In this paper we evaluated the performance of a reconfigurable intelligent surface tested with a fifth generation signal provided by a commercial fifth generation base station. We adopted a reverberation chamber as a real life propagating environment. Tests were conducted at the millimeter wave frequency range. This measurement campaign was carried out under the H2020 European project RISE-6G and a collaboration program between TIM S.p.A., Nokia and Università Politecnica delle Marche.

The performance of a real fifth generation base station was studied by using a reverberation chamber as a real life propagating environment. Preliminary tests were conducted in order to define 5G base station operation conditions at mm-wave and emulated scenarios where reconfigurable intelligent surface(s) (RISs) will successively be tested. Measurements campaign was carried out under the H2020 European project RISE6G and a collaboration program between TIM S.p.A., Nokia and Universita Politecnica delle Marche.

Testing of wireless devices and systems is becoming increasingly important in the technological development of Long Term Evolution (LTE) and 5G mobile networks. Both mobile and base station manufacturers are interested in assessing system performance and user perceived quality in realistic propagation environments, including indoor and outdoor conditions. Real-life electromagnetic environments exhibit rich multipath propagation and a strong attenuation of the wireless signal over the propagation channel. Emulating those conditions in anechoic chambers requires the careful arrangement of many interference sources in multiple configurations, which leads to complex and time-consuming measurements. The reverberation chamber (RC) is a metallic cavity where the signal created by a single source is reflected and diffused to create multipath fading. This paper gives an overview of how an RC can be tuned to emulate channel parameters, e.g., power delay profile, time delay spread, coherence bandwidth and Rician K-factor, of real-life environments The addition of absorbing material inside the RC allows for varying those parameters, thus recreating line of sight and imperfect propagation conditions experienced by the user equipment (UE). Compliant electromagnetic compatibility downlink and uplink tests are shown for selected MIMO configurations as well as for Internet of Things devices. The tests are carried out using a commercial base station connected to the live national mobile network of a mobile operator. Evaluated network parameters are throughput, signal to noise ratio, modulation schemes and other settings of both the base station and of the UE to assess the quality of the digital communication.

Electromagnetic shielding and propagation in concrete structures are getting more and more interest in radiation hazard problems and wireless communications. The protection of sensitive environment is nowadays carried out by appropriate shielding room made of metallic walls. Their efficacy is counteracted by their heaviness, not adequate for the installation over existing building walls. The using of concrete composites filled by conductive elements represents a valid alternative to metallic shielded room since they can be adopted to directly build up the building walls and/or to easily plaster existing walls. Graphene oxide powder and metallic fibers are being currently investigated as fillers in the manufacturing of electromagnetic shielding cementitious composites. The novelty of the present work is the characterization of a multi-reinforced cement realized by combining such two filler typologies: the synergistic effects of graphene oxide microparticles and short steel fibers result in enhancement of both mechanical properties and EMI effectiveness of the cementitious composites.

The electromagnetic (EM) absorbing cross section (ACS) of carbon foams in the mm-wave frequency range 50-70 GHz is analyzed by means of a reverberation chamber (RC) set-up. Carbon foams are lightweight cellular materials which are believed to provide benefits in EM interference/compatibility (EMI/EMC) issues, due to their significant thermo-mechanical and electrical properties. With respect to usually employed microwave test set-up, the range of frequency investigated allows to analyze the details of the foam bulk structure using shorter wavelengths. Moreover, the RC method allows to study the EM interaction with materials by taking into account not a single wave propagation mode (like in transmission line methods) but rather an homogeneous and statistically random EM field propagation. A full analysis of the material behavior can be thus carried out, by reproducing conditions similar to what really happens within operational environments. The foam EM properties are related to specific structural parameters, such as apparent density, open porosity, cell size/shape and 3-D arrangement. Significant ACS values are appreciated in low density foams; further, a functional dependence between EM mm-wave absorption capability and foam inner morphology is revealed, thus promoting the employed microwave set-up as effective method for supporting the structural analysis of porous materials. (C) 2018 Elsevier Ltd. All rights reserved.

The present work analyzes the possibility to employ carbon nanostructures as a basic material to prevent the erosion effects of atomic oxygen suffered by the carbon fiber reinforced polymeric material used in low earth orbit space environment. The application of thin protecting coatings to base materials is a widely used method for preventing the atomic oxygen induced erosion, and thus degradation. The generic purpose is to integrate carbon nanostructures onto carbon composites surface in order to develop the basic substrate of advanced nanocomposite for atomic oxygen protection. The final goal is the characterization of carbon nanostructures-reinforced carbon composites by means of on-ground atomic oxygen simulation facility, with the future objective to assess and optimize the process of carbon-multiscale advanced composites production. With such an aim, a wide investigation on the methane chemical vapor deposition (CVD) over catalyzed carbon fiber-based substrates has been carried out. The as grown nanostructures have been analyzed in terms of morphology, as well as regarding the main features of the resulting growth (yield, purity, homogeneity, coating uniformity, etc.) and the influence of the deposition route operating parameters (catalyst typology, gas flowing rate, growth time/temperature, etc.). A high degree of reproducibility in terms of the relationship between the carbon deposit type/yield and the main process variables (catalyst and protocol) has been thus obtained. Finally, atomic oxygen ground tests have been conducted in order to evaluate the coating process effectiveness. The on-ground test in atomic oxygen environment, with respect to the performances of the reference carbon composites (in terms of total mass loss and atomic oxygen rate of erosion), showed a worsening for the disordered carbon deposit, while an intriguing improvement was achieved by the high-yield carbon nano-filaments deposition.

Reverberation chambers are successfully adopted to test last generation wireless communication systems. The aim is the replication of realistic propagation condition in outdoor and indoor situations where the multipath contribution statistically overlaps to the direct path between the base station and the user terminal. The insertion of quantified absorbing materials allows to tune the power delay profile, the Rician K-factor, and the coherence bandwidth according to real life situations.

The use of laminated composite shells in many engineering applications has been expanding rapidly in the past five decades due to their higher strength and stiffness to weight ratios when compared to most metallic materials. There are multiple options for dealing with the severe thermal environments encountered during hypersonic flight. Passive, semi-passive, and actively cooled approaches can be utilized. The aim of this paper is to study a shell structure for space applications such as leading edges of a re-entry vehicle. The structure has to be reusable, lightweight and thin. The use of Carbon/Carbon composites for the design of shells allows structures to withstand temperatures over 1600°C. The main features of these composites are the high resistance, high elongation modulus, high mechanical properties at high temperature and very low CTE. The key factor for using this kind of material in re-entry applications is the high stability at high temperature, preserving its mechanical properties. A 3-D shell prototype manufactured via CVI will undergo to the stabilization process. The manufacturing process will be controlled via testing control samples which follows the prototype during its production cycle. The samples will be tested in order to analyze the morphological and thermo-mechanical characteristics.

The growing quantity of debris in Earth orbit poses a danger to users of the orbital environment, such as spacecraft. It also increases the risk that humans or manmade structures could be impacted when objects reenter Earth's atmosphere. During the design of a spacecraft, a requirement may be specified for the surviv-ability of the spacecraft against Meteoroid / Orbital Debris (M/OD) impacts throughout the mission; further-more, the structure of a spacecraft is designed to insure its integrity during the launch and, if it is reusable, during descent, re-entry and landing. In addition, the structure has to provide required stiffness in order to allow for exact positioning of experiments and antennas, and it has to protect the payload against the space environment. In order to decrease the probability of spacecraft failure caused by M/OD, space maneuver is needed to avoid M/OD if the M/OD has dimensions larger than 10cm, but for M/OD with dimensions less than 1cm M/OD shields are needed for spacecrafts. It is therefore necessary to determine the impact-related failure mechanisms and associated ballistic limit equations (BLEs) for typical spacecraft components and subsys-tems. The methods that are used to obtain the ballistic limit equations are numerical simulations and la-borato-ry experiments. In order to perform an high energy ballistic characterization of layered structures, a new ad-vanced electromagnetic accelerator, called railgun, has been assembled and tuned. A railgun is an electrically powered electromagnetic projectile launcher. Such device is made up of a pair of parallel conducting rails, which a sliding metallic armature is accelerated along by the electromagnetic effect (Lorentz force) of a cur-rent that flows down one rail, into the armature and then back along the other rail, thanks to a high power pulse given by a bank of capacitors. A tunable power supplier is used to set the capacitors charging voltage at the desired level: in this way the Rail Gun energy can be tuned as a function of the desired bullet velocity. This facility is able to analyze both low and high velocity impacts. A numerical simulation is also performed by using the Ansys Autodyn code in order to analyze the damage. The experimental results and numerical simulations show that the railgun-device is a good candidate to perform impact testing of materials in the space debris energy range.

The reverberation chamber (RC) method is used to estimate the average absorption cross section of building materials at mm wave frequencies. Analysed samples include concrete, travertine and bricks of different types. The investigation is carried out in the frequency range between 50 GHz and 68 GHz, which is of interest in the next generation of mobile telecommunication system. A cylindrical cavity is transformed into a RC through the use of a mechanical model stirrer. The chamber field is statistically homogeneous and depolarized; therefore it can be used to probe the average response of the sample under test. In particular, through a differential measure of the average quality factor (average insertion loss) it is possible estimate the fraction of power absorbed by the sample under test. Several cube-shape samples have been characterized and compared. Obtained results show that analysed samples have remarkably different levels of the electromagnetic wave absorption, depending on both material density and chemical composition. The absorption of pure water is used as a baseline to determine the dynamic range of the measurement.

Aim of the work is to present a method to evaluate the electromagnetic absorption properties of spacecraft and space debris. For these objects, the radar detection ability depends mainly on volume, shape, materials type and other electromagnetic reflecting behaviour of spacecraft surface components, such as antennas or thermal blankets, and of metallic components in space debris. The higher the electromagnetic reflection coefficient of such parts, the greater the radar detection possibility. In this research an electromagnetic reverberation chamber is used to measure the absorption cross section (ACS) of four objects which may represent space structure operating components as well as examples of space debris: a small satellite, a composite antenna dish, a Thermal Protection System (TPS) tile and a carbon-based composite missile shell. The ACS mainly depends on geometrical characteristics like apertures, face numbers and bulk porosity, as well as on the type of the material itself. The ACS, which is an electromagnetic measurement, is expressed in squared meters and thus can be compared with the objects geometrical cross section. A small ACS means a quite electromagnetic reflective tendency, which is beneficial for radar observations; on the contrary, high values of ACS indicate a strong absorption of the electromagnetic field, which in turn can result a critical hindering of radar tracking.

Aim of the work is the characterization of carbon nanotubes filled composite material in terms of radiation shielding capability. The evaluation of both linear and mass attenuation coefficient in low energy (up to 30keV) X-ray range for different carbon-based polymeric composites is presented. The preliminary results show the intriguing capability provided by composites realized by including few weight percentages (< 2%) of carbon nanotubes within a commercial epoxy matrix, thus suggesting the effective possibility to employ such materials for both structural and radiation shielding applications.

A numerical and experimental characterization of multilayered composite plates reinforced with micro- and nano-fillers to withstand high velocity impacts (HIV) is reported. Main objective of the work is to identify a feasible time/cost saving approach for the production of lightweight structures with significant ballistic capabilities for anti-debris aerospace application. Such procedure is based on the molding system process which is typically adopted for the composite laminates manufacturing, thus avoiding any autoclave processing. The materials employed and the production route are described, then the preliminary results of the ballistic characterization are reported and compared to the numerical simulations.

Aim of the work is to analyze the effects of medium/high energy impacts on layered nanostructured composites for aerospace applications. Ballistic tests have been carried out by means of a linear electromagnetic accelerator, called Rail Gun, that has been in-house assembled and tuned in order to perform impact testing at different bullet velocities. A tunable power supplier has been used to set the system capacitors charging voltage at the desired level in order to tune the Rail Gun energy as a function of the desired bullet velocity. The composite materials under testing have been manufactured by integrating several layers of Kevlar fabrics and carbon fiber ply within a polymeric matrix (epoxy resin) also reinforced with carbon nanotubes at 1wt%. Several plate-shaped multilayered structures have been realized and characterized in terms of energy absorbing capability upon impact. The effect of the introduction of the filling nanostructured material within the bulk matrix has been qualitatively evaluated. A numerical simulation by Ansys code has been also performed in order to analyze the impact dynamic. The obtained results show that the proposed material could be employed for aerospace application, such as lightweight box assembling for electronic equipment mechanical protection from shock or impacts.

The thermal protection structure made of ceramic materials like C/C and C/SiC are currently adopted in hypersonic and vehicle reentry system. In particular, C/C is used for its capability of resistance to high temperature range. There are few studies in literature related to the electromagnetic characterization of C/C and C/SiC in microwave ranges. This research is focused on the microwave absorption cross section (ACS) analysis of C/C and C/SiC in the range 800MHz-6GHz and 50GHz-63GHz. The use of reverberation chamber and vector network analyzer allows to compute the ACS thanks to the homogeneous distribution of the electromagnetic field within the chamber. A mechanical rotating stirrer is also used to increase the statistical homogenization of the electromagnetic field distribution in the testing environment. The results show that C/C and C/SiC possess high electric conductivity within this range of frequency, having absorption performances quite similar to that of metallic materials.

Carbon nanotube reinforced concrete composites (RCC) were characterized in microwave bands currently employed in wireless telecommunication systems. Dielectric permittivity was retrieved by waveguide method and adopted to compute shielding effectiveness of RCC structures having different thickness/filler content. The shielding was also evaluated by reverberation chamber set up; theoretical calculations and measured values are in close agreement, thus testifying to the procedure reliability. Finally, a frequency selective absorber made of RCC layers was designed with the aid of a numerical optimization tool (particle swarm algorithm); the discussion of results is supported by a finite element method analysis of the layered structure.

Aim of the research is the development of a procedure for the production of items with electromagnetic properties addressing any a priori defined behavior. The microwave range 2-18 GHz is analyzed, and a series of both physically real and unreal reflection coefficient profiles are proposed are target to be followed. The proposed structures are multilayers made of polymeric material enriched by carbon-based micro- and nano-powder at different weight percentages. A mathematical modelling which lays down the interaction between electromagnetic field and multilayer structure drives the optimization design by a customized numerical tool based on the particle swarm algorithm framework; this latter gives optimal solutions in terms of layering sequence (i.e., indicating composition and thickness of each layer) to replicate the specific target properties. Both numerical simulations and experimental validations testify the mimic capability provided by the designed/manufactured structures. The proposed strategy thus opens a broad spectrum of novel applications for metrological purposes, as well as for electromagnetic compatibility issues.

Microwave absorbing and shielding material tiles are proposed for improving the stealthness capability of nanosatellites, by using composite materials consisting in polymeric matrix filled by carbon nanotubes. The electric permittivity of the composite nanostructured materials is measured and discussed, and the data allow the modeling algorithm to design the microwave absorbing and shielding faces of the cube satellite. The electromagnetic modeling takes into account for several incidence angles (0-80°), extended frequency band (2-18 GHz), and minimization of the electromagnetic reflection coefficient. The proposed structure is experimentally validated by comparing the electromagnetic simulation to the measurement of the manufactured radar absorber tile. Finally, a finite element method analysis of the electromagnetic scattering by cube stealth satellite is performed.