Wireless energy harvesting from Hz to GHz

In this paper, wireless energy harvesting from Hz to GHz is discussed. At lower frequencies, the focus is on harvesting energy around 50 Hz power lines while at higher frequencies, the attention is paid to harvesting the energy from radio communication systems such as WiFi and mobile radio in the frequency range from 470 MHz to about 3 GHz. The main technology for both the lower and higher frequencies is the same: to use rectennas to receive the wireless energy and then covert it to DC energy. But the frequency difference has resulted in very different antenna designs and the bandwidth requirements. Some novel ideas have been introduced and discussed. At lower frequencies, a narrow band system is developed while at higher frequencies, a broadband system is produced in order to maximize the harvested energy. The designs are optimized to obtain the maximum energy conversion efficiency and then validated by experiments. The results demonstrate the excellence of these designs which can be applied for a wide range of applications.