【作者】 刘阳；

【导师】 宿富林；

【作者基本信息】 哈尔滨工业大学 ， 信息与通信工程， 2008， 硕士

【摘要】 当逆合成孔径雷达(ISAR)成像的目标含有螺旋桨等快速旋转部件时,目标的雷达回波中会产生螺旋桨回波调制(JEM)干扰信号。这种JEM干扰信号一方面自身无法正常成像,另一方面又会影响正常目标的成像效果。JEM干扰信号会影响运动补偿算法的实现,也会在最终成像时形成条带干扰影响成像质量。针对这一问题,本文对螺旋桨目标ISAR回波信号进行了数学分析和计算机仿真,并研究了JEM信号的规律性及抑制方法。首先本文研究了ISAR成像的原理及在ISAR转台成像中螺旋桨目标回波的JEM调制原理。分析螺旋桨回波时域、频域的特征;讨论了螺旋桨散射点回波与普通散射点回波在成像过程中的差异。并对不同旋转速度和不同桨叶尺寸的螺旋桨目标进行了成像对比和分析,深入了解ISAR成像中JEM信号的特性。然后本文介绍了螺旋桨部件散射点回波在ISAR中的多普勒效应。先介绍了窄带信号下多普勒效应的表达式和物理意义,又讨论了由于宽带信号的转台中心与螺旋桨的旋转中心位置的不同而导致的雷达回波多普勒频率的差异。并在此基础上研究了影响多普勒频率变化的相关因素,而后用仿真模型加以分析。本文的最后也是中心环节,就是讨论了ISAR成像中JEM干扰的抑制方法。首先介绍了chirplet基信号的原理和参数的特性,然后阐述了如何应用chirplet基信号进行信号的分解和重建。随后详细说明了在使用chirplet基信号分解ISAR回波信号时,JEM干扰信号和正常信号在信号分解后参数的差异。利用这种差异就可以在信号重建的过程中抑制JEM信号分量,实现ISAR成像中JEM信号的抑制。文章的最后用仿真模型进行了JEM抑制处理的实验并用实测数据对该抑制方法进行了验证。更多还原

【Abstract】 Targets including propeller or other fast-rotating components can cause Jet Engine Modulation (JEM) interference in the received radar signal in the Inverse Synthetic Aperture Radar (ISAR) imaging. The JEM signal will not be normally imaged and it will do harm to natural scatters of interest while imaging. JEM signal make it difficult to do motion compensation and will even disturb the ultimate image. Consequently, this paper proposes a model of ISAR echoes from propeller blades and then researches into characteristics of the JEM signal and how to restrain them.Firstly, this paper describes fundamental principle of ISAR imaging and how the JEM signal modulates received radar signal. This paper presents time-domain and frequency-domain analysis of echoes from propeller blades and also discusses the difference between echoes from propeller and echoes from rigid body. Then the papers pay attention to the contrast and analyze of the JEM signals due to propellers with different size and circumrotating rate. After the above research we would have insight knowledge about JEM signal in ISAR imaging.Secondly, we take aim at Doppler Effect of the JEM signal in ISAR imaging. The expression and signification of Doppler Effect in the narrow band radar system is introduced. Again we discuss the difference of Doppler frequency caused by location shift between the centre of rotating part and the centre of turntable in ISAR imaging. Based on these works, we find out the factors that can work on the Doppler frequency and give emulation at last.Finally, we conclude the method of restraining the JEM interference signal in ISAR imaging. The paper introduced the chirplet basis function and its parameter characteristics, followed by the way of how to make use of the chirplet basis function to decompose and rebuild signals of interest. Noticing that there exist differences between the parameters of JEM interference signal and natural signal when we are decomposing return signal of ISAR, we can make use of these differences to restrain the JEM signal in ISAR imaging. At last an experiment is given to simulate the process of JEM signal restraining and the method is also validated using real data.更多还原