IET Microwaves Antennas & Propagation vol:6 issue:15 pages:1696-1703
For reliable on-body communications, the antennas involved need to meet certain requirements such as minimal frequency de-tuning and minimal efficiency degradation. The textile antenna has emerged as a promising candidate for the role in on-body communications but its performance characteristics have not yet been adequately treated in literature; particularly so in the on-body scenario. In a recent investigation into small-sized textile antennas, the authors remarkably determined that a lossier free-space antenna could outperform an antenna with higher free-space efficiency when placed on-body. The purpose of this study, therefore is to determine the practical on-body performance of two larger sized dual-band textile antennas using human subjects to see if this relation holds. The results show that a higher conductivity-based textile material in conjunction with a suitably large-sized ground plane performs more resiliently when placed on-body; about a 20% degradation in radiation efficiency is observed as compared with free-space levels, which is much less than the lower conductivity textile material in this study. The authors concur therefore that in addition to the conductivity of the textile material, the ground plane dimension is also of crucial importance in relation to how efficient the textile antenna performs on human subjects. The on-body frequency de-tuning of these antennas is also investigated, concluding that in the higher frequency sub-band, both antennas remain well matched. However, de-tuning is apparent in the lower band, which should be taken into account when designing these antennas for on-body applications. Theoretical, simulated and experimental evidence is provided to verify the conclusions.