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 bended and placed on human body, two shorting probes are used to connect the radiation patch and ground plane.
Compared with the antenna without shorting probes, the size of proposed antenna is reduced from 96 mm ??? 47 mm to 70 mm ??? 25 mm, and the measured minimum value of S11 in free space is also decreased from -14.59 dB to -33.30 dB. Furthermore, an antenna with smaller size of 46 mm ??? 25 mm is designed by modifying the proposed structure and it can act as a wearable antenna as well.