IN our days radio frequency (RF) energy harvesting is an atractive way to capture power in conditions where light or wind sources are not available. Broadcasting RF transmitters like FM/TV, cellular networks base stations, WiFi routers,andfrequencyidentification(RFID)readers,havebeen increasing rapidly around us, due to the huge development of wireless technologies. In 1964 William C. Brown proposed a system for transformation of RF power to dc power. In this RF-to-dc converter, an antenna is combined with a rectifier, which consists of one or more diodes in specific configuration, forming a rectenna. One significant limitation in rectenna design is the relatively low available ambient power density level as well as the RF-to-dc power efficiency of the circuit. It remains an engineering challenge how to capture unused ambient RF energy and use it to supply small sensor nodes, such as radio frequency identification (RFID) tags. Interest in Internet of Things (IoT) low-power sensors powered by RF ambient power or wireless power transmission has increased due to the vision of ubiquitous sensing as part of 5G mobile networks. Wireless powering in the 2.4 GHz industrial, scientific and medical (ISM) band can enable applications where a large number of mobile devices with WiFi/Bluetooth transceivers can act as RF sources to power the sensors.