C. Vicente

Multipactor breakdown prediction in rectangular waveguide based components

In this paper the multipactor power threshold in arbitrary complex components based on rectangular waveguide technology is investigated. The two required computations when studying such a phenomenon have been performed: calculation of the electromagnetic fields inside the component and determination of the multipactor breakdown onset itself. A full multipactor model is described and tested for a particular set of devices for which experimental measurements have been also performed. The good agreement between the predicted breakdown values and the experimental results shows the validity of the approach followed.

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 has been accurately predicted for two practical waveguide filter structures. The results provided by our tool have been successfully compared with data from standard multipactor susceptibility curves and experimental measurements.

Nonstationary statistical theory for multipactor

This work presents a new and general approach to the real dynamics of the multipactor process: the nonstationary statistical multipactor theory. The nonstationary theory removes the stationarity assumption of the classical theory and, as a consequence, it is able to adequately model electron exponential growth as well as absorption processes, above and below the multipactor breakdown level. In addition, it considers both double-surface and single-surface interactions constituting a full framework for nonresonant polyphase multipactor analysis. This work formulates the new theory and validates it with numerical and experimental results with excellent agreement.

Long-term multipactor discharge in multicarrier systems

A new mechanism of long-term multipactor in multicarrier systems is studied employing both analytical and numerical methods. In particular, the investigation is focused on the impact that a realistic secondary emission yield at low energies produces on the development of long term multipactor. A novel analytical model for this interperiod charge accumulation is presented using the traditional multipactor theory for parallel plates, and approximating the multicarrier signal as a single-carrier signal modulated by a pulsed signal envelope. The analytical predictions are verified by numerical simulations for a typical rectangular waveguide. The analytical and numerical results demonstrate that the susceptibility of the system to develop a long-term multipactor discharge increases with higher values of low-energy secondary emission yield.

Multipactor theory for multicarrier signals

This work presents a new theory of multipactor under multicarrier signals for parallel-plate geometries, assuming a homogeneous electric field and one-dimensional electron motion. It is the generalization of the nonstationary multipactor theory for single-carrier signals [S. Anza et al.,Phys. Plasmas 17, 062110 (2010)]. It is valid for multicarrier signals with an arbitrary number of carriers with different amplitude, arbitrary frequency, and phase conditions and for any material coating. This new theory is able to model the real dynamics of the electrons during the multipactor discharge for both single and double surface interactions. Among other parameters of the discharge, it calculates the evolution in time of the charge growth, electron absorption, and creation rates as well as the instantaneous secondary emission yield and order. An extensive set of numerical tests with particle-in-cell software has been carried out in order to validate the theory under many different conditions. This theoretical de...

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. 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

An Experimental Investigation on Passive Intermodulation at Rectangular Waveguide Interfaces

In this paper, the generation of passive intermodulation (PIM) at rectangular waveguide flange connections is investigated. An exhaustive test campaign has been followed in order to provide understanding on the physics lying behind such a phenomenon. In particular, the PIM response of the system has been studied as a function of parameters such as the applied torque to the flange screws, the total combined input power level and the power ratio between the carries. It is found that, in some situations, the intermodulation response differs from its expected behavior. An interpretation of such discrepancies is given 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 considering 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 multi-carrier 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.

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.

Analysis of the multipactor effect in circular waveguides excited by two orthogonal polarization waves

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.