Full modal analysis of confocal coaxial elliptical waveguides

An efficient method for analysing confocal coaxial elliptical waveguides is presented. Using elliptical coordinates, the differential Helmholtz equation is transformed into a linear matrix eigenvalue problem by means of the method of moments. The expressions of the vector mode functions for the full spectrum of these guides are constructed, including the TEM, TM and TE modes. The convergence of the method is very good, giving an efficient and accurate code. Comparisons with numerical results found in the technical literature validate the presented theory.

High power analysis and design of dual-mode channel filters

In this paper, we present two dual-mode channel filter topologies which are able to withstand more than 600 W in Ku-Band. The two different designs (one with elliptical cavities and the other one with rectangular cavities) implement the same transfer function: four order, elliptical response centered in 12 GHz, with 40 MHz bandwidth and two transmission zeros. It is shown that the critical dimensions for the power-handling of these filters are the dimensions of the input-output irises. In fact, in order to rigorously obtain these conclusions and to reach these high-power levels (including margins), it is essential to use the advanced numerical techniques described in the paper to predict th…

Wavelet-like efficient analysis of two-dimensional arbitrarily shaped radomes using a surface formulation

[1] Radomes are usually made of lossy dielectric materials, and their accurate analysis is often cumbersome because of their typical large electrical size and geometrical complexity. In real reflector antenna structures, there are always complex interactions between the radome, the reflector surfaces and the directional feeds, which are typically neglected for the sake of simplicity. In this paper we will consider all such interactions in a very accurate way, thus requiring a high number of unknowns for the numerical solution of the problem. To overcome such drawback, an integral equation formulation based on the Equivalence Principle in combination with the wavelet transform has been emplo…

Efficient and accurate computation of Green's function for the Poisson equation in rectangular waveguides

[1] In this paper, a new algorithm for the fast and precise computation of Green's function for the 2-D Poisson equation in rectangular waveguides is presented. For this purpose, Green's function is written in terms of Jacobian elliptic functions involving complex arguments. A new algorithm for the fast and accurate evaluation of such Green's function is detailed. The main benefit of this algorithm is successfully shown within the frame of the Boundary Integral Resonant Mode Expansion method, where a substantial reduction of the computational effort related to the evaluation of the cited Green's function is obtained.

Accurate consideration of metal losses at waveguide junctions using admittance and impedance integral equation formulations

[1] At higher frequencies, metal loss effects in passive waveguide components become more pronounced and hazardous. In this paper, we propose two integral equation techniques, based on the generalized admittance and impedance matrices, for the accurate consideration of losses in the metal walls of waveguide junctions. Both techniques have been evaluated in terms of accuracy and numerical efficiency, and conclusions are drawn regarding the best properties of the admittance parameter formulation. Finally, combining such technique with a classical perturbative method for considering propagation losses, we have successfully predicted all loss effects in two real waveguide filters used for comme…

Efficient Design of Waveguide Manifold Multiplexers Based on Low-Order EM Distributed Models

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 …

Electron Emission of Pt: Experimental Study and Comparison With Models in the Multipactor Energy Range

Experimental data of secondary emission yield (SEY) and electron emission spectra of Pt under electron irradiation for normal incidence and primary energies lower than 1 keV are presented. Several relevant magnitudes, as total SEY, elastic backscattering probability, secondary emission spectrum, and backscattering coefficient, are given for different primary energies. These magnitudes are compared with theoretical or semiempirical formulas commonly used in the related literature.

Study of the Secondary Electron Yield in Dielectrics Using Equivalent Circuital Models

[EN] Secondary electron emission has an important role on the triggering of the multipactor effect; therefore, its study and characterization are essential in radio-frequency waveguide applications. In this paper, we propose a theoretical model, based on equivalent circuit models, to properly understand charging and discharging processes that occur in dielectric samples under electron irradiation for secondary electron emission characterization. Experimental results obtained for Pt, Si, GaS, and Teflon samples are presented to verify the accuracy of the proposed model. Good agreement between theory and experiments has been found.

An efficient integral equation technique for the analysis of arbitrarily shaped capacitive waveguide circuits

In this paper a new and efficient integral equation formulation is presented for the analysis of arbitrarily shaped capacitive waveguide devices. The technique benefits from the symmetry of the structure in order to reduce the dimensions of the problem from three to two dimensions. For the first time, this technique formulates the waveguide capacitive discontinuity problem as a 2D scattering problem with oblique incidence, combined with an efficient calculation of the parallel plate Green's functions. Results for a capacitive impedance transformer are successfully compared with measurements for validation of the proposed theory.

Calculation of the electrostatic field in a dielectric-loaded waveguide due to an arbitrary charge distribution on the dielectric layer

The goal of this paper is to study the electrostatic field due to an arbitrary charge distribution on a dielectric layer in a dielectric-loaded rectangular waveguide. In order to obtain this electrostatic field, the potential due to a point charge on the dielectric layer is solved in advance. The high computational complexity of this problem requires the use of different numerical integration techniques (e.g., Filon, Gauss-Kronrod, Lobatto, …) and interpolation methods. Using the principle of superposition, the potential due to an arbitrary charge distribution on a dielectric layer is obtained by adding the individual contribution of each point charge. Finally, a numerical differentiation o…

Multipactor radiation analysis within a waveguide region based on a frequency-domain representation of the dynamics of charged particles

[EN] A technique for the accurate computation of the electromagnetic fields radiated by a charged particle moving within a parallel-plate waveguide is presented. Based on a transformation of the time-varying current density of the particle into a time-harmonic current density, this technique allows the evaluation of the radiated electromagnetic fields both in the frequency and time domains, as well as in the near- and far-field regions. For this purpose, several accelerated versions of the parallel-plate Green's function in the frequency domain have been considered. The theory has been successfully applied to the multipactor discharge occurring within a two metal-plates region. The proposed…

Multipactor Analysis in Circular Waveguides

[EN] This paper mainly focuses on demonstrating that a multipactor discharge can occur within a circular waveguide operating under the fundamental TE11 circular mode. Circular waveguides are widely used in the fabrication of many passive components, in order to implement resonant cavities as well as irises to connect adjacent guides for both application domains, particle accelerators and satellite subsystems applications. Thus, we present the first study of the multipactor effect in a circular waveguide, demonstrating its existence and providing a susceptibility chart for such a structure, which will be of great interest for the better understanding of multipactor physical phenomena.

Efficient Pole Expansion of the Generalized Impedance Matrix Representation for Planar Waveguide Junctions

This paper proposes a novel pole expansion of the generalized impedance matrix representation for planar waveguide junctions. Proceeding in this way, we have obtained a very efficient algorithm for the accurate wide-band modelling of such junctions, since the most expensive computations are performed outside the frequency loop. For verification purposes, several practical examples are shown in order to prove the numerical efficiency and accuracy provided by this new technique.

Contributions to the analysis and design of all-inductive filters with dielectric resonators

In this work, three modern full-wave methods will be employed for the accurate analysis and efficient design of a novel family of all-inductive filters loaded with dielectric resonators. These techniques are the bi-orthonormal-basis combined with the orthonormal-basis method, the hybrid mode-matching/spectral method, and, finally, the BI-RME (Boundary Integral-Resonant Mode Expansion) method. Then, two prototypes of band-pass filters have been designed in this work using a CAD tool developed in the research groups implicated in this manuscript. The procedure described in this paper only involves a limited number of actual physical parameters at each step so that it is computationally very e…

Efficient analysis of waveguide filters by the integral equation technique and the BI-RME method

This paper presents the study of rectangular waveguide filters with rounded corners in the cross-section of the waveguides. These components are suitable for low-cost mass production and can be rigorously analyzed by efficient CAD tools. The analysis approach described in this paper is based on the integral equation technique in conjunction with the boundary integral-resonant mode expansion method. Two representative examples are also reported.

Efficient analysis of general waveguide multi-port junctions using a segmentation technique and hybrid matrix formulations

Dans cet article on propose une technique de segmentation basee sur des representations matricielles hybrides (impedance et admitance) pour ľanalyse efficace et exacte de jonctions multi-port de guides ľondes rectangulaires aux ports de forme arbitraire. La technique est expliqee en detail et ľon en deduit une nouvelle methode pour resoudre la connection de matrices hybrides sans inversions intermediaires. Pour valider la theorie, on compare les resultats obtenus avec une jonction T-magique et avec une jonction a six ports avec des donnees experimentales de la litterature. La nouvelle methode proposee est aussi employee avec succes pour resoudre des jonctions T des plans E et H ayant des co…

Multipactor Analysis in Coaxial Waveguides for Satellite Applications using Frequency-Domain Methods

This work presents the analysis, manufacturing and testing of a coaxial sample in order to investigate the multipactor effect in this kind of waveguide structures. Several in-home and commercial software have been used to design a quarter-wave transformer coaxial circuit centered at 1.35 GHz. The multipactor analysis of this device has been carried out allowing the prediction of the RF breakdown multipactor threshold. Moreover, the multipactor onset of such a prototype has been measured showing a very good agreement with our simulations. In addition to this, comparison has been also done with results from the technical literature fully validating the new algorithm developed.

New distributed model for synthesis of classical dual mode filters

Up to now, distributed models for classical dual mode filters have not been developed. In this paper, the whole procedure to derive such distributed models is shown step by step. The resulting formulas are very similar to those standard ones used for in-line filters since the 1960s. Model limitations, very similar to those related to classical formulas, in terms of precision and bandwidth, are pointed out. Finally, two practical examples of distributed models of dual mode filters for satellite transponders with different orders have been extracted.

Efficient and Accurate Consideration of Ohmic Losses in Waveguide Diplexers and Multiplexers

The accurate consideration of all ohmic losses effects in waveguide manifold diplexers and multiplexers is rigorously studied in this paper. For such purposes, a full-wave CAD tool based exclusively on modal methods is originally proposed. Proceeding in this very efficient way, losses are precisely considered in all common components of such complex devices, i.e. planar junctions, uniform lines and multi-port circuits implemented in waveguide technology. For verification purposes, we have successfully compared our results for a magic-T junction and a manifold diplexer with experimental and numerical results.

Multipactor Effect in a Parallel-Plate Waveguide Partially Filled With Magnetized Ferrite

The aim of this paper is the analysis of the multipactor effect in a parallel-plate waveguide when a ferrite slab, transversally magnetized by a static magnetic field parallel to the waveguide walls, is present. Employing an in-house developed code, numerical simulations are performed to predict the multipactor radio frequency voltage threshold in such a ferrite-loaded waveguide. Variations of the ferrite magnetization field strength and the ferrite slab height are analyzed. Effective electron trajectories are also shown for a better understanding of the breakdown phenomenon, finding different multipactor regimes.

On the Fast and Rigorous Analysis of Compensated Waveguide Junctions Using Off-Centered Partial-Height Metallic Posts

In this paper, we present an efficient and rigorous method, based on the 3-D boundary integral-resonant-mode expansion technique, for the analysis of multiport rectangular waveguide junctions compensated with partial-height cylindrical metallic posts. The electrical performance of a great variety of commonly used wideband microwave circuits has been improved drastically thanks to the introduction of a new design parameter, i.e., the relative position of the metallic post in the structure. To the authors' knowledge, this parameter has not been taken into account in previous studies concerning compensated junctions using partial-height metallic posts. The developed tool has been successfully …

Experimental Analysis of the Multipactor Effect With RF Pulsed Signals

The main goal of this letter is the analysis of the multipactor effect within a coaxial waveguide excited by an RF pulsed signal. The variation of the multipactor RF voltage thresholdwiththe ON interval length of the pulse has been analyzed. To reach this aim, an in-house multipactor simulation code based on the Monte-Carlo algorithm has been implemented. The numerical simulations show that the multipactor RF voltage threshold increases as the ON pulse interval diminishes. In addition, an experiment was carried out to validate the proposed theoretical model, and demonstrating the excellent agreement between the theory and the experimental data. Finally, the results are compared with the 20-…

Experimental Analysis of Passive Intermodulation at Waveguide Flange Bolted Connections

[EN] In this paper, the generation of passive intermodulation at rectangular waveguide flange bolted connections is investigated. An exhaustive series of tests has been performed in order to provide understanding on the physics lying behind such a phenomenon. In particular, the intermodulation response of the system has been studied as a function of the applied torque to the flange screws. It has been found that, in some situations, the intermodulation response differs from its expected behavior. An interpretation of such discrepancies is given, and practical guidelines for the design of waveguide flanges free of passive intermodulation are provided as well.

RF Breakdown Prediction for Microwave Passive Components in Multi-carrier Operation

This work addresses the multipactor problem for multi-carrier operation inside rectangular waveguide based devices, by means of numerical simulations of the electron trajectories and multiplication inside the structure. Accurate field calculation and taking into account space charge effects are mandatory. For this, a PIC-FDTD method has been employed. As a result, novel software has been implemented offering the possibility of predicting multipactor in multicarrier systems for a wide variety of situations. Simulation results show that multipactor can occur even for short pulse durations if an inter-period charge accumulation is present.

Advanced Analysis of Propagation Losses in Rectangular Waveguide Structures Using Perturbation of Boundary Conditions

In this paper, propagation losses effects present in rectangular waveguide structures are rigorously considered. For this purpose, a new formulation based on the perturbation of the boundary conditions on the metallic walls of the waveguides combined with an Integral-Equation (IE) analysis technique is proposed. Following this advanced technique, the drawbacks of the classical power-loss method are overcome and a complex modal propagation constant is computed. To validate this theory, we have successfully compared our results with numerical data of lossy hollow waveguides. Next, a Computed-Aided-Design (CAD) software package based on such a novel modal analysis tool has been used to predict…

Efficient CAD of Optimal Multi-Port Junctions Loaded with Partial-Height Cylindrical Posts using the 3D BI-RME Method

A rigorous full-wave technique based on the 3D BI-RME (Boundary Integral-Resonant Mode Expansion) method for the analysis and design of compensated waveguide junctions is presented. This method is used to investigate the electrical performance of right-angled bends and rectangular waveguide T-junctions loaded with partial-height cylindrical posts, with the aim of extending the typical usable bandwidths of such components. It is found that the electrical performance of a two-way power divider can be significantly improved by considering a post displaced along the symmetry plane of the structure. Therefore, this contribution reveals a new crucial design parameter not considered in previous wo…

Investigation of Multipaction Phenomena in Passive Waveguide Filters for Space Applications

This paper presents an investigation on multipaction risk in microwave bandpass filters. The study reveals higher multipaction risk for narrower bandpass filters. To alleviate the problem with multi-paction generation, different novel filtering structures are proposed. Results demonstrate that using the new structures multipaction risk can be reduced as much as 30% with regard to the initial design.

Multipactor prediction with multi-carrier signals: Experimental results and discussions on the 20-gap-crossing rule

This work analyzes the 20-gap crossing rule from a theoretical point of view. It has been found that, depending on some signal parameters, the 20-gap-crossing rule yields predictions laying between two limit cases: It may be either excessively conservative or closer to breakdown value with little (or nonexistent) margin. Such limit cases have been experimentally assessed with two test campaigns in C and Ku-bands. © 2014 European Association on Antennas and Propagation.

Performance analysis and comparison of symmetrical and asymmetrical configurations of evanescent mode ridge waveguide filters

[1] In this paper, the trade-offs between out-of-band performance, filter length, power-handling capability, and insertion loss of both symmetrical and asymmetrical evanescent mode ridge rectangular waveguide filters are investigated. As a result, clear design methodologies for optimizing such performances are proposed. The developed methodologies are then applied to design several evanescent mode filters, and a complete performance analysis of the symmetrical and asymmetrical structures is performed. From the performance analysis results, the designer can choose the more appropriate filter topology and design strategy to satisfy the prescribed specifications.

Efficient analysis of in-line waveguide filters and frequency-selective surfaces with stepped holes

This paper presents a novel method for the analysis of large classes of microwave and mm-wave passive components, including in-line waveguide filters, single- and multi-layer frequency selective surfaces, and open-ended waveguide array antennas. This method is based on the segmentation technique, which permits us to reduce complex components to cascaded waveguide step discontinuities, which are separately characterized through their generalized impedance matrices, as calculated by the integral equation (IE) technique and the boundary integral-resonant mode expansion (BI-RME) method. Some examples demonstrate the flexibility and efficiency of the IE/BI-RME method, and its utility in investig…

Two-dimensional photonic-crystal microwave waveguide

This paper reports on the use of 2D photonic crystals to design microwave waveguides. The waveguide consists of a periodic arrangement of holes, with a square or rectangular cross section, that extends along the waveguide with a central defect defined by the absence of a hole. The theoretical analysis of such a structure is based on a biorthogonal-basis method and provides a full-vector description of the modes guided by the defect. Our results show that such a waveguide can be designed to support only one mode at any operating frequency. This mode is a polarization doublet whose dispersion is controlled by the geometrical parameters, thus permitting the design of a novel polarization-maint…

Compensation of the impact of low-cost manufacturing techniques in the design of E-plane multiport waveguide junctions

In this work, a full-wave tool for the accurate analysis and design of compensated E-plane multiport junctions is proposed. The implemented tool is capable of evaluating the undesired effects related to the use of low-cost manufacturing techniques, which are mostly due to the introduction of rounded corners in the cross section of the rectangular waveguides of the device. The obtained results show that, although stringent mechanical effects are imposed, it is possible to compensate for the impact of the cited low-cost manufacturing techniques by redesigning the matching elements considered in the original device. Several new designs concerning a great variety of E-plane components (such as …

Design of compensated multiport waveguide junctions considering mechanization effects

Abstract A new tool for the rigorous and efficient design of compensated multiport waveguide junctions, considering the mechanization effects due to low-cost manufacture techniques, is presented. Several new designs for a great variety of key components, present in modern microwave and millimetre-wave equipment, are proposed taking into account the introduction of rounded corners in the rectangular waveguide access ports. The new implemented tool permits to control and compensate for the potential degradation of the wide-band performance of such components prior to their fabrication, thus achieving an optimal design. All the presented results have been successfully validated by comparing th…

Highly efficient full-wave electromagnetic analysis of 3-D arbitrarily shaped waveguide microwave devices using an integral equation technique

A novel technique for the full-wave analysis of 3-D complex waveguide devices is presented. This new formulation, based on the Boundary Integral-Resonant Mode Expansion (BI-RME) method, allows the rigorous full-wave electromagnetic characterization of 3-D arbitrarily shaped metallic structures making use of extremely low CPU resources (both time and memory). The unknown electric current density on the surface of the metallic elements is represented by means of Rao-Wilton-Glisson basis functions, and an algebraic procedure based on a singular value decomposition is applied to transform such functions into the classical solenoidal and nonsolenoidal basis functions needed by the original BI-RM…

Design of a narrow-band filter based on the Brewster phenomenon for microwave applications

A high-efficiency narrow-band filter based on a Dielectric Frequency-Selective Surface (DFSS) has been predicted theoretically for oblique plane-wave incidence. A DFSS showing total reflection at a frequency of 10.5 GHz, based on the Brewster phenomenon for TM polarization, has been designed with a single dielectric grating, showing extremely low-reflectance sidebands adjacent to the resonance peak. The angular and spectral response of the designed filter has been studied. In addition, dielectric ohmic losses have been accounted for in this structure. This work was supported by the Agencia Estatal de Investigación (AEI) and by the Unión Europea through the Fondo Europeo de Desarrollo Region…

Experimental Study of the Multipactor Effect in a Partially Dielectric-Loaded Rectangular Waveguide

This letter presents the experimental study of the multipactor threshold in a partially dielectric-loaded rectangular waveguide, whose results validate a multipactor model recently developed by the authors, which includes the charge distribution appearing on the dielectric surface during the multipactor discharge. First, the variation of the multipactor RF voltage threshold has been theoretically analyzed in different waveguide configurations: in an empty waveguide, and also in the cases of a one-sided and two-sided dielectric-loaded waveguides. To reach this aim, an in-house Monte Carlo simulation tool has been developed. The Secondary Electron Yield (SEY) of the metallic and dielectric ma…

Efficient boundary integral-resonant mode expansion method implementation for full-wave analysis of passive devices based on circular waveguides with arbitrary perturbations

In this study, the efficient full-wave analysis of passive devices composed of circular and arbitrarily-shaped waveguides is considered. For this purpose, the well-known boundary integral-resonant mode expansion (BI RME) method has been properly extended. Circular waveguides are used for resonant mode expansion, whereas the arbitrary contour is defined by any combination of straight, circular and elliptical segments, thus allowing the exact representation of the most widely used geometries. The proposed algorithm extends previous implementations of the BI RME method based on circular waveguides by considering circular and elliptical arcs for defining arbitrary geometries. Similarly, it allo…

Multipactor Mitigation in Coaxial Lines by Means of Permanent Magnets

The main aim of this paper is the analysis of the feasibility of employing permanent magnets for the multipactor mitigation in a coaxial waveguide. First, the study of a coaxial line immersed in a uniform axial magnetic field shows that multipactor can be suppressed at any RF if the external magnetic field is strong enough. Both theoretical simulations and experimental tests validate this statement. Next, multipactor breakdown of a coaxial line immersed in a hollow cylindrical permanent magnet is analyzed. Numerical simulations show that multipactor can be suppressed in a certain RF range. The performed experimental test campaign demonstrates the capability of the magnet to avoid the multip…

Design of Compensated Multiport Waveguide Junctions considering Mechanization E ects

An analytical model to evaluate the radiated power spectrum of a multipactor discharge in a parallel-plate region

This paper is aimed at studying the electromagnetic radiation pattern of a multipactor discharge occurring in a parallel-plate waveguide. The proposed method is based on the Fourier expansion of the multipactor current in terms of time-harmonic currents radiating in the parallel-plate region. Classical radiation theory combined with the frequency domain Green's function of the problem allows the calculation of both the electric and the magnetic radiated fields. A novel analytical formula for the total radiated power of each multipactor harmonic has been derived. This formula is suitable for predicting multipactor with the third-harmonic technique. The proposed formulation has been successfu…

Wideband modeling 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…

Waveguide filters for satellites

This article describes the historical evolution, and its theoretical and technological features of waveguide filters. All-metal waveguide filters have been widely used in satellite payloads since the advent of the first space communication systems four decades ago. In this period, such technology has been continuously evolving due to the increasing requirements demanded to these components. Special attention has also been paid to present the most recent advances in the development of CAD tools for satellite filters, which are based on full-wave electromagnetic analysis methods. Finally, the compact solutions for the input and output stages of satellite payloads are focused on, thus consider…

Three-dimensional scattering of dielectric gratings under plane-wave excitation

The problem of scattering of electromagnetic plane waves by one-dimensional (1D) periodic dielectric gratings, under the most general condition of oblique incidence (3D incidence), is rigorously solved. A recently developed vectorial modal method for obtaining the modal spectrum of 1D dielectric periodic guiding media has been extended to consider 3D incidence. Polarization coupling effects are included in the analysis, just demonstrating the impossibility of the separation between the transverse electric and transverse magnetic polarizations traditionally employed in the two-dimensional (2D) case. A study of the scattering parameters of a multilayered dielectric periodic structure is accom…

Fast and accurate analysis and design of substrate integrated waveguide (SIW) filters

This paper describes the application of the boundary integral-resonant mode expansion (BI-RME) method to the accurate modelling of substrate integrated waveguides (SIW). The new formulation fully exploits the particular geometry of this class of structures, thus providing a very efficient analysis method to be used within CAD tools of SIW filters. The advantages of this method have been proved with the successful design of two filters operating in the microwave and millimeter-wave bands.

On the Rigorous Calculation of All Ohmic Losses in Rectangular Waveguide Multi-Port Junctions

In this paper, all ohmic losses effects present in rectangular waveguide multi-port junctions are rigorous and efficiently computed. For this purpose, a new formulation based on the theory of cavities, which provides generalized admittance matrix representations for such junctions, is proposed. To validate this theory, we have successfully compared our results with numerical data of a lossy E-plane T-junction and of a hollow waveguide, as well as with experimental measurements of a real H-plane T-junction.

Analysis of Cylindrical Dielectric Resonators in Rectangular Cavities Using a State-Space Integral-Equation Method

In this letter, a state-space integral-equation method in the s-domain has been employed for the accurate analysis of rectangular cavities loaded with cylindrical dielectric resonators. The dielectric obstacles have been treated in terms of their polarization equivalent charge and current densities. The dielectric resonator can be placed at any arbitrary position inside the cavity. The presented technique allows to calculate in a very efficient way a large number of solenoidal modes. The resonant frequencies of dielectric-loaded cavities are calculated and compared with data from literature and a commercial finite element method software, showing a good agreement

Efficient CAD of Generalized Coaxial Probes in Rectangular Waveguide using the 3D BI-RME Method

An efficient full-wave method based on the 3D BI-RME (boundary integral-resonant mode expansion) technique for the accurate design of generalized probe-excited rectangular waveguides is presented. The flexibility of the developed CAD tool allows to analyze two common configurations frequently used in modern coaxial-fed microwave devices: conventional and disc-ended coaxial probe excitation. This last configuration is used to drastically improve the electrical response of the classical coaxial probe excitation. Moreover, the influence of the distance from the probe to the waveguide shortcircuit is also discussed, and it is shown that it plays a very important role in the design of probe-exci…

A rigorous and efficient full-wave analysis of uniform bends in rectangular waveguide under arbitrary incidence

In this paper, a rigorous full-wave analysis of uniform bends in rectangular waveguides is performed. An accurate and efficient method-of-moments solution combined with the generalized-admittance-matrix (GAM) formulation is proposed in order to achieve a full-wave characterization of the analyzed structures. This full-wave modal solution turns out to be necessary for modeling complex microwave devices involving an arbitrary number of discontinuities between curved and straight waveguides, where all the modes of the involved guides are excited. The key feature of the presented method lies in the GAM representation of single and cascaded curved E- and H-plane uniform bends, which allows the c…

A commercial EM solver using the BI-RME method

Efficient Analysis and Design Strategies for Evanescent Mode Ridge Waveguide Filters

In this paper, a research on the compromises arisen in the design of traditional evanescent mode waveguide filters is carried out. As a result, clear design methodologies for optimizing length, losses, power handling and spurious-free out-of-band response are developed. In addition, an efficient and very accurate modal analysis tool for this kind of structures is presented. Several filters have been designed according to the different strategies proposed, and a prototype has been finally manufactured. Measurements and filter dimensions validate the proposed design procedures.

Study of the multipactor phenomenon using a full-wave integral equation technique

Abstract Multipactor effect is a well-known phenomenon of RF breakdown in satellite payloads which degrades components, generates undesirable harmonics, contributes to power dissipation and increases noise in communications. Traditionally, multipactor has been investigated with the aim of obtaining the so-called multipactor threshold voltage, or to present different multipaction detection methods. However, very little attention has been focused on analysing this phenomenon using a multimodal approach. The main goal of this work is to analyse the interaction between a multipactor current and a realistic microwave cavity by means of a rigorous and accurate formulation. For the first time to t…

An E-plane EBG waveguide for dispersion compensated transmission of short pulses

The resolution of radar applications can significantly suffer from pulse broadening along the propagation in homogeneous hollow waveguides. The latter occurs due to the strongly dispersive nature of the fast waves in the waveguides. A low-cost solution to this problem is here proposed, employing an EBG type of waveguide, compatible with traditional E-plane fabrication techniques. By means of an example, here we demonstrate the reduction of the pulse spreading as it propagates along this type of waveguide.

Analysis of inhomogeneously filled waveguides using a bi-orthonormal-basis method

A general theoretical formulation to analyze inhomogeneously filled waveguides with lossy dielectrics is presented in this paper. The wave equations for the tranverse-field components are written in terms of a nonself-adjoint linear operator and its adjoint. The eigenvectors of this pair of linear operators define a biorthonormal-basis, allowing for a matrix representation of the wave equations in the basis of an auxiliary waveguide. Thus, the problem of solving a system of differential equations is transformed into a linear matrix eigenvalue problem. This formulation is applied to rectangular waveguides loaded with an arbitrary number of dielectric slabs centered at arbitrary points. The c…

Enhanced prediction of multipaction breakdown in passive waveguide components including space charge effects

An enhanced prediction software tool of multipaction breakdown effect in passive waveguide components is proposed in this work. For such purpose, the space charge field effects are included employing a particle-in-cell code and finite differences in time domain integration techniques. As a result, the novel prediction tool models all the physical effects derived from multipactor such as reflected power, noise and/or harmonics, thus improving the accuracy of the threshold predictions and providing very valuable additional information of the phenomena. Such tool has been integrated within a full-wave modal analysis software for complex waveguide geometries (FEST3D), and the multipactor effect…

Analysis of the electromagnetic radiation generated by a multipactor discharge occurring within a microwave passive component

International audience; Multipactoring is a non-linear phenomenon that appears in highpower microwave equipments operating under vacuum conditions and causes several undesirable effects. In this manuscript, a theoretical and experimental study of the RF spectrum radiated by a multipactor discharge, occurring within a realistic microwave component based on rectangular waveguides, is reported. The electromagnetic coupling of a multipactor current to the fundamental propagative mode of a uniform waveguide has been analyzed in the context of the microwave network theory. The discharge produced under a single-carrier RF voltage regime has been approached as a shunt current source exciting such a…

Time evolution of an electron discharge in a parallel-plate dielectric-loaded waveguide

The objective of this letter is to study the time evolution of a multipactor discharge in a simple dielectric waveguide structure. In particular, the investigation is performed on the case of a parallel-plate waveguide structure partially filled with a dielectric layer. The main consequence of the specific case studied in this letter is the fact that the dielectric layer charges negatively, allowing a negative static field to build up. This dc field eventually leads to a single-surface multipactor in the metallic surface before finally turning off the electron discharge.

Study of periodic Dielectric Frequency-Selective Surfaces under 3D plane wave incidence

A periodic Dielectric Frequency-Selective Surface (DFSS) is studied under 3D plane-wave incidence, whose unit cell in the periodic direction is composed of a dielectric grating and a homogeneous dielectric layer. The structure is excited by a linearly polarized plane-wave. The procedure for computing the Brillouin diagram of the structure under 2D plane-wave incidence with TE or TM polarization was already described by the authors, and the extension to the 3D incidence case has been performed in a similar way. Following the same formalism, it has been obtained the Generalized Scattering Matrix (GSM) of one period of the infinite periodic lattice. This requires the knowledge of the modal spe…

Multipactor RF Breakdown in Coaxial Transmission Lines With Digitally Modulated Signals

The aim of this paper is the study of the RF multipactor breakdown in coaxial transmission lines excited by a single carrier with a digitally modulated signal. Employing an in-house developed code, numerical simulations are performed to determine the RF multipactor voltage threshold for several digitally modulated signals under different modulations schemes: quadrature phase-shift keying, 16-quadrature amplitude modulation, 16-amplitude and phase-shift keying, and 32-amplitude and phase-shift keying. Moreover, a coarse method based on the envelope integration to determine the RF multipactor voltage threshold when involving arbitrary digital modulations is also presented. These results are a…

Multipactor Effect Characterization of Dielectric Materials for Space Applications

[EN] The objective of this paper is to advance the state of the art in the characterization of the multipactor effect in dielectric materials. The materials studied are the most commonly used dielectrics in space applications, namely, Alumina, Rexolite, Rogers RT5870, Rohacell, Teflon, and Ultem 1000. In this paper, a new family of coaxial waveguide components, covering the L- and S-bands, with a wideband, low-pass response has been designed, and six different prototypes have been specifically optimized and manufactured. The six prototypes have then been used to simulate and measure the multipactor breakdown susceptibility charts for the six dielectric materials investigated. Finally, the s…

Wideband impedance matrix representation of passive waveguide components based on cascaded planar junctions

[1] A very efficient technique for the full-wave analysis of passive waveguide components, composed of the cascade connection of planar junctions, is presented. This novel technique provides the wideband generalized impedance matrix representation of the whole structure in the form of pole expansions, thus extracting the most expensive computations from the frequency loop. For this purpose, the structure is segmented into planar junctions and uniform waveguide sections, which are characterized in terms of wideband impedance matrices. Then, an efficient iterative algorithm for combining such matrices, and finally providing the wideband generalized impedance matrix of the complete structure, …

Multipactor Discharges in Parallel-Plate Dielectric-Loaded Waveguides Including Space-Charge Effects

[EN] The objective of this paper is to study the time evolution of multipactor discharges in a parallel-plate dielectric-loaded waveguide. The electron discharge phenomena investigated in this paper include the effects of space charge, as well as the presence of time varying static fields. In order to perform the simulations presented in this paper, an approach considering simultaneously multiple effective electrons has been used. The results obtained demonstrate that multipactor discharges do turn off by themselves under certain circumstances when they occur in such dielectric-loaded structures.

Corrections to “Multipactor Susceptibility Charts for Ridge and Multi-Ridge Waveguides” [Dec 12 3601-3607]

The authors have detected an error in Section IV-A in the above paper (ibid., vol. 59, no. 12, pp. 3601-3607, Dec. 2012). The analyzed rectangular waveguide in the actual version of the article is the WR137, instead of the WR90. As a consequence, the corrections presented here have to be implemented.

Flexible and efficient computer-aided design tool for advanced comb-line rectangular waveguide filters

A very flexible and efficient computer-aided design CAD tool, specifically suited for advanced comb-line rectangular waveguide filters, is presented in this work. The developed software tool, which makes use of a full-wave analysis technique based on the Boundary Integral-Resonant Mode Expansion method, allows loading the considered comb-line resonators with any number of radially symmetrical partial-height metallic posts. The implemented CAD tool also allows dealing with coupling windows of arbitrary cross-section, thus drastically enhancing the flexibility of the CAD process. The excitation of the analyzed components, which is performed using generalized coaxial probes, has also been inte…

High-Power Multicarrier Generation for RF Breakdown Testing

Testing of satellite components for high RF power breakdown effects, such as multipactor and corona or passive-intermodulation, is a topic of growing interest in the aerospaceindustry. Switching fromthe classical single carrier approach to the more realisticmulticarrier scenario is very challenging from the experimental point of view. Themulticarrier signals, amplifiedby several RF power amplifiers, need to have controlled phase, amplitude, and frequency in each carrier. Fine tuning of the signal generator phases is required in order to compensate the phase drift occurring in the active elements of the test bed. This paper presents an efficient and low-cost technique to generate multicarrie…

Rigorous investigation of RF breakdown effects in high power microstrip passive circuits

This work presents a new rigorous investigation of corona effects in microstrip components. To carry out the investigation, a new software tool has been developed. The new tool first calculates the electromagnetic fields in complex microstrip structures using a Volume Integral Equation (VIE) formulation. Novel numerical techniques have been incorporated in the VIE to increase the accuracy during the computation of the electromagnetic fields. This includes novel techniques introduced to treat the singularities of the Green's functions. Once the electromagnetic fields are computed accurately, corona effects in the relevant structures are investigated. For this, a numerical solution of the fre…

Novel multipactor studies in RF satellite payloads: Single-carrier digital modulated signals and ferrite materials

In this work it is reviewed the most novel advances in the multipactor RF breakdown risk assessment devoted to RF satellite microwave passive devices employed in space telecommunication systems. On one side, it is studied the effect of transmitting a single-carrier digital modulated signal in the multipactor RF voltage threshold in a coaxial line. On the other hand, an analysis of the multipactor phenomenon in a parallel-plate waveguide containing a magnetized ferrite slab it is presented.

Analysis of multipactor RF breakdown in a waveguide containing a transversely magnetized ferrite

In this paper, the multipactor RF breakdown in a parallel-plate waveguide partially filled with a ferrite slab magnetized normal to the metallic plates is studied. An external magnetic field is applied along the vertical direction between the plates in order to magnetize the ferrite. Numerical simulations using an in-house 3-D code are carried out to obtain the multipactor RF voltage threshold in this kind of structures. The presented results show that the multipactor RF voltage threshold at certain frequencies becomes considerably lower than for the corresponding classical metallic parallel-plate waveguide with the same vacuum gap

Recent advances of the multipactor RF breakdown in RF satellite microwave passive devices

The main goal of this work is the review of the recent advances in the study of the multipactor RF breakdown phenomenon in RF satellite microwave passive devices for space telecommunication applications developed in the Val Space Consortium. In this work several topics related with the multipactor phenomenon will be discussed.