Bending and On-Arm Effects on a Wearable Antenna for 2.45 GHz Body Area Network

Three types of flexible textile antennas for 2.45 GHz body area network (BAN) are compared in this letter. Two types of conducting materials are used to form radiation patch and ground plane; they are called copper foil tape (CFT, 0.05 mm thickness) and Shieldex (SH, 0.13 mm thickness, 0.009 Ohm surface resistivity). The substrate is a thin felt with relative permittivity of 1.2 and the thickness of 2 mm. In order to satisfy these requirements of small frequency shifting when the antenna is bent and placed on human body, two shorting probes are used to connect the radiation patch and ground plane. Compared to the antenna without shorting probes, the size of proposed antenna is reduced from 96 × 47 to 70 × 25 mm², and the measured minimum value of S₁₁ in free space is also decreased from - 14.59 to - 33.30 dB. Furthermore, an antenna with smaller size of 46 × 25 mm² is designed by modifying the proposed structure, and it can act as a wearable antenna as well.