Research On MIMO Terminal Test System Based On Radiated Two-Stage Method

OTA(Over-the-Air)measurement is to evaluate the real radio frequency performance of wireless terminals in the complete state,which is a required item for all terminals to access the network,and also the basic support technology to ensure that the current tens of billions of wireless devices can access the network at the same time and communicate together.MIMO(Multi-input Multi-output)OTA measurement is to evaluate the real performance of wireless terminals in a real complex electromagnetic propagation environment,and will be a required test for 5G wireless terminal network certification.Radiated Two Stage(RTS)is one of the MIMO OTA measurement methods that can build multipath channel.This dissertation systematically studies the key technologies of RTS MIMO OTA measurement,and solves the key technical problems in the RTS method,making the RTS method theoretically complete,error-controllable,and consistent in measurement results,and finally promotes the RTS method to become one of the only two international standard methods of MIMO OTA measurement.The main research and innovative results of the dissertation are as follows:Aiming at the problem that the cross-coupling between the anechoic chamber antennas and the terminal receiving antennas cannot be measured and eliminated in RTS MIMO OTA measurement,this dissertation proposed a mathematical model of this propagation matrix,based on which,the solution for solving its inverse and auto-search the best location were presented.The problem of operability of RTS was solved in engineering,automated RTS MIMO OTA measurement was realized,the measurement time of RTS method was reduced,and the stability of RTS measurement was improved.RTS MIMO OTA measurement accuracy may be affected by the reporting error of the device under test(DUT)itself.This dissertation proposed a reporting error elimination method to free the RTS MIMO OTA measurement accuracy from the limitation of the DUT itself.For any DUT,The RTS method can guarantee the comparability of measurement results.This method is a key theoretical supplement to promote RTS into international standards.The standard MIMO OTA measurement methods can only provide the final performance measurement results,and cannot give rectification guidance.For solving this,a diagnostic measurement scheme based on the RTS method was proposed,which measures the antenna module,receiver module,and noise module in the itegrated state.The performance indicators of each component are used to locate the shortcomings of the terminal performance,so as to help the research and development of efficient positioning and problem solving.The standard MIMO OTA measurement requiring 7 to 14 hours,the dissertation proposed an efficient measurement method based on the facts that the receiver does not have directivity,and the terminal received signal under different measurement states can be obtained through mathematical calculations.This method can reduce 3D MIMO OTA measurement from 7-14 hours to about ten minutes,without loss of measurement accuracy.The dissertation proposed a 2×2 and 4×4 RTS MIMO OTA measurement system,and gives detailed information such as RTS channel model verification,measurement process,system error analysis,and actual measurement data analysis.In this dissertation,the solution of key technologies in the RTS method and the implementation promoted the RTS method to be included in the 3GPP(3GPP: 3rd Generation Partnership Project)international standard in 2018,and into the CTIA(Cellular Telecommunication and Internet Association)international standard in 2020.