| With development of continuous improvement of communication industry, as the system components of the radiation and receiving of electromagnetic wave, the requirements of the antenna are becoming strict. Miniaturization, broadband and multi band antenna has become the development trend. The microstrip antenna will do a good job in wireless communication system terminal applications with its small size, low profile, easy manufacture and other advantages.In this thesis, the application background and development status of the antenna are reviewed, the basic parameters of the microstrip antenna, including the S parameters, input impedance, bandwidth, efficiency, direction coefficient, polarization and gain have been discussed. The principle of operation, theoretical analysis method and several ways of antenna feeding are also studied, at the same time the multi-frequency, broadband, miniaturization technology of antenna are considered.Ultra wideband antenna with notch characteristics is designed first, based on the theory of monopole antenna and the open circuit microstrip line. An open rectangular slot in the ground plane, which broadens the antenna impedance bandwidth effectively, can meet the requirements of ultra wideband antenna, and covering 2.9-10.8GHz band. The relative bandwidth is 115.3%. Adding cross in the internal circular patch, a notch frequency 5.4GHz has appeared, the bandwidth is 5-6GHz, realized a notch characteristic and make the ultra wideband antenna and wireless local area network(WLAN) design without collision frequency. Then, using slotted and adding minor patch on the radiation method to achieve a work in a WLAN systems, a antenna working the WLAN is designed. The simulation and actual measurement results showed a wide impedance bandwidth, good direction map and gain of antenna used in 2.4GHz, 5.2GHz and 5.8GHz band. Finally, two tri-band microstrip antennas used in WLAN and world interoperability for microwave access(WiMAX) system are designed. The one adopt multi-branch manner, the other through opening slot in radiation patch with comb- and ring-shape and undoes circular gap in ground plane to realize tri-band characteristic. The antenna has good omnidirectional radiation characteristics, simple structure and small size, can easily integrated with microwave circuits. |
PDF Full Text Request