Design and Development of Graphene Antennas

Abstract

Nanotechnology enables many applications in fields like health-care, security, biomedical, environmental, industrial, military, etc. Establishing wireless communication among nano networks is a big challenge. To enable communication between the nanomachines is still in the research process. Any communication network requires an antenna and designing antennas for nano-networks is a difficult task. To meet the design requirements of nano machines one way is to reduce the size of existing metallic antennas. Reduction in the size of metallic antennas makes the antenna to resonate at high frequencies, which degrades the performance of metallic antennas. There is difficulty in fabrication, lack of compactness, improper impedance matching, degradation of radiation properties, high propagation loss, etc. These problems with metallic antennas have driven the need for new materials that are capable of performing their best at higher frequencies. Researchers across the globe are trying to study the potential applications of ‘graphene’, which is based on honeycomb lattice of carbon atoms, for antenna designing. The limitations of metallic antennas can be compensated by graphene antennas, and the antenna performance parameters like return loss, gain, directivity, radiation pattern, radiation efficiency, voltage wave standing ratio (VSWR) are maintained. Graphene antennas support the propagation of surface plasmon polaritons (SPP) waves, which allows the miniaturization of the antenna while operating the antenna in lower ends of the Terahertz (THz) frequency range. At THz frequencies, metallic antennas can be used, but they do not allow tunability at different resonant frequencies. Graphene, on the other hand, has this feature, whereby applying external DC voltage, tunability can be easily achieved. Recent researchers have shown the full potential of graphene at THz frequencies, but the material properties in the GHz range have not been fully explored. In this thesis, the characterization of graphene material is done by studying all the physical and electrical parameters. A MATLAB code is generated to verify the tunable conductivity of graphene. Once the conductivity property is analyzed, a graphene patch antenna is designed using graphene as a patch material using ANSYS High Frequency Structural Simulator (HFSS) software and then various antenna parameters are analyzed in the Ka-Band (26-30 GHz). The simulated results of graphene patch antenna are compared with a copper patch antenna and the results show that the performance of graphene patch antenna is better than copper patch antenna in terms of gain and directivity. The gain is increased from 5.1 dB to 6.56 dB, so there an improvement of 1.49 dB. Similarly, the directivity is also increased from 6.1 dB to 7.16 dB, hence an improvement of 1.5 dB. Further, two element graphene patch array antenna is designed and simulated using ANSYS HFSS and its results are compared with the single element graphene antenna. The simulated results show an improvement in return loss by -9.1 dB, improvement in gain by 2.49 dB and improvement in directivity by 2.41 dB.