# Zero Energy IoT Devices in Smart Cities Using RF Energy Harvesting
## 3 Materials and Methods  
### Experimental Setup Devices  
In this report, we have used Powercast Technology Company (Pittsburgh-PA-USA)-provided devices for our research and practical testbeds. There are four components of the Powercast energy harvesting model: an energy transmitter, a sensor board, an evaluation board, and antennas. The Powercast technology company introduces RF-based energy harvesting WCD to replenish the sensor devices' energy. The Powercast Technology Company has provided energy harvesting devices that power IoT devices since 2003. It provides a temperature scanning system, a wireless charging grip for the Nintendo joy-con, power spot, a UHF RFID retail price tag, and development kits. The development kits are used for research and powering IoT devices, which consist of evaluation boards (P1110, P2110), antennas, RF field-detecting light sticks, and sensors. We are using the P2110-EVAL-01 development kit for our research work, which is designed for extremely low-power IoT devices. Our focus is to study the data received from dipole and patch antennas. We aim to find the relationship between distance, RSSI, recharge time of the capacitor, angle impact on the packet transmission time and energy harvesting, and the routing of a packet to the access point. The following devices are used in our testbeds:  
1. RF Transmitter  
The RF Powercast transmitter omits both data and power in the form of RF signals with a unique ID and 915 MHz frequency. The output power (Pt) is 3 w EIRP with a beam pattern of 60\({}^{\circ}\) in vertical polarization, and the frequency range is 915 MHz. The distance for permanent installations of the TX91501B transmitter is eight feet or more above floor level. The Powercast Company provides the transmitter, which is covered in a black box with fixed output power and settings. The user cannot make changes to the transmitter.  
2. Wireless Sensor Board  
The board can measure and transmit light, temperature, humidity data, and external inputs. The sensor board is connected with the evaluation board through a 10-pin connector to obtain the energy from the evaluation board for the transmission of data. We can set the ID of the sensor nodes from 0 to 7 by using ID SELECT switches. The sensor board has a PICkit connector, through which the PICkit programmer can be connected.  
3. P2110 Evaluation Board  
The evaluation board has the responsibility of energy harvesting. The board contains the functionality of energy storage JP1 (C3, C4, and C5 jumpers), a 10-pin connector (J2) for wireless sensor board connection, a rectifier to convert the RF energy into DC, an SMA connector for an antenna or RF input (J1), and a visual LED indicator. The sensor board obtains the harvested energy from the evaluation board.  
4. Powercast Antennas  
The Powercast development kit comes with two types of antennas: dipole and patch. These antennas are connected to the evaluation board through an SMA connector for the antenna (J1). The dipole antenna has the RF connector at the bottom, and the patch antenna has the RF connector in the middle. The dipole antenna is flat, omnidirectional, and vertically polarized, and the gain power is 1.0 dBi with a 360-degree reception beam pattern. The patch antenna is two-layered, directional, and vertically polarized, and the gain power is 6.1 dBi with a 120-degree reception beam pattern.  
5. Vehicle for TransmitterThe energy transmitter is equipped with a vehicle to make it mobile, and then it moves in a circle to charge the devices.