Design of a closely-spaced-element rectenna for low-power wireless energy harvesting

In this paper, a compact rectenna with two closely spaced elements is proposed for the low-power energy harvesting application. To compensate the low RF-to-dc conversion efficiency of rectifier due to the low input power, an asymmetric configuration of antenna is designed, which achieves 7.3-dBi gain at 2.45 GHz. The rectifier is further embedded in the antenna without any additional circuit area. A prototype with a compact area of 11.5 mm × 60.0 mm is designed and evaluated with an incident power density of 1 μW/cm2. The measured results show that the proposed rectenna can produce 26.1-μW dc power with over 40% RF-to-dc conversion efficiency.