Research On High Edge-Selectivity Balanced Or Balun Type Filtering Antenna For 5G Communication

With the advent of the fifth generation of mobile communication(5G),it is of highly demand for compact,high performance and easy to be integrated devices.The design of filtering antenna that integrates antenna with filter greatly reduces the size of the radio frequency front-end and improves the edge selectivity of the gain of the antenna,thus become a hot spot in the field of research and production.By introducing radiation nulls to the antenna,the edge selectivity of the antenna can be further improved and interference between different systems can be reduced.Due to balanced circuits have the advantages of high common-mode rejection,high anti-interference characteristics,and low common-mode noise,it is of great theoretical significance to carry out research on balanced or balun filtering antennas with high-edge selectivity.In this thesis,the comprehensive design theory of resonator-coupled filtering antenna are studied in systematic,and the miniaturization of the balanced/balun filtering antenna with high out-of-band selectivity are explored.The main research contents include the following three parts:Firstly,a wideband filtering dipole antenna based on short-circuited three-mode resonator is proposed.The equivalent circuit model of the short-circuited three-mode resonator is established and its modes characteristics are analyzed.A compact wideband balun filter is then designed based on the resonator and the microstrip-slotline transition structure.Due to the coupling between source and load,a transmission zero is produced at the edge of the operating frequency band,edge selectivity of filter is improved.By properly design the coupling between the dipole antenna and the resonator,a wideband filtering dipole antenna for 5G band is designed.Experimental results show that maximum gain of 5.1 d Bi is achieved.Secondly,a filtering antenna with high-edge selectivity is designed based on the parallel coupled-line structure.The theory of filtering antenna using the parallel coupled-line structure is analyzed in detail,the passband of this structure and the principle of radiation null are obtained.Then equivalent circuit of the patch antenna is built,the characteristics of feeding and working are analyzed.The patch antenna is equivalently replaced by the last-order resonant circuit and load of the filter based on the integrated design theory of filtering antenna that evolved from the resonator coupled filter,the relationship between radiation unit and resonator is obtained.Finally,a balanced filtering patch antenna with high-edge selectivity for5G communication(3.41-3.6 GHz)is designed and fabricated.Its common-mode reflection coefficient is better than 0.25 d B,the maximum gain is 6.6 d Bi,the circuit area is 0.45?_g×0.61?_g,and the position of the radiation null is consistent with the theoretical result.Finally,based on the terminal stubs-loaded structure,design theory for a dual-band balun-type filtering antenna with high-edge selectivity is proposed.The equivalent circuit of balun-type antenna is established and a parameter study of its dual-band characteristics is done in the detailed.Then,the resonant characteristics of the structure with terminal stubs-loading and the mechanism of the transmission zero are analyzed.The structure of end-loaded stubs,generate resonant poles in the filtering antenna,together with radiation nulls near the working band.Finally,a dual-band filtering dipole antenna that operating in 3.1-3.6GHz and 4.65-5.55 GHz for 5G is designed.The experimental results show that bandwidth of the antenna is widened and high-edge selectivity is achieved.