Internal Vth cancellation scheme for RF to DC rectifiers used in RF energy harvesting

In this work, an internal threshold voltage (Vth) cancellation (IVC) scheme is proposed for the rectifiers used in the RF energy harvesting systems. Conventionally, the CMOS-based rectifier is used for performing RF to DC conversion. The proposed IVC scheme has been implemented in PMOST of the conventional CMOS rectifier. The single stage conventional and the proposed rectifiers have been designed and fabricated in a standard 0.18μm CMOS technology. The measurements have been done for the resistive load of 1 KΩ, 10 KΩ and 100 KΩ. In the measurement a 433 MHz RF signal with input power ranges from -24 to +10 dBm was used. The power conversion efficiency (PCE) is selected as a performance metric for the rectifiers. The conventional rectifier achieved maximum PCE of ≈16% at the RF input power of -8 dBm for the resistive load of 10 KΩ, while after implementing the proposed IVC scheme in the PMOST, the measured PCE was ≈35% at the same input power level.