Efficiency Enhanced Seven-Band Omnidirectional Rectenna for RF Energy Harvesting

In this article, a seven-band omnidirectional rectenna is proposed for the first time to harvest RF energy. The designed rectenna operates in the following practical and up-to-date frequency bands: GSM1800 (1.8 GHz), LTE (2.1 GHz), WLAN/Wi-Fi (2.4 and 5.8 GHz), and 5G bands (2.6, 3.5, and 4.9 GHz). To obtain the multiband rectenna, a novel seven-band rectifier is introduced and composed of three optimized single shunt diode rectifiers in parallel. Overall RF-to-dc conversion efficiencies as high as 44.4% @ 1.84 GHz, 43.9% @ 2.04 GHz, 45.4% @ 2.36 GHz, 43.4% @ 2.54 GHz, 36.1% @ 3.3 GHz, 32.4% @ 4.76 GHz, and 28.3% @ 5.8 GHz are achieved at an input power level of -10 dBm. Moreover, a broadband omnidirectional monopole antenna is further codesigned with elaborate impedance matching to the rectifier. The antenna can harvest RF energy in the bandwidth of 1.67-5.92 GHz (S-11 no more than -10 dB) with stable omnidirectional radiation patterns. By integrating the rectifier and the monopole antenna in a low profile, a prototype of the rectenna was manufactured and tested. The experimental results demonstrate that the proposed rectenna has competitive performance in terms of RF-to-dc conversion efficiency and band coverage, indicating enormous potential for numerous battery-free or low-power-needed applications in the real world.