【作者】 杨辉；

【导师】 朱国富；

【作者基本信息】 国防科学技术大学 ， 信息与通信工程， 2009， 硕士

【摘要】 近年来,合成孔径雷达技术取得了迅猛的发展。在此期间,分辨率的提高依然是重要的发展方向。距离向实现超高分辨率需要超大带宽信号,以0.1m分辨率为例,需要1.5GHz的信号带宽,直接实现如此大的信号带宽是相当困难的,采用常规方法也是不现实的。本文采用基于频率步进线性调频信号的合成带宽技术用来实现超大带宽信号。合成带宽技术的基本思路是把一个大带宽的线性调频信号分割成几个子线性调频信号,子信号的中心频率以一定的步长增加。每次发射一个子信号,回波信号使用信号处理技术联合各个子信号得到一个全带宽的合成信号,实现高距离分辨率。本文提出了一种脉冲压缩先于合成带宽的处理方法,具有处理步骤简单,运算量小的优点。接着讨论了雷达与目标的相对运动对合成带宽的影响,并给出了这种影响可以忽略的约束条件。方位向高分辨率要求更长的孔径积累时间,导致距离弯曲增大；加上距离向分辨率很高,这都要求成像算法更加精确。本文基于脉冲压缩先于合成带宽处理的原理,采用成像处理先于合成带宽的方法,提出了结合合成带宽的距离迁移算法和后向投影算法,使成像算法可以方便地和合成带宽技术结合起来,具有操作简便,运算量小的优点。从理论上说明了距离迁移算法与后向投影算法的一致性。针对目前缺乏可用于合成带宽的实测数据的情况,提出了一种将一般数据转换成频率步进线性调频信号数据的方法,为在没有合成带宽实测数据的情况下研究合成带宽方法提供了一种途径。更多还原

【Abstract】 Recently, Synthetic Aperture Radar (SAR) has been developing quickly. In these years, improving the resolution is still an important tendency of development.Ultra-high range resolution requires ultra-wideband signal. For example,0.1m range resolution requires 1.5GHz signal bandwidth, implementing this type of ultra-wideband signal directly is very difficult and normal method is unrealistic. In this paper, a synthetic bandwidth method which based on stepped-frequency chirps is used to realize the ultra-wideband signal.The basic thinking of this method is cutting the total bandwidth signal to several sub-signal, each sub-signal have a smaller bandwidth, the center frequency of each sub-signal is stepped-frequency, and then combining each sub-signal to a total bandwidth signal to attain high range resolution. A pulse compression before synthetic bandwidth processing method is proposed in this paper. This method has the advantages of simple processing steps and less computational amount. The influence of the motion between radar and target to synthetic bandwidth processing is discussed, and the constraint under which the influence can be neglected is derived.Ultra-high azimuth resolution imaging requires long integration time, which leads to a serious range curvature, considering ultra-high range resolution additionally, there requires a high precise imaging algorithm. Based on the principle of pulse compression before synthetic bandwidth processing, we use the method of imaging before synthetic bandwidth processing, and proposed the range migration algorithm and backprojection algorithm which combined with synthetic bandwidth. This lead to the convenience of combing imaging algorithm with synthetic bandwidth and the advantages of simple processing and less computational amount. The consistency of range migration algorithm and backprojection algorithm is discussed theoretically. Considering the lack of real SAR data for synthetic bandwidth, this paper proposed an approach to transform the common SAR data to frequency-stepped chirps, this transform supplies an approach to investigate synthetic bandwidth method under the condition of lack of real synthetic bandwidth data.更多还原