With the rapid advancements in electronics industry and radio communication technology, mankind has enjoyed abundant life. On the other hand, serious social problems such as electromagnetic interference (EMI) and electromagnetic susceptibility (EMS) have arisen due to the increasing use of electromagnetic waves.
Therefore, the countermeasure against electromagnetic waves obstacle was embossed to important subject. International organizations such as CISPR, FCC, ANSI, etc. have provided the standards for the EM wave environments and for the countermeasure of the electromagnetic compatibility (EMC).
Unwanted electromagnetic waves leakage from the circuits of communication equipment and electronic equipment can cause a malfunction of the other equipments. Problems regarding EMC are more likely to occur, as smaller, lighter, and more sophisticated electronic equipment, and thus the packaging density of electronic components must be increased drastically. These problems can be eliminated by using EM wave absorbers.
Soft and hard ferrites are well-known as absorption materials for EM wave absorbers. Soft ferrites, such as MnZn ferrite and NiZn ferrite are useful materials for EM wave absorbers, but the magnetic loss of them decreases quickly in the GHz range. Hard ferrites, such as Ba ferrites and Sr ferrites show high magnetic loss in the GHz range, so they are useful materials for EM wave absorbers in high frequency range.
In this thesis, the improvement of EM wave absorption characteristics of the EM wave absorber with mixture of Sendust, and Carbon, Al(OH)3 was studied and analyzed in the case of a mixture rate of sendust to 75 wt%, 80 wt%, and 85 wt%, and a mixture rate of carbon to 40 wt%, 45 wt%, and 50 wt%. The permittivity and permeability is calculated by the measured data, and the EM wave absorption abilities are simulated according to different thicknesses of the EM wave absorbers. Then double-layer type EM wave absorbers for improved absorption characteristics are simulated and fabricated in accordance with different layer-sequences.
As a result, in the case of Sendust the absorption ability of EM wave absorber was obtained over 7.9 dB at 2.6 GHz, and in the case of Carbon the absorption ability of EM wave absorber was obtained over 40 dB at 10.2 GHz. In addition, the double-layered EM wave absorber consists of sendust : Al(OH)3 : CPE=85 : 5 : 10wt% and Sendust : Al(OH)3 : CPE=75 : 5 : 20 wt% showed an improvement of the EM wave absorption characteristics of over 10 dB at 2.4 GHz with the thickness of 1.5 mm