Radio frequency (RF) provides reliable wireless communication between two electrical devices by using electromagnetic radiation. Electromagnetic waves are generated by the time-varying voltage and current. RF communication systems generate, manipulate and interpret the electromagnetic waves, allowing the transfer of meaningful information.
In 2004, researchers first managed to isolate graphene—a one-atom thick layer of carbon arranged in a honeycomb lattice. This development has triggered a revolution among physicists, chemists and engineers eager to explore the advantages of the new material’s unique and advanced properties. Graphene brings new opportunities in improving RF circuits, low-power switches, sensors, solar cells and batteries, as well as applications in RF communications, the focus of this article.
Graphene-based RF communication devices have the potential to overcome some of the main limitations in traditional RF electronics—maximum frequency, power dissipation and linearity.
Graphene, a 2D shape of carbon, is strong, solid and lightweight, and has a high electrical conductivity. Graphene conducts electricity with almost zero resistance, thus allowing electrons to move much faster than in traditional silicon (Si) circuits when they conduct electricity.
Super-fast RF communication systems require high performance in all their parts: antennas, signal generators, amplifiers, filters, and so on. Graphene could potentially be used to improve the performance of all those parts individually, as well as the system as a whole.
High-performance graphene-based antennas can be designed by using a combination of both graphene and semiconducting materials. Since graphene is a very flexible material, the extremely tiny graphene narrow strips (10-100nm wide and 1μm long) can be employed in the design of very small-sized antennas (μm and even nm size). Sucha small form factor antenna can be then be embedded in very small objects. This has great potential in smartphones, the computer industry, smart cards, electronic keys and RFID tags, among others.
EPFL scientists have already developed a graphene-based microchip that can filter out unwanted noise and protect a meaningful radiation signal. Each radiation signal vibrates in a specific way. The microchip the researchers developed can pass only a desirable signal that vibrates in a certain manner. Depending on the orientation of the vibration, graphene can be transparent or opaque to the processed electromagnetic radiation. Another benefit of this technology is that it has the potential to significantly increase data transfer speed.
Today, RF communications work in the gigahertz range, but the graphene-based microchip operates in the terahertz gap, a frequency band that is not currently employed. By using this additional bandwidth, devices could transfer data tens of times faster than is possible with current technology.
Graphene is also perfectly suited for amplifier construction, improving its high frequency and low noise characteristics. Graphene amplifiers allow a simplified structure with larger bandwidth and lower energy consumption. In addition, graphene has excellent thermal properties, which can solve the problems caused by heating and allows devices to have a simpler thermal management.
The handling of graphene can be challenging. This material easily interacts with other materials, which can then change its properties. This is why the controlling of graphene degradation has been performed by charging impurities. While the impurities, usually high-quality dielectric materials, decrease the high performance of the graphene, they are still necessary. Scientists work to strike a good balance by optimizing performance and reducing graphene degradation. The MIT faculty researching graphene (published in IEEE Communication magazine, 2010) has shown that the mobilities of 20 000 cm2/Vs can be reached by carefully controlling the graphene-substrate interface. This somewhat high mobility is still far from the one reached in suspended graphene at 200000 cm2/Vs—reached by Columbia University scientists(ScienceDirect), which means that further research in this field could still yield results.
The high performance of graphene in electron conduction has huge potential for the development of a new generation of electronic devices. Graphene has an amazing 100 times higher electronmobility than do commonly used Si-based materials. The strong, flexible and small-sized material has caught the attention of engineers for its potential use in the development of advanced electronic devices. Graphene also has great potential for improving communication systems and RF circuits. In order to optimize this potential, further research is needed to provide a better understanding of graphene’s main parameters: breakdown voltage, saturation current, maximum electron velocity and graphene surface interaction with the environment. With further developments, this nanomaterial could make RF communication systems even more popular than they are today.