中文摘要：

为同时解决穿墙雷达成像中墙体参数未知和实时性要求这两个关键问题，提出了先利用支持向量机对墙体参数进行回归预测、再采用相移偏移算法进行成像的两步成像方法。重点介绍了墙体参数预测方法，讨论了目标的大小、位置、形状和个数及墙体长度、采样间隔、噪声对墙体参数预测的影响，仿真结果表明预测方法精度高、耗时短。对实际案例进行仿真分析，结果表明该两步方法成功地实现了墙体参数未知时的实时成像，成像结果令人满意。

英文摘要：

In order to solve two key problems in through-the-wall imaging which are ambiguities of wall parameters and real-time imaging simultaneously,a two step imaging procedure is presented in which firstly the wall parameters are esti-mated by support vector machine and then the targets behind the wall is located and focused by phase shift migration algo-rithm.The estimated method is introduced emphatically,and the influence of the size,the location,the shape,the number of the targets and the length of the wall,sampling interval,noise on the estimated wall parameters is mainly discussed.The re-sults demonstrate that the method based on SVM（Support Vector Machine）has the advantages of high precision and low computational time.Finally,the performance of two step imaging procedure is tested by a practical case of through-the-wall imaging,the results show that the procedure can realize real-time imaging under unknown wall characteristics,and also a rel-atively satisfactory image focusing is obtained.