Research On Polarization Modulation Of Electromagnetic Waves Based On Metasurface

With the increase of large-scale wireless communication devices,spectrum resources become extremely scarce,and how to efficiently realize frequency and polarization regulation of multiple polarization states of electromagnetic waves becomes critical.As a two-dimensional artificial electromagnetic material,the electromagnetic reconfigurable metasurface is considered as one of the most effective means to solve the spectrum resource problem due to their real-time tunability and functional reuse.Therefore,it is important to investigate and design multifunctional multiplexed electromagnetic devices with polarization and frequency reconfigurability.In thesis,the research on electromagnetic wave polarization regulation is carried out based on metasurface,and the reflective ultra-wideband polarization converter is designed to realize the polarization reconfiguration device in the same frequency band by PIN diode control.In addition,electromagnetic device with multi-band polarization selection is designed and implemented.The specific research are as follows:Firstly,the principle of polarization conversion is studied from the electric field of polarization waves,and an ultra-broadband polarizer is designed and implemented by combining the classical open resonant ring with a fan-shaped patch.The polarizer can realize polarization conversion of linear and circular polarization in X-band,and can convert the incident linearly polarized waves to vertically polarized waves,while the circularly polarized waves keep the polarization mode unchanged.In addition,the conversion from linear to circular polarization waves and the function switching of total reflection are completed by PIN diode control.When the diode is turned on,the polarization conversion from linear to circular is realized,and the relative bandwidth of 3 dB axial ratio is 29.8%.When the diode is turned off,the total reflection function of the linear polarization wave in the whole frequency band is realized,and the polarization conversion rate and absorption rate are less than 0.05.This metasurface with polarization reconfigurability has important applications in polarization multiplexing and multifunctional polarization modulation device design.Secondly,a multifunctional device with frequency domain polarization selection is studied and designed.By controlling the on-off state of PIN diode,the connection mode and coupling mode of the metasurface structure can be changed,and the polarization reconfiguration in different frequency bands is realized.The diode code state "10" realizes the orthogonal polarization conversion of linear polarization waves with a relative bandwidth of 12.1%and a conversion rate of more than 0.9.The diode code state "01" realizes the conversion of linear polarization waves with an axis ratio of less than 3 dB and a relative bandwidth of 15.1%.The diode code state "00" achieves a relative bandwidth of 17.5%with a polarization conversion rate and absorbance of less than 0.1 Total reflection function.The diode code state "11" achieves a relative bandwidth 11.0%of relative bandwidth and a conversion rate of more than 0.9 for a linear polarization wave with quadrature polarization conversion.This kind of metasurface with polarization selection in frequency domain not only show the characteristics of reconfigurable,but also realize the conversion of different polarization waves.The device has a wide range of applications in polarization modulation,frequency control,intelligent reflective surface design and antenna design.In Summary,The reconfigurable metasurface studied in thesis has reconfigurable functions of polarization and frequency domain multiplexing,and has important applications in the design of broadband polarization modulation devices,radar scattering cross-section reduction,antenna design and other fields.In addition,it will also play a role in regulating the polarization state of electromagnetic waves on wireless communication systems with multiplexing functions,and has wide application prospects in electromagnetic holography,electromagnetic stealth and beam modulation based on electromagnetic wave polarization modulation technology.