A Broadband Active Microwave Monolithically Integrated Circuit Balun in Graphene Technology

This paper presents the first graphene radiofrequency (RF) monolithic integrated balun circuit. It is composed of four integrated graphene field effect transistors (GFETs). This innovative active balun concept takes advantage of the GFET ambipolar behavior. It is realized using an advanced silicon carbide (SiC) based bilayer graphene FET technology having RF performances of about 20 GHz. Balun circuit measurement demonstrates its high frequency capability. An upper limit of 6 GHz has been achieved when considering a phase difference lower than 10° and a magnitude of amplitude imbalance less than 0.5 dB. Hence, this circuit topology shows excellent performance with large broadband performance and a functionality of up to one-third of the transit frequency of the transistor.