Research On Peak-to-average Power Ratio Reduction Methods For OFDM Integrated Radar Communication System

In recent years,the integrated technology of radar communication has received widespread attention.This technology can simultaneously achieve two functions: radar target detection and communication information transmission,which not only saves the space occupied by the integrated combat platform,but also improves the utilization efficiency of integrated system’s spectrum resources.At present,Orthogonal Frequency Division Multiplexing(OFDM)signals have become one of the commonly used transmission signals in radar communication integrated systems.However,the biggest drawback of OFDM signals is their high peak to average ratio,which affects the radar’s target detection performance.In response to this issue,this article mainly studies a radar communication integrated signal peak to average ratio suppression method based on OFDM.The main work is as follows:1.In order to investigate the radar detection performance of sequence modulated OFDM signals,the characteristics of ZC-OFDM and Oppermann-OFDM signals were analyzed and compared,and the performance differences between the two waveforms were compared.Theoretical analysis and simulation experiments show that the OFDM signal waveform modulated by ZC sequences has better radar target detection performance than that modulated by Oppermann sequences.2.Although traditional amplitude limiting methods can reduce the peak to average power ratio(PAPR)of OFDM signals in the system,they can cause an increase in the integrated signal bit error rate(BER)and the problem of out of band spectrum leakage.This article improves traditional limiting method by first suppressing integrated signal above the limiting threshold,and then iteratively filtering the signal to solve problem of spectral efficiency reduction caused by out of band signal dispersion.Simulation experiments show that proposed method can effectively reduce PAPR of OFDM integrated signals under certain conditions by setting reasonable amplitude limiting thresholds and selecting iterative filtering times,and has little impact on radar detection performance and communication performance.3.In order to better suppress the PAPR of OFDM integrated signals,the Partial Transmission Sequence(PTS)method is combined with the improved amplitude limiting method.Firstly,subcarriers are divided into V sub-sequences using the partial transmission sequence method.Each sub-sequence is multiplied by corresponding phase factor,and the PAPR of each sub-sequence is calculated and compared.Then,set of sub-sequences with the smallest PAPR is filtered through multiple amplitude limiting filters,Further reduce PAPR of the OFDM radar communication integration system.Simulation experiments show that the proposed method combines PTS and improved amplitude limiting method,and under the condition of ensuring a certain bit error rate,PAPR can be reduced by 2.3d B.The signal ambiguity function before and after PAPR suppression does not change much,and the impact on radar detection performance is relatively small.