Study On Characteristics And Sensing Application Of Graphene Microstrip Antenna

With the rapid development of the Internet of things,electronic communications and other industry areas,microelectronics has broken through the Moore's Law and entered the Nano era.Under such circumstances,to meet the needs of rapidly developing information,further development in the nanomaterials field is urgently needed.Graphene,as a rising star of nanomaterials,has attracted worldwide attention due to its excellent performance.In this thesis,theoretical simulations are conducted to analyze the radiation characteristics of a metal dipole antenna embedded with a single-layer graphene reflector structure.On this basis,a flexible antenna strain sensor based on multi-layer graphene films is proposed and explored systematically.The detailed research work and results of the thesis are presented as follows:Firstly,the conductivity characteristics of single-layer graphene and multi-layer graphene are introduced in this paper.By utilizing MATLAB simulation tool and theoretical formulas,the tunable conductivity of monolayer graphene is theoretically modeled.Then,the electromagnetic properties of graphene can be dynamically controlled via changing the graphene chemical potential.In addition,the transmission characteristics of graphene surface plasmon polariton waves are also introduced.Secondly,based on the tunability of single-layer graphene and the theoretical calculation and simulation,the radiation characteristics of a metal dipole antenna are improved by employing a single-layer graphene reflector.Traditional metal dipole antennas have several disadvantages such as fixed working frequency,poor directionality,narrow frequency band and low gain.By using the graphene as a tunable reflector,the resonant frequency of the proposed antenna can be dramatically tuned in the range of 35 GHz-45 GHz.The directivity is improved to 3.75 dBi whereas the directivity of original metal dipole antenna is only 0.42 dBi.The antenna gain is increased from 0.41 dBi to 2.65 dBi,and the half-power beam width is improved from 78.6° to 225°.The results confirm the radiation performance of the conventional metal antenna is greatly improved by backing with a graphene reflector.Finally,motivated by the previous research,a novel eco-friendly,low-cost flexible antenna pressure sensor is presented with a multi-layer graphene film radiator and paper-based substrate,and then the antenna is simulated and optimized by using full-wave numerical tool.Also,the fabrication and measurement of this antenna is conducted.The measured results show good radiation performance and great strain sensing characteristics,which are well consistent with the simulation results.Compared with the metal copper antenna with the same dimension,the graphene-film-based flexible antenna shows a higher sensitivity(9.36-9.8,much larger than the 4.05-5.39 of the copper antenna)and more stable performance.Furthermore,this sensor is attached to human skin to act as a wearable device and it works well to trace the movement of human body,which indicates the proposed antenna sensor is an exciting device with flexible mechanical performance,reversible deformation and excellent thermostability.This sensor is very suitable for wearable devices,wireless sensors and other potential aspects.In this thesis,several ways for utilizing graphene in microwave antennas are proposed and evaluated.Both antenna reconfigurability and high sensitivity are realized in the proposed antenna designs.This work provides a new material and gives out a creative thinking of the way to design and manipulate the material in antenna engineering and relevant areas.