Fast and accurate permittivity estimation algorithm for UWB internal imaging radar

Ultra-wideband (UWB) pulse radar has high-range resolution and permeability in a dielectric medium, and has great promise for non-destructive inspection or early-stage detection of breast cancer. We have already proposed an accurate imaging algorithm for targets in a dielectric medium, which employs the advanced principle of the RPM (Range Points Migration) algorithm. Although this method offers an accurate internal target image, it is based on the ideal assumption that the permittivity of the dielectric medium is completely known. Although there are various permittivity estimation algorithms, they require an enormous amount of computation, or are hardly applicable to an arbitrary dielectric boundary. To tackle this difficulty, we propose a fast permittivity estimation algorithm suitable for arbitrary dielectric boundaries. In particular, this method makes use of the dielectric boundary points and their normal vectors, preliminarily determined by the existing RPM method. Then, the actual time delay in dielectric permeation is calculated from the ranges observed under Snell´s law. The calculation time is about 5 sec with a Xeon 3.0 GHz processor. Results from numerical simulation verify that our algorithm estimates permittivity with less than 10% error even in noisy situations.