Voltage-Controlled and Input-Matched Tunable Microstrip Attenuators Based on Few-Layer Graphene

This article presents novel tunable microstrip attenuators based on few-layer graphene. The proposed topology consists of a microstrip line sided by pairs of grounded metal vias, with graphene pads located between the microstrip line and the vias. The possibility to control the graphene resistance through an applied bias voltage is exploited with the aim to modify the insertion loss of the attenuators. Several pairs of metal vias are adopted to achieve large tuning range, good input matching, and broadband operation. A systematic investigation of the structure with two, three, and four pairs of vias is presented, along with the experimental validation. Prototypes operating in the frequency range from 1 to 10 GHz and with maximum insertion loss exceeding 60 dB are fabricated and tested.