Research On The Millimeter-wave Nonsymmetrical Massive MIMO Transceiver System For Fifth Generation Communication

With the development of 5G communication technology at home and abroad,the millimeter-wave communication has become a research hotspot in the future because of its larger bandwidth and lower delay.At present,millimeter-wave massive MIMO transceiver systems mostly adopt symmetrical design with the same number of transmit channels and receive channels.It is difficult to balance the performance,power consumption,cost and system complexity of the traditional symmetric transceiver system.Recently,a new nonsymmetrical transmission solution was first proposed by the State Key Laboratory of Millimeter Waves in Southeast University,which has attracted more and more attention.According to the idea of nonsymmetrical architecture mobile communication system,a new nonsymmetrical architecture millimeter-wave communication system is proposed in this paper:The transmitter adopts a hybrid beamforming structure with two digital channels and 16antenna units,and the receiver adopts a full digital beamforming structure with four antenna units.The scheme has the following characteristics:the transmitter adopts hybrid multi-beam architecture,which can reduce the cost and significantly improve the efficiency of transmission power;the receiver adopts full digital beamforming architecture,which can obtain a wide coverage,simplify the complexity of beam scheduling and optimization,and speed up the user's beam positioning;the transceiver adopts independent antenna array,which can greatly reduce the number of RF transmitter switches,improve the transmission power of the transmitter and reduce the noise figure of the receiver,so as to improve the overall performance of the transceiver system.The developed nonsymmetrical transceiver system is operated at 28.3GHz band with400MHz signal bandwidth,and the time division duplex(TDD)mode.The baseband processing part,filter and antenna,local oscillator clock system and RF transceiver circuit of the proposed millimeter-wave nonsymmetrical large-scale MIMO transceiver system are systematically studied and designed in this paper:(1)For the baseband data processing part of nonsymmetrical transceiver system,a set of performance test platform for 5G millimeter-wave transceiver system is designed.The system supports the generation of 400MHz baseband signal and the direct sampling of 400MHz IF signal.The EVM of 400MHz OFDM self return loop is only 1.36%.And the synchronization of multi-channel ADC and DAC is realized,which provides guarantee for baseband data processing of nonsymmetrical system;(2)A SIW filter with passband frequency of 27GHz-29GHz is designed,the fluctuation is less than 0.5dB,and S₁₁<-15dB in passband;A broadband end-fire antenna operating at 28GHz band is developed,with the coefficient is less than-15dB and the gain achieves 6dBi,and the transverse spacing of the antenna is only 5.7mm,which is convenient to form a linear array;(3)A high-performance clock board based on SIW-DGS filter is designed for the transceiver system.It can generate multi-channel high-precision 100MHz reference clock and multi-channel 6.4GHz RF local oscillator clock through external 10MHz reference.The integrated phase noise of the RF local oscillator is only-53.92dBc;(4)For the RF hardware part of the system,the link budget,circuit design,performance debugging and RF performance test of the transmitting part and receiving part are completed respectively.A single RF channel of the transmitter can provide about 6dBm linear output power with flatness less than 2dB,and the EVM degradation of 400MHz 5G NR signal is only1.95%;The equivalent EIRP of a single transmitting board is about 30dBm,and the scanning range of transmitting beam is±40°.The noise figure of the receiver is only 3.4dB,the maximum receiving gain is more than 65dB,the adjustable gain range is more than 50dB,the receiver sensitivity is-62dBm(400MHz 64QAM 5G NR signal),and the EVM degradation of the standard 400MHz 5g NR signal is only 1.6%;The full digital beam forming can be realized with the digital baseband board,and the scanning range of the received beam can reach±30°.In addition,the OTA communication performance test of the nonsymmetrical system is carried out:The test results show that the system supports the demodulation of 256QAM signal with 400MHz bandwidth in the case of single data stream,the throughput can reach 2.8512Gbps,and the spectral efficiency is 7.128bps/Hz;In the dual data stream test,the system can support the demodulation of dual data stream with 64QAM modulation format signal with 400MHz bandwidth,and the maximum throughput can be up to 4.2768Gbps in theory,and the spectral efficiency is 10.692bps/Hz;Data throughput and spectrum efficiency have reached the leading level at home and abroad.