Ellipse based image extrapolation method with RPM imaging for through-the-wall UWB radar

Through-the-wall radar (TWR) technique with UWB (ultra wide-band) signals are promising candidates for nondestructive testing or reliable human detection buried under collapsed walls in disaster scenes. As an efficient 3-dimensional imaging approach, the range points migration (RPM) method has been established, which can transcend the performance limitation of the conventional delay-and-sum approaches, in terms of computational burden, accuracy and spatial resolution. This paper extends the RPM method to the TWR imaging model, called as TW-RPM, where the principle of the original RPM is appropriately extended to this model by considering the propagation path and delay in wall. In addition, this paper introduces the image expansion scheme, based on ellipse fitting approach. As a notable point, this fitting process is not carried out in real space but in data space, which is spanned by range points (a set of antenna location and range) to avoid the extrapolating error due to TW-RPM imaging process. The FDTD (finite time domain difference) based numerical simulation shows that our proposed method accurately expands the TW-RPM image even in narrower aperture case.