Research On Small Multi-band Microstrip Antennas

With development of communication industry,as a key component of radiating and receiving electromagnetic wave equipment,the requirements of the antenna are becoming more and stricter.Miniaturization and multi-band antenna has become the development trend.The microstrip antenna plays an important role in wireless communication system terminals,with its small size,low profile,easy manufacture and other good advantages.In this thesis,the application background and development status of the antenna have been reviewed,the basic parameters of the microstrip antenna,consisting of S parameters,input impedance,bandwidth,efficiency,directional coefficient,polarization and gain have been discussed.The principle of operation,theoretical analysis and other methods of antenna feeding are also studied.Meanwhile,the multi-band and miniaturization technology of antenna are considered.According to the theory of monopole antenna and microstrip line technology,a tri-band antenna is designed first.The antenna can meet the frequency requirements of satellite communications in C-,X-and Ku-bands.By adjusting slot structures on the radiation patch,the antenna performs better characteristics.It can also be reduced the volume and cost of the system effectively.Through the result of current distribution analysis on the surface of a microstrip antenna fed by coaxial,an L-shaped slot is grooved along the edge.After that,the antenna can work in four bands,which contain the fourth generation mobile communication network and a new generation of wireless local area network working frequency.Finally,based on planar inverted F-shaped antenna structure,an antenna which can combine positioning system and wireless local area network is designed.The antenna obtains tri-band radiation characteristics after grooving two L-shaped slots on radiating element.It has the advantages of good omnidirectional radiation pattern,simple structure,small volume and the facility to install in small handheld devices.In accordance with the requirements of size analyzed by high frequency simulation software,material objects were processed.Simulation results and measured results from vector network analyzer were contracted.It shows the consistency between two,although there are some indifferent errors.Therefore,these designs in this thesis have strong practicability in industry application.