A Dual-Port Grid Array Rectenna for Third-Harmonic Feedback Enabled Wireless Power Transfer Systems

This letter presents a two-port grid array rectenna (GAR), which rectifies the received fundamental frequency ($f_{o}$) signals and radiates back the third harmonic (3$f_{o}$) as a feedback signal to the transmitter. The proposed grid array structure functions simultaneously as an antenna and a terminated 180$^\circ$ hybrid coupler operating at 2.4 GHz. This unique feature enables the structure to divide (combine) the incoming (transmitting) first (third) harmonic signals with 180$^\circ$ phase difference. The differential rectifier configuration across the matched and isolated grid array ports, operating at 2.4 GHz, exhibits RF to dc conversion efficiency $ \ge$50% for a range of 0 dBm to 16 dBm with a peak of 72% at an input power level of 12 dBm for a load of 2 k$ \Omega$. The proposed scalable rectenna offers an output dc voltage of 0.5 V across a resistive load of 2 k$ \Omega$ and a received third harmonic signal of −81 dBm at the transmitter for an incident power density of 238 mW/$ \text{m}^{2}$ with a distance of 2.1 m. The simultaneous third harmonic power feedback link ensures continuous monitoring of the receiver unit performance, making the configuration suitable for wireless power transfer applications in dynamic scenarios.