Investigations On Digital-to-analog Circuit And If Circuit In Millimeter Wave Large Scale Array System

With the commercial application of low-frequency 5G,the development of 5G millimeter wave is also changing with each passing day.The massive MIMO technology based on multi beam array is one of the key core technologies of 5G.Each antenna unit of multi beam array is followed with a RF transceiver channel,and intermediate frequency(IF)and digital-to-analog converter(DAC)circuit are an indispensable parts of the key circuit between baseband and RF.In this paper,DAC and IF circuits in millimeter-wave large-scale array systems are studied.The main contributions of this paper are as follows:1)Designed and implemented a DAC circuit board that can support 100 MHz analog baseband bandwidth,including simple principle analysis of DAC,digital-analog circuit board hardware design and software design.The DAC sampling rate is 1Gsps,the number of bits is16 bit,and the data line rate is up to 10 Gbps.It is connected to the FPGA through the high-speed serial port protocol JESD204 B.The PC transfers the digital baseband data to the DAC through the FPGA and converts it into analog baseband signals,and controls the register configuration of the DAC through the microcontroller.The actual measurement results show that the spurious-free dynamic range of the DAC output is greater than 70 d Bc,and the demodulation EVM of 16 QAM modulated signal with a symbol rate of 100 Msps and a roll down coefficient of 0.35 is 0.34%.2)Designed and implemented a frequency source which can provide high-quality local oscillator signals for intermediate frequency circuits.At the same time,in order to meet the requirements of one-time calibration of the 64-channel local oscillator,a Wilkinson power divider of one to eight was designed and implemented to distribute the local oscillator signal generated by the frequency source.The test results show that the unbalance between the channels of the power divider is only 0.18 d B,the integrated phase noise of the frequency source is only-52.87 d Bc,and the impact on the EVM is only 0.227%.3)Designed and implemented an IF transmission link with automatic carrier leakage suppression calibration,and formed a multi-channel module,and conducted joint testing with the frequency source and DAC circuit.The test result shows that the demodulation results of the IF transmission circuit for the 256 QAM modulated signal with a symbol rate of 100 Msps after the carrier leakage suppression calibration meets the requirements of relevant standards.At the same time,the ACPR test results of each channel are less than-46 d Bc.