The remarkable progress of electronics and radio communications technology has made mankind very convenient. On the other hand, the countermeasure of EMC becomes more important socially according to the increas of electromagnetic waves. It often causes TV ghost, radar false echoes by the reflected waves from adjacent constructions. Especially, in the area where strong reflectors such as high building, steel tower, iron bridge, etc. exist around radio wave facilities, the performance of such apparatus often deteriorates due to multipath interference between direct wave and reflected wave from these constructions. To meet the circumstance, the international or local regulations and rules suggest the standards for Electromagnetic Compatibility (EMC) in which there are EMI (Electromagnetic Interference) and Electromagnetic Susceptability (EMS).
Especially, it has been reported by many researchers that microwave radiated from mobile phones may be a cause of biological influence such as cancer. So, it is very important to develop absorbing and/or shielding material for preventing EMI. Ferrite or Sendust is very useful as a microwave absorbing material because its magnetic loss contributes to the microwave absorption efficiently.
This thesis deals with basic research for development of EM wave absorbers for multi-layer using carbon. The multi-layered type EM wave absorber was simulated and designed by using the measured complex relative permittivity by changing the thickness and layer, which was fabricated based on the simulated design.
First, the fabricated EM wave absorber consists of 1 mm first layer sheet facing metal with composition ratio of Carbon : CPE = 40 : 60 wt% and 0.8 mm second layer sheet with Carbon composition ratio of Carbon : CPE = 45 : 55 wt%.
Secondly, the fabricated EM wave absorber consists of 0.7 mm first layer sheet facing metal with composition ratio of Carbon : CPE = 50 : 50 wt% and 0.7 mm second layer sheet with Carbon composition ratio of Carbon : CPE = 45 : 55 wt% and 0.7 mm third layer sheet with Carbon composition ratio of Carbon : CPE = 40 : 60 wt%.
As a result, the optimized absorption ability of the 2-layered type EM wave absorber with thickness of 1.8 mm is 30.6 dB at 9.4 GHz. The optimized absorption ability of the 3-layered type EM wave absorber with thickness of 2.1 mm was obtained by 14.6 dB at 9 GHz. It has been a bandwidth from 8 GHz to 12 GHz of 10 dB in reflectivity.