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

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 • 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 • 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.

Assessing the Figures of Merit of Graphene-Based Radio Frequency Electronics: A Review of GFET in RF Technology

“…These structures were adapted to reduce the complexity of the circuit and achieve an output with high precision. As an alternative, GFET-based phase shifters with the schematic shown in Figure 4 have been demonstrated [21,22]. For both phase shifters, a pair of bias tees are used to combine the signals and the DC biases.…”

“…Each bias tee consists of an ideal capacitor, C and an inductor, L to block the DC or AC signal, respectively. The GFET-based phase shifter presented in [21] has also included the input matching networks (IMN) and output matching networks (OMN) in their design. IMN and OMN allow the phase shifter to maximize the power transfer and minimize the signal reflected from the load.…”

“…One of the best properties of a GFET is its ambipolar characteristics, and it is best used in RF components [10][11][12][13]. To date, several GFET-based RF components have been demonstrated, such as oscillators [14][15][16][17][18][19][20], phase shifters [21,22], amplifiers [23][24][25][26], mixers [27][28][29][30][31], and frequency multipliers [32,33]. A GFET in RF was first demonstrated in 2008 [34], and since then, its performance has gradually improved.…”

“…Finally, the paper concludes with an outlook on the future enhancement that can be done to best utilize the GFET in RF components. in selecting the RF band of operation [21]. For GFETs in RF components, the two most widely used FoMs are the cutoff frequency, , and the maximum oscillation frequency, .…”

Integrated 10-GHz Graphene FET Amplifier

“…Until today, several graphene RF/microwave circuits have been reported. This includes frequency converters [3], phase shifters [4], power detectors [5]- [7], multiplier [8], rectifier [9], as well as microwave amplifiers [10]- [13]. Still, the power gain in such amplifiers is limited due to inherent challenges associated with the zero bandgap in graphene that results in poor current saturation.…”