A Wearable Self-Grounding Slit Antenna for ISM/4G/5G/Bluetooth/WLAN Applications

This design proposes a self-grounding semi-circular gap dual-band flexible antenna in the context of the rapid development of wireless body area networks. The antenna combines the slit structure with the characteristics of traditional rectangular monopole antenna to realize dual-band. In addition, the antenna’s grounding structure adopts the self-grounding structure, which is less used nowadays, to extend the bandwidth. The antenna is designed on a dielectric board of polyimide material with a relative dielectric constant of 3.5. The overall dimensions of the antenna are 44 mm
$\times 40$
mm
$\times 0.2$
mm with two different sized gaps in a rectangular patch, similar to the geometry of an umbrella handle. Measured data shows that the structure has higher gain and efficiency in the bent state than in the flat state, making it ideal for wearable smart terminals. It can be combined with a smart armband for sports and medical applications or for a single soldier wearable wristband smartwatch. The article explores the effect of different slot sizes and different bending angles on the performance of the antenna, as well as the specific absorption rate values of the antenna for the human body. Finally, two frequency bands with good omnidirectional radiation characteristics are obtained: 2.38–2.81 GHz and 4.28–5.10 GHz. The antenna covers ISM, 4G, 5G, Bluetooth, WLAN, and other common communication frequency bands. The results of the study show that the design method is highly reliable.