| Microstrip antennas have attracted much attention in recent years.The microstrip antennas with stable structure have many advantages,such as small thickness,completely conformal to the surface of the body,and easy to achieve polarization suppression interference,etc,which meets the requirements of the antennas in terms of versatility.Therefore,this thesis focuses on the research of small-scale,wide-band and multi-band methods of monopole microstrip antennas,and four new monopole microstrip antennas are proposed.At the same time,the particle swarm algorithm and its application in microstrip antennas are studied.The improved PSO algorithm is applied to optimize the new antennas,so as to obtain the better performance monopole microstrip antennas.The main work of the thesis are as follows:1.Analyze and improve the PSO algorithm.The basic principle,key parameters and research difficulties of the algorithm are analyzed,and a dynamic inertia weight PSO algorithm is proposed,which adjusts the inertia weight according to the change of fitness of the upper and lower iterations.Select six common testing functions to find the optimal solution to verify its performance.In addition,the improved PSO algorithm is proposed to optimize the design of the antenna.2.Analyze the microstrip antenna structure and summarize the small size,multi-band and broadband technology of the monopole microstrip antennas.Using the existing antenna technology to design four new monopole microstrip antennas.An open square monopole antenna is adopted in the first antenna,and double-frequency characteristic is realized by loading the branches(1/2 ring,1/4 ring and strip)in the radiating unit and slot in the ground plate.And it is optimized by the improved PSO algorithm to expand the bandwidth,the double-band of antenna are extended by 37.5%(3.5-4.6GH)and 26%(5.1-8GHz)respectively.The antenna occupies a small volume and it is suitable for WiMAX and C-band communication systems.The second model,a symmetrical triangular monopole microstrip antenna,is proposed.The antenna is loaded a symmetrical strip-shaped branch that rotates 45 degrees,and simultaneously opens a ring on thetriangular radiation patch to realize tri-band characteristic.The slot is used to enhance impedance matching.The simulation and measured results showed that the impedance bandwidth of the antenna is 200MHz(1.1-1.3GHz),500MHz(3.3-3.8GHz)and 800MHz(5.2-6GHz),respectively,while satisfying GPS(1.227GHz),WLAN(5.2/5.8GHz)and WiMAX(3.5/5.5 GHz).The third one is designed with a broadband microstrip antenna.The radiating unit consists of a C-shaped ring and a quasi-q-shaped branch.The algorithm optimized the absolute bandwidth of the antenna from 5 GHz to 5.5 GHz(1.5-7 GHz),and the relative bandwidth is 129%.The antenna can cover multiple working bandwidths such as Bluetooth,Wi-Fi,S band,and C band,which has a simple structure and good gain.The fourth zigzag ultra-wide band monopole microstrip antenna is formed with 23 small triangular slits at the edge of the circular patch to form a zigzag shape,and an elliptical slot is opened at the center and a symmetric ring is loaded to realize ultra-wide band characteristics,and the relative bandwidth is 150%(2.2-15.4 GHz),the antenna gain peaks at 12.1dB,which can work in the S/C/X band. |
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