a half-way point between the fast, but imprecise, analytical models, and the more accurate, but costly, full-wave EM models. The method can be applied to contiguous and noncontiguous channel multiplexers, in both E-plane or H-plane configurations. This paper covers the complete design procedure for manifold multiplexers, starting from the required specifications and finishing with the physical dimensions. After explaining the general design technique for multiplexers with channel filters based on transmission-line resonators, the method is specialized for the design of classic multiplexers with circular-waveguide dual-mode filters. As a further application example, the same methodology is also used for the design of a nonconventional tuningless wideband multiplexer with a new type of rectangular waveguide filters. This paper is concluded with a comparison between simulation and measurements for the wideband multiplexer. Excellent agreement between measurements and simulations are demonstrated, thereby validating the complete design procedure.

We present a solution of the inverse problem of reconstructing boundary deformations in a coaxial cylindrical waveguide by using a first order perturbation method applied to the dominant TEM-mode. We have applied and investigated different orders of Tikhonov regularization using the L-curve criterion. The reconstruction results from using reflection data are presented and they indicate an agreement between the reconstructed and true continuous functions that describe the deformations of the waveguide boundaries., QC 20150521

Circular waveguides, either employed as resonant cavities or as irises connecting adjacent guides, are widely present in many passive components used in different applications (i.e., particle accelerators and satellite subsystems). In this paper, we present the study of the multipactor effect in circular waveguides considering the coexistence of the two polarizations of the fundamental TE11 circular waveguide mode. For a better understanding of the problem, only low multipactor orders have been explored as a function of the polarization ellipse eccentricity. Special attention has been paid to the linear and circular polarizations, but other more general configurations have also been explored.

This paper presents a hybrid antenna design for an optically powered super high frequency (SHF) radio frequency identification transponder applicable for the integration into metal. The key feature of the antenna is its ability to receive microwave signals at SHF for data communication and optical signals for the power supply of the transponder. The antenna design is based on a circular waveguide which is filled with a bundle of polymer optical fibers to guide light to the photodiodes. In addition, a transition is placed within the circular waveguide to transfer the waveguide mode of the SHF signal into a microstrip mode which is a more suitable structure for the integration of electronic transponder components. This paper discusses the constraints and solutions for the aforementioned combination of SHF microwave and light. The figures of merit of the optical power supply are presented, including considerations of the light distribution and the obtained power as a function of the incident angle and the used polymer optical fiber diameter. Furthermore, the measured gain and return loss of the SHF antenna structure is compared to the simulated results. © Cambridge University Press and the European Microwave Association, 2013.

[EN] A polarization rotator in silicon-on-insulator technology based on breaking the symmetry of the waveguide cross section is reported. The 25-mu m-long device is designed to be integrated with standard grating couplers without the need for extra fabrication steps. Hence, fabrication is carried out by a 2-etch-step complementary metal-oxide-semiconductor compatible process using 193-nm deep ultraviolet lithography. A polarization conversion efficiency of more than -0.85 dB with insertion losses ranging from -1 to -2.5 dB over a wavelength range of 30 nm is demonstrated. © 1989-2012 IEEE

[EN] A polarization rotator in silicon-on-insulator technology based on breaking the symmetry of the waveguide cross section is reported. The 25-mu m-long device is designed to be integrated with standard grating couplers without the need for extra fabrication steps. Hence, fabrication is carried out by a 2-etch-step complementary metal-oxide-semiconductor compatible process using 193-nm deep ultraviolet lithography. A polarization conversion efficiency of more than -0.85 dB with insertion losses ranging from -1 to -2.5 dB over a wavelength range of 30 nm is demonstrated. © 1989-2012 IEEE

[EN] A polarization rotator in silicon-on-insulator technology based on breaking the symmetry of the waveguide cross section is reported. The 25-mu m-long device is designed to be integrated with standard grating couplers without the need for extra fabrication steps. Hence, fabrication is carried out by a 2-etch-step complementary metal-oxide-semiconductor compatible process using 193-nm deep ultraviolet lithography. A polarization conversion efficiency of more than -0.85 dB with insertion losses ranging from -1 to -2.5 dB over a wavelength range of 30 nm is demonstrated. © 1989-2012 IEEE

“© 2012 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”, In this paper, a full-wave method for the electromagnetic analysis of dielectric-loaded cylindrical and coaxial waveguides and cavities is developed. For this purpose, a new four-port ring network is proposed, and the mode-matching method is applied to calculate the generalized admittance matrix of this new structure. A number of analyses on dielectric-loaded waveguide structures and cavities have been conducted in order to validate and to assess the accuracy of the new approach. The results have been compared with theoretical values, numerical modeling from the literature, and data from commercial electromagnetic simulators. The method has been also applied to the accurate determination of dielectric properties, and we provide an example of these measurements as another way to validate this new method. © 1963-2012 IEEE.

We present an accurate approach to compute the attenuation of waves, propagating in circular waveguides with lossy and superconducting walls. A set of transcendental equation is developed by matching the fields at the surface of the wall with the electrical properties of the wall material. The propagation constant kz is found by numerically solving for the root of the equation. The complex conductivity of the superconductor is obtained from the Mattis-Bardeen equations. We have compared the loss of TE11 mode computed using our technique with that using the perturbation and Stratton’s methods. The results from the three methods agree very well at a reasonable range of frequencies above the cutoff. The curves, however, deviate below cutoff and at millimeter wave frequencies. We attribute the discrepancies to the dispersive effect and the presence of the longitudinal fields in a lossy waveguide. At frequencies below the gap, the superconducting waveguide exhibits lossless transmission behavior. Above the gap frequency, Cooper-pair breaking becomes dominant and the loss increases significantly.

Using near-field, terahertz time-domain spectroscopy (THz-TDS), we investigate how the addition of a dielectric material into a subwavelength-diameter, cylindrical waveguide affects its transmission properties. The THz electric near-field is imaged with deep subwavelength resolution as it emerges from filled and unfilled waveguides. Spectroscopic data measured for waveguides filled with polycrystalline D-tartaric acid, and with polyethylene and silicon powders, illustrate the feasibility of this approach for obtaining spectroscopic information from a tiny sample volume., Imaging Science and Technology, Applied Sciences

We present an accurate approach to compute the attenuation of waves, propagating in circular waveguides with lossy and superconducting walls. A set of transcendental equation is developed by matching the fields at the surface of the wall with the electrical properties of the wall material. The propagation constant kz is found by numerically solving for the root of the equation. The complex conductivity of the superconductor is obtained from the Mattis-Bardeen equations. We have compared the loss of TE11 mode computed using our technique with that using the perturbation and Stratton’s methods. The results from the three methods agree very well at a reasonable range of frequencies above the cutoff. The curves, however, deviate below cutoff and at millimeter wave frequencies. We attribute the discrepancies to the dispersive effect and the presence of the longitudinal fields in a lossy waveguide. At frequencies below the gap, the superconducting waveguide exhibits lossless transmission behavior. Above the gap frequency, Cooper-pair breaking becomes dominant and the loss increases significantly.

We present an accurate approach to compute the attenuation of waves, propagating in circular waveguides with lossy and superconducting walls. A set of transcendental equation is developed by matching the fields at the surface of the wall with the electrical properties of the wall material. The propagation constant kz is found by numerically solving for the root of the equation. The complex conductivity of the superconductor is obtained from the Mattis-Bardeen equations. We have compared the loss of TE11 mode computed using our technique with that using the perturbation and Stratton’s methods. The results from the three methods agree very well at a reasonable range of frequencies above the cutoff. The curves, however, deviate below cutoff and at millimeter wave frequencies. We attribute the discrepancies to the dispersive effect and the presence of the longitudinal fields in a lossy waveguide. At frequencies below the gap, the superconducting waveguide exhibits lossless transmission behavior. Above the gap frequency, Cooper-pair breaking becomes dominant and the loss increases significantly.

We present an accurate approach to compute the attenuation of waves, propagating in circular waveguides with lossy and superconducting walls. A set of transcendental equation is developed by matching the fields at the surface of the wall with the electrical properties of the wall material. The propagation constant kz is found by numerically solving for the root of the equation. The complex conductivity of the superconductor is obtained from the Mattis-Bardeen equations. We have compared the loss of TE11 mode computed using our technique with that using the perturbation and Stratton’s methods. The results from the three methods agree very well at a reasonable range of frequencies above the cutoff. The curves, however, deviate below cutoff and at millimeter wave frequencies. We attribute the discrepancies to the dispersive effect and the presence of the longitudinal fields in a lossy waveguide. At frequencies below the gap, the superconducting waveguide exhibits lossless transmission behavior. Above the gap frequency, Cooper-pair breaking becomes dominant and the loss increases significantly.

We present an accurate approach to compute the attenuation of waves, propagating in circular waveguides with lossy and superconducting walls. A set of transcendental equation is developed by matching the fields at the surface of the wall with the electrical properties of the wall material. The propagation constant kz is found by numerically solving for the root of the equation. The complex conductivity of the superconductor is obtained from the Mattis-Bardeen equations. We have compared the loss of TE11 mode computed using our technique with that using the perturbation and Stratton’s methods. The results from the three methods agree very well at a reasonable range of frequencies above the cutoff. The curves, however, deviate below cutoff and at millimeter wave frequencies. We attribute the discrepancies to the dispersive effect and the presence of the longitudinal fields in a lossy waveguide. At frequencies below the gap, the superconducting waveguide exhibits lossless transmission behavior. Above the gap frequency, Cooper-pair breaking becomes dominant and the loss increases significantly.

We present an accurate approach to compute the attenuation of waves, propagating in circular waveguides with lossy and superconducting walls. A set of transcendental equation is developed by matching the fields at the surface of the wall with the electrical properties of the wall material. The propagation constant kz is found by numerically solving for the root of the equation. The complex conductivity of the superconductor is obtained from the Mattis-Bardeen equations. We have compared the loss of TE11 mode computed using our technique with that using the perturbation and Stratton’s methods. The results from the three methods agree very well at a reasonable range of frequencies above the cutoff. The curves, however, deviate below cutoff and at millimeter wave frequencies. We attribute the discrepancies to the dispersive effect and the presence of the longitudinal fields in a lossy waveguide. At frequencies below the gap, the superconducting waveguide exhibits lossless transmission behavior. Above the gap frequency, Cooper-pair breaking becomes dominant and the loss increases significantly.

This contribution deals with guided radar distance measurements in the field of industrial tank level control. The aim is to achieve a submillimeter gauging accuracy even when conducting the measurement within a highly dispersive environment of large and thus overmoded circular waveguides. Normally, multimode propagation causes a decrease in measurement precision. Therefore, the effects of intermodal dispersion are fundamentally reviewed and, based on these results, a correlation-based signal processing method is presented. This method is able to exploit the otherwise parasitic dispersion effects to enhance the measurement precision even in constellation with a simple waveguide transition or antenna, respectively. Furthermore, considerations on the mode variety and its influence on the signal complexity as well as investigations on the technique's reliability and accuracy are presented. Measurement results in a frequency range of 8.5-10.5GHz are provided for three different kinds of waveguide transitions proving the capability of the method. © Cambridge University Press and the European Microwave Association 2010.

Using near-field, terahertz time-domain spectroscopy (THz-TDS), we investigate how the addition of a dielectric material into a subwavelength-diameter, cylindrical waveguide affects its transmission properties. The THz electric near-field is imaged with deep subwavelength resolution as it emerges from filled and unfilled waveguides. Spectroscopic data measured for waveguides filled with polycrystalline D-tartaric acid, and with polyethylene and silicon powders, illustrate the feasibility of this approach for obtaining spectroscopic information from a tiny sample volume., Imaging Science and Technology, Applied Sciences

We present a procedure to reconfigure microring resonators based on liquid surface adhesion. Droplets of organic solvents were deposited over Si3N4/SiO2 strip- and slot-waveguide ring resonators, and the transmission spectra were measured several hours after the evaporation of the droplets at room temperature. Our measurements show that the optical properties of the microrings are significantly modified by liquid adhered to the waveguides, persisting even 96 h after bulk evaporation. Liquid-solid interfacial forces slow down liquid evaporation at the nanoscale, enabling permanent photonic configurations. Rewriteability is achieved by removing the adhered liquid with heat., QC 20100525, Sabio

This contribution deals with guided radar level measurements of liquid materials in large metal tubes, socalled stilling wells, bypass or still pipes. In the RF domain these tubes function as overmoded circular waveguides and mode-matched excitation structures like waveguide tapers are needed to avoid higher order waveguide modes. Especially for high-precision radar measurements the multimode propagation effects need to be minimized to achieve submillimeter accuracy. Therefore, a still pipe simulator is introduced with the purpose to fundamentally analyze the modal effects. Furthermore, a generalized design criterion is derived for the spurious mode suppression of compact circular waveguide transitions under the constraint of specified accuracy levels. According to the obtained results, a promising waveguide taper concept will finally be presented. © Author(s) 2008.

Resonances and/or singularities during measurement and calibration often limit the precision of acoustic impedance spectra. This paper reviews and compares several established techniques, and describes a technique that incorporates three features that considerably improve precision. The first feature is to minimize problems due to resonances by calibrating the instrument using up to three different acoustic reference impedances that do not themselves exhibit resonances. The second involves using multiple pressure transducers to reduce the effects of measurement singularities. The third involves iteratively tailoring the spectrum of the stimulus signal to control the distribution of errors across the particular measured impedance spectrum. Examples are given of the performance of the technique on simple cylindrical waveguides.

In this paper, a new spatial-images procedure has been applied to the analysis of microstrip-to-circular waveguide transitions. The numerical technique is based on the utilization of stratified image rings, from which the weights and orientations of either discrete charges or dipole images are determined. This is accomplished by enforcing the scalar and vector potentials' boundary conditions on the cavity walls. The results obtained with the new Green's functions have been compared to those given by a standard integral-equation method based on the free-space Green's functions, and a finite-element implementation. Good agreement is shown between the different techniques, thus demonstrating the usefulness of the new approach.

In this paper, a spatial images technique is used to efficiently calculate the mixed potential Green's functions associated to magnetic sources when they are placed inside a circular cylindrical cavity. The technique places magnetic dipole images and charges outside the cylindrical region. Their strength and orientation are then calculated by imposing the appropriate boundary conditions for the fields at discrete points of the metallic wall. In this paper, the basic technique is combined with spatial domain multilayered Green's functions formulated with Sommerfeld integrals. This allows the analysis of practical multilayered circuits shielded in circular cavities. Convergence results are shown to demonstrate the usefulness of the technique. Two practical microwave circuits are also analyzed to show the validity of the formulation.

Here we study the scattering properties of the section of circular waveguide containing lossy isotropic chiral rod. The effects of the chirality on the polarisation state (electromagnetic field rotation and axial ratio) of fundamental mode propagate in the guide are discussed and verified experimentally., Presented at Intl. Conference on Electromagnetics of Complex Media (8th), Lisbon, PT, 27-29 Sep 2000, p301-304. This article is from ADA398724 International Conference on Electromagnetics of Complex Media (8th), Held in Lisbon, Portugal on 27-29 September 2000. Bianisotropics 2000

A modal analysis of a ridged circular waveguide is presented. The method of Kühn [1] is used to find suitable expressions for the vectorpotentials, wherefore the ridged waveguide is intersected into a lot of regions. With the mode-matching method an infinite set of linear equations is derived. This set of equations is truncated and the behaviour of the eigenvalues is shown.

This paper presents a novel widely tunable, pulsed dye laser with single transverse mode narrow bandwidth which can be constructed by using a grazing- incidence grating in conjunction with a hollow circular dielectric waveguide. The experimental results show that the single transverse mode narrow bandwidth laser output can be obtained while maintaining a high lasing efficiency. The mechanism of the improvement is also discussed in this paper., Trans. of Guangxue Xuebao (China) v11 n9 p844-847 Sep 91.

A circularly polarized, axially symmetric, wide-beam radiator is required in many applications, including TT&C for UAVs and satellites. This report discusses some existing wide-beam antenna designs including divergent lenses and reflectors and introduces a new antenna design. Using a simple dielectric ring in conjunction with a dielectric loaded circular waveguide opening, a near ideal, axially symmetric, hemispheric coverage antenna with circular polarization of good axial ratio and wide-band impedance match is realized. Mechanically, the antenna is small, lightweight, and low cost. The dielectric used is the common Rexolite. Since no lossy materials or resonant scatterers are used, the antenna performance is inherently broadband and low loss. A K sub a-band prototype as well as compact designs for both Q- and K-bands are described.

A broad passband pressure barrier arrangement is provided for insertion in a circular waveguide between a source and a receiver of radio frequency (RF) energy with a spatially circumferential electric field characteristic of the TE 01 mode. At least three abutting cylindrical barrier regions are coaxially aligned and arranged symmetrically in mirror image fashion about a radial plane of the circular waveguide. The cylindrical barrier regions include: at least one solid cylindrical plug region sealed in a cross-section of the circular waveguide and having a longitudinal thickness sufficient to withstand a predetermined pressure load, and at least one solid cylindrical tuning region having a radius less than that of the circular waveguide and further having a longitudinal thickness. Each of the cylindrical barrier regions are defined by a characteristic impedance at opposing end faces thereof and a by characteristic impedance between the opposing end faces. A region-by-region impedance analysis process begins with an end face of the arrangement that is furthest from the source and is completed with an end face of the arrangement that is nearest the source.

Es wird ein Berechnungsverfahren zur Bestimmung der Streuparameter der seitlichen Ankopplung eines Rechteckhohlleiters an einen Rundhohlleiter vorgestellt. Die Anordnung wird in einen Resonator- und drei Hohlleiterbereiche unterteilt. Mit der Methode nach Kühn [1] lassen sich geeignete Ansätze für die Vektorpotentiale finden. Aus den Randbedingungen für das elektromagnetische Feld ergibt sich mit Hilfe der Orthogonalreihenentwicklung ein unendliches System linearer Gleichungen für die Bestimmung der Streuparameter, das abgebrochen und mit numerischen Verfahren gelöst wird. An zwei Beispielen wird die Richtigkeit des Rechenverfahrens durch den Vergleich der berechneten mit gemessenen Streuparametern belegt. © 1994, Walter de Gruyter. Alle Rechte vorbehalten.

Two identical rectangular waveguides are fed by means of two symmetrically placed apertures in a circular waveguide. Power is transmitted from the TMOI mode in the circular waveguide to the TE10 dominant mode in each rectangular waveguide. A computer program for evaluating this power is described and listed. This computer program also evaluates. the magnitude of each orthogonal component of the tangential electric field in the apertures. Sample input and output are provided. Several plots of data obtained by means of the computer program appear in a previous technical report.

Open circular waveguides are used to model jet engine inlets. The exact Wiener-Hopf solution for scattering by a semi-infinite cylinder is studied in the resonance region, where the cylinder diameter is of the order of a wavelength. In particular, the Wiener-Hopf factorization functions are calculated by numerical integration and compared to various approximations, to define regions of validity. Scattering from the rim is studied as a function of frequency, incidence angle, and time. A ray-optic model for rim backscatter is discussed. The relative power absorption of the five lowest order waveguide modes is evaluated. Coupling of incident plane waves to waveguide modes, and radiation by these modes are shown to be related by reciprocity. The waveguide termination model for a jet engine assumes an incident waveguide mode strikes an axially symmetric cone on a flat plate. The various techniques for evaluating scattering by this structure are discussed, and the problem is solved for a few cases. (Author)

An analytical expression for the efficiency of the gyrotron travelling wave amplifier is derived for the case of nonfundamental cyclotron harmonic operation. It scales the efficiency with respect to the modes and parameters of operation and gives the conditions for optimum performance. (Author)

Surface waveguides radiate energy at bends. The asymptotic problem of solving for the radiated power and the radiation pattern for large radius of bend have been studied theoretically for the slab waveguide and for the circular cylindrical waveguide. The slab configuration consists of two semi-infinite slabs joined by a circular bend. The cylindrical configuration consists of two straight circular cylinders joined by a circular bend. The results indicate that the discontinuities at the transitions between the straight sections and the bend cause the radiation to differ significantly from the radiation of a bend of the same size but being part of a uniform circular structure rather than being joined to two straight sections. The radiated power for both the slab and circular cylinder configurations is found to vary inversely as the square of the radius of curvature, and the radiation pattern is composed of many closely spaced narrow lobes. As the radius of curvature of the bend increases the lobes become more numerous and more closely spaced. The results can be extended for use to calculate approximate power loss due to radiation from bends in open waveguides in close proximity to the earth. (Author)

An unsymmetrically corrugated TE01 mode circular waveguide bend. Unsymmetrical corrugations approximately one=aurater wavelength deep are utilized to suppress energy transfer to other modes inherent in smooth wall circular guide bends. The corroguations are comprised of a plurality of adjacent internal ridges and valleys having substantially parallel walls such that the distance between the parallel walls of the internal ridges are at least twice the distance between the parallel walls of the internal valleys. (Author), Supersedes PAT-APPL-089 058-79, AD-D006 740.

A Te sub 01 circular mode waveguide expansion joint, tapered transition device in which the expansion joint includes a linear tapered section, the greatest diameter of which does not exceed the cutoff diameter for the Te sub 01 spurious mode. A second taper of the cosine or other suitable type minimizes Te sub 02 mode generation as the guide diameter increases past the Te sub 02 cutoff value. The expansion, transition device simultaneously performs the functions of expansion section and waveguide diameter transition for the Te sub 01 circular mode while minimizing spurious mode generation., Supersedes PAT-APPL-230 995-81, AD-D008 843.

The rectangular waveguide to circular waveguide coupler includes a first section of circular waveguide spaced by a gap from a reflective-plane conducting wall, the latter having a hole for passage of an electron beam if the coupler is used in a traveling wave tube, and a second section of circular waveguide disposed external to, and coaxial with, at least a portion of the first waveguide section and extending to the wall to provide a conductive boundary surrounding the gap. The region between the first and second waveguide sections forms an input port of the coupler; the first waveguide section forms the output port of the coupler. Electromagnetic waves in a TE(01) coaxial waveguide mode are applied to the input port from a rectangular waveguide supporting the dominant TE(10) mode. The second waveguide section has a cutoff determining dimension r(e) proportioned to support both the TE(01) and TE(02) circular electric modes in the region of the gap at the frequency of the applied waves. The first waveguide section has cut-off determining dimensions r(i) proportioned to support the circular electric TE(01) mode to the exclusion of all higher-numbered circular electric modes at the frequency of the applied waves.