A Pattern Reconfigurable Flexible Wearable Antenna for On/Off-Body Communications Applications

Abstract

In wearable applications, the wearer is fully monitored and tracked, where the data are sent to, either, close wearable devices or distant ones. The former type of communication is expressed as on-body communication, while the latter is denoted as off-body communication. It is desirable that a single antenna serves both types of communication links, instead of utilizing a number of wearable antennas. This will lead to reductions in size and cost. As a result, the antenna should possess the reconfiguration feature. For that reason, the aim of this project is to design, simulate, implement, and measure a printed modified pattern reconfigurable antenna on a flexible substrate. The antenna should possess wearable specifications, especially a low Specific Absorption Rate (SAR) which complies with the international standards, in order to operate at close distances from the human body.

Therefore, in this project, a single antenna that has the property to work in on-body and off-body communications is proposed. The reconfigurable patterns are the main concern for this antenna. Different configurations of the proposed antenna are investigated, and comparisons between them are presented. The antenna has been designed on two other materials to fit different scenarios; firstly, it designed on Roggers substrate with r=2.2 and h=0.5 mm, it considers a flexible material, and on the other hand, it is designed on wool felt material with r=1.65 and h=1.5 mm, which achieves properties of wearability. In all scenarios, the overlapped impedance bandwidth with |S11| < -10 dB for the three pattern modes is from 2.34 GHz to 2.6 GHz. Throughout the overlapping bandwidth, the front-to-back (F/B) ratios are higher than 15 dB for the two unidirectional radiation modes, and out-of-roundness is less than 1.2 dB for the omnidirectional radiation mode. The peak realized gain of the proposed pattern reconfigurable antenna is 6 dBi for unidirectional mode.