Radio Frequency (RF) Energy Harvesting is a method of wireless power generation by harvesting RF signals by using RF sensors and antenna receivers that sense a broad range of frequencies (LF, HF, VHF, UHF). RF Energy harvesters generate power needed to charge batteries for cell phones, smartphones, PDA mobile phones, laptops, tablet PCs and other portable devices. RF energy harvesters harvest radio energy from wireless networks such as GSM, CDMA, WiFi, Satellite RF (GPS, TV), wireless broadband, WiMax, LTE, etc. The batteryless RFID systems, wireless sensor networks, and wireless power chargers are the applications of RF energy harvesters.

Radio frequency (RF) energy is emitted by sources that generate high electromagnetic fields such as TV signals, wireless radio networks and cell phone towers, but through using a power generating circuit linked to a receiving antenna this free flowing energy can be captured and converted into usable DC voltage.

These days everyone has a cell phone, and wireless RF signals available as ready energy everywhere. With increasing cell phones and wireless internet/broadband technologies, the wireless radio carriers transmitting more RF power/energy to support high speed internet and/or voice and live video broadcasting over mobile phones. With the help of RF energy harvesters, we can recharge the batteries of cell phones and other portable devices while roaming. The cell phone company Nokia, is trying to build a smartphone that harvests RF energy without the need to recharge the handset.

As of now, the energy harvesting and wireless battery charging is limited to portable gadgets only. The advancements in RF energy harvesting are leading to wireless battery charging of high power appliances. A best example is instant wireless battery charging of Electric vehicles. Already, the wireless charging stations available for electric cars, but they are slower. Electric car companies are working for designing of instant/fast charging of electric vehicles.