Andrea Delfini

Measurement of Electromagnetic Field Attenuation by Building Walls in the Mobile Phone and Satellite Navigation Frequency Bands

The electromagnetic (EM) wave attenuation by building walls is experimentally investigated, focusing on the frequency range 700 MHz-5 GHz. The results of this research can be used in the planning of the indoor radio coverage of wireless access networks like 2G, 3G, 4G, WiFi, and future 5G mobile phone systems, in the study of satellite navigation applications, and in the evaluation of the resident population exposure to electromagnetic fields emitted by the radio base stations (RBSs) of the mobile phone radio access network (RAN). Measurements are obtained using a portable vector network analyzer (VNA) connected to two light Vivaldi antennas. Time-domain methods are used to reduce errors caused by multiple paths. Measurements of EM building wall attenuation have been carried out in the city of Rome, Italy, in different buildings topologies: historical buildings from the Roman Empire up to middle 19th-century and modern reinforced concrete buildings. Measurements of EM shielding effectiveness (SE) show values even greater than 80 dB.

Electromagnetic Shielding of Building Walls: From Roman times to the present age.

We have investigated the electromagnetic (EM) shielding effectiveness (SE) of building walls built in different ages. The measurements were carried out in the city of Rome, analyzing different building typologies from Roman Empire historical ruins up to modern reinforced concrete and steel/glass buildings. The method consisted of a measurement performed by means of a portable two-port vector network analyzer (VNA) connected to a couple of light antennas located in opposite positions with respect to the middle wall. The explored frequencies were in the range of 0.7-5.0 GHz, which many countries have currently adopted for mobile-phone radio access network (RAN) and satellite positioning services. The SE measurements showed values of up to 100 dB, and the analysis of the results showed that ancient Romans building walls and steel/glass building structures have the highest shielding capability. A numerical simulation of the outdoor-to-indoor transition attenuation and a statistical analysis of the signal code power in the live RAN of Telecom Italia integrate the discussion of the results.

Electromagnetic Characterization of Materials by Vector Network Analyzer Experimental Setup

Abstract This chapter deals with the vector network analyzer systems used for the study of the electromagnetic properties of materials. The focus of the chapter is not the device itself, about which plenty of literature is available, but its application in materials characterization at the microwave and millimeter wave levels. Some interesting measurement techniques are presented and discussed in detail with the help of numerous experimental results. Moreover, the measurement criteria are commented on as a function of the materials under test. The waveguide, coaxial air line, Naval Research Laboratory Arch bistatic system, free-space, and reverberation chamber methods are presented and analyzed. Examples of measurements of conventional materials used in architectural building up to advanced foam and nanocomposite materials considered in defense and aerospace applications are presented. The authors have tried to transfer their wide laboratory expertise in this chapter, with the aim to be useful to other researchers in the field of electromagnetic characterization of materials.

Advanced Radar Absorbing Ceramic-Based Materials for Multifunctional Applications in Space Environment

In this review, some results of the experimental activity carried out by the authors on advanced composite materials for space applications are reported. Composites are widely employed in the aerospace industry thanks to their lightweight and advanced thermo-mechanical and electrical properties. A critical issue to tackle using engineered materials for space activities is providing two or more specific functionalities by means of single items/components. In this scenario, carbon-based composites are believed to be ideal candidates for the forthcoming development of aerospace research and space missions, since a widespread variety of multi-functional structures are allowed by employing these materials. The research results described here suggest that hybrid ceramic/polymeric structures could be employed as spacecraft-specific subsystems in order to ensure extreme temperature withstanding and electromagnetic shielding behavior simultaneously. The morphological and thermo-mechanical analysis of carbon/carbon (C/C) three-dimensional (3D) shell prototypes is reported; then, the microwave characterization of multilayered carbon-filled micro-/nano-composite panels is described. Finally, the possibility of combining the C/C bulk with a carbon-reinforced skin in a synergic arrangement is discussed, with the aid of numerical and experimental analyses.

Is Montgomery tracheal Safe-T-Tube clinical failure induced by biofilm?

Objectives Montgomery Safe-T-Tube deterioration and early biofilm colonization may explain the discomfort claimed by many patients and clinical failures. The aim of the study was to analyze the deterioration of Montgomery Safe-T-Tube morphological and mechanical properties in vivo in 16 patients by using microbiological methods, optical and electron microscopy, and engineering tests. Study Design Prospective controlled study at a single medical center. Setting University hospital. Subjects and Methods The study, conducted from April 2007 to February 2012 at the “Sapienza” University of Rome, was designed to collect 2 Montgomery Safe-T-Tubes from each patient. The first was removed 3 to 15 days after insertion (group A) and the second at least 90 days after (group B). Specimens underwent microbiologic assays, electron microscopic analysis, immunocytologic analysis, and mechanical tests. Results Microorganisms were not isolated in 2 group A cases (12%), whereas they were in all group B cases. Biofilm was identified in 11 of 16 (69%) group A samples and in 16 of 16 (100%) group B samples (P = .0149) using scanning electron microscopy. Immunohistochemistry showed monocyte-granulocyte line cells producing interleukin-1β on the external surfaces of Montgomery Safe-T-Tubes. The tensile test showed that the wear related to the longer period of use makes Montgomery Safe-T-Tubes more rigid than newer ones. Conclusion Early biofilm colonization takes place in Montgomery Safe-T-Tubes in most cases. The mechanical decay could be justified in part by the destructive biofilm activity and by the release of inflammatory effectors and enzymes.