A 900 MHz All-NMOS RF-DC Rectifier With Internal <i>V</i> _TH Cancellation Technique for RF Energy Harvesting

This paper presents an all-NMOS RF-DC rectifier with internal <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {TH}}$</tex-math> </inline-formula> cancellation (IVC) technique to achieve an ultra-wide high-PCE input power range for RF energy harvesting. The all-NMOS topology replaces the PMOS transistor in the conventional cross-coupled rectifier with a diode-like NMOS transistor to obtain the maximum current driving capability while effectively reducing the reverse leakage current at higher input power, combining the strengths of diode-based and cross-coupled rectifiers. The IVC unit is used to compensate for the threshold voltage of the diode-like rectifying transistor on the output side and improve the PCE at low input power. As a result, the sensitivity and the input power range are improved simultaneously. The proposed rectifier is fabricated with a 0.18-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula>m standard CMOS technology. The measurement results show that the IVC all-NMOS rectifier achieves 55% PCE, −15.5 dBm sensitivity and 18.6 dB input power range when operating at 900 MHz with a 30 k<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $</tex-math> </inline-formula> load.