0000000000061658
AUTHOR
Carlos Vicente
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.
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.
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.
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.
High selective H-plane TE dual mode cavity filter design by using nonresonating nodes
The design of H-plane TE dual mode cavity filters using models containing nonresonating nodes is presented. From the models a coupling matrix is derived and decomposed into submatrices, each representing a subcircuit. The optimization and cascading of subcircuits represents a good starting point for the global optimization. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:161–166, 2014
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…
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.
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.
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