A Compact Rectenna Design With Wide Input Power Range for Wireless Power Transfer

A compact rectenna with a wide input power range is proposed for wireless power transfer (WPT). Two different diodes, having distinct operating powers, i.e., high-input-power diode and low-input-power diode, are introduced to the rectenna design for extending the operating input power range. A mid-inductor is placed in the rectifying circuit to isolate the radio frequency (RF) signal from dc power, thereby delivering the rectified dc power to the load. Also, with the aid of mid-inductor, the fundamental RF signal and harmonic signals could flow back to the two rectifying diodes for achieving higher conversion efficiency via the means of harmonic signal re-rectification. Owing to the mid-inductor, the sub-rectifier circuit can be avoided, and a compact structure can therefore be realized. Over 50% measured conversion efficiency, η
_c
can be achieved in a very wide input power range of 35 dB (-10 to 25 dBm). The proposed rectenna can be widely used in WPT systems with unpredictable and variable RF energy levels.