Higher order asymptotic analysis of impedance wedge using uniform theory of diffraction

In this paper a high-frequency asymptotic method is used to obtain the solution for diffraction of an isolated right-angled impedance wedge. By using an additive approach in Uniform Theory of Diffraction (UTD)fonnat, leading terms up to (kp)(-5/2) (k is the wave number and p is the distance from the origin) has been considered. A comparison has been made between Uniform Asymptotic Theory (UAT) and UTD when a finite number of terms in the series is retained. It is shown that with leading terms of (k rho)(-1/2), UTD is sufficient to provide an accurate solution to a field point on the wedge surface whereas UAT gives vanished diffraction coefficient. In order to study the validity of the model for dielectric wedge, the impedance model with leading terms of (k rho)(-5/2) has also been extended to study the diffraction of photoresist and polysilicon wedge. The total field results for E-polarization show an excellent match with the solution obtained from finite difference time domain method. However the results for H-polarization show slight discrepancy due to the properties of diffracted field.