Fabrication Process Optimization And Performance Of 3D Fabric Microstrip Antenna Based On Carbon Fiber

With the development of the information age,more requirements have been needed for the upgrading antenna equipment.People are paying more and more attention to lightweight,stable and intelligent antennas.Compared with the traditional metal materials such as copper,aluminum,etc,carbon fiber which is a new type of conductive materials has higher strength and modulus,lower density and corrosion resistance,great resistance to higher and lower temperature.Due to these outstanding properties,numerous scholars around the world have shown great interests in the research of carbon fiber.In addition,the researches on carbon fiber reinforced composite materials used for antenna applications have been popular.Taking carbon-fiber composite materials or nickel-plated carbon fibers instead of traditional metal will not only lighten the weight of antenna,also improve the stability of antennas in harsh environment,which is benefit for the development of the stable and lightweight antennas.In this paper,carbon fibers or nickel-plated carbon fibers treated by coating process was woven into a microstrip antenna through the 3D weaving technology.Firstly,the electrical properties of the conductive yarns were systematically studied after coating process.Secondly,the structural parameters of 3D spacer fabrics,transmission lines and microstrip antennas were designed and determined.The weaving process of the microstrip antennas based on carbon fibers was optimized.Finally,the electromagnetic performance of microstrip antennas were simulated,tested and analyzed.The main findings include:(1)In order to avoid the wear and tear of carbon fiber and the short circuit of antenna structure in the weaving process,carbon fibers and nickel-plated carbon fibers were coated with flexible resin,polyvinyl alcohol and polydimethylsiloxane respectively.The electrical properties of the composite yarns were measured and analyzed.The conductivity of3%PVA/Ni-Coated CF、3%PVA CF、PDMS/Ni-Coated CF was 2.0×10~4/m、7.4×10~3s/m、1.5×10~3s/m respectively.The above three composite yarns were used as conductive materials for the weaving of microstrip antennas and transmission lines.In order to reduce the friction between carbon fibers,a moderate yarn density was selected.Fabric specification was as follows,with 50 yarns per centimeter along the direction of weft,100yarns per centimeter along direction of warp.The epoxy resin has been chosen due to the excellent dielectric properties with a dielectric constant of 4.0.3D woven spacer fabric was prepared by hand paste procedure.Dielectric constant and dielectric loss of dielectric substrates were measured using the PNA3766 vector network analyzer.(2)Microstrip transmission lines were designed and measured by Txline2003 and HFSS for verifing the transmission loss of carbon fiber fabric’s structure and the electromagnetic properties of the antennas.Microstrip transmission lines were prepared through 3D weaving and hand paste process.Each transmission lines of S21 was tested by PNA3766 vector network analyzer.Compared with the simulated results of S21 that all of them were less than 0.1dB/cm,the measured results of insertion loss of four transmission lines closing to 0.5dB/cm increased slightly,meeting the requirements of signal transmission.The simulation model of microstrip antenna was established and measured by HFSS.The simulated results showed that the resonant frequency of each antenna was 2.45GHz with return loss below-10dB,significant directivity of E and H surface,which met the requirements of the antenna.At the same time,the gain reached more than 6d B.(3)The 3D woven spacer microstrip antennas were prepared,measured and analyzed.The measured results showed that the resonant frequency of microstrip antennas were close to 2.45GHz with the return loss less than-10d B,significant directivity.The main lobe of directivity diagram was bigger than the posterior lobe,the side lobe was narrower than the main lobe.Above all met the requirements.With the conductivity of yarns declined,the gain and efficiency of microstrip antennas decreased,and the transmission signal was weaker.Taking 3D woven spacer fabric as dielectric substrate of the microstrip antenna,compensated effectively for the attenuation of electromagnetic performance due to low conductivity,and solved the problems of laminated antennas.The measured gains of 3%PVA/Ni-Coated CF and 3%PVA CF microstrip antenna are 2.97d B,2.43dB respectively.Compared with copper wire microstrip antenna,the density of the above two antennas decreased nearly 28%.On the premise of normal operation of antennas,they improved the working stability of antennas and lightened the antenna’s weight,adapting to the development trend of stable and lightweight antennas.