A novel direct approach for calculation of the polarimetric scattering fields from a narrow 3-D rectangular crack in an infinite ground plane underneath a dielectric layer is presented. Since the electromagnetic fields are directly calculated and thus the approach in inversible, this technique is suitable for microwave NDT applications where cracks of narrow width, arbitrary length and depth under a dielectric layer are frequently encountered. A set of coupled field integral equations (FIE) with logarithmic and hypersingular kernels are derived and then descritized by a collocation method based on Chebyshev polynomials. The results of this direct approach are in good agreement with noninversible full numerical FEM and MoM results
