Circularly Polarized Button Antenna with Omnidirectional Radiation for On-Body Communications

An omnidirectional circularly polarized button antenna in the 5.8-GHz Industrial, Scientific, and Medical (ISM) band is investigated for on-body applications. The proposed antenna has a rigid jeans button shape and is mounted on flexible textile. Vertical polarization is realized by a monopole with sleeve which enhances the mechanical stability of the antenna. Horizontal polarization is generated by four arc-shaped elements. Simulated result shows the overlapping of -10-dB impedance bandwidth and 3-dB axial ratio bandwidth ranges from 5.59 to 6.01 GHz, covering the whole the 5.8-GHz ISM band. The average gain of-3.6 dBic with a roundness of less than 1 dB and a radiation efficiency of 59% in azimuth plane is achieved. The dimensions of the antenna are π × (0.19λ
0
)
²
× 0.19λ
0
(λ
0
is the wavelength at the center frequency).