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.
Highlights
In the last few years the number of applications where graphene is involved has increased drastically in almost every field of electronics
We propose a bias-controlled analogue phase shifter based on a graphene field-effect transistor (GFET) by taking advantage of the possibility of tuning the graphene quantum capacitance with the FET terminal biases thanks to its low density of states around the Dirac point [34]
This work presents a graphene-based phase shifter operating in the S-band, able to produce a phase shift on an input RF signal while maintaining a constant gain
Summary
In the last few years the number of applications where graphene is involved has increased drastically in almost every field of electronics. In spite of the increasing number of effective prototypes of graphene RF devices such as graphene fieldeffect transistors (GFETs) [32], as well as one-dimensional (1D) flexible RF diodes [33], none of them have already been explored for the aforementioned purpose In this context, we propose a bias-controlled analogue phase shifter based on a GFET by taking advantage of the possibility of tuning the graphene quantum capacitance with the FET terminal biases thanks to its low density of states around the Dirac point [34]. Is the use of graphene-based technology for this application novel and relevant, and the fact that the phase shift can be controlled solely by an analogue signal without impacting on its gain In this regard, the proposed phase shifter architecture consists of only one device and the role of the control signal is played by the gate bias with the drain bias linearly depending on the former. The performance and main figures of merit (FoMs) of the proposed graphene-based phase shifters are compared against the state-of-the-art with promising results
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