Investigation On Microwave Noise Suppression Effect Of Composites Containing Circular Cross-section Amorphous Microwires

With development of electronic products towards high-frequency, digital and miniature, portable, multifunctional, the operative frequency of many electronic products has got above GHz. The component density increases continually too, which incur serious electromagnetic interference. Using noise suppression sheet is an important countermeasure for the interference. High electromagnetic loss and high resistivity are primary requirements of noise suppression sheet. The composite containing glass-covered wires show both nature ferromagnetic resonance and dielectric loss in microwave frequency range. The glass-covered amorphous wires could be used to made composites with high resistivity for its high resistivity and insulating glass outlet. So the glass-covered amorphous wires are good candidate materials for noise suppression.The goals of this thesis are to investigate noise suppression effect of composites containing circular cross-section amorphous microwires (glass-covered amorphous wires) and to develop novel broadband noise suppression materials. The thesis is organized as follow:1、 The influence of distribution characteristics of the wires on the noise suppression effect of the composites containing random distributed or parallel distributed wires were investigated, in where the distribution characteristics include wire length, wire content, wire direction and sample size. The optical wire length, wire content and wire direction are founded out. The results show that the sample size influence noise suppression effect faintly when the sample size perpendicular to the microstrip is not less than50mm.2、 The influence of glass-removal, anneal and the composition of the wire on the noise suppression effect of the composite films containing circular cross-section amorphous microwires was investigated. The results show that glass-removal and anneal may improve the noise suppression effect of the composite films. The composite film containing Fe-based wires depends on the length of random distributed wires and on the row distance between parallel distributed wires in the same way as the composite film containing CoFe-based wires.3、 A novel broadband noise suppression material with important practical value was developed with random distributed Fe-base wires after glass-removal with the content of30pieces/cm2and with the length of10mm, which power loss was great than80%from1.5GHz to8.5GHz.The noise reflection due to the sample is below4.8%.4、 The noise suppression effect of the "sandwich" noise suppression sheet containing glass-covered wires was investigated. It’s shown that adding the random distributed wires led to obvious increase of the frequency band with high power loss. This method posse practical value for to adjust and to improve the performance of the traditional metal granular noise suppression sheet.5、 A composite film with advantage of high power loss was fabricated with parallel distributed Fe-base wires with the row distance of lmm, which power loss was great than92%from2.4GHz to8.5GHz.The noise reflection due to the sample is below3%.6、 The influence of magnetic field on noise suppression effect of the composites containing circular cross-section amorphous microwires was investigated. The results shown that the magnetic field may affect some samples significantly, and the influence obeys the same law for most the samples. A new attenuation peak appears with applied magnetic field, and the frequency of the attenuation peak increases linearly with the increase of the applied field.