Design And Research Of Beam Steering System On 5G NG-RAN

With the rapid development of Internet technology and Internet of Things technology,various industries have higher and higher requirements for the throughput of communication systems.Traditional mobile communication technologies are gradually unable to meet the new communication needs brought by the development of the times,so the fifth generation mobile communication system(5G)came into being.5G mobile communication technology supports three application scenarios: Enhanced Mobile Broadband(e MBB),massive Machine Type of Communication(m MTC),and Ultra High Reliability and Low Latency Communication(URLLC),which is much richer than the previous generation.Besides,the communication speed has also been greatly improved.The peak rate of a single user can reach 20Gbit/s on the downlink and 10Gbit/s on the uplink.The increasement in communication rate also reduces the delay of transmission.According to the existing plan,5G includes the Sub-6GHz frequency band and the millimeter wave frequency band.Among them,the Sub-6GHz frequency band is an important frequency band for the early development of 5G communication,and it deserves attention.As for the millimeter wave frequency band is a key frequency band for the future development of 5G,which can provide a broader spectrum for future communication equipment.Due to the high frequency,the absolute bandwidth of this frequency band is higher when the relative bandwidth remains the same,and a faster communication rate can be obtained.At the same time,due to the higher frequency of the millimeter wave frequency band,the antenna and microwave components used are also smaller,which is also beneficial for the miniaturization of antennas and other equipment.However,due to the high frequency and short wavelength of electromagnetic waves in the millimeter wave band,they will produce more serious multipath effects and high path loss,which will adversely affect the communication rate,limiting the application of this technology to a certain extent.Because the gain of the array antenna is higher and circular polarization can effectively deal with the multipath effect and polarization matching problems,so the use of millimeter wave antenna arrays and circular polarization technology can solve the problem of millimeter wave antennas to a certain degree.In addition of increasing the frequency,beam steering technology can also increase the communication rate by improving the efficiency of the communication system.Beam steering is a technology that can rotate the main lobe of an antenna array by controlling radio frequency signals.Its controllable directionality means higher space utilization and higher communication efficiency,which can bring higher communication speed and capacity,so this technology will be widely used in 5G millimeter wave communications.The main work of this thesis includes the following aspects:1.Designed a millimeter wave transmitter and receiver based on software defined radio(SDR)equipment and external frequency conversion circuit.It has beamforming function and can control the beam direction of the array antenna to a certain degree.The maximum output power of the external circuit of the transmitter is about 19 d Bm,and the maximum output power of the external circuit of the receiver is about 17 d Bm.This receiver and transmitter have the advantages of low cost,strong flexibility,and it have broad application prospects because it can be programmed to meet different needs.2.Aiming at the Sub-6GHz frequency band of 5G,a broadband circularly polarized dielectric resonator antenna is designed.The core of the antenna is the four-segment 90° broadband phase shifter proposed in this thesis.The broadband phase shifter has excellent performance,-15 d B impedance bandwidth reaches 63.5%,±3° phase shift bandwidth is 84.4%.And its size is small.The longest path is only half of the wavelength corresponding to the center frequency.Due to the wider bandwidth of the phase shifter,this four-point-fed broadband circularly polarized antenna has a wider bandwidth,with an impedance bandwidth greater than 80.0% and an axial ratio bandwidth greater than 73.3%.Then,based on this antenna,a2×2 circularly polarized array antenna was designed,with an impedance bandwidth of 80.5%and an axial ratio bandwidth of 63.2%,which can cover the Sub-6GHz frequency band.Besides,the isolation of each port of the array is good in the working frequency band.Therefore,it is suitable for the application of MIMO technology.3.Aiming at the millimeter wave frequency band of 5G mobile communication,this thesis proposes a broadband circularly polarized dielectric resonator antenna based on traveling wave structure and coupling feed,which has a small size and low profile.Through simulation,it can be proved that the impedance bandwidth of the antenna is 53.8%,the axial ratio bandwidth is 57.9%,the 3d B gain bandwidth is 30.2%,and it can cover the required N257 and N258 frequency bands.The average efficiency in the 3d B gain bandwidth is above 74%,illustrating the design is feasible.After that,a 4×4 array was proposed based on the abovementioned new dielectric resonator antenna.Simulations showed that its impedance bandwidth was greater than 38.9%,and AR bandwidth was greater than 47.8%.It can also cover the N257 and N258 frequency bands,and the isolation between each port of the array is good,greater than 15 d B,suitable for the application of MIMO technology.