The objective of the project is to harvest the energy and to power the sensor based networks, RFID tags, medical implants and other low power devices. The system, which is responsible to harvest the energy from RF sources is known as “RECTENNA”. One of the subsystems of the rectenna is a rectifier, which is responsible to convert the RF power to DC. This project is carried out on improving the design of the rectifier to achieve maximum efficiencies for lower powers. Here a two stage Dickson charge pump is considered as rectifier circuit to achieve the maximum output voltages.In this project single band and dual band rectifiers are designed.