RF energy harvesting system with power management within a multiple source environment

• Main Author: Manee Sangaran Diagarajan, Dr.
• Format: text::Thesis
• Language: English
• Published: 2023
• Subjects: RF energy harvesting system with power management within a multiple source environment
• Institution: Universiti Tenaga Nasional

Radio frequency (RF) energy harvesting promises a future for energy constrained networks such as the wireless sensor networks. RF energy harvesting can be utilized as a form of renewable energy to power up low power devices in wireless communication electronic circuits. Some of the common energy sources used for energy extraction are electromagnetic RF, thermal and vibration. Studies have been done to scavenge RF energy from ambience and convert into usable direct current (DC) to power up low power devices. Some areas have RF energy readily available such as broadcast stations, military hubs, satellite hubs etc. These areas have ample of RF energy that can be scavenged and used as a form of renewable energy. This thesis presents a complete RF energy harvesting system designed in a television broadcast station. There are a wide range of frequency sources available within the vicinity of this broadcast station. RF harvesting in these stations or areas are less common and should be considered for harvesting as there are vast amount of unused energy. Broadcast stations operates 24/7 and energy saving initiatives are required to reduce electrical cost. This project is aimed to harvest unused RF energy for powering low power sensors and also for smart phone charging applications in line with promoting energy savings and cost reduction initiatives. A RF energy harvesting operating on multiple frequency bands which are the Intermediate Frequency (IF), 70 MHz, wireless fidelity (Wi-Fi) frequency band, 2.4 GHz and the Kurtz-under (Ku) band frequency, 13 GHz was designed in this work. Energy harvesting from the IF 70 MHz and Ku 13 GHz frequency bands is done via the uplink transmission path and have not been explored in previous works. There will be two separate systems with two different applications. The RF harvested via the 2.4 GHz frequency band is converted into DC which is optimized and managed by a power management system. An Eshaped patch antenna with wide bandwidth covering the 2.4 GHz frequency band was designed with a perfect matching network. An efficient 8-stage voltage doubler circuit was carefully design to feed the DC power to the BQ25570 which handles the MPPT power management and battery charging. The power management system powers up a low power motion sensor and charges a battery at the same time. The battery will act as a backup power supply in case the RF energy is absent. The 2.4 GHz system achieves a 3 V DC output with an input level as low as -30dBm at a distance of 4m. RF power from the 70 MHz and 13 GHz frequency bands are harvested from the uplink transmission line and converted into high DC power which is handled and managed through a power mux that has power switching capabilities and outputs the highest power. 5-stage voltage doulber circuits were used to convert the RF to DC with a perfect LC matching network at the input of the circuit. The DC power is managed by the TPS2121 circuit which outputs the higher voltage. The high voltage is further regulated down to 5 V with a charging current of 0.25 A for the IF 70 MHz system and 0.5 A for the Ku 13GHz system. This charging current is by far the highest achieved via RF energy harvesting.