Research On Broadband Filters And Filtering Power Dividers Based On Coupling Microstrip Structures

With the widespread use of 4G communication technology and the popularity of Wifi and other wireless technology,as long as the surging 5G communications,the design of portable RF front end devices with high performance is becoming more and more important.As the indispensable parts of the RF/microwave devices,the property of the filter and power divider directly affects the performance of the whole circuit.Nowadays,how to implement a wideband filter with high selectivity and controllable passband is a fundamental trend.At the same time,by combining the characteristics of filter and power divider,a new device thrives,attracting more and more attentions of the researchers.In this article,through theoretical discussions and implementations of the coupled microwave lines,two wideband filters together with many two-way and four-way power divider with filtering responses are designed respectively.These designs lower the insertion loss and improve the selectivity and amplitude balance performance of passband effectively.In addition,they also reduce the circuit size relatively.The main work is as follows:1.Two planar wideband filters based on spiral resonators have been proposed.First,based on coupled microstrip characteristics,spiral resonators loaded with stubs have been proposed.A signal travels through feed line at the input termination to the resonator by coupling method.Then,it goes from the spiral resonator to the output termination in the inverse process.Due to the symmetry of the spiral resonators,the even-mode frequency point can be shifted by loading stubs in the center of the symmetry.After the mode resonances are adjusted well between each other,a good response characteristic of the passband can be obtained by enhancing the coupling.Based on the concept,a tri-mode and a quad-mode wideband filter are designed respectively.Detailed theoretical analysis are provided in the design process,and the final tests are carried out for verification.2.Two types of filtering power dividers based on two coupled microstrip lines have been presented.Applying different designing method,the power divider with good in-band and out-of-band frequency responses are projected.In the design,the comparisons of theoretical analyzed results to the corresponding simulated results are also presented.Besides,by exploring the theoretical formulas,multiple transmission zeros are obtained,helping to improve the selectivity of the power dividers.In the end,simulated results along with the measured results are given,verifying the feasibility of the designs.3.A two-way and a four-way filtering power divider based on the three coupled microstrip lines structure have been presented.In the design,the matrix property of the three coupled lines structure is firstly explored.Then,the feasibility of the implementation of the structure to the power dividers are verified through theoretical analysis.Thus,the design is carried out for the improvement of the power dividers.Finally,a two-way and a four-way power divider are designed and fabricated.The measured results of the fabrications are compared with the simulated results of the corresponding models,which show good consistence with each other.