Research On The Method Of RF Device Performance Test In OFDM System:LTE Signal Generation And Analysis

With the rapid development of science and technology,more and more attention has been paid to communication technology.As a vital part of communication system,RF performance is one of the important factors that affect the quality of communication system.How to determine whether RF devices can meet certain communication standards is very important.In the traditional testing methods,oscilloscope,spectrum analyzer and vector analyzer are often used to test the different parameters of the RF device separately.The test results can not reflect the overall performance of the RF simulator.It is necessary for professional test staff to make a complex comparative analysis of multiple parameters to draw a conclusion.In order to evaluate the performance of wireless communication chips in mobile communication applications quickly,intuitively and accurately,this paper proposes a new testing method for RF devices.This method creates the idea of combining signal source and analyzer together,and integrates five communication protocols: GSM,EDGE,W-CDMA,HSPA+ and LTE.The test source can be flexibly configured according to the needs of users,and at the same time,it has a complete signal analysis function of communication system.The signal analysis function can demodulate all kinds of digital modulation signals such as ASK,FSK,PSK,QAM and so on.Finally,the test results can be judged by the constellation diagram and the EVM value of the demodulator.The new test method greatly saves the cost of instruments during the testing process.The test process is more convenient,the test results are more intuitive,and the effect of human cost and human factors on the test results can be effectively reduced.In this paper,the LTE signal source under the OFDM system is used to represent the method.The main research results are as follows:Firstly,the performance testing method of RF components in communication system is studied.In order to meet the requirements of communication system,a new method for testing RF devices is proposed.This method does not need to test 1d B compression point,in-band flatness,IP3 and other parameters one by one,but obtains the overall performance of RF devices conveniently and accurately by observing the constellation diagram and EVM values of the devices to be measured by the standard signal source.In the choice of communication mode,this paper takes LTE signal source as the representative to carry out a comprehensive simulation of the new test method with MATLAB software,and verifies the feasibility of the test method from the theoretical level..Secondly,the OFDM wireless communication system is studied.The methods and performance of various digital modulation methods are analyzed,and the processes of serial to parallel conversion,IFFT/FFT,cyclic prefix and spectrum shaping are deeply studied.The key modules and synchronization algorithms in the OFDM process are simulated and analyzed based on MATLAB,which verifies the correctness of OFDM algorithm and lays the foundation for the hardware realization of LTE baseband signal.Thirdly,the generation and analysis of LTE test signal source are studied.A research scheme based on MATLAB for simulation analysis and hardware implementation based on FPGA is proposed.The key process of LTE baseband signal generation is studied in depth,including modulation mapping,resource mapping and OFDM multiplexing module.MATLAB is used to simulate the business channel,synchronous channel and baseband signal,and the simulation results are analyzed by spectrum,time domain waveform,constellation chart and eye diagram.The FPGA hardware implementation of LTE baseband signal is completed by using ALTERA chip,and modelsim and Quartus are used for cascading debugging.The timing diagram and result analysis of each sub module and baseband signal are given.