Design energy harvesting device of UHF TV stations

Electromagnetic waves are one of alternative energy sources that can be converted to DC power source. UHF TV transmitter station is one of the electromagnetic wave sources. This is very potential to drive ultra low power devices at nodes of WSN. The Radio Frequency Energy Harvesting (RFEH) system efficiency is the main concerned issue beside voltage multiplication. By using commercial antenna log periodic gain 7 dBi this research focused on matching circuit and power harvester circuit. Designed matching circuit is open circuit single stub tuner built of coaxial cable. While power harvester circuit is combination circuit of Villard and Dickson voltage multipliers (2 stages Villard, 3 stages Dickson). Based on measurement of power receive level from UHF TV Stations in Pekanbaru, the highest result is 4.1 dBm radius 200 m from the station at 655.75 MHz. In laboratory works, by generated signal from SSG (frequency: 655.75 MHz, Tx Power: 4.1 dBm) the output of RFEH system is 2.1 V at no load condition and without single stub tuner. When single stub tuner inserted to the system (d₁: 7.4 cm and d₂: 15.1 cm) the output of system is 2.7 V at no load condition. System efficiency without matching circuit is 1.2%. While system efficiency with matching circuit is 0.4%. It caused by matching circuit loss. If SSG generates higher power level (frequency: 655.75 MHz, Tx Power: 13 dBm) the RFEH system output is 4V at no load condition without single stub tuner, efficiency is 3.9%. When single stub tuner inserted to the system, the output is 8.8 V at no load condition, efficiency become 14.6%. However if frequency varied in the system without matching circuit, the efficiency can reach 17.3%.