Research On Waveform Design And Processing Technique Of OFDM Radar Communication Integration

As the two most important applications of modern electronic technology,radar sensing and wireless communication are widely used in military and civil scenes.Radar and communication equipment respectively have independent functions and working frequency bands.With the lack of spectrum resources and the diversified development of combat styles,and in order to reduce the electromagnetic interference when the equipment is running,the demand for radar communication integration is becoming increasingly prominent.To realize radar communication integration,we must first solve the waveform design problem of radar communication integration,including waveform system,waveform parameters and waveform performance to meet the system index requirements.From the perspective of radar detection requirements,it is required that the transmission waveform envelope fluctuates gently,the detection performance is good and the resolution is high;From the demand of communication transmission,it requires high transmission rate,efficient spectrum utilization and low bit error rate.As a key technology in 4G and 5G,OFDM has the advantages of easy generation,anti multipath and easy equalization in communication.It also has the advantages of anti-interference and low interception in radar application.It is a popular technology in the integrated design of radar communication.Focusing on the background of radar communication integration,this paper studies the key technologies of OFDM radar communication integration waveform design and processing,including waveform design,characteristic analysis,waveform optimization,adaptive optimization method and parameter estimation.Chapter 1 introduces the research background and significance,expounds the concept and characteristics of radar communication integration,summarizes the research status and development trend of radar communication integration,and gives the main research content and organizational structure of the paper.In Chapter 2,aiming at the integrated waveform design of multi symbol OFDM radar communication,a mathematical model of comprehensive weight selection,communication modulation mode and phase coding sequence is proposed,which lays a foundation for the integrated waveform design.The ambiguity function of multi symbol OFDM integrated waveform is deduced,the performance of Doppler ambiguity function and range ambiguity function is analyzed,the influencing factors of ambiguity function in different cases are discussed,and the OFDM integrated signal after pulse compression under the condition of the same phase coding sequence is studied;Simulation results show that the integrated waveform with good performance of PSLR and PAPR can be obtained by comprehensively considering the selection of weight,communication modulation mode and phase coding sequence.In Chapter 3,aiming at the problems of high peak sidelobe and large envelope fluctuation in OFDM integrated waveform,a method of simultaneously optimizing PSLR and PAPR is proposed.At the same time,the optimal power allocation method is designed to ensure the detection probability and channel capacity.The constraints of PSLR optimization are derived,a PSLR optimization method based on random phase coding is proposed;the optimization model of PAPR is given,and a Lagrange weight search algorithm is proposed to improve PAPR;For radar detection performance and communication transmission performance,the optimal power allocation method is proposed respectively,and a joint integrated exponential weighting model is designed.Simulation results show that the proposed waveform optimization method can improve PSLR below-30 d B and PAPR below 2.At the same time,the designed joint measurement model can also provide guidance for waveform optimization under different performance requirements.In Chapter 4,for the problem that it is difficult to solve the probability density function of echo signal in the case of unknown noise distribution,an approximate estimation method is proposed.When the noise distribution is unknown,based on target generalized scattering matrix estimation of generalized likelihood ratio detection,the optimal power allocation method of radar detection probability,communication channel capacity and its joint model under power constraints is proposed.Simulation results show that the proposed method can achieve radar and communication performance consistent with deterministic Gaussian mixture noise.Aiming at the problem that it is difficult to allocate OFDM integrated waveform subcarrier power through echo signal measurement model when the target impulse response is random,a mutual information method under the condition of target randomness is proposed.Based on the approximate mutual information model between echo signal and target impulse response,the radar power allocation method to improve mutual information is proposed,the optimal communication power allocation method to improve channel capacity is given,and the corresponding joint weighting model is established.Simulation results show that the proposed optimal allocation method can effectively improve mutual information and reach capacity,and the power allocation in the case of single Gaussian noise has performance loss in the case of mixed Gaussian noise.In Chapter 5,aiming at the problem of low degree of freedom and limited communication transmission performance of integrated waveform using OFDM,a parameter estimation method of MIMO-OFDM integrated waveform is proposed.The integrated MIMO-OFDM system is designed,the echo signal model including range,velocity and angle information is derived,and a range-angle estimation MUSIC method for stationary targets is proposed,which has better range estimation performance than traditional MIMO arrays;A velocity-angle estimation method with known distance is proposed.SNR has a greater impact on the performance of velocity-angle estimation than the number of snapshots;An improved DFT method for range-velocity estimation under directional communication is proposed.Its estimation performance is better than the traditional DFT method,and its complexity is lower than MUSIC method;Simulation results show that for MIMO-OFDM with higher degrees of freedom,the proposed method can effectively estimate the corresponding range-angle,velocity-angle and range-velocity in different scenarios,and its performance is better than the traditional array design or parameter estimation methods.Chapter 6 summarizes and looks forward to the research work of this paper,and points out the future research direction.