Research Of Pattern Control Based On Linear Polarization Element Rotation And Reconfigurable Antenna Array

As an important characteristic of antenna,polarization has always been the crucial factor that should been considered in modern wireless communication systems design.With the development of the wireless communication technique,the limited frequency spectrum has become more and more crowded.But if we can consider antenna polarization while synthesizing array patterns,not only the degree of freedom will be increased,but also the frequency spectrum can be reused because of the diversity of polarization.In this essay,we will introduce some methods that synthesize dipole arrays or polarization reconfigurable array to obtain low sidelobe,low cross-polarization,and shaped beam patterns using some stochastic optimization algorithms like binary coded genetic algorithm and dynamic differential evolution method.First,we will briefly introduce the background of array pattern synthesis in the world.Compared to a single antenna element,antenna array possess many advantages,including narrow main beam,high gain,high directivity,and scanning beam.Then we will introduce some array synthesis methods and background knowledge,and some reference patterns about the pattern synthesis using polarization rotation.Next,we will introduce an array pattern synthesis method that synthesizes low sidelobe and cross-polarization patterns through dipole selection.Suppose several dipoles are put on every element position of an array,and they have different orientations and with fixed interval angles.We will select one dipole at every one position using a binary coded genetic algorithm to obtain low sidelobe and low cross-polarization level patterns.Different orientations of dipoles in an array can be another degree of freedom which can be utilized to synthesize array patterns.Compared to the dipole rotation method,the proposed method are more efficient while maintain almost the same synthesis effects.After that,we introduce a method which can obtain shaped beam patterns by optimizing the rotation angles and excitation phases of the dipoles in an array.This method have higher degree of freedom compared to those phase-only methods so as to obtain better synthesis performance.On the other hand,our proposed method avoids the amplitude modulation of array which can relatively simplify the complexity of the feeding network.That is because the amplitude modulated array need to design unequal power divider,the introduction of the attenuator will increase the complexity of the feeding network.The method of optimizing rotation angles and excitation phases,on the other hand,avoids this shortcoming.At last,we propose a seven-linear-polarization reconfigurable antenna based on a previous published work.In that work,the authors proposed a four-linear-polarization reconfigurable circular patch antenna with polarization angles of 22.5,67.5,112.5 and 157.5 degrees,respectively.Considering that the number of polarization states might not enough to be utilized in the polarization reconfigurable array synthesis,we propose an antenna with seven polarization states while maintain the same radiation characteristics.The improved antenna has the polarization angles of-45,0,45,90,135,180,and 225 degrees,respectively.The simulated and measured results show that this proposed antenna has good radiation characteristics.After that,we propose a method that through appropriate selecting the polarization states of every element in a 16-element-linear array using binary coded genetic algorithm to obtain low sidelobe and cross-polarization patterns.The full-wave simulation results by the software HFSS validate the feasibility and effectiveness of the synthesis method.The polarization reconfigurable antenna array has broad application prospects especially in the conformal array synthesis,that is not only because it can avoid complicated feeding network compared to the amplitude modulation method,but also due to the controllable polarization diversity of the conformal array.In the application of Radar and electromagnetic countermeasure,arrays with controllable polarization could have high probability of target detection and ability of tracking,stronger universality of target scattering characteristics,better anti-interference performance and ability of intercept.