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.