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…

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.

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.

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.

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…

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…

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…

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

A commercial EM solver using the BI-RME method

CAD of complex passive devices composed of arbitrarily shaped waveguides using Nyström and BI-RME methods

In this paper, a novel computer-aided design (CAD) tool of complex passive microwave devices in waveguide technology is proposed. Such a tool is based on a very efficient integral-equation analysis technique that provides a full-wave characterization of discontinuities between arbitrarily shaped waveguides defined by linear, circular, and/or elliptical arcs. For solving the modal analysis of such arbitrary waveguides, a modified version of the well-known boundary integral-resonant-mode expansion (BI-RME) method using the Nyström approach, instead of the traditional Galerkin version of the method of moments, is proposed, thus providing significant savings on computational costs and implement…

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…

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.

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