With the progress of electronics industry and radio communicaton technology, mankind might enjoy its abundant life. On the other hand, serious social problems such as electromagnetic interference (EMI), have arisen due to the increased use of electromagnetic (EM) waves. Therefore, International organizations such as CISPR, FCC, ANSI, etc., have provided the standards for the EM wave environment and for the countermeasure of the electromagnetic compatibility (EMC).
EM wave absorbers are used for constructing an anechoic chamber in order to test and measure EMI and electromagnetic susceptibility (EMS). It has been recognized that the absorption ability of the EM wave absorber has more than 20 ㏈, and the absorption frequency band is required through 30 ㎒ to 1,000 ㎒ for satsfying the international standards about an anechoic chamber for EMI/EMS measurement.
From November of 1998, however, the CISPR has acccepted the extended frequency band from 1 ㎓ to 18 ㎓ additionally in the bandwidth of EMI measurement.
In this dissertation, an EM wave absorber with super wide-band frequency characteristics was proposed in order to satisfy the above requirements and designed using the EMCM. Furthermore, a new simulation and analysis methods were adopted by the FDTD method. The bandwith of the proposed EM wave absorber was confirmed by simulation and experiments, which has the bandwidth from 30 ㎒ to above 6 ㎓. In the experiments, tapered rectangular coaxial line was used.
In addition, to improve absorption ability of Ferrite EM wave absorber, the ferrite EM wave absorber on which pyramidal EM wave absorber is attached.
As a result, the frequency band from 30 ㎒ to 18 ㎓ obtained under the tolerance limits of more than 20 ㏈ absorption.