RF energy harvesting using a compact rectenna with an antenna array at 2.45 GHz for IoT applications

This work addresses the design, fabrication, and implementation of an RF energy harvester 2.45 GHz using a compact rectenna. Our proposed rectenna focuses on development of an antenna array and rectifier circuit. The proposed rectenna is fabricated using FR4 substrate with its overall size of 12.24 cm × 18.17 cm with a thickness of 1.6 mm. The measured results show that a 10 dB bandwidth covering in 2374-2549 MHz (175 MHz) with center frequency 2415 MHz at S₁₁ of −18.2 dB. There is a bandwidth enhancement of 57.6% compared to the single antenna. Gaining of the antenna array is 6 dB that is double a single antenna gain. Spatial diversity technique in antenna array yields a bigger antenna gain thereby increasing the received power level. Experimental measurements are carried out that the rectenna is placed indoor (LOS) at 5 m and outdoor (NLOS) at 15 m. Furthermore, we also explore the rectifier circuit that to maximize the output voltage. The received RF power that transmitted from WiFi router is −55 dBm (0.15 nW/cm²) at 5 m and −59 dBm (0.06 nW/cm²) at 15 m, respectively. The output voltages are achieved that 1092.5 mV at a distance of 5 m (LOS) and 5.48 mV at a distance of 15 m (NLOS). The highest RF-DC conversion efficiency of our proposed rectenna reaches 77.6%. The rectenna potentially meets all requirements to power up the IoT applications.