Analysis on bending performance of the electro-textile antennas with bandwidth enhancement for wearable tracking application

Abstract

Frequency detuning issues in antenna operation due to structural deformation have become a concern, especially for flexible devices such as a textile antenna. Under deformed conditions such as during bending, the antenna might not operate at the desired frequency, causing performance degradation. Therefore, a 1.575 GHz textile antenna for GPS tracking application with defected ground structure is proposed in this paper to alleviate the frequency detuning issues and is demonstrated under two bending conditions, H-plane and E-plane. The implementation of DGS is expected to minimize the frequency detuning by increasing the bandwidth. Hence, the frequency detuning effects could be minimized under bent conditions with broader bandwidth and acceptable antenna performance. In this paper, a planar textile-based antenna with the dimension of 90mm (L) × 100mm (W) was designed, and three rectangular slots were applied at the ground to create DGS. A self-developed electro-textile and polyester were used as the antenna conductive material and substrate. Through the study, a detailed analysis was conducted for both antennas, with and without DGS. The significance of DGS in the proposed design is evaluated and clarified by comparing electric and magnetic field intensities in non-radiating and radiating edges. The detailed performance comparison were observed and analyzed through S-parameter, gain, radiation pattern, and current distribution. The technical performance of the proposed technique is validated through simulation and measurement. DGS implementation has improved the antenna bandwidth from 4.04% to 12.20%, with 1.45dB gain and 23.75% radiation efficiency. As a result, the antenna can operate at the desired frequency under both bending conditions. DGS method provides simplicity in its design, and this method has been widely used in conventional antennas previously. However, the detailed behaviour of field intensity around the non-radiating and radiating edges have not been demonstrated and analyzed. Therefore, the validation of the proposed design through a detailed analysis of E-field and H field intensity concerning antenna configurations, with and without DGS becomes the main contribution of this paper. In addition, the study of bending on different bending radius is also conducted in this paper.