Analysis on shielding effectiveness of electromagnetic field of building components in the range of communication networks fields
We are exposed electromagnetic radiation anytime and everywhere. However, during the 20th century, environmental exposure to man-made electromagnetic fields has been steadily increasing with growing electricity demand, ever-advancing technologies and changes in social behaviour have created more and more artificial sources. The quantity of the electromagnetic field is increased. This trend is likely to continue. This paper consists of two parts. Tiny electrical currents exist in the human body due to the chemical reactions that occur as part of the normal bodily functions, even in the absence of external electric fields.
We present the influence of RF field exposition on biological samples during short-time period tests in first part this article. The exposition was carried out in transversal waveguide. The samples were observed and results recorded. The analytical monitoring methods were applied. The experiment confirmed that short-time exposition in the range of today communication networks causes serious changes in biological systems. It is necessary to protect against effects of electromagnetic fields.
The shielding is used to protect against effect of electromagnetic field. Commercially available shielding are building materials, for example window, brick, polystyrene, roof and so on. Quality of shielding materials is determined by three coefficients, shielding effectiveness SE, absorption coefficient A and a reflection coefficient R. The measuring of shielding effectiveness and reflection of electromagnetic field is observed in the second part this article. The measurements were focused on measuring of shielding effectiveness in the range of high frequencies from 1 GHz to 9 GHz by step 0.2 GHz. The measured object was a wooden window and plastic window. Size of window was 1.5x1 m. The measured objects were placed at a distance of 30 cm from the transmitting antenna. From measuring of shielding effectiveness and reflection of electromagnetic field was calculated absorption of electromagnetic field. Measurement was preformed according IEEE Standard, Method for Measuring the Effectiveness of Electromagnetic Shielding Enclosures. For measuring purposes was used horn type of transmitting and receiving antenna. Measurement was performed in the non-reflection chamber because exterior influence.
The result of the measurement is dependence of shielding effectiveness, reflection and absorption on frequency for wooden and plastic window. In conclusion, will be compared results from measuring of shielding effectiveness, reflection and absorption of electromagnetic field.Shielding characteristics of building materials can be used in the later planning of location of electromagnetic fields sources.