Three Dimensional Woven Spacer Microstrip Antenna By Using New CNT Yarn

With the development of the aerospace and information industry,the requirements for the electromagnetic and mechanical performance of the antenna are higher.In the traditional microstrip antenna,the conductive material is mostly copper material which has the disadvantage of high density and bad corrosion resistance.As a new type of conductive material,carbon nanotubes have received more and more attention in recent years.Compared with the traditional metal materials,carbon nanotubes have higher tensile strength,better corrosion resistance,lower density and good conductivity.Nowadays,many scholars have studied the application of carbon nanotube material in the microstrip antenna.Using carbon nanotube material instead of copper material can effectively reduce the antenna weight and make the antenna more stable in harsh environments.In this paper,two kinds of new conductive yarns(glass fiber/CNT film wrapping yarn and CNT film twisting yarn)were prepared by laboratory-designed equipment.The radiation unit of the three dimensional woven spacer microstrip antenna was wove by two new yarns.In this paper,the electrical properties of the new conductive yarns and the dielectrical properties of the matrix were systematically studied.The electromagnetic loss and transmission performance of the antenna were also characterized in detail.The main conclusions include:1.The production process of glass fiber/CNT film wrapping yarn and CNT film twisting yarn was determined in this paper.The conductivity of two yarns was respectively 13600s/m and 13400s/m.The production process of 3D woven spacer fabric including the design of spacer fabric,loom reformation and the practical weaving method was determined.The preparation of 3D woven spacer fabric composites including the selection and match of resin and curing agent,the hand lay-up fabrication process was also determined in this paper.The thickness of the 3D woven spacer fabric composites was 4.85 mm,the resin volume fraction was 19.38% and the void volume fraction was 67.2%.The dielectric properties of the composite was tested by new methods.The dielectric constant was 1.75 and the dielectric loss was 0.0085.2.Microstrip transmission lines were designed by Txline software and simulated by HFSS software.The simulated results showed that the insertion loss(S21)and return loss(S11)of each transmission line were basically the same.In simulation,glass fiber/CNT film wrapping yarn and CNT film twisting yarn could be used as conductive materials in signal transmission.3.The 3D woven spacer microstrip transmission lines were prepared and the transmission performance was tested.The tested results showed that the insertion loss(S21)and return loss(S11)of each transmission line were also basically the same.The insertion loss of each transmission lines was less than 0.45dB/cm at 2.5GHz and the return loss was less than-10 dB.In test,glass fiber/CNT film wrapping yarn and CNT film twisting yarn could be used as conductive materials in signal transmission.4.The microstrip antenna was designed by empirical formula and Txline software and simulated by HFSS.The simulated results showed that the resonant frequency of each antenna was 2.4GHz and the return loss was below-10 dB which met the requirements of the antenna.The radiation patterns were basically the same and all the gain could reach more than 6.5dB which was better than the traditional microstrip antenna.The performance of the antenna decreased with the decreasing of conductivity,but it was not obvious.In simulation,glass fiber/CNT film wrapping yarn and CNT film twisting yarn could be used as conductive yarn in microstrip antenna.5.The 3D woven spacer microstrip antennas were prepared and tested.The tested results showed that the resonant frequency of each microstrip antenna was close to 2.4GHz and the return loss was less than-10 dB which met the requirements.Because the loss would increase obviously when the conductivity of conductive materials was low,the gain and efficiency of CNT film wrapping yarn /copper and CNT film twisting yarn/copper microstrip antenna decreased.But the gain of two antennas was still 3dB which was better than traditional microstrip antenna(2.5dB).This was because that the dielectric constant and loss of 3D woven spacer structure was much lower which could effectively compensate for the degradation caused by the low conductivity.In test,the microstrip antenna prepared by glass fiber/CNT film wrapping yarn and CNT film twisting yarn could meet the requirements.6.Compared with the copper wire,the density of the antenna could be reduced by 20% when the conductive material was glass fiber/CNT film wrapping yarn or CNT film twisting yarn.Using new yarns could not only meet the requirements of antenna,but also reduce the weight.