| With the development of society,the application scenarios of wireless technology are becoming more and more complex and the requirements are getting higher and higher.The frequency spectrum resources of microwave frequency band is drying up day by day.The millimeter wave frequency band has a large information capacity.The millimeter wave band has gradually become the focus of research because it has a long propagation distance,is non-ionizing,and has little impact on the human body compared with infrared and lasers,and can be applied to various scenarios.In this thesis,we focus on the design of millimeter wave antenna.Three types of millimeter wave antenna for different applications have been designed.The main work of this thesis is as follows:1.A 8×10 microstrip array antenna working in the frequency band of 24 to 24.3 GHz was designed.The Chebyshev synthesis algorithm was used to obtain the current amplitude distributions in the elevation and azimuth planes respectively.Then,for the one-dimensional array in the elevation plane,a microstrip series feeder is designed by combination of tapered microstrip gradient line and ordinary microstrip line to reduce the reflection produced by the step impedance transformation of the transmission line.An isolation band structure is introduced at both sides of the one-dimensional array in the elevation plane to prevent the surface wave radiation,decrease coupling,and then reduce the design difficulty of the feeder in the azimuth plane.In the azimuth plane,series quarter-wave impedance transformers are used to design the series feeder.The designed antenna covers the operating frequency band of 24~24.3GHz with s11 below-10 d B.Its half-power beam width is about 13° and 14°,and the sidelobe level is lower than-20 d B and-28 d B,in the elevation plane and azimuth plane,respectively.Its gain is higher than 20 d B.The antenna has the features of high gain,low side lobe and narrow beam,and it can be applied to the automobile anti-collision radar system.2.An omnidirectional circularly polarized microstrip array antenna working in the 27.5~28.35 GHz frequency band was designed.Firstly,a dual-layer stacked patch antenna element with a parasitic patch is designed.It has the wide-band circular polarization characteristic because the parasitic patch broadens the axial ratio bandwidth.Then,the element is rotated in sequence to form a 2×2 microstrip antenna array,and a four-way divider is designed using a tapered gradient line to achieve equal-amplitude and in-phase feeding to the four microstrip antenna element.The array not only has an omnidirectional pattern shape similar to that of a monopole antenna,but also has good right-handed circular polarization performance.In the 27.5~28.35 GHz operating frequency band,its s11 is lower than-10 d B,and the axial ratio is lower than 3d B.The gain is above 4.7d B and has a good frequency stability.The antenna size is only 8.4mm×8.4mm×1.3mm and it is easy to integrate since the effect of ground is taken into account in the design.Therefore,it is suitable for D2 D communication of the future 5G portable terminal equipment.3.A frequency-diversity cavity antenna that can be used for computational imaging is designed.The antenna consists of a PCB resonator and 10 non-resonant radiation holes etched on the upper surface of the resonator.When two such antennas are placed orthogonally to form a transceiver system,the transmitter holes and receiver holes will form a Mills-Cross distribution,which can achieve minimum redundant sampling.For most of the frequency points in the range of 17.5-26.5 GHz,the |S11| is lower than-10 d B and the radiation efficiency is between 0.35 and 0.55.Observing the field distribution on the upper surface of resonant cavity,we find that the resonant cavity can produce different resonant modes at intervals about 0.2 GHz,which shows good frequency diversity characteristics and meets the requirements of computational imaging system. |
PDF Full Text Request