A Broadband Tunable Coaxial Attenuator Based on Graphene

A dynamically tunable coaxial attenuator based on graphene is presented in this paper. The attenuator is achieved by inserting a graphene sandwich structure (GSS) inside the dielectric of coaxial line along the propagation direction of electromagnetic waves to dissipate the electromagnetic field. The mechanism of attenuator is theoretically analyzed, and an approximate formula to calculate attenuation with different parameters is proposed. We experimentally demonstrate that attenuation of the attenuator can be tuned from 3 dB to 14.5 dB with good flatness in broad operation frequency from 2 GHz to 9 GHz when graphene impedance is changed by different bias voltage. The theoretical calculation and simulation results have a good agreement with experimental results, while the vertical bar S-11 vertical bar can always remain low level under -15 dB.