# Dual-Band RF Wireless Power Transfer System with a Shared-Aperture Dual-Band Tx Array Antenna
## 3 Experimental Results of RF Wireless Power Transmission
### Single-Band RF WPT Experiment
#### 3.1.2 WPT Experiment (2): Varying the Rx Position and the Direction of Beam-Forming  
The RF WPT experiment at 2.482 and 5.73 GHz was conducted by changing the position of the Rx antenna on a virtual plane with a spacing of 0.3 m at a distance of 1 m or 2 m, as shown in Figure 16. At this time, the power received by the Rx antenna according to the beam-steering method (i.e., either beam-forming or beam-focusing) was measured. In the 2.482 GHz WPT experiment, the 2.4 GHz patch antenna shown in Figure 2a was applied as the Rx and the total transmitted power at 2.482 GHz is 40 dBm (=10 W) with power uniformly radiated by the 32 elements. Figure 17 shows the distribution of the 2.482 GHz received power by the Rx antenna when transmitting 2.482 GHz power to various Rx positions, as depicted in Figure 16, depending on whether beam-forming or \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Distance**} & \multicolumn{2}{c}{**Beam-Forming**} & \multicolumn{2}{c}{**Beam-Focusing**} \\ \cline{2-5}  & \multicolumn{2}{c}{**(In-Phase)**} & \multicolumn{2}{c}{**Calculated**} & \multicolumn{2}{c}{**Measured**} \\ \hline
**1 m** & 24.63 dBm (0.2904 W) & 24.05 dBm (0.2541 W) & 25.13 dBm (0.3258 W) & 24.75 dBm (0.2985 W) \\
**1.5 m** & 21.65 dBm (0.1462 W) & 21.20 dBm (0.1318 W) & 21.87 dBm (0.1538 W) & 21.60 dBm (0.1445 W) \\
**2 m** & 19.36 dBm (0.0863 W) & 19.10 dBm (0.0813 W) & 19.49 dBm (0.0889 W) & 19.25 dBm (0.0841 W) \\
**2.5 m** & 17.51 dBm (0.0564 W) & 17.10 dBm (0.0513 W) & 17.59 dBm (0.0574 W) & 17.30 dBm (0.0537 W) \\
**3 m** & 15.98 dBm (0.0396 W) & 15.90 dBm (0.0389 W) & 16.04 dBm (0.0402 W) & 16.00 dBm (0.0398 W) \\
**3.5 m** & 14.67 dBm (0.0293 W) & 14.10 dBm (0.0257 W) & 14.72 dBm (0.0296 W) & 14.50 dBm (0.0282 W) \\
**3.92 m** & 13.71 dBm (0.0235 W) & 13.50 dBm (0.0224 W) & 13.74 dBm (0.0237 W) & 13.50 dBm (0.0224 W) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Experimental results of 2.482 GHz received power when total transmitted power is 40 dBm (=10 W). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Distance**} & \multicolumn{2}{c}{**Beam-Forming**} & \multicolumn{2}{c}{**Beam-Focusing**} \\ \cline{2-5}  & \multicolumn{2}{c}{**(In-Phase)**} & \multicolumn{2}{c}{**Calculated**} & \multicolumn{2}{c}{**Measured**} \\ \hline
**1 m** & 19.18 dBm (0.0828 W) & 18.60 dBm (0.0724 W) & 19.87 dBm (0.0971 W) & 19.25 dBm (0.0841 W) \\
**1.5 m** & 16.07 dBm (0.0405 W) & 15.70 dBm (0.0372 W) & 16.39 dBm (0.0436 W) & 15.80 dBm (0.0380 W) \\
**2 m** & 13.72 dBm (0.0236 W) & 13.00 dBm (0.0200 W) & 13.90 dBm (0.0245 W) & 13.25 dBm (0.0211 W) \\
**2.5 m** & 11.85 dBm (0.0153 W) & 11.30 dBm (0.0135 W) & 11.97 dBm (0.0157 W) & 11.40 dBm (0.0138 W) \\
**3 m** & 10.31 dBm (0.0107 W) & 9.10 dBm (0.0081 W) & 10.39 dBm (0.0109 W) & 9.30 dBm (0.0085 W) \\
**3.5 m** & 8.99 dBm (0.0079 W) & 8.00 dBm (0.0063 W) & 9.05 dBm (0.0080 W) & 8.00 dBm (0.0063 W) \\
**3.92 m** & 8.02 dBm (0.0063 W) & 6.80 dBm (0.0048 W) & 8.07 dBm (0.0064 W) & 7.00 dBm (0.0050 W) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Experimental results of 5.73 GHz received power when total transmitted power is 40 dBm (=10 W). beam-focusing is used. The received power when applying beam-focusing was higher than that with beam-forming, and these results were more remarkable when the transmission distance was 1 m (see Figure 17a) compared to 2 m (see Figure 17b). When applying the beam-focusing at 2.482 GHz, the WPT efficiencies at 1 m and 2 m have a range of 2.985-0.257% and 0.841-0.316%, respectively. It can also be seen the measured and calculated results were well matched, indicating that the RF WPT experiment was feasible using the implemented system. As a result of the 5.73 GHz WPT experiment, Figure 18a,b shows the received power distribution when the Rx antenna, as in Figure 2b, is moved on a virtual plane at a distance of 1 m or 2 m, as shown in Figure 16, and 5.73 GHz wireless power of 40 dBm is transmitted to this Rx antenna.