Abstract :
Microwave UWB radars have a great advantage for high range resolution and penetrating ability for dielectric object, and are promising for non-invasive bio-medical applications, such as breast tumor detection in early stage, or non-destructive investigation for aged or cracked concreate road or bridges. There are various permittivity estimation methods aiming at the above applications, mainly based on the solution of the domain integral equation derived from Helmholtz equation. However, the existing methods require non-linear optimization process for multi-dimensional variables to obtain sufficient reconstruction accuracy. Then, their accuracy or spatial resolution strongly depends on the assumed pixel size, namely, the number of optimization variables. In addition, there is unavoidable problem that the conventional approaches cannot maintain the reconstruction accuracy around discontinuous region, e.g. the boundary between air and dielectric object.
