Research On The Range Profile Of High Speed Moving Targets

Range profile is amplitude distribution image formed by the vector superposition of all the scatters on the target along the radar range direction. Range profile can reflect the fine physical structure of the target, and its one of the most important features in target recognition. Range profile has very important practical value, and is widely used in the field of civil and military fields, because of the range profile has low computational complexity, good real-time performance and high stability. However, when the target moves with very high speed, the range profile of the target will be fuzzy, spectral split, broadened or distorted. In order to obtain correct range profile, motion compensation must be done for reducing the effect of high speed. The main research content is as follows:1. For high speed moving target, the range profile based on the fractional Fourier transform(FrFT) is studied. LFM signal after FrFT will occur time-frequency concentration in a specific FRFT domain, and it’s amplitude will appear obvious peak. This chapter use modified FrFT based on the two step peak search. First, searching by large step length, the rough estimation of the peak will be obtained. Then, searching by small search step length, to get the exact value of the peak. The parameters of LFM signal can be estimated according to the position of the peak. The simulation results show that this method has high parameter estimation accuracy, low computational complexity and strong noise robusticity. The method is successfully applied to the speed compensation of the range profile for high speed moving targets. The estimation of the chirp rate reached a very high precision, and achieved a good range profile imaging results. Finally, simulation results verify the above conclusion is correct.2. The range profile of the high speed moving targets based on Wigner-Hough transform is studied. Wigner-Hough transform joints Wigner-Ville distribution(WVD) and Hough transform(HT), and WHT is an important time-frequency analysis. LFM signal after WVD mapped to a straight line in WVD plane, then after HT, namely made linear projection integral transform, it will be mapped to the peak point. The speed compensation of the high speed moving targets will be achieved according to the position information of the peak point. The method can restrain cross-term suppression and noise impact, has high parameter estimation precision, and simulation results achieve good imaging effect.3.The range profile of the large acceleration moving targets based on Discrete Polynomial-Phase Transform(DPT) was studied in this chapter. The echo of the large acceleration moving targets can be regarded as three order polynomial phase signals(PPS). Achieving the estimation of the second order and third-order coefficients by using DPT, then the speed compensation factor can be calculated, the impact of imaging by high-order terms can be eliminated effectively. The DPT has high parameter estimation accuracy, the signal after motion compensation by FFT can obtain the clear range profile of the target, simulation results show the effectiveness of this method. Multicomponent polynomial phase signal after DPT will produce cross-term interference, in order to solve this problem, product high-order ambiguity function(PHAF) was used for reducing the influence of cross terms.