Integration of Antenna Array and Self-Switching Graphene Diode for Detection at 28 GHz

In this letter, a rectenna based on a graphene self-switching diode is presented. The nonlinear behavior of the diode is beneficial to efficiently detect the RF power in the Ka-band. The target operating frequency of 28 GHz is of particular interest for the upcoming 5G and the Internet-of-Things telecommunication systems in the range from 1 to 100 GHz. The four-element patch antenna array was designed for an on-wafer high-resistivity silicon/silicon dioxide/graphene multi-layer system. Then, the optimal number of parallel channels for the diode was calculated by using analytical formulas, in order to achieve the highest possible dc current and nonlinearity. Finally, the diode was integrated in a coplanar waveguide structure with open stub, in order to maximize the array-to-diode power transfer. This step-by-step optimization resulted in a high-yield rate, a dc current of over ±1.2 mA at ±3 V, a responsivity of 96 V/W at 28 GHz, and a NEP of 692 pW/√Hz, with maximum measured values of 95 mV for the dc voltage and of almost 4.5 μW for the dc power, for an RF input power of about 500 μW.