A High-Gain Microstrip RF Energy Harvester for IoT Sensors in 5G Network

As the implementation of fifth-generation (5G) wireless networks expands, the interest in using radio frequency energy harvesting (RFEH) as a power source for low-power Internet of Things (IoT) devices increases. RFEH has the potential to eliminate the need for batteries, providing a reliable and sustainable power source for these devices. However, the efficiency of RF to dc converters at high frequencies, commonly used in 5G networks, is relatively low. This article proposes a new high-gain RFEH circuit that incorporates a 2 x 2 patch array antenna, a reflector, and a cascade microstrip L-matching network used as a passive voltage amplifier to increase the induced voltage across the antenna. The RFEH receiver is fabricated on a low-cost FR-4 substrate with a dielectric constant of 4.6 and a copper thickness of 0.035 mm. To enhance efficiency in RF to dc conversion, a novel microstrip voltage amplifier is designed, resulting in an overall gain of 30 dB at an input power of -30 dBm with a 1-M ohm load. This amplifier exclusively utilizes traces on the printed circuit board (PCB), eliminating the need for low-efficiency voltage doublers. A prototype has been fabricated and measured. The results show that the proposed RFEH can capture signals at 5.2 GHz and amplify the induced voltage across the antenna. The efficiency exceeds 70% in the frequency range of 5-5.4 GHz, with a peak efficiency of 74.82% at an input power of -10 dBm and a 10-k ohm load.