Research On Broadband Technology Of Microstrip Reflectarrays

For satellite communications,long-distance communications,and radar systems,high-gain antennas play a huge role and are an integral part of the system.However,traditional high-gain antennas all have more or less defects.Microstrip reflectarray antennas can be used as a substitute for traditional high-gain antennas.With the advantages of planar structure,simple feeding,low profile,convenient fabrication,and easy beamforming,reflectarray has become a research hotspot in recent years.In this context,the design methods of reflectarrays have been studied in this paper.Considering the shortcoming of narrow bandwidth for microstrip reflectarrays,this paper makes a thorough research on the wideband technology of microstrip reflectarrays.The main contents of this paper and research results have been obtained are as follows:1.The study of Broadband Reflectarray Based on Vivaldi elements.The method of constructing a reflectarray using the broadband Vivaldi antenna is studied.By adjusting the lengths of microstrip lines in the Vivaldi elements,compensation for the reflection phase is achieved and the variation range of the phase shift curve covers 360~o.The influence of oblique incident electromagnetic waves on the reflection phase stability is analyzed.The reflectarray based on Vivaldi elements is modeled and simulated.The focal length is optimized and the reflectarray is processed and measured.The measured results verified the feasibility of the design method.2.The study of 1-bit Wideband Reflectarray Based on Polarization Converter.Aiming at the demand of 5G communication systems for high-gain antennas,a method for designing a1-bit wideband reflectarray using the reflective metasurface polarization converter is studied.A reflective metasurface polarization converter with wideband and high polarization conversion rate is designed.The stability of reflection phase versus to the incident angle of electromagnetic waves is discussed.Based on this polarization converter,a 1-bit wideband reflectarray is designed.The measured results show that the design method greatly extends the bandwidth of reflectarray.3.The study of 1-bit Wideband Reflectarray Generating OAM Waves.The OAM waves with different modes have the characteristic of being orthogonal to each other.By adopting the method of mode division multiplexing,multiple mode OAM waves can alleviate the problem of the current tight wireless spectrum resources.Therefore,based on the reflective metasurface polarization converter,this paper proposed a 1-bit reflectarray to generating specific mode OAM waves.The experimental results show that the designed refelctarray can generate OAM waves with good performance in a wide frequency range.The OAM waves produced by the reflectarray have the small divergence angle not exceeding+/-4~o.The designed antenna can be widely applied in long-distance communication systems based on OAM waves.