Amplitude Modulator Design Using Series Graphene Transmission Lines in Terahertz Frequency Band

In this paper, a layered transmission line based on graphene is designed and investigated to provide amplitude modulation in the low terahertz frequency band. The proposed primary structure is composed of a graphene transmission line on a dielectric layer, as substrate, loaded by a transverse graphene strip and backed by a continuous graphene sheet, as ground plane. The intermediate graphene strip is electrically isolated from the input and output ports. The structure is first investigated by full-wave simulation method, with various chemical potentials of graphenes, and the ABCD matrices are extracted. Then, applying the analytical method based on the ABCD matrices, the scattering parameters of the cascade of several segments of the proposed primary transmission line are investigated, and the promising configuration for the amplitude modulator is derived. It is shown that, variations of signal transmission required by amplitude modulation performance are achieved by cascading six segments of the proposed transmission line and changing the chemical potential of graphene parts. The designed amplitude modulator is investigated, and high modulation depth of nearly 100% and flat response in 3.4–3.8 THz frequency band is achieved.