# Dual-Band Wearable Antenna Integrated with Glasses for 5G and Wi-Fi Systems
## 2 Materials and Methods
### Antenna Design--Computer Simulations  
The FDTD method that is implemented in the XFdtd software version 7.9 used in this research facilitates the accurate simulation of the interaction between the antenna and the human body, particularly in near-field scenarios relevant to this application. The numerical  
Figure 5: Geometry of the modified F antenna—dimensions given in mm. Figure 6: Current distribution in the designed antenna for 3.5 GHz. Figure 7: Current distribution in the designed antenna for 5.8 GHz. model depicting the antenna positioned on the head, corresponding to the temples of eyeglasses, is presented in Figure 8. In this configuration, the antenna is situated at a distance of 8 mm from the surface of the head. For the simulations, the heterogeneous human head model available in the XFdtd software was used, with an elementary cell size of 1 mm. The antenna's impedance matching characteristics, expressed as the voltage standing wave ratio (VSWR) with respect to a 50 \(\Omega\) reference impedance, are depicted in Figure 9. A VSWR of \(\leq\)2 defines the impedance bandwidth, which spans 3.4 GHz to 3.6 GHz in free space and remains consistent when positioned on the human body. In the higher band, the proximity of the human head introduces a minor impedance detuning. Nevertheless, the impedance bandwidth in the free space extends from 5.61 GHz to 6 GHz, and for on-head placement, it ranges from 5.7 GHz to 6.05 GHz, effectively encompassing the target frequency bands in both scenarios. The simulated radiation patterns in the horizontal plane (x-y plane as defined in Figure 8) are presented in Figure 10 for 3.5 GHz and in Figure 11 for 5.8 GHz. For 3.5 GHz, the total gain of the antenna was \(G_{total}\) = 4.8 dBi. The component of gain for linear polarization parallel to \(\varphi\) versor was \(G_{pli}\) = 2.9 dBi. For \(\theta\), \(G_{theta}\) = 1.7 dBi. For 5.8 GHz, the total gain of the antenna was \(G_{total}\) = 4.3 dBi. The component of gain for linear polarization parallel to \(\varphi\) versor was \(G_{pli}\) = \(-\)1.5 dBi. For \(\theta\), \(G_{theta}\) = 4.2 dBi. The investigation of the designed antenna's characteristics was supplemented by an analysis of the energy absorbed by human tissues in close proximity to the antenna. This was achieved through simulations of the specific absorption rate (SAR) parameter. For this purpose, maximum power values for 5G transmitters in the 3.5 GHz band and Wi-Fi in the 5.8 GHz band were assumed. At a frequency of 3.5 GHz, the power of the transmitter connected to the on-body antenna was set at 250 mW. Under these conditions, the maximum SAR value averaged over 10 g of tissue was 1.8 W/kg, while the maximum value averaged over 1 g of tissue reached 4.8 W/kg. The distribution of the SAR parameter averaged over 1 g of tissue in the z-y plane cross-section, where the highest values occur, is illustrated in Figure 12. The white areas visible in the SAR distribution result from the averaging of results for volumes containing 1 g of tissue and appear in regions where air is present within the human body, such as the nasal sinuses and larynx. Figure 8: Antenna located on the numerical model of a human head. Figure 11: Results of radiation pattern simulations for 5.8 GHz in the horizontal (x-y) plane for the on-head location, gain vs. \(\varphi\) angle. Figure 9: Results of impedance matching simulations of the designed antenna, VSWR coefficient vs. frequency. Similar results were also determined for a frequency of 5.8 GHz. Here, the maximum transmitter power was assumed not to exceed 200 mW, which is typical for the WiFi standard. For this frequency, the maximum SAR value averaged over 10 g of tissue was 0.6 W/kg, and the maximum value averaged over 1 g of tissue was 1.4 W/kg.