Research On Duplex Antenna Based On Bandstop Filter With Open-circuited Stub

With the development of the modern wireless communications,miniaturization and integration of the system has become a hot topic.In recent years,more and more device-combined-design methods have been proposed,which provide a lot of effective methods to realize a smaller and more integrated system.Antenna is a component to converted cable signal to wireless signal at the front-end of the wireless communication system.The miniaturization and integration of the antenna system also has been attracted the focus of academic field and industry.Filtering antenna combines the design theories of the antenna and the filter.Compared with the antenna cascaded the filters,filtering antenna has better performance in many aspects,such as wider bandwidth,better out-of-band suppression level and so on.The intensive study of the filtering antenna makes it possible to combine the design of antenna,filter and duplexer,and to achieve a more compact antenna system with better performance.Based on the integration design of antennas,three duplex antennas based on open-circuited stub band-stop filter have been proposed in this paper.The works are summarized as follow:1?linearly polarization duplex slot antenna.Two slot antennas with same polarization are integrated on a single ground plane to realize simultaneously transmitting and receiving.By employing open-circuited stub band-stop filter feeding network,the port-to-port isolation is improved and two second-order filtering characteristics at both operating bands are obtained.The antenna can realize more than 30 dB port-to-port isolation,when the transmitting and receiving operating frequencies are close to each other.2?linearly polarization duplex microstrip antenna array.The transmitting and receiving operations are realized by the common radiating patches.The antenna is designed based on cascading antenna and filters.However,the difference is that this antenna use open-circuited stub bandstop filters to generate transmission zeros,which is the key to improve the port-to-port isolation of the antenna.Besides,the bandwidth of the antenna is improved by the second-order filtering characteristics created by the patches,probes and the filters.3?circularly polarization duplex microstrip antenna.The working principle of the dual-fed circularly polarization microstrip antenna is analyzed firstly.Then the power distribution as well as the phase shift is realized by a power distribution microstrip line without introducing extra matching network.Finally,a high transmitting and receiving isolation circularly polarization duplex microstrip antenna is presented.