| DAB is the third generation broadcasting system following traditional AM and FM.It is a new generation broadcasting with perfect timbre like CD.In addition,DAB can provide people with convenient digital information services.According to WARC-92,the DAB system operating frequencies cover FM band and 1.452-1.492 GHz.The antenna for DAB system is my thesis's main contribution.Microstrip antennas have many advantages such as lighter weight,smaller geometry,lower section plane and so on.So microstrip antenna is very popular. However,narrow bandwidth limits microstrip antenna in many fields,the bandwidth with VSWR＜1.2 especially smaller than percentages.So the suspended probe-fed structure is proposed in this thesis which can broaden the bandwidth with VSWR＜1.2 and lower the cross-polarization in the H plane.All above make it fit for the DAB emission system.Firstly the antenna is calculated by Method of Moment(MoM),and its feasibility is validated.Then the novel DAB microstrip antenna is designed,simulated and optimized in HFSS.The influence of antenna's structure on its performance is investigated.Afterward the DAB antenna array is designed and simulated.And the simulation results turn out that the antenna works well in the desired bandwidth, achieving S11＜-22 dB(with VSWR＜1.15),the half-power beam-width of the H plane is larger than 65°.The half-power beam-width of E plane for single-dement antenna, two-element liner antenna array and four-dement liner antenna array are 57°, 29.2°and14.09°,respectively,which meets the criterion of the DAB system.The DAB feeding network is designed by ADS 2005 electromagnetic simulation software and the simulation results show that the feeding network meets the DAB antenna array's demand.The DAB element antenna is fabricated and tested by VNA.The simulation results and test results have reasonable consistency.The test outcomes show that the antenna has lower VSWR,higher gain,lower cross-polarization.In addition,the designed antenna has lower section plane,lighter weight and less cost etc.So the antenna designed in this thesis meets the specification and will works well in the DAB system. |
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