Reflection and Transmission Properties of Common Construction Materials at 2.4 GHz Frequency

Abstract

Having an adequate shielding from radiofrequency (RF) electromagnetic fields (EMFs) may serve many causes: to protect sensitive electronic equipment from outside interference; to protect the environment from the high radiation generating equipment; to protect humans from excess radiation etc. Strong RF EMFs may be encountered in public domain but especially in occupational settings, where the process and technology of work requires the usage of RF EMFs. Technical measures to reduce the levels of EMFs include using construction materials with attenuation properties. Generally three types of microwave behavior can be observed: transmission, reflection and absorption. In this study the radiofrequency reflection and transmission characteristics of common building materials were investigated. The investigated materials can broadly be divided into three groups: 1) load bearing materials – concrete, aerated concrete, LECA concrete; 2) thermal insulation materials - foamed polystyrene, mineral wool; 3) cover materials – gypsum based plates and wood dust/chips boards. The samples were square shaped, with the size of 300 x 300mm. The testing frequency was 2.4 GHz and the output power of the generator was 0 dBm. The study used three standard gain horn antennas for reflection and transmission measurements. The results show relatively good transmission properties for most of the materials. The least transmittance was measured in high performance concrete plate where only 34% of the waves penetrated the material and 35% were reflected off. Also with low transmission properties are gypsum board and oriented strand board. These materials were also measured to give low reflectance, 17% by both. Besides concrete, waterproof plywood and particleboard with veneer gave off somewhat reflections. Other materials exhibited very small reflection properties.