In the recent years, the wireless power transfer technique has attracted a lot of attention in research. As a result, it is becoming an increasingly popular technology in consumer electronic devices and electric vehicles. However, there are other methods in which energy could be transmitted, and they could be further classified according to their working ranges, namely the near-field and the far-field transmission. In this chapter, an overview on the principles of different types of wireless power transmission is described. Then, the investigation of the receiver block is discussed through studying the features of rectifier technologies. Later, the book continues to describe the Rectenna system (rectifying antenna) adopted to the Internet of Things (IoT) wireless charge in remote locations.