A Modified Kirchhoff Migration for Microwave Imaging in Superluminal Propagation Region

Microwave imaging has been developed recently and is used in many applications. Kirchhoff’s migration technique is one of the most popular methods to recover the geometric info of any inaccessible target from raw data. The conventional Kirchhoff’s migration assumes a uniform propagation velocity in the far-field region of the transceiver, i.e., the antenna. In the near-field region of the antenna, the pulse propagation happens at a significantly greater speed compared with the far-field region. The propagation speed of the pulse depends on the antenna dimensions and varies as a function of the distance and angle of the antenna in a nonlinear manner. This nonlinearity causes nonfocused images. In this work, a modified Kirchhoff’s migration method is proposed to take into account the nonuniformity of the propagation speed. Then, the proposed method is verified through several simulations and experiments and it is shown that the modified Kirchhoff’s migration results in focused images in the near-field region.