A Graphene Field-Effect Transistor Based Analogue Phase Shifter for High-Frequency Applications

TL;DR

This paper introduces a graphene-based RF phase shifter utilizing GFETs that achieves nearly 200 degrees phase variation with constant gain, advancing high-frequency analog phase control technology.

Contribution

The work demonstrates a novel graphene-based phase shifter with significant phase tunability and low loss, suitable for high-frequency applications, using simple biasing schemes.

Findings

Phase shift of nearly 200 degrees with constant gain of 2.5 dB.

Achieves 85 degrees phase shift using only gate bias with minimal gain variation.

Balanced branch-line configuration enhances performance against existing solutions.

Abstract

We present a graphene-based phase shifter for radio-frequency (RF) phase-array applications. The core of the designed phase-shifting system consists of a graphene field-effect transistor (GFET) used in a common source amplifier configuration. The phase of the RF signal is controlled by exploiting the quantum capacitance of graphene and its dependence on the terminal transistor biases. In particular, by independently tuning the applied gate-to-source and drain-to-source biases, we observe that the phase of the signal, in the super-high frequency band, can be varied nearly 200 degrees with a constant gain of 2.5 dB. Additionally, if only the gate bias is used as control signal, and the drain is biased linearly dependent on the former (i.e., in a completely analogue operation), a phase shift of 85 degrees can be achieved making use of just one transistor and keeping a gain of 0 dB with a maximum variation of 1.3 dB. The latter design can be improved by applying a balanced branch-line configuration showing to be competitive against other state-of-the-art phase shifters. This work paves the way towards the exploitation of graphene technology to become the core of active analogue phase shifters for high-frequency operation.