Abstract:
The electromagnetic wave absorption characteristics of composite cement-based building
material have attracted much interest in recent times. Researchers have mainly focused on
the 2 GHz to 12 GHz frequency range. Mobile and wireless communication systems use
frequencies from 800 MHz upwards. The determination of characteristics such as reflection
loss, absorption, attenuation and shielding effectiveness are crucial in the evaluation
and development of these materials for the building industry. Absorption is an indication of
how much of the EMW energy enters the material. Attenuation indicates how much of the
absorbed energy is converted into other forms of energy by the material. Shielding effectiveness
(SE) is a combination of reflection loss, attenuation and multiple internal reflections
and attenuations.
This research determined these characteristics by measuring the S11 and S21 parameters
of the composite cement-based material in the GSM and WiFi frequency bands. The time domain gating function of a vector network analyser is applied to measure the reflection
from the material. The data was then used to obtain the reflection and absorption losses
in the frequency bands. The transmission loss was measured by placing the sample in the
propagation path between two antennas.
MnZn-ferrite and electrolytic manganese dioxide in powder form were evaluated as absorber
material to increase the permeability of the cement-based material to improve absorption
and attenuation capabilities to create a cost-effective practical electromagnetic wave absorber.
The compound of the cement-based material was cement, sifted river sand and filler
powder.
The results achieved in the research showed the uniqueness of electrolytic manganese dioxide
as filler in composite cement based material for electromagnetic wave shielding effectiveness
improvement. The combined measurement techniques used in this research were
uniquely used to determine the required electromagnetic wave absorption characteristics and
shielding effectiveness of 10 dB was measured in the GSM850 and GSM900 frequency
bands.
