Avaliação das propriedades elétricas de paredes de alvenaria convencionais na faixa de micro-ondas por um método não-destrutivo

Abstract

The propagation characteristics of microwave signals, such as power loss and speed, in buildings significantly determine the operational performance of mobile devices inside buildings. These characteristics are determined by the electrical properties of the walls that make up the masonry of these buildings. Therefore, evaluating the power loss caused by the main materials used in masonry, as well as the electrical properties of these materials, is fundamental for the design of indoor wireless communication links. In this sense, this research aims to evaluate the attenuation of microwave signals and the electrical properties of different materials used in building masonry (ceramic blocks, concrete blocks and plaster walls). Three wall samples were produced from each of these materials for characterization purposes regarding their structure, microstructural organization and electrical properties. The attenuation in the wireless signal caused by each type of material, and the electrical properties such as electrical permittivity, shielding efficiency and electrical conductivity were determined using an experimental measurement scheme proposed in this work. Average values for attenuation coefficients as a function of frequency for the operating range of the main 5G and Internet of Things (IoT) services were obtained. Furthermore, the dependence of wireless signal attenuation on the type of material and its composition and the influence of the type of wall covering on signal attenuation were evaluated. The results indicated that walls made of ceramic blocks caused the greatest attenuation of the signal, among all types of masonry analyzed; while plaster walls were those that caused the least attenuation. When comparing non-structural block masonry, it appears that cement block walls showed lower attenuation when compared to ceramic block walls. After analyzing the micrographs of the ceramic and cement blocks, it can be stated that the higher the void index and the porosity of the material the wall was manufactured from, the lower the value of its electrical permittivity and consequently the lower the attenuation caused in the wireless signals in today's commercial service bands.