tailieunhanh - Wave Propagation Part 13

Tham khảo tài liệu 'wave propagation part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 412 Wave Propagation a Composite A Sendust 25 vol Al 25 vol Frequency GHz b Composite B Sendust vol Al vol Frequency GHz c Composite c Sendust 10 vol Al 40 vol Fig. 13. Frequency dependences of return loss for composites made of both sendust and aluminum particles dispersed in polystyrene resin. The frequency range is from 1 to 10 GHz. Composite Electromagnetic Wave Absorber Made of Soft Magnetic Material Particle and Metal Particle Dispersed in Polystyrene Resin 413 n loss dB N _ o o c i y -J X 1 ợ .Y Ỉ 5 73 f 3 Q - mm Ct -30 s mm -40 I- I I I 1 1 5 20 25 30 35 40 Frequency GHz a Composite B Sendust vol Al vol Frequency GHz b Composite c Sendust 10 vol Al 40 vol Fig. 14. Frequency dependences of return loss for composites made of both sendust and aluminum particles dispersed in polystyrene resin. The frequency range is from 15 to 40 GHz. less than -20 dB at frequencies above 15 GHz and the normalized -20 dB bandwidth of these two composites was broader than that for the composite made of only sendust. In addition the sample thicknesses where the return loss is less than -20 dB were very thin. In particular composite c had high values of normalized -20 dB bandwidth in spite of the high frequency range and the frequency where the return loss is less than -20 dB can be selected by changing the sample thickness in the range from to mm. It is concluded from these results that the absorption characteristics of the composite made of sendust in the high frequency range could be improved by adding aluminum particles. Moreover aluminum is low cost abundant chemical element and light wight. For example the mass densities of composites A B and c were approximately and g cm3 respectively while the mass density of the composite made of 53 vol -sendust is approximately g cm3. Therefore a light-weight absorber can be fabricated by incorporating both sendust and .