This paper presents an implementation of an iterative method based on the wave's concept, for analysing a ring resonator. This method includes a two-dimensional fourier modal transformation (2D-FMT) in a wave guide environment. The method has the advantage of simplicity in that it does not involve basis functions and inversion of matrices, as used in other calculation methods. Therefore, it is capable of analyzing larger bodies than other classical techniques. An implementation of the iterative calculation is shown for the extraction of S parameters of microwave components. The good agreement between simulation results and experimental published data justifies the design procedure and validates the present analysis approach.