基于OFDM-LFM的弹载广域SAR成像距离模糊抑制

Range ambiguity suppression of the missile-borne SAR wide area imaging based on OFDM-LFM

高弹道弹载合成孔径雷达(synthetic aperture radar,SAR)在对中大型舰船目标进行广域成像时,其高弹道高度和高机动速度特性使图像易产生多重距离模糊,图像质量严重恶化。针对这一问题,提出了一种基于正交频分复用线性调频(orthogonal frequency division multiplexing-linear frequency modulation,OFDM-LFM)信号的正交波形设计方案,该方案采用Bernulli映射的混沌调制序列,对OFDM-LFM信号基进行频率调制,降低了信号的互相关峰值电平和自相关峰值旁瓣电平,进一步提高了发射脉冲间的正交性,且该调制方式可产生多个相互正交的波形,以解决多重距离模糊问题。目标成像仿真结果证明,混沌序列调制的OFDM-LFM信号可有效抑制弹载广域SAR成像的距离模糊。

Wide area imaging of medium and large ship targets with the high trajectory altitude and high maneuvering speed of high ballistic missile-borne synthetic aperture radar(SAR)make the image easily producing multi-range ambiguity and the image quality deteriorates seriously.In order to solve this problem,a orthogonal waveform design scheme based on orthogonal frequency division multiplexing-linear frequency modulation(OFDM-LFM)signal is proposed,the scheme uses Bernulli mapping chaotic modulation sequence to carry out frequency modulation of the OFDM-LFM signal base,the cross-correlation peak level and autocorrelation peak sidelobe level of signal are reduced,and the orthogonality among the transmitting pulses is further improved.The modulation method can generate multiple orthogonal waveforms to solve the problem of multiple distance ambiguity.The simulation results of the target imaging show that the OFDM-LFM signal modulated by chaotic sequence can effectively suppress the range ambiguity of the missile-borne SAR wide area imaging.