도전성 섬유를 이용한 전파흡수체에 관한 연구

Abstract

In this thesis, EM wave absorbers were fabricated with MnZn, NiZn, Ba ferrites, and Sendust on the basis of very thin conductive fibers. The purpose of this research is to develop a complex EM wave absorber with superior EM wave absorption based on conductive fibers.

A conductive fiber which has shield property of 20~40 dB in GHz was used in this work. The absorption ability of EM wave absorber can be increased by using the conductive fibers, because some absorbtion and return losses can be occurred by the conductive fibers. Moreover, the conductive fibers are of light weight, thin thickness, and can be used as binders to fabricate complex EM wave absorbers, therefore it is possible to apply them to the fabrication of EM wave absorber without influencing their weight and volume. Complex EM wave absorbers were made by pasting a sheet of fiber on the backside of existing absorber using epoxy paint which is flexible and not fragile.

In this thesis, two types of fibers, (one is gold-plated with about 0.1Ω/ ㎠ surface resistance, and the other is alumina-plated with 60 Ω/ ㎠ surface resistance), are used, and some EM wave-absorbing materials with high absorption ability, such as MnZn, NiZne, Ba ferrite, and Sendust are used.

As the experimental results, the gold-plated fibers couldn't increase absorption ability but could be used as EM wave shielding materials because of their high shielding efficiency, light weight, and thin thickness (about 0.09 mm).

Comparing the EM wave absorbers composed of the alumina-plated sheet with ones fabricated without the alumina-plated sheet, the former improve the absorption abilities due to the reflection and absorption losses resulted from the alumina-plated sheet itself. Shielding efficiency of alumina-plated sheet is not better than the gold-plated sheet. However, it can be used as EM wave absorbers materials because of its average shielding efficiency of 20 dB to the EM wave absorbers in GHz band, and its thickness is 0.25 mm, weight is light as well as the gold-plated sheet.

Fabricated MnZn ferrite, Ba ferrite, NiZn ferrite, and Sendust EM wave absorbers are useful as a EM wave absorber for S-Band, Ku-Band and C-Bnad, respectively.

This thesis shows that EM wave absorber fabricated with conductive fibers can be a candidate of EM wave absorber with superior EM wave absorption ability for GHz band and do not allow permeation of unwanted EM waves.