Some computational problems in electromagnetism have high computational cost, which makes it is necessary to solve them efficiently in today's computational systems. This chapter studies the efficient solution of electromagnetism problems based on integral equation formulations in clusters of CPU + GPU nodes.

Multipactor effect is a resonant avalanche of secondary electrons induced by an RF electromagnetic field, which endangers high-power payloads on satellites and particle accelerator structures. The main goal of this letter is to present a multimodal network characterization of a multipactor discharge occurring in a bounded waveguide region. This will allow to perform a rigorous analysis of a complete passive component considering the presence of a discharge. In order to verify the present formulation, we have measured the power spectrum generated by a multipactor event excited in a simple microwave circuit based on rectangular waveguides, which has been compared with the theoretical results, obtaining good agreement.

A new integral equation formulation is presented for the analysis of capacitive waveguide components, including metallic and dielectric objects. The technique exploits the symmetry of the structure by formulating a 2D scattering problem with oblique angle of incidence. As a consequence, the analysis of complex waveguide capacitive devices results to be very efficient, as compared to other 3D numerical techniques. As practical application, the paper proposes a low-pass filter loaded with dielectric and magnetic materials. Results are validated with commercial full-wave simulators showing the validity and accuracy of the novel integral equation technique.

There is a large number of applications in the design of telecommunication devices where it is necessary to apply optimisation techniques to find the best values for a set of parameters [2, 5]. Normally, it is not possible to solve those optimisation problems with analytical techniques, and the alternative is to use metaheuristic methods [6]. In this work we tackle the problem of designing coupled resonator filters [1], which are used in the RF-frontends of communication devices. There are different phases in the design of these filters. In a first approximation, the desired topology of the filter and the basic characteristics of the technology to use are established, and then it is necessary to obtain the theoretical coupling matrix which implements the desired transfer function. We analyse the application of metaheuristics to obtain that matrix. Furthermore, the numerical software Matlab is frequently used to work on the design of those devices, and a good option would be to also develop in Matlab the optimisation tools. Thus, this work analyses the application of Matlab optimisation toolboxes to tackle this optimisation problem with different metaheuristics. A detailed experimental analysis is carried out to obtain the tools in Matlab which best fit the problem, and some tools are personalised to improve the quality of the design.

Multipactoring is a non-linear phenomenon that appears in high-power microwave equipment operating under vacuum conditions and causes several undesirable effects. In this paper, 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 analysed 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 mode in a transmission-line gap region. By means of a simple equivalent circuit, this model allows prediction of the harmonics generated by the discharge occurring in a realistic passive waveguide component. Power spectrum radiated by a third-order multipactor discharge has been measured in an E-plane silver-plated waveguide transformer, thus validating qualitatively the presented theory to simulate the noise generated by a single-carrier multipactor discharge.

In this paper, we present the outcomes of a specific software designed for the ESTEC project No. AO-5086: New investigations of RF breakdown in microwave transmission Lines. The objective of the project is to develop a software tool capable to predict the multipactor and corona breakdown onsets in shielded microstrip devices, paying special attention to elements like connectors, bridges or ribbons. In the first step, the electromagnetic fields of the devices are computed using an efficient implementation of a volume/surface integral equation technique. Secondly, the high power breakdown onsets are determined, employing accurate and realistic models for the electron trajectories and the secondary electron emissions. Also, the corona discharge breakdown level is computed by means of the numerical solution of the free electron density continuity equation.