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The increasing number of electronic devices on board and the use of novel composite materials in the aerospace industry create a harsh electromagnetic environment that must be studied. In this article, a UAV demonstrator (DEMO-E3) with different test cases is evaluated through the low-level swept field test following a nested resonant chambers approach, which is framed under the high intensity radio frequency measurements. The aim is to analyze the difference in terms of the shielding effectiveness of the enclosure considering the different materials and apertures of each test sample. Some of the test cases had been previously measured independently, according to the IEC 61000-4-21 standard, while in this study, they are incorporated into the demonstrator and former results are used as a comparison. This work was supported by the Ministry of Science and Innovation (MICINN) under the eSAFE-UAV Project under Grant PID2019-106120RB-C32. (Corresponding author: David Poyatos Martínez.) Peerreview

The finite-difference time-domain (FDTD) method is not able to efficiently model thin features without a drastic reductions of the spatial mesh size, potentially yielding an unfeasible use of memory and CPU requirements. In this work we propose two stable and efficient techniques for dealing with thin apertures in FDTD, one based on conformal and one based on subgridding. These are compared, in two different scenarios, with the classical dispersive magnetic material approximation [DMMA] based on Gilbert-Holland's models. 10.13039/501100004837-Spanish Ministry of Science and Innovation (Grant Number: eSAFE-UAV PID2019-106120RB-C32) Peerreview

INSPEC Accession Number: 19976292 This letter addresses on the design of a planetary protection shell for performing the Electro-Magnetic Compatibility (EMC) tests of the Anisotropic Magneto-Resistance (AMR) sensor of the ExoMars mission. This mission has strict bio-burden requirements. The ElectroMagnetic (EM) properties of several materials have been investigated for measuring their transmission coefficients and the novelty of this letter is the use of Fused Deposition Modeling (FDM) technology as the production method. Additive manufacturing is presented as a promising technology in the field of radiofrequency since it can use a wide range of materials (including thermoplastics) with high and low transmission coefficient. The investigation comprises the analysis of the electromagnetic properties of several 3D printer materials in order to study their transmission coefficients. Seeing the EM characterization results, it was decided to produce a shell using FDM technology because it provides control over the grounding of the instrument and makes easier the integration, cleaning and protection against impacts during the operation, with great versatility and low cost. To finish, the shell has been proved during the acceptance EMC tests of the flight model and flight spare AMR instrument. Ministerio de Economía, Industria y Competitividad (Grant Number: UAVE3 TEC-2016-79214-C3-1-R and MAGARES ESP2017-88930-R) Peerreview

It is increasingly common in aerospace industries to take advantage of novel composite materials in their manufacturing processes to improve performance and reduce costs. Obtaining the electromagnetic (EM) characterization of these materials or a combination of them is essential to ensure safety and EM compatibility.In this paper, a laminate of the central fuselage of an aircraft developed at INTA is recreated. This aircraft is called MILANO and it is mostly made of Carbon Fiber Composite (CFC). The same material is used for the laminate. Besides, another metallic plate is built in order to compare the performance of the former one with respect to a Perfect Electric Conductor (PEC). The main goal of this work is studying the coupling between the cable bundles embedded in the MILANO and how is this affected by the different materials of the ground plate (metal and CFC). Two kind of tests are carried out: S-parameters measurents and injection of Lightning Indirect Effect (LIE) waveforms. S-parameters results are then obtained through simulation too and compared with both the metallic and the CFC sample. The work described in this paper has been funded by the Spanish Ministry of Science and Innovation (MICINN) under projects UAVE3 (TEC2016-79214-C3-1-R) and eSAFE-UAV (PID2019-106120RB-C32). Peerreview

Novel materials, as multi-ply carbon fiber composites (CFC), are increasingly used in the industry due to their outstanding mechanical properties in relation to their weight. In this regard, from the standpoint of electromagnetic compatibility (EMC), shielding effectiveness (SE) is a key parameter that often determines the scope for application of a given material. This article addresses the application of two complementary standards, ASTM D4935 and IEC 61000-4-21, to the SE measurement of different CFC test samples with more than 10 layers and a very large expected shielding. The analysis of the limitations encountered and the description of applied improvements on the traditional measurement procedures on each method are also included, showing promising results. On the other hand, there are alternative methods to evaluate the SE of CFC based on their DC square resistance. Consequently, and forthe shake of completeness, a novel setup for high precision measurement of the DC square resistance of CFC samples is also described along the article. The work described in this paper has been funded by the Spanish Ministry of Science and Innovation (MICINN) under projects UAVE3 (TEC2016-79214-C3-1-R) and eSAFE-UAV (PID2019-106120RB-C32). Peerreview

Along the years, RADAR absorbing materials (RAM's) have been widely introduced in aeronautic applications and platforms. However, this kind of materials presents three main problems for certain applications when they are intended to be used in real operations. First, they must be scalable from a laboratory sample to actual size, at a reasonable cost. Second, they must be able to work without metal backing for applications in non-metallic vehicles or other objects which surface might not be flat. Indeed, they should also be flexible and surface adaptable. Finally, their absorbing properties against electromagnetic fields should be preferably characterised under real conditions, that is, in free space (FS), in order to design and fabricate an appropriate material for the intended application. In this study, a self-developed, low-cost, bilayer, X-band RAM, composed of a lower layer of polyaniline silicon rubber and a top layer of silicon rubber with graphite was characterised in a bistatic anechoic chamber called BIANCHA, and the results are presented, analysed and compared with software simulation and with the typical single polarisation waveguide measurement method, showing the adequacy of FS measurements for the development of this type of RAM. This study was partially funded by the Spanish Ministry of Economy and Competitiveness (MINECO) within the projects UAVEMI (TEC2013-48414-C3-2-R) and UAVE3 (TEC2016-79214-C3-1-R) and was possible thanks to the Detectability and Electronic Warfare Laboratory of the National Institute for Aerospace Technology (INTA), Spain, the Research and Development Institute for Defense (CITEDEF), Argentina and the National University of San Martín (UNSAM), Argentina. Peerreview

We provide a model able to predict the shielding effectiveness (SE) of carbon fiber composite (CFC) panels made of stacked layers of conducting fibers. This model permits us to obtain simple formulas in which the only parameters needed are the sheet square resistance and the effective panel thickness. These tools let us predict a minimum SE, which always increases with the frequency and therefore constituting the worst case, from an electromagnetic shielding perspective. Consequently, the measurement of minimum SE requirements can be simply measured with a micro-ohmmeter using an specific experimental setup which is also described here. Additionally, this method allows to measure very high SE falling far beyond the dynamic range of the values measurable with the most commonly used standard, the ASTM D4935. After describing the modeling technique and the different test setups used, across-validation between theoretical and experimental results is made for four different samples of CFC; two designed to test the modeling assumptions and two which are representative of the ones nowadays used in a real aircraft. This work was supported in part by the Spanish MINECO and EU FEDER under Project TEC2016-79214-C3-1,2,3-R (MINECO, Spain),in part by the EU PRACE project 2018184436 ESECELS, and in part by the Alhambra-LFT contract with AIRBUS (Spain). Peerreview

Modern aircraft employ profusely carbon fiber composites (CFC) for their construction. Then, it is mandatory to characterize the behaviour of this kind of materials for its use under harsh electromagnetic environments. In that sense, this paper presents the application of two standards, the ASTM D4935 and the IEC 61000-4-21, to the measurement of the shielding effectiveness (SE) of aeronautical multi-ply CFC laminates frequently used for the construction of aircraft. Each technique is well suited for a specific material or realization and a specific frequency range. So, both techniques are complementary and should be developed in parallel. Taking into account the high SE expected for this kind materials, the set-ups imply the measurement of very low signals, that poses an experimental challenge that has to be faced. Then, in this study, different test samples and realizations of CFC materials have been fabricated and measured. Improvements on the traditional measurement procedures have been applied, obtaining promising results. This work has been funded by the Spanish Ministry of Science (MCIU) under project UAVE3 (TEC2016-79214-C3-1-R). Preprint

This paper explains the research process carried out for the development and manufacture of the planetary protection cover for carrying out the electromagnetic compatibility (EMC) tests of the an-isotropic magneto-resistance (AMR) sensor of the ExoMars 2020 mission. This mission has strict bioburden requirements. The electromagnetic properties of several materials have been analyzed in order to study their transmission coefficient and the innovation of this project is the use of fused deposition modeling (FDM) technology as manufacturing method. Additive manufacturing is presented as a promising technology in the field of radiofrequency since it can use a wide range of polymeric materials (thermoplastics) with low transmission coefficient. Observing the electromagnetic (EM) characterization results, it was decided to manufacture a protective cover using FDM technology, because it allows control over the grounding of the instrument and facilitates the integration, cleaning and protection against impacts during the manipulation, with great versatility and low cost. Finally, the cover has been verified during the acceptance EMC tests of the flight model AMR instrument. This work has received funding from the Ministerio de Econom´ıa, Industria y Competitividad (MEIC) Projects TEC2016-79214-C3-1-R, ESP2015-70184-R and ESP2017- 88930-R. Preprint

Electrical and electronic systems on board air vehicles are susceptible to electromagnetic interference (EMI). This has made the topic of electromagnetic compatibility (EMC), a major concern for aircraft safety. The use of composite materials worsens this situation, for their poor shielding and low conductive capabilities. Some of the main experimental E3 certification scenarios used in aeronautics are revisited in this chapter. Guidelines to achieve simple, yet accurate, numerical models of them are provided, with appropriate tradeoffs between computational simplicity and accuracy. The numerical method, endowed with extended capabilities, has been chosen for this task for its ability and efficiency to deal with complex problems of arbitrary materials. The feature selective validation (FSV) IEEE standard procedure, commonly used to quantify the comparison of data in electromagnetic problems, is also revisited. The simulation of three different air vehicles in several certification scenarios is finally described and the numerical results compared to experimental data.