Tunable Grounded Coplanar Waveguide Attenuator Based on Graphene Nanoplates

In this letter, a novel tunable grounded coplanar waveguide (GCPW) attenuator based on graphene nanoplates is proposed. The attenuator consists of a 50-Ω GCPW transmission line and three pairs of graphene nanoplate pads periodically located in the gap between the signal line and the upper metal ground. The resistance of graphene pad can be tuned from high to low by increasing the bias voltage, thus changing the attenuation level. Particularly, the distance between two pairs of graphene pads can be adjusted to achieve good impedance matching in different working bands. The impedance matching principle is analyzed in theory. Two prototypes are designed, fabricated, and measured, whereas the other two prototypes are verified by simulation. Attenuation amplitude of the attenuators can be tuned from 2.5 to 14 dB with a low reflection below -10 dB as the bias voltage varies from 0 to 6 V, and the working frequency bands (|S
₁₁
| <; -10 dB) cover from 3.5 to 38 GHz.