A Perspective on the Recent Progress of Graphene in Microwave Applications: Problems, Challenges and Opportunities

Over a decade ago, graphene became a hot topic in academic research, and its outstanding physical properties were measured and reported [1], [2], [3]. At that point, this novel two-dimensional material consisting of an atomic thick layer of carbon atoms had been widely applied in a variety of fields due to its unique characteristics, including its high electron mobility, light weight, mechanical strength, impermeability, planarization, and flexibility [4], [5]. In particular, its high carrier mobility makes graphene an outstanding electronics material for high-speed device applications such as field effect transistors, switches, and photodetectors [6], [7], [8], [9], [10]. However, the available graphene samples in the early years were limited to very small sizes by the growth and preparation process, which resulted in the frequency domain of initial research being mainly focused on the THz, infrared, and optic regimes [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23]. Similarly, there was very little work using graphene in the microwave region, particularly in passive devices such as antennas, because the size of such devices generally is on the order of wavelengths. As a result, the outstanding tunable characteristics of graphene were mostly utilized to uncover the best in the higher THz region, while doubts remained regarding the possibilities of using graphene for microwave applications.