Design Of Integrated Filtering Antenna Based On The Multilayer Structure

With the rapid development of modern communication technology,as the front end of the electronic equipment,the development of the radio frequency microwave circuit system has increasingly tended to be low cost,high reliability,integration,miniaturization,and multi-functionality.As an essential part of communication equipment,antennas and filters play an indispensable role in the realization of the overall function of the equipment.In traditional RF communication systems,filters and antennas are generally designed separately and then cascaded through 50 ohms or 75 ohms impedance matching circuits.This design method not only makes the antenna and filter module occupy a large size and area,and may bring the risk of impedance mismatch,and even reduce the overall performance of the RF front-end system.To solve this problem,researchers pointed out that the filter and antenna are combined into a small sub-system solution,namely a filtering antenna.On the one hand,this scheme eliminates the matching circuit and greatly reduces the overall structure volume.On the other hand,the filtering antenna has both the inherent radiation characteristics of the antenna and the frequency selection characteristics of the filter.Firstly,based on the research background of the filtering antenna,and the concept of miniaturization and integration of the front-end components of the wireless communication system,the development course of the filtering antenna from the “filter plus antenna” to the integrated filtering antenna is briefly introduced;The current status of development and future trends of multi-layer structure integrated filtering antennas are investigated.Based on a series of basic theories of filters and antennas,the research on multi-layer structure integrated filtering antennas has been completed.The content of the dissertation consists of the following parts:1.Starting from the two-port network of the filter and the equivalent circuit of the coupling network,the cross-coupling matrix synthesis theory of the filter is studied,and the method of calculating the coupling coefficient is deduced.According to the coupling topology of the filter,the ideal cross-coupled circuit model of the selected filter is built in Microwave Office which is the circuit simulation software,and the corresponding coupling matrix of the topological structure is obtained.Then the radiation theory of the microstrip antenna and the electrical parameters and physical parameters of the antenna are analyzed.Two design methods of the filtering antenna that are the design method of the filter structure introduced from the feeder and the integrated design method of the filtering antenna are studied.2.According to the research idea of introducing the filter structure from the feeder,a multi-layer end-fire filtering antenna is implemented.A multi-layer structure balun filter is introduced into the feed part of the quasi-Yagi antenna,which replaced the feed section of traditional quasi Yagi antenna from microstrip line to the CPW.The balun filter is composed of four step impedance resonators.The two unbalanced output ports maintain a phase difference of 180 degrees.The resulting filtering antenna not only has a wide operating bandwidth,but also exhibits excellent frequency selection performance and end-fire performance.3.According to the integrated design method of the filtering antenna,a multi-layer structure MIMO filtering antenna based on a multi-mode resonator is realized.The filter is first designed,then the rectangular patch antenna is used as the final resonator and load of the filter,and the filtering antenna exhibits a frequency response similar to that of the filter.Finally,the above implemented filtering antenna is used as a unit to form a MIMO filtering antenna with good isolation performance.