An Efficient Dual-Circularly Polarized Rectenna for RF Energy Harvesting in the 2.45 GHz ISM Band

This paper reports a 2.45 GHz, low power dual circularly polarized (DCP) and dual access rectenna. It contains two de-recombined rectifiers and a cross-slot coupled square patch antenna fed by a microstrip line. A judicious de recombination scheme allows to minimize the RF power imbalance between accesses caused by multipath effects and consequently arbitrary polarized incident waves. The proposed rectenna is then able to harvest linearly polarized, right-hand circularly polarized (RHCP) and left-hand circularly polarized (LHCP) electromagnetic waves, with nearly stable performances. The rectenna has been optimized at -15dBm per access and dedicated to remote and contactless supply low consumption sensors. It has been experimentally tested with very low power densities from 0.057 mu W/cm(2)(E-rms = 0.46 V/m) to 2.3 mu W/cm(2) (Erms = 2.95 V/m). At 1.49 mu W/cm(2) (-15 dBm on each rectifier), the structure exhibits an output de voltage and a global efficiency of 189 mV and 37.7%, respectively when the azimuthal angle (Phi) of the incident field is equal to 0 degrees. Due to the nearly constant total gain of the DCP antenna and an appropriate de recombination of the two rectifiers, the global efficiency slightly varies between 37.7% and 41.4% when the azimuthal angle (Phi) varies between -90 and 90 degrees.