Research On Key Technologies Of Millimeter Wave Multi-beam Self-calibration Receiver Array

Massive MIMO has significant advantages in using space diversity to improve spectrum resource utilization,multi-user access,and beam synthesis against millimeter wave spatial transmission loss.However,in large-scale MIMO systems,the introduction of hundreds of antennas and RF channels makes system calibration more complicated.In addition,after the system is put into use,as the temperature,time and other factors change,the initial phase shift of each channel will no longer be consistent.Therefore,it is necessary to develop a transceiver system with self-calibration function.This paper mainly studies the millimeter wave multi-beam receiver array with selfcalibration function.By inserting a directional coupler between the antenna and the low-noise amplifier as the feed port of the self-calibration signal,the receiving array can realize the selfcalibration function.The structure of self-calibration scheme studied in this paper is simple and does not require the introduction of additional self-calibration channels.The signals of eight channels are combined into one by a combiner while implement self-calibration.Only one ADC is needed to calibrate the eight-channel array,which reduces the overhead of the system.In order to realize the verification platform of mm W multi-beam self-calibration receiver array which operates at 24-28 GHz,in this paper,a digital control phase shifter array based on vector synthesis is developed.The RMS of amplitude error is 0.125 d B and the RMS of phase error is 0.75 degrees under the phase-shifting accuracy of 5.625 degrees.Besides,the RF frontend of the self-calibration receiver array is developed.In order to solve the problem of the recessed pattern caused by the reflection of the clamp,the tapered slot antenna(TSA)using the metal clamp for the interconnection between front-end and antenna is replaced by the double E-shaped microstrip antenna array which is feed by SIW vertically.The antenna array can achieve a beam scan of ± 44 degree theoretically.In addition,the SIW to microstrip vertical transfer structure used for the separation measurement of the front-end and the antenna is also designed.The test results show that the antenna and its transfer structure have good performance.In order to improve the accuracy of the self-calibration system and suppress the stray signal,in the paper,a local filter based on SIW-DGS and an IF filter based on microstrip multimode resonance are developed.The test results show that the bandwidth,insertion loss,stray suppression and other characteristics satisfy the design goals.Finally,combined with the simulation and test results of each discrete device,ADS is applied to verify the self-calibration scheme of the receiver array.The results show that after the system self-calibration,the accuracy of the beam direction and the suppression of the beam sidelobe level are improved,which indicates that the self-calibration scheme of the receiver array is feasible.