Imaging of Objects Near Rough Surfaces Based on Time-reversal Signal Processing and Surface Flattening Transform

摘要

This paper considers the imaging of objects located close to rough surfaces such as ocean or terrain. If transmitters and receivers are also located close to rough surfaces, incident wave is no longer a plane wave, nor a spherical wave in free space and it is necessary to consider Green's functions with the point source located close to the surface, similar to the Sommerfeld dipole problem. This paper considers the near surface imaging by making use of time-reversal imaging and surface flattening transform. Surface flattening transform convert the rough surface problem into flat surface with inhomogeneous random medium. MCF (Mutual Coherence Function) is obtained and used to obtain imaging of point target near rough surface, making use of the multi-static data matrix, time-reversal matrix, the eigenvectors, and the steering matrix. Numerical examples are given. An important point is that integration of stochastic wave propagation and signal processing is necessary to obtain imaging through complex clutter environment.