Research On Miniaturization Of VHF Broadband Vehicle Antenna

With the continuous development of wireless communication technology,the requirements of miniaturization,wideband and high gain of vehicle antenna become the hotspot of research in this direction for the adaptability of vehicle antenna in increasingly complex environment.Combining with the current mainstream miniaturization and wideband technologies,three different structure models are studied and designed for VHF band vehicle antennas by using different feeding methods and loading techniques,and the corresponding prototypes are made for testing.The main research contents of this paper are as follows.1.Research and design of VHF vehicle-mounted double whip antenna.According to the actual engineering requirements,the antenna structure and vehicle environment are analyzed,and two design schemes to meet the index are proposed by using different feeding methods.Scheme I proposes the same amplitude binary array dual whip antenna structure model based on the co-channel feed of T-type power divider,so as to improve the overall gain of the antenna.In order to effectively reduce the insertion loss caused by the matching circuit,scheme 2 proposes a dual whip antenna structure model with heterodyne combining and magnetic loop loading techniques,and single port feeding with high and low pass complementary filters,so as to improve the overall average gain of the antenna.Through simulation optimization and testing,both solutions are able to achieve VSWR less than 3 in the 3-frequency bandwidth and gain above-8d Bi in the operating band.2.Research and design of VHF vehicle-mounted dual whip antenna based on loaded folding line.In order to effectively solve the problem of low gain in the low frequency part,based on the previous research,the structure model of bending line dual whip antenna based on top loading is proposed.By top loading and bending line structure,the purpose of extending the antenna electric length and reducing the matching difficulty is achieved.And the impedance matching is carried out by using broadband matching network with Barron,which makes the VSWR of the antenna in the whole frequency band meet the requirements.Finally,the whole antenna is tested,and the results show that the gain of the antenna in the low frequency band is improved significantly,and the overall gain of the whole band reaches more than-4d Bi.