A Compact Dual-Band Wearable Button Antenna Design for WBAN Applications

A dual-band wearable button antenna for wireless body-area network (WBAN) applications is proposed. With a compact structure, the antenna is capable of providing an omnidirectional radiation pattern in the lower band for on-body communications and a broadside radiation pattern in the upper band for off-body communications. Numerical analysis is presented to better understand the underlying mechanism for the formation of the different radiation patterns in the two bands. In addition, the bandwidth enhancement principle of the parasitic patch is studied. The bandwidth and radiation performance of the antenna operating in free space and in on-body scenario are numerically and experimentally studied. The measured on-body impedance bandwidths are 290 MHz (2.33-2.62 GHz) in the lower band and 2.90 GHz (5.13-8.03 GHz) in the upper band. An efficiency of about 70% is obtained for both bands for the free-space scenario but decreases as expected for the on-body scenario. The peak gains in free space are spanning from 0.9 to 1.4 dB in the lower band and from 5.2 to 6.4 dB in the upper band. The measured results demonstrate that the antenna is suitable for WBAN applications.