A Novel Rectenna With Class-F Harmonic Structure for Wireless Power Transfer

The concept of wireless power transfer for powering a low-power electronic circuit is demonstrated in this brief using a novel rectifying-antenna (rectenna). The proposed rectenna is consisted of by a wide-band antenna and a modified rectifier. The antenna bandwidth has been optimized to cover both the <inline-formula> <tex-math notation="LaTeX">$f _{1}\,\,=$ </tex-math></inline-formula> 868 MHz and <inline-formula> <tex-math notation="LaTeX">$f _{2}\,\,=$ </tex-math></inline-formula> 915 MHz UHF-RFID bands. A dual-band Class-F harmonic structure is employed to maximize the power conversion efficiency (PCE) at both the <inline-formula> <tex-math notation="LaTeX">$f _{1}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$f _{2}$ </tex-math></inline-formula> at low levels of radio frequency (RF) input power (–30 dBm <inline-formula> <tex-math notation="LaTeX">$ < {P} \mathrm {_{IN}} < 10$ </tex-math></inline-formula> dBm) compared to conventional designs. The dual-band class-F harmonic load compensates for the capacitive reactance of the rectifier diodes at the fundamental frequencies <inline-formula> <tex-math notation="LaTeX">$(f _{1}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$f _{2}$ </tex-math></inline-formula>) and controls the rectifier output harmonics at <inline-formula> <tex-math notation="LaTeX">$2f _{1}$ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">$2f _{2}$ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">$3f _{1}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$3f _{2}$ </tex-math></inline-formula>. The proposed modified rectifier depicts a measured maximum PCE of 71% (at <inline-formula> <tex-math notation="LaTeX">$f _{1}$ </tex-math></inline-formula>) and 64% (at <inline-formula> <tex-math notation="LaTeX">$f _{2}$ </tex-math></inline-formula>) for an RF input power <inline-formula> <tex-math notation="LaTeX">${P} \mathrm {_{IN}}\,\,=$ </tex-math></inline-formula> 0 dBm with an optimum load resistance <inline-formula> <tex-math notation="LaTeX">$({R} \mathrm {_{L}}$ </tex-math></inline-formula>) of 7 <inline-formula> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula>. To demonstrate the proof of concept of wireless powering and validate of the rectenna performance, a DC-DC boost converter, a supercapacitor <inline-formula> <tex-math notation="LaTeX">$(C \mathrm {_{OUT}}\,\,=\,\,370\,\,\mu \text{F}$ </tex-math></inline-formula>), and a low-power electronic circuit is connected to the presented rectenna. According to measured results, the proposed rectenna demonstrates wireless powering of an LED at different distances and various <inline-formula> <tex-math notation="LaTeX">$P \mathrm {_{IN}}$ </tex-math></inline-formula> levels (at both the <inline-formula> <tex-math notation="LaTeX">$f _{1}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$f _{2}$ </tex-math></inline-formula>). The proposed circuit can be used in wireless power transfer and battery-less wireless sensing systems.