*Introductory Chapter: Advances in Green Electronics Technologies in 2023 DOI: http://dx.doi.org/10.5772/intechopen.112615*

if we collect electromagnetic energy that can charge electronic devices. Energy harvesting units can eliminate the need to charge batteries by using electrical cables. It is crucial to harvest electromagnetic energy from many transmitting RF modules and systems. Multiband wideband antennas should be employed to harvest as much RF energy as possible. Due to low RF energy densities in free space, wideband efficient

**Figure 3.**

*Sensors with RF energy harvesting unit. (a) Circular polarized active receiving sensor with energy harvesting unit. (b) Wearable medical system. (c) Dual mode energy harvesting concept.*


**Table 2.**

*Measured harvester efficiency as function of input collected power.*

antennas should be developed. The antennas should radiate efficiently at a specific frequency range and polarization. To meet the RF system requirements, the antenna radiation pattern should have a wide beam width. Printed antennas were used to harvest RF energy as presented in the literature, [4–10]. RF energy harvesting systems collect electromagnetic waves propagating in the air. This RF energy is stored and used to recharge phones, batteries, and other electrical modules. In the last 20 years, there has been a huge increase in the amount of electromagnetic energy in the air. The electromagnetic energy harvesting system operates as a Dual Mode harvesting unit. The Low Noise Amplifier, LNA, is part of the RF system. The LNA DC bias voltages are supplied by the DC unit of the RF system. The programmable array, shown in **Figure 3c**, consists of antennas that can harvest electromagnetic energy from around 0.15GHz up to 18GHz. The received electromagnetic energy is transformed into DC energy. The energy coupled to the built-in test port, 20 dB, may be used to recharge electronic devices, batteries, and phones.
