Grid-Array Rectenna With Wide Angle Coverage for Effectively Harvesting RF Energy of Low Power Density

It is difficult to effectively rectify or convert low power in the circuit stage of harvesters. The high-gain antenna can offer a higher level of power and is beneficial to RF power harvesting in a low power density environment. To extend the narrow beam of the conventional high-gain rectenna, the multiport and multibeam antenna is promising. To pursue a simple configuration and avoid extra beamforming networks, a traveling-wave grid-array antenna (GAA) with two isolated ports and two symmetrically tilted beams is proposed. A prototype is designed and fabricated after a detailed analysis of the GAA with tilted beams and the coplanar stripline-based rectifier. The measured results show that the proposed rectenna is sensitive and effective in a wide-angle range. The harvesting angle range is extended by combining two tilted beams and can be greater than 70°, where the level of dc power exceeds $100~\mu \text{W}$ when the power density is as low as $1~\mu \text{W}$ /cm2. A maximum dc output of 3.6– $203.8~\mu \text{W}$ and a maximum RF-to-dc conversion efficiency of 16.3%–45.3% are available at 2.45 GHz, under the condition that the power density ranges from 0.052 to $1~\mu \text{W}$ /cm2.