Study On Compact Broadband Vehicular Antennas

With the rapid development of Internet of Vehicles(Io V)technology and intelligent vehicles,compact broadband vehicle antennas have attracted wide attention in academia.In order to satisfy the characteristics of broadband/multiple frequency points and high gain,multi-mode resonance theory is widely used in antenna design.By incorporating stubs into the resonator,the impedance bandwidth of the antenna can be effectively expanded.However,the introduction of stubs may cause higher cross-polarization and lead to more bulky antenna size.In this thesis,based on multi-mode resonance theory,a series of broadband miniaturized monopole antennas with simple structure,good performance and hybrid lumped-distributed parameters loading are designed.This method is expected to be applied to shark-fin vehicle antennas.The main contributions of this thesis include:1.Based on the classic monopole antenna,a quarter-wavelength,multi-mode resonant monopole antenna loaded by stubs is designed.By changing the length of the stubs,the excited high-order modes are disturbed and moved to the lower frequencies,so that the bandwidth of the antenna is increased.The radiation pattern of dipole and loop oscillator combination is deduced and verified by MATLAB simulation.2.Based upon the multi-mode resonant monopole at its basic form,the length of the stubs loaded on the antenna is shortened.Lumped inductance elements are embedded in the stubs to compensate the distributive parameters caused by the reduction of the stubs.Based on parametric studies,the length of the stub and the load inductance value are determined.In order to verify the correctness of the theory,a five-quarter-wavelength monopole antenna is designed.By loaded lumped inductor on the stubs and the gap capacitor on the resonator,the excited mode of the antenna is disturbed and the impedance bandwidth is increased.Compared to the pure distributed stub-loading scheme,the length of the perturbed stub can be reduced by 60%.3.The proposed method is applied to the designed shark-fin antenna which is composed of a monopole-loop combination.The impedance bandwidth can be effectively extended by adding stubs to disturb the excited modes.By loading lumped inductor in the stubs,the size of the added stubs can be effectively reduced,and the radiation performance of the antenna is less affected.Finally,antenna sample is fabricated and measured,which proves that the design method can effectively shorten the length of the added stubs.