The Several Key Technologies Research Of OFDM Radar

Orthogonal Frequency Divis ion Mult iplexing(OFDM)radar signal,as an emerging wideband modulation signal,has broad prospect of application in radar systems due to its flexib le waveform design,high resolution,strong anti-interference ability,high spectrum effic iency and easy to realize digital technology.However,based on the published literatures,there are few research toward the application of OFDM signa l in radar seeker.So in the paper,the range-Doppler two-dimensional imaging processing,the PAPR problem and the LPI performance evaluations of O FDM radar signal are thoroughly researched.The main research of this paper are as follows:First,the transmitter model of O FDM radar signal is described from the perspe ctive of the radar system,the difference of the signal form and signal processing method between OFDM communication signal and OFDM radar signal are analyzed,the non-constant envelope of O FDM signal is also introduced in this part.For the common range-Doppler imaging method in coherent radar,the signa l models and the signal processing models are built,the OFDM radar range-Doppler imaging method based on the matched filtering processing and the real time realizat ion algorithm of missiles are proposed.The theoretical analysis and simulation results demonstrate that the proposed method can improve the peoformance effectively.Secondly,the PAPR of OFDM signa l and its influence to the radar system are analyzed,the existing methods of the PAPR reduction includes limit ing class technologies,techniques and signal scrambler technologies are analyzed;the partial transmit sequence(PTS)technique is discussed emphatically.For the phase factor optimization of PTS,we propose a genetic-simulated annealing algorithm(GSAA)with PTS technique(GSAA-PTS)to reduce the peak-to-average power ratio(PAPR)for OFDM system,this method can achieve a reasonable compromise between t he PAPR reduction and the effic iency of the phase factor optimization.For the un-weighted OFDM radar signal,the IS OFDM radar signa l,the phase angle and ampl itude weighted OFDM radar signal,the COCS OFDM radar signa l,the MATLAB simulation are carried out,the valid ity of this method has been proved by theoretical analys is and simulation.Finally the common LPI radar signals such as a chirp signa l,the phase encoded signals,frequency encoded signal are analyzed from the perspective of anti-interception,we mainly discuss the LPI performance of O FDM signal.In this paper,for the modern intercept processing method such as cyclic autocorrelation method,the expression of intercept receiver signa l processing gain was derived from the perspective of the discrete-time signal processing.The analysis and comparison method of anti-interception performance of radar signals was proposed based on cyclic autocorrelation accumulation factor.First,the value of cyclic autocorrelation accumulation factor denoted by U of Linear Frequency Modulation(LFM)signa l,two-phase encoded signal and OFDM signal is calculated to analyze the anti-interception performance.Then,in order to analyze the anti-interception performance of large time-bandwidth product signals,the above three signals are used for simulations in the case of low SN R.The theoretical analysis and simulation results show that the High/Medium pulse repetit ion frequency OFDM signal has a relatively good anti-interception performance and the high pulse repetition frequency OFDM signal is much easier to fulfilling the LPI performance requirements.The results show that O FDM radar signal has a good imaging capabilit y and good anti-interception performance and robustness,the disadvantage of high PAPR can be overcome through the PAPR reduction method.