| With the advent of the 4G era,the moblie phone antenna operating bands are increasing while the antenna space is getting smaller.How to design a broadband antenna in a narrow space is a main topic in the research of mobile phone antenna nowadays.Antenna matching network design is one of the important directions for that.In order to solve the problem of complicated searching for components value of matching network and insufficient bandwidth optimization of low frequency,NSGA? is adopted to get matching network components value and a design of two ports feeding matching network is presented.In this paper,the traditional matching network,low pass and high pass filter and two ports feed matching network are designed by combining theoretical calculation and numerical simulation.Firstly,the network characteristic parameters are studied in this paper.This paper also analyzes and summarizes the methods of designing matching network with smith chart and the common forms of matching network.Besides,the design process and main ideas of NSGA? are briefly introduced.Secondly,the characteristics of Butterworth filter,Chebyshev filter and elliptic filter are studied.The design of Butterworth low-pass and high-pass filter for mobile phone antenna matching network based on NSGA? is adopted.The simulation results show that the performance of the filter designed by NSGA? is obviously better than that of the traditional method.Finally,NSGA? is used to design and optimize the traditional matching network.The results show that the optimization effect is obvious by comparing with the results before optimization.In addition,a dual-port feeding matching network is proposed to overcome the shortage of lowfrequency bandwidth optimization in traditional matching networks.The simulation results show that the lowfrequency bandwidth is increased to about 3 times comparing the original bandwidth,and the high frequency performance is also improved.The isolation between high and low frequency is below-20dB. |
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