| As microstrip antenna possesses various attractive features like light weight, small size,low cost and easy to shape with crafts, it has been widely used in wireless communication systems. However, the application range is limited because of its relative narrow bandwidth. In recent years, slot-shape structure microstrip antenna is more and more popular with its broad-band property of wide-slot by many scholars. As the hotspot of a great deal of areas, the fractal structure has self-similarity and space filling. To the research of combining slot antenna with fractal technique, increasing the bandwidth of microstrip antenna further more and decreasing the antenna's volume will have a bright future.Through researching on the fractal theory, this article takes more research on the fractal techniques which is applied in the cell of the antenna. Firstly on the basis of researching two kinds of slot structure microstrip antennas, the fractal structure is embedded in the slot antenna. The S-band and C-band broadband antenna are designed. The impedance bandwidth of two all reaches 90 percent, there will be 10 to 20 percent promoting in bandwidth compared with no fraction of the antenna at the same volume, and decreases the antenna's resonant frequency. And then, to solve the interference to UWB system brought by WLAN, the band-notched function of the wide-band antenna has been studied, and combining dendriform fraction with wide slot structure is realized. The simulation results show that the impedance bandwidth is 3 to 5GHz, covers with the bandwidth of UWB (3.1~10.6GHz), and appears notched property in 5 to 6.25GHz, hence reduces the disturbance to system caused by wireless LAN.Finally, three antennas of formal design are made according to the actual size derived from simulation. The VSWR, radiation plot and gain of the antennas are measured, the experimental results and the simulation results show a good agreement, which verify the feasibility and effectiveness of the antenna design. |
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