Design Of Reconfigurable Metasurface For Indoor 5G Communication

With the development and progress of social economy,the development of mobile communications is increasingly fast,and connections are ubiquitous.More than 70% of mobile communications services take place indoors according to operator surveys.However,for the common indoor non-line-of-sight(NLOS)scene,due to the influence of various obstacles on electromagnetic wave propagation,the coverage capacity of base station is limited,resulting in weak coverage area or blind area,which is difficult to maintain normal communication.Therefore,this thesis analyzes the entire communication link budget of the NLOS scene,and then proposes the use of reconfigurable reflectarray as passive relays to achieve the blind area coverage of NLOS scenes.The specific research contents of this thesis include the following aspects:1.Firstly,the domestic and foreign research progress and current status of reconfigurable reflectarrays and indoor blind area coverage are introduced,which laid a foundation for the research on indoor NLOS blind area coverage.Then the basic theory of conventional microstrip reflectarrays are analyzed,and further studied the working mechanism of the reconfigurable reflectarray.Then,in order to reduce the number of PIN diodes loaded on the reconfigurable reflectarray,and reduce the design complexity and cost,this thesis analyzes the design principle of partially active reconfigurable reflective metasurfaces.By connecting multiple units together to form N-element subarray,the 1:N driving ratio of electronic loading elements and unit is realized.Finally,the design idea of quasi 2-Bit is proposed,which can realize ±50° single beam scanning under plane wave incidence.2.Aiming at the blind area coverage problem of indoor NLOS scenes,this thesis proposes a blind area coverage method based on reflectarrays.The radio wave propagation and network planning software Win Prop,which is suitable for the blind area coverage of indoor NLOS scenes,is introduced,and the specific functions of its various modules are analyzed.Then,the L-shaped scene and T-shaped scene of the school building are modeled by the Wall Man module of Win Prop.In addition,the power intensity distribution of the scene with only active base station is analyzed by Pro Man module,and then the effect of different reflectarray parameters on the blind area coverage of the scene is further studied.The budget of the communication link in the NLOS scenario is analyzed,and finally summarizes the whole process and steps of the blind area coverage method based on the reflectarray.3.Aiming at the problem of the huge number of PIN diodes loaded on the reconfigurable reflectarray,this thesis designs a partially active reconfigurable reflectarray,which can reduce the PIN diode by 60% while ensuring the performance of the reconfigurable array.One-control-two broadband reconfigurable reflectarray unit cell that meet the phase difference within 180±20° in the 3.5GHz-3.8GHz frequency band when the reflection loss is less than 1dB is designed.Partially active reconfigurable refletarray is designed with Onecontrol-two units and sparseness,which can reduce the number of PIN tubes by 60% while ensuring a beam scanning capability of ±50° and a beam scanning resolution of 2°.The result of sparseness shows that the directivity coefficient after sparseness is less than 1.5dB smaller than that of the non-sparsed array,indicating that the sparseness of the array is at the cost of reducing the directivity coefficient of the main beam.In order to verify the validity and correctness of the designed partially active reconfigurable reflectarray,a horn feeding test was carried out in a microwave anechoic chamber.By adjusting the state of the PIN tube,20°-50° beam scan was achieved.The measured results and the simulation results are overall consistent,which proves the design of the reconfigurable refletarray validity and correctness.Then the partially active reconfigurable refletarray is applied to the blind area of the Tshaped corridor,which increases the power intensity by 8dB compared with the absence of the reflective array.4.This thesis realizes the design of a single beam array by loading a single PIN diode in the reconfigurable unit under plane wave incidence.First,two units with a phase difference of90° are designed which are based on the principle of quasi 2-Bit proposed in this thesis,the reflection loss in the working frequency band 3.6-3.75 GHz is less than 1dB,and the phase difference of ON/OFF state meets 90±20°;Then the different unit arrangements of the quasi2-Bit reconfigurable array are analyzed,and the center beam is selected to be 50° for the quasi 2-Bit array design by comprehensively considering the array performance,the overall design process of the 10-element linear array is explained and analysis.Afterwards,a 30-element linear array composed of the above two types of reconfigurable units was designed.By adjusting the state of the PIN tube,a single beam scan of ±50° can be achieved;and compared with the conventional 1-Bit dual-beam array,the quasi 2-Bit single-beam array has a greater directivity coefficient in the main beam and a wider beam width than that of the dual-beam.Finally,the designed quasi 2-Bit array is applied to the blind area coverage of the L-shaped corridor.After the reconfigurable refletarray is set up,the power intensity is increased by about 10 dB compared with the absence of the reflectrray,and the power intensity of a single beam is 5dB higher than that of a dual beam.