A Dual-Band Circularly Polarized Textile Antenna with Gain Enhancement and Bandwidth Extension

A dual-band circularly polarized flexible wearable antenna, which exhibits gain enhancement and axial ratio bandwidth extension in the high-frequency range, has been presented for off-body communication. The antenna operates in the 3.5 GHz WiMAX band and the 5 GHz WBAN band. The antenna achieves dual-band operation by exciting two pairs of odd modes, TM10/TM01 and TM30/TM03. In order to expand the axial ratio bandwidth at high frequencies, a pair of circular arc-shaped parasitic patches are loaded. Meanwhile, a metasurface structure loaded on the top of the patch antenna can be equivalently seen as a high permittivity layer to enhance the gain at high frequencies. The proposed dual-band circularly polarized antenna has a −10dB impedance bandwidth of 9.4% (3.25-3.58GHz) and 30% (4.91-6.58GHz) respectively, with an axial ratio bandwidth of 2% (3.34-3.41GHz) and 9.3% (5.52-6.03GHz), and a peak gain of 7.2dBi and 9.7dBi, respectively. The proposed antenna is made of flexible textile material and exhibits a low SAR value, making it suitable for human body applications.