Graphene-Based Balanced Nonlinear Transmission-Line Frequency Doubler

This paper introduces a tunable balanced Nonlinear Transmission-Line (NLTL) frequency doubler topology designed using graphene-based Monolithic Microwave Integrated Circuit (MMIC) technology. The frequency doubler chip, operating at a centre frequency of 1.6 GHz, is presented alongside its validation through a proof-of-concept Printed Circuit Board (PCB). The proposed topology offers significant advantages, including high harmonics suppression and exceptional phase noise performance. We employ two measurement setups to evaluate the PCB's performance, showcasing the practical applicability of the design. The frequency doubler design achieved remarkable performance, featuring a conversion gain of -11 dB with high tunability. The circuit exhibited good fundamental suppression below -25 dB, and third and fourth harmonic suppression lower than -35 dB. Moreover, the circuit showcased low-phase noise with a delta carrier-to-noise ratio (CNR) of 6.33 dB.