Electromagnetic Simulation and Measurement of Carbon Nanotube Thread Dipole Antennas

Abstract

The conductivity, current distribution, and radiation efficiency for a variety of dipole antennas constructed from carbon nanotube thread/rope are simulated using Hallen's integral equation for a thin wire applied to the method of moments and are compared to a standard copper wire dipole antenna. Next, the conductivity and weight of fully fabricated carbon nanotube thread and rope samples are measured and analyzed. Finally, half-wavelength copper and carbon nanotube (CNT) thread dipole antenna prototypes are fabricated, measured, and analyzed. Simulation results indicate that the CNT thread/rope antenna performance improves with increased diameter and that the application of these materials as a half wavelength dipole antenna yields manageable losses of less than 1-5 dB at RF frequencies above 10 GHz. Measured sample results demonstrate that the existing single-ply CNT thread exhibits a conductivity approximately 2-3 orders of magnitude lower than copper. The braiding method employed to produce large diameter CNT rope was demonstrated to be a poor method for increasing thread diameter and conductivity due to the additional resistive losses that the braiding geometry introduced. Dimethyl sulfoxide densification was found to be a valuable method for improving CNT thread conductivity and lowering the thread contact resistance. Dipole antenna prototype measurements confirm the functionality of the CNT thread as an antenna, albeit with a 4% downward frequency shift due to reactance effects and material losses of greater than 12 dB at 2.45 GHz as predicted by the results from the method of moments simulations.