Radio frequency energy is energy transmitted from sources capable of generating electromagnetic fields such as TV signals, radio signals, wireless networks and cell phone towers, using circuits specially designed devices connected to an antenna electromagnetic energy can be collected and converted into a usable DC voltage. One of the applications of this technology is in radio frequency identification tags where the collecting device can receive an RF signal from a sensing device; this RF signal can provide enough energy to allow the RFID tag to return radio frequency, including identification information, to any item of interest. Circuits designed for such applications can be made relatively small and convert ambient electromagnetic waves into a usable DC voltage at distances up to 100 meters from the RF signal source. Depending on the environment and available RF signal strength, the power conversion circuit would be connected to a capacitor capable of providing a required constant voltage to the device in question when there is not enough power available, also this RF power can be used to charge batteries. Another interesting feature of available RF energy harvesting is that it can be used as a supplement to conventional energy harvesting methods. These energy harvesting techniques can be used to charge batteries at night when solar energy is not available and could be used as a backup system if the main power supply fails and keep the device running or send an alarm . This technology can extend battery life, and this can be achieved by compensating for the sleep current required by the low-power microcontroller. Antenna design and power management for wireless energy harvesting applications: In several...... middle of paper..... .action of rectenna array configurations for improved RF power harvesting”, Loughborough Antennas & Propagation Conference, 2009.[4] U. Olgun et. al. “Efficient Environmental WiFie Energy Harvesting Technology and Its Applications,” IEEE, Volume:10, 2012.[5] D. Bouchouicha. “An Experimental Evaluation of Surrounding RF Energy Harvesting Devices,” Proceedings of the 40th European Microwave Conference, France, 2010.[6] CEO Gianfranco. et. al. “Design of a 2.45 GHz rectenna for electromagnetic (EM) energy scavenging,” IEEE, 2010.[7] T. Mishara et. al. “2.4 GHz Square Slot Antenna and Power Management Circuit for Wireless Power Harvesting Applications,” IEEE Conference on Antennas and Propagation, Singapore, 2012.[8] K. Kholostov. Et. al. “3D Antenna for GHz Applications and Vibration Energy Harvesting,” IEEE Conference on Electronic Components and Technologies, 2013.