Fully Integrated 2.4-GHz Flexible Rectifier Using Chemical-Vapor-Deposition Graphene MMIC Process

This article presents a fully integrated radio frequency (RF) rectifier on a flexible polyimide (PI) substrate. This circuit is designed and implemented using a chemical-vapor-deposition (CVD) graphene monolithic microwave integrated circuit (MMIC) process, where a metal–insulator–graphene (MIG) diode is employed to obtain the necessary nonlinearity for the rectifier. The smooth surface enables good titanium dioxide (Tio
₂
) barrier interface formation and a higher carrier transport performance of the graphene. Passive components are also developed on the same substrate. To carry out the circuit design, a large-signal diode model is created based on measured results on a test key. A rectifier is deliberately designed for eliminating the input matching network by properly sizing the MIG diode and the load impedance. Removing the matching network results in a compact size and reduces the loss of the input of the rectifier. Nevertheless, the measured input reflection coefficient at 2.4 GHz is −17.5 dB, and measured, peak output dc voltage is 93 mV at an input power of 15.7 dBm. To the best of the authors’ knowledge, this design achieves the highest output voltage of all graphene-based rectifiers on a flexible substrate at 2.4 GHz. Thanks to the CVD graphene MMIC process, a rectifier array could be realized and thus, low-energy devices such as wireless-sensor-network (WSN) and medical implants are potential applications.