Research On Signal Design And Processing Technology For Radar Communication Integration

In more and more fields such as unmanned aerial vehicles and autonomous driving,equipment miniaturization and functional diversification are required,and equipment is required to realize radar sensing and communication at the same time,which puts forward a strong demand for the integrated design of radar and communication.Meanwhile,with the rapid development of radar system and communication system,the two have gradually overlapped in operating frequency bands,and many similarities have appeared in the structure of the system,which makes it possible to realize an integrated radar communication system.This thesis studies the signal design for radar communication integration based on OFDM.First,the correlation of the four discrete chaotic maps is compared and analyzed,and it is found that the performance of the Logistic map is better,which means that Logistic map is more suitable for phase coded OFDM signal.Then,in view of the poor information carrying capacity of OFDM-IS-LC signal using the same chaotic sequence for each sub-carrier,a phase-coded OFDM radar communication integrated signal OFDM-DS-LC is designed based on Logistic chaotic code.The integrated signal uses different chaotic sequences as phase encoding sequence for each sub-carrier to achieve a greater improvement in the carrying capacity of communication bits.The simulation result shows that compared with the OFDM-IS-LC signal,the signal not only has a pin-like ambiguity function,which enables the radar to have better target resolution,but also greatly increases the communication transmission rate by log2M times.However,the OFDM-DS-LC signal is an OFDM-based integrated signal,which has high peak-to-average power ratio(PAPR).Aiming at this problem,this thesis designs an algorithm for reducing PAPR based on chaotic code grouping and permuting.The algorithm first generates a chaotic phase sequence based on the chaotic initial value in the OFDM-DS-LC signal,groups and permutes the sequence to obtain multiple phase permutations.Then the transmitted signal is phase-weighted using these phase permutations to obtain multiple candidate signals,and the signal with lowest PAPR of the candidate signals will be chosen as the final transmission signal.Because the algorithm directly uses the chaotic initial value in the OFDM-DS-LC signal,it no longer needs to send the initial value of the chaotic phase sequence to the receiver separately,only the number corresponding to the selected permutation needs to be sent,which reduces the auxiliary side information that needs to be sent and reduces the complexity of the implementation because only one chaotic sequence needs to be generated.If the ordinate of CCDF is taken as 10-1,the simulation result shows that the algorithm can reduce the PAPR of integrated signal by 17.5%,31.3%and 52.5%when G is 2,4 and 8,respectively.In view of the high computational complexity of the algorithm when the number of groups is large,this thesis further introduces a threshold-based judgment mechanism.Once the candidate signal whose PAPR is less than or equal to the threshold is found,the search is immediately stopped,which reduces the number of searches of the algorithm.The simulation result shows that although the algorithm has a little loss in performance after the threshold value is introduced,its computational complexity is also effectively reduced.