| Antenna is an important component in communication systems,and the rapid development of modern wireless communication technology has put forward stricter requirements for antennas.Parasitic layer antennas have been widely studied due to their excellent performance,and their implementation forms are very rich,such as stacked antennas,parasitic pixel layer-based antennas,metasurface antennas,etc.With the application of parasitic layer antennas in more scenarios and their complex structures,although traditional methods can solve some problems,they still have certain limitations.How to adopt more effective methods to design parasitic layer antennas has become a new challenge.Characteristic mode theory(CMT)provides a better solution to balance the antenna design process,which can apply various shapes of boundaries and has a good and wider application range.At the same time,in the antenna analysis process,it can fully understand the physical characteristics of the antenna.This thesis focuses on the current development needs of wireless technology and uses the CMT to study parasitic layer antennas,obtaining parasitic layer antennas with different characteristics.The main work is as follows:1.Design of dual-polarization parasitic layer antenna.Using the CMT,starting from traditional microstrip patches,by gradually optimizing and stacking parasitic layer structures,a parasitic layer with two lateral radiation modes is ultimately obtained.By using mode current to guide the design of the feed network,two parasitic layer modes are simultaneously excited to achieve broadband characteristics.In addition,due to the layered feed network design,good port isolation has been achieved.The test results show that the vertical polarization port of the dual-polarization antenna has an impedance bandwidth of 37.8%,the horizontal polarization port has an impedance bandwidth of44.7%,and the port isolation within the working frequency band is greater than 37 dB.2.Broadband parasitic layer antenna design.Firstly,the characteristic modes of the initial 3×3 parasitic layer and the slot are analyzed separately,and then analyze the characteristic modes of the slot combined with the parasitic layer to obtain two resonance modes.By adding reflective flooring to the parasitic layer,the radiation characteristics are optimized while also increasing its mode bandwidth.Using slot coupling to excite the parasitic layer antenna,The simulation results show that the antenna has an impedance bandwidth of 73%,a gain greater than 7.3dBi in the operating frequency band,and gain fluctuation is less than 1.6dB.3.Wide-angle scanning parasitic layer antenna array design.Firstly,the characteristic mode analysis of the proposed initial parasitic layer structure is carried out.At the same time,the CMT is used to simplify the parasitic layer structure,and the mechanism of generating wide beam mode is obtained,and the wide beam parasitic layer antenna with simple structure is realized.In addition,the advantages and disadvantages of the two feeding methods were compared,and the slot coupling excitation was used to create a symmetrical wide beam pattern of the parasitic layer antenna.Further,utilizing a wide beam antenna unit to form 1×4 array,the 3dB gain coverage range of -83°～82°on the E-plane is achieved. |
