Research Of Textile Wearable Antennas And Their Applications

Textile antennas are planar, highly integratable and flexible for wearable applications. The design of the textile antenna and its applications is of great importance to the development and popularization of the wearable technology.In this dissertation, the cavity models of two typical half-structure antennas, the quarter-wave patch antenna and half-mode substrate-integrated cavity antenna, are presented. The expressions of the internal E-field distributions and resonance frequencies for the lowest modes of these two antennas are respectively deduced. Based on theoretical analysis, these two antennas are compared for wearable applications. An accurate modelling method is proposed for the textile antennas with embroidered side walls to avoid the mismatch between the simulated antenna performance and the measured counterpart on the fabricated antenna prototype. The accurate value of the seam compression depth is obtained through simulation parameter fittings. The effects of the seam compression are analyzed for the two antennas. The antenna dimensions and feeding positions are re-optimized for proposed various bending conditions to increase the operational bandwidths for the two antennas and to offset the shift of the central frequency. Finally, textile prototypes of these two antennas are fabricated using conductive textiles, conductive threads, PF-4 foam, and digital embroidery, and the measured results verified the designs.The performance of the half-mode substrate-integrated cavity antenna in 180 degree folding conditions is investigated, and the effects of different folding diretions and folding positions are analyzed. Two folded geometries of the half-mode substrate-integrated cavity antenna with respectively a probe feed and a shielded stripline feed are modelled and simulated to reduce the antenna width and to meet the requirement for the planar design. And the later folded geometry also shows easier integration into clothes and provides a solution for the connection between the wearable antenna and other devices or circuits. The effects of different thickness combinations of the two substrate layer and the width of the conductive ground are simulated and analyzed. The textile prototype of the folded half-mode substrtae-integrated cavity antenna with a shielded stripline feed is fabricated for the practical measuremens of the antenna performances on the human body and with bending conditions.Based on the half-mode substrate-integrated cavity antenna, the cheap, durable and non-flamable leather is selected as the substrate material considering the practical wireless communication environment in underground coal mine tunnels. The performance of the half-mode substrate-integrated cavity antenna with a shorting pin inside the cavity is simulated, and the relationship between the resonance frequency, impedance matching and the shorting position. A removable metallic screw is employed as the shorting pin with three pre-drilled holes to obtain four switchable resonance frequencies, namely 2.45 GHz, 2.67 GHz, 2.87 GHz and 3.08 GHz. A frequency-switchable textile half-mode substrate-integrated cavity antenna for coal mine workers is designed, and this antenna meets the requirement of the essential safety in coal mines. The textile antenna prototype is fabricated and measured to validate the expected frequency-switching function.