| Summary: | 碩士 === 中國文化大學 === 材料科學與製造研究所 === 91 === ABSTRACT
In this paper, we use copper wires, 5% steel stainless-95% polyester blended yarns, 10% steel stainless-90% polyester blended yarns and 100 % steel stainless blended yarns in the structure of texture for designing electromagnetic wave absorbing screens. By experiment, the performance of single-layer copper wire screens and single-layer steel stainless blend- ed yarn screens are measured. According to analysis of the performance of single-layer screens, the assembly of two-layer screens must design for having performance and effective bandwidth improved by impedance match.
Parts of single-layer electromagnetic wave absorbing screens:
The performance of single-layer copper wire screens is relative to the geometric distance that each copper wire arranges in the structure of texture. When the geometric distance is 0.5cm, the performance of single- layer copper wire screen is highest. The absorption of it can reach above -40 dB, but the bandwidth is very narrow. The performance of single- layer steel stainless blended yarn screens is relative to the percentage of steel stainless in blended yarns and the geometric distance that each steel stainless blended yarn arranges in the structure of texture. When the content of steel stainless is higher, the steel stainless blended-yarn geometric distance must be larger to get better performance. Because single-layer steel stainless blended yarn screens have electric and magnetic properties, the performance and bandwidth of single-layer steel stainless blended yarn screens are better than single-layer copper wire screens which have electric property only.
Parts of two-layer electromagnetic wave absorbing screens:
The widest effective bandwidth for -10dB absorption of two-layer copper wire screens is 15.89%. The widest effective bandwidth for -20dB absorption of two-layer copper wire screens is 4.2%. The most increment of effective bandwidth for -10dB absorption is 7.45% when two-layer copper wire screens compare with single-layer copper wire screens. The most increment of effective bandwidth for -20dB absorption is 2.8% in the comparison between two-layer copper wire screens and single-layer copper wire screens. The widest effective bandwidth for -10dB absorption of two-layer steel stainless blended yarn screens is 91.59%. The widest effective bandwidth for -20dB absorption of two-layer steel stainless blended yarn screens is 26.17%. The most increment of effective bandwidth for -10dB absorption is 35.8% when two-layer steel stainless blended yarn screens compare with single-layer steel stainless blended yarn screens. The most increment of effective bandwidth for -20dB absorption is 17.34% in the comparison between two-layer steel stainless blended yarn screens and single-layer steel stainless blended yarn screens. The performance of two-layer steel stainless blended yarn screens is much more than two-layer copper wire screens.
In conclusion, electromagnetic wave absorbing screens made by steel stainless blended yarns has higher performance and wider bandwidth than those made by copper wires. By the assembly of two-layer screens, the narrow bandwidth of single-layer screens has improved. The most important of having bandwidth increased is matching for impedance of each two screens. To have two-layer screens impedance matched completely, the content of steel stainless must fit in with stainless blended-yarn geometric distance. In this way, two-layer steel stainless blended yarn screen is thin and very good flat-plane electromagnetic wave absorber.
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