Effect of coupling capacitance in voltage multiplier design optimization for RF energy harvesting

Electromagnetic energy harvesting has been identified as a free compliment resource to wireless sensor nodes, which essentially prolongs the operating lifespan of built-in batteries. Voltage multiplier is a critical component in energy harvesting circuits and it attracted plenty of efforts in studying how to optimize the design. However, little information was found on how to determine the necessary amount of coupling capacitance required in a voltage multiplier design. This paper aims to fill in this gap and provides an analysis on how coupling capacitance affects voltage and power outputs. Computer simulations affirm that as long as the coupling capacitance is beyond a certain value, e.g., 10pF for Wi-Fi energy harvesting circuit operating at 2.45GHz, it has limited effect on voltage output and power output of a voltage multiplier.