The RF Front-end Design Of The MIMO Channel Emulator

With the commercialization of 4G communication systems and the development of the future 5G communications,the complexity and diversification of wireless channels are increasing rapidly and the quality of wireless communications is affected by some negative factors in wireless channels,such as multipath effects and noise,etc.A good approximation of the wireless channel can be created by a Multiple-Input Multiple-Output(MIMO)channel emulator,which can effectively reduce the testing time of researchers in outdoor scene,improve and ensure the communication quality.This project comes from the enterprise project "LTE MIMO Channel Emulator",which mainly focuses on the RF front-end design of the massive MIMO channel emulator for TD-LTE duplex communications.The frequency range is 0.5GHz to 4GHz,and the bandwith is 40MHz.According to the requirements of the project,several popular RF architectures are compared and the zero-IF structure is adopted,because it has the advantages of small size,low cost,wide bandwidth,and miniaturization,whichwill make future integration easier in the massive MIMO system.Based on the zero-IF structure,the specific implementation methods of the different parts in the RF receiver and transmitter are determined with power calibrations after an evaluation and link budget simulation,and some test results of the receiver and the transmitter are given.After a self-receive and self-transmit test,the measurement results of the RF front-end module are given in the thesis.The EVM of the 40-MHz QPSK signal and 20-MHz TD-LTE signal is less than 2%and 1.5%,respectively.Good loopback results show the excellent performance of the RF front-end module.Finally,the RF front-end module is cascaded together with "LTE MIMO channel emulator" for more testing,including the input power detect accuracy,the output level accuracy,the dynamic range,the EVM of QPSK and TD-LTE signal of the LTE MIMO channel emulator system.The system measurement results show that the RF front-end works well and satisfies the requiements of the LTE MIMO channel emulator system.