# Zero Energy IoT Devices in Smart Cities Using RF Energy Harvesting
## 3 Materials and Methods
### Testbeds Studies
#### 3.3.6 Optimal Points/Area for Sensor Devices
``` Input Set of Sensor v\({}_{\text{k}}\) ={1,2,3..}, Charger Points M\({}_{\text{kp}}\) = {M\({}_{\text{k1}}\) M\({}_{\text{k2}}\), M\({}_{\text{k3}}\),...,122\({}^{0}\)},  Distance d\({}_{\text{k}}\) = {1,2, M\({}_{\text{k}}\)\({}^{\text{r}}\)}, Tx value Output Optimal Points/area for charger tour, IA, \(\theta\), IP
1. For every point M\({}_{\text{M}i}\)\(\in\

#### 3.3.7 Experimental Setup with a Patch Antenna

The patch antenna has 122-degree reception. From the experiment, we have observed that the path antenna worked properly within the \(122+\varepsilon\) (where \(\varepsilon\) represents some benefits from the charger's angle) direction and the charging devices would receive the energy, but when the charger moved in another direction, the charging device went into a dead position or data sending and the energy harvesting process degraded to zero. We have obtained the experimental data and shown them in Table 1. According to Figure 3, it is clear from the table that when the charger moves from \(0^{\circ}\) to \(250^{\circ}\), it degrades the energy harvesting and data sending processes accordingly, but when the charger moves to \(240^{\circ}\), the energy harvesting and data sending processes gain power. Consequently, from these experimental data, we can say that the area or points shown in Figure 5 are the optimal points/area for placing the sensors, and the points \(340^{\circ}\) to \(100^{\circ}\) are the optimal charger tour points or path to provide unstoppable energy to the sensors. For more clarification, see Table 2. We have also added some figures (Figures 6-11) to better understand the patch antenna sensed data. \begin{table}
\begin{tabular}{l l l l l l l l l l} \hline \hline Point 1 (\(0^{\circ}\)) & & & & & & & & & & \\ \hline RSSI & 33.88 & 33.88 & 32.73 & 31.92 & 32.73 & 31.92 & 31.92 & 32.73 & 30.13 & 30.13 \\ \hline Temp & 70.5 & 70.5 & 70.5 & 70.5 & 70.5 & 70.5 & 70.5 & 70.5 & 70.5 & 70.5 \\ \hline Humidity & 46 & 46 & 46 & 46 & 46 & 47 & 46 & 46 & 46 & 47 \\ \hline Light & 37 & 25 & 29 & 48 & 51 & 40 & 44 & 40 & 29 & 48 \\ \hline External & 1331 & 1352 & 1325 & 1382 & 1393 & 1343 & 1346 & 1358 & 1393 & 1340 \\ \hline Point 2 (\(50^{\circ}\)) & & & & & & & & & & \\ \hline RSSI & 12.11 & 12.97 & 10.45 & 11.86 & 12.11 & 10.45 & 12.71 & 12.11 & 12.97 & 11.27 \\ \hline Temp & 70.5 & 70.5 & 70.5 & 70.5 & 70.5 & 70.5 & 70.5 & 70.5 & 70.5 & 70.5 \\ \hline Humidity & 47 & 47 & 47 & 47 & 47 & 47 & 47 & 47 & 47 \\ \hline Light & 48 & 40 & 48 & 44 & 48 & 48 & 51 & 44 & 29 & 51 \\ \hline External & 1686 & 1687 & 1695 & 1687 & 1690 & 1690 & 1690 & 1686 & 1692 & 1690 \\ \hline Point 3 (\(100^{\circ}\)) & & & & & & & & & & \\ \hline RSSI & 3.18 & 3.66 & 1.74 & 3.96 & 3.96 & 3.66 & 3.96 & 3.47 & 3.32 & 3.66 \\ \hline Temp & 70 & 70 & 70 & 70 & 70 & 70 & 70 & 70 & 70 & 70 \\ \hline Humidity & 48 & 47 & 48 & 48 & 47 & 48 & 47 & 48 & 48 & 48 \\ \hline Light & 40 & 37 & 48 & 22 & 29 & 48 & 40 & 48 & 48 & 40 \\ \hline External & 1670 & 1678 & 1676 & 1669 & 1678 & 1673 & 1665 & 1662 & 1666 & 1663 \\ \hline Point 4 (\(150^{\circ}\)) & & & & \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline Humidity & 48 & 47 & 48 & & & & \\ \hline Light & 51 & 48 & 29 & & & & \\ \hline External & 1581 & 1574 & 1584 & & & & & \\ \hline Point 6 (340\({}^{\circ}\)) & & & & & & & \\ \hline RSSI & 11.86 & 12.71 & 12.42 & 12.11 & 11.53 & 11.86 & 12.11 & 12.97 & 11.53 & 13.3 \\ \hline Temp & 70.7 & 70.7 & 70.7 & 70.7 & 70.7 & 70.7 & 70.7 & 70.7 \\ \hline Humidity & 47 & 47 & 47 & 47 & 47 & 47 & 47 & 47 \\ \hline Light & 37 & 55 & 51 & 48 & 51 & 44 & 48 & 33 & 29 & 51 \\ \hline External & 1696 & 1693 & 1698 & 1693 & 1689 & 1685 & 1689 & 1701 & 1695 & 1698 \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._

Figure 5: Sensor Device Placement for Patch Antenna. Figure 8: 100\({}^{\circ}\) Sense Data from Patch Antenna. Figure 6: 0\({}^{\circ}\) Sense Data from Patch Antenna. Figure 7: 50\({}^{\circ}\) Sense Data from Patch Antenna. Figure 11: 340\({}^{\circ}\) Sense Data from Patch Antenna.