Development and characterization of electro-textile antenna for wearable application / Muhammad Shakir Amin Nordin

Nowadays, wearable antennas for body area networks, especially textile-based antennas, have gathered much attention due to being resilient, lightweight, and easily embedded into garments. Wearable antennas are highly in demand to support the Internet of Things (IoT) application, which includes tracking and navigation, mobile computing, public safety, and wireless communication. However, conventional textile-based wearable antennas such as copper tape, copper foil, or copper powder will lead to many related antenna performances. For example, the fabricated antennas can be easily detached from the fabric after being washed or worn many times, causing degradation in antenna performance. Thus, developing a new Self-Manufactured Electro-textile (SME-t) with a more structurally practical conductive fabric was proposed and analyzed in this research work. A rectangular patch wearable antenna fabricated using a SME-t material designed at 1.575 GHz based on the allocated spectrum for Global Positioning System (GPS) application is presented in this research. The SME-t was made up of 0.14mm copper threads as the conductive element and polyester threads as the non-conductive element with the weight ratio of 83:17 respectively using the plain weaving technique. To ensure the textile model's accuracy in the electromagnetic solver, the new textile's characteristics shall be taken into consideration. The dielectric constant, loss tangent, and fabric thickness were measured for the non-conductive element to determine the dielectric properties and electro-textile material's electrical properties. Meanwhile, for the radiating elements, the electrical conductivity was measured and analyzed, accordance to the American Society for Testing and Materials (ASTM) standards. Four design antennas were developed and analyzed to analyze and validate the capability and performance of the SME-t as a radiating element for the wearable antenna. As a reference and for performance comparison, two antennas were developed using established materials such as adhesive copper tape as a radiating element for Design-1 antenna (CPC antenna) and commercial off-the-shelf conductive fabric named SHIELDITTM as radiating element for Design-2 antenna (SPC antenna). Meanwhile, the Design-3 antenna (EPC antenna) is formed by fabricating the SME-t at the front(patch) and copper tape as the ground, while for the Design-4 antenna (EPE antenna), both sides are using the SME-t. The measured return loss values at the desired resonant frequency for the CPC antenna is -20.75dB with 1.5dB gain, while the measured return loss for the SPS antenna is -15.34dB, with 1.23dB gain. The fabricated EPE antenna gives good return loss performance, which is -17.83 dB at 1.575 GHz resonant frequency with 68MHz bandwidth. However, the frequency is slightly shifted by about 1% to the left due to fabrication and measurement uncertainties. Meanwhile, acceptable antenna gain and efficiency of 0.61 dB, and 25.95% are obtained through measurement. The deformation condition for the electro-textile antenna was conducted by focusing on a wearable implementation. For that reason, the bending effect of the EPE antenna was performed and analyzed for two specific bending angles associated to a 125° arc of radius, which resembles the human upper arm, and 171° for the human wrist. Moreover, the effect of bending on the electro-textile antenna in the H-plane and E-plane have also been simulated, measured and analyzed. Based on the results, both planes give relatively good agreement with return loss values of -16.52 dB and -11.03dB at 1.575GHz for H-plane and E-plane, respectively.