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

This article presents a two-port Grid Array Rectenna (GAR), which rectifies the received fundamental frequency (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$f_{o}$</tex-math></inline-formula>) signals and radiates back the third harmonic (3<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$f_{o}$</tex-math></inline-formula>) as a feedback signal to the transmitter. The proposed grid array structure functions simultaneously as an antenna and a terminated 180<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{o}$</tex-math></inline-formula> 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<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{o}$</tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \ge$</tex-math></inline-formula> 50% for a range of 0 dBm to 16 dBm with a peak of 72% at an input power level of 12 dBm for a load of 2 k<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \Omega$</tex-math></inline-formula>. The proposed scalable rectenna offers an output DC voltage of 0.5 V across a resistive load of 2 k<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \Omega$</tex-math></inline-formula> and a received third harmonic signal of -81 dBm at the transmitter for an incident power density of 238 mW/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ m^{2}$</tex-math></inline-formula> 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.