Multiband textile antenna for wearable application

Abstract

In recent years, wearable computing system, also called “smart clothing”, has been developed for monitoring, tracking and navigating application especially in medical, healthcare and military sectors. One of the considerations for wearable system is to design suitable antenna with good performance while providing comfort to the user. Robustness, flexibility and compactness are required as wearable antenna. In this project, textile antennas using denim materials which has and = 0.085 are chosen to fulfil the requirements of the antenna. The antenna model is designed using Microwave Studio CST software. Several antenna prototypes are fabricated and evaluated with different conducting elements (Shieldit fabric and copper foil tape). For the multiband antenna, a triple band fractal Koch dipole antenna was designed to operate at 0.9 GHz, 2.45 GHz and 5.8 GHz. The fractal Koch antenna is reduced to about 15% of length size of the straight dipole antenna. Both antenna performances with different conducting elements were observed in terms of return loss, bandwidth, radiation pattern and gain. Three types of analysis are evaluated on fractal Koch multiband antenna which measures performance with bending, human body and wet conditions. The performances of the antennas are conducted based on resonant frequency and bandwidth. From the analysis, it is found that the bending of copper fractal antenna on human body drastically shifted the resonant frequency from 0.90, 2.45 and 5.16 GHz to 0.49, 1.16 and 3.03 GHz. The suitable antenna placement on human body has been discovered at the chest with resonant frequencies of 0.80, 2.56 and 5.16 GHz and the backside with resonant frequencies of 0.88, 2.48 and 5.8 GHz. The fractal Koch multiband antenna maintains performance with less 3% of water absorption in the antenna under wet conditions. The performance of copper tape was shown to be more profound than Shieldit antenna in terms of return loss, radiation pattern and gain due to the minimization of the electrical loss of material. However, Shieldit antenna is more flexible and robust than the copper antenna.