Resrearch On RF Front-End Of Millimeter Wave 5G Mobile Communication Systems

The requirement for data services are increasing dramatically with the continuous development of mobile Internet.In the foreseeable future,the existing 4G mobile communication system will not be able to meet such a huge business needs and the 5G mobile communication system will be an effective way to solve this problem.In this paper,the millimeter-wave frontend for 5G mobile communication system is studied.The frontend is divided into three parts including frequency source,transmitter and receiver.In this thesis,a frequency source is designed based on the structure of DDS +PLL with frequency range from 10.5GHz to 12GHz.The PLL frequency synthesis is built with the discrete PLL and the VCO chip.The DDS frequency synthesis outputs a 100MHz point frequency signal as the reference signal of the PLL frequency synthesizer,in order to get better phase noise performance.The phase noise of frequency source is about-95dBc/Hz at 1KHz offset of the output frequency,-100dBc/Hz at 10KHz and 100KHz offset of the output frequency and-120dBc/Hz at 1MHz offset of the output frequency.At the same time,a millimeter-wave frontend based on the superheterodyne structure is designed in this thesis.A harmonic mixer is used to reduce the design difficulty of the local oscillator.The RF frequency range is from 24.5GHz to 27.5GHz and IF frequency is 3.5GHz.Measured results show that the in-band gain flatness of the transmitter link is less than 2dB,the input 1dB compression point is 6dBm,and the saturated output power is about 15dBm.The gain of the receive link is 12.5dB,the in-band gain flatness is less than 1dB.EVMs of QPSK,16QAM,64QAM and 256QAM modulation modes are 2.73%,1.98%,1.75%and 1.65%respectively in the 50MHz bandwidth of the center frequency.The test results show that performance of the millimeter-wave frontend is good and could meet the system requirements.