Characterisation and Testing Shielding Fabrics

Abstract

In connection with rapidly increasing progress in the radio communication ser- vices and other technical branches, which in∞uence electromagnetic environment, the problems connected with electromagnetic compatibility occur. Because of the electromagnetic interference minimization it is necessary to ensure the shielding of sensitive devices, buildings and also per- sons. The suitable alternative to the classical shielding materials can be special shielding-fabrics. The main advantages of these fabrics are their low weight, ∞exibility and their easy processability. Shielding is a very popular method of ensuring electromagnetic compatibility and of protecting electronic and electrical equipment and human beings against radiated electromagnetic energy. The knowledge of shielding efiects of difierent types of material represents a basic prerequisite for further development and implementation of shielding devices. This paper presents an analysis of the measuring methods and a comparison of difierent materials in terms of their speciflc shield- ing efiects. The absorption properties of the various submitted samples were measured using both a Crawford chamber and the Insertion loss method. In the samples, the capacity to absorb electromagnetic waves was determined with the help of a spectral analyzer. Shielding is a very popular method to ensure the electromagnetic compatibility, protection of elec- tronic equipments and human beings against radiated electromagnetic energy. Decrease of radiation disturbances and increase of immunity to electromagnetic flelds is obtained with grounded shield- ing eventually in combination with other suppression components. The shielding is also used to isolate some places from the external source of electromagnetic interference or to prevent radiation electromagnetic disturbance from the internal shielded source. There were used metallic materials with well known electromagnetic qualities for the shielding. There are more and more used plastic materials for shielding with a conductive coating or with embedded conductors which ensure the shielding ∞exibility. Recently the researchers' attention is focused on even lighter and more ∞exible materials which are fabrics coated with absorptive fllm. These materials due to their ∞exibility and low cost price are promising candidates for instruments and human protection against unwanted electromagnetic radiation efiect. Measuring shielding and absorption qualities of fabrics and plastic materials is relatively di-cult. There were developed many measuring methods that are used in various laboratories to solve these problems. A lot of producers who develop this type of fabrics are searching for relatively simple, not time-consuming and reliable measuring methods to measure shielding and absorption qualities which operate in a wide frequency range.