Research On Vehicle-mounted Radar Range And Velocity Measurement Method Based On LFM-OFDM System

Range and velocity measurement for vehicle-mounted radar in vehicular networking environment is one of the important aspects of future unmanned technology,it can extract range and velocity information of the target vehicle from signal delay and Doppler frequency shift.Linear frequency modulation signal(LFM)of which frequency shows linear change with time has been widely used in radar system,and through the use of LFM,the contradiction between radar coverage-distance and spatial resolution has been solved well.As a kind of spread spectrum signal,LFM is not sensitive to Doppler shift,has strong anti-interference performance and robustness,it also makes LFM very popular in the wireless communication market.However,the main limitation of LFM signal is that the sufficient diversity between the pulses is complicated to achieve,there is a distance Doppler coupling,single-channel LFM signal transmission rate is too low,and the spectral efficiency is not high.At present,OFDM signal has been applied to range and velocity measurement for vehicle-mounted radar,in order to meet the needs of higher resolution and accuracy,and utilizing both advantages of OFDM and LFM signal,a new type of spread-spectrum multi-carrier system for vehicular applications called LFM-OFDM system is proposed.This paper aims at the new method of range and velocity measurement based on the LFM-OFDM signal and pilot signal,as well as the performance analysis.Firstly,in this paper,the channel model and application scenario on which the research is based are given,linear frequency modulation signal and OFDM system are introduced,and establishing the LFM-OFDM signal model.In detail,the LFM-OFDM transmitting signal model and receiving signal model in vehicle-mounted environment,the LFM-OFDM characteristics which are different from other signal,as well as the demonstration of orthogonality are given.Next,the range and velocity measuring method using LFM-OFDM signal is derived after the relationship between frequency domain matrix and target range as well as velocity is revealed by detailed theoretical analysis.And a relatively optimal frequency estimation algorithm which has no side-lobe effect and has fast spectrum attenuation is obtained through comparison and analysis.Then,from resolution and precision,the simulation results of range and velocity measurement using classical OFDM signal and LFM-OFDM signal are compared.It is found that the method can improve the performance indeed in the case of selecting the appropriate simulation parameters,which is consistent with the theoretical derivation,and better to meet the needs of the vehicular networking system.Finally,the LFM-OFDM pilot signal model and its range-velocity measurement method are given,and the design of LFM-OFDM pilot is carried out from the aspects of quantity and structure on the basis of the pilot design criteria.In detail,the characteristics of range and velocity measurement using block,comb and discrete LFM-OFDM pilot signals are analyzed respectively.Then,the range and velocity measurement method using LFM-OFDM pilot signal is derived,in the meantime the simulation analysis of performance is operated.It is found that the resolution and anti-noise performance of LFM-OFDM comb pilot velocity measurement and block pilot range measurement are similar to those of a frame LFM-OFDM signal,and the communication performance is good.