A new method for calculating the microstrip discontinuities by using the planar waveguide model and planar Green’s function is presented. It is possible to obtain the Z parameters or S-parameters of the microstrip circuits with discontinuities in the boundary area connected to the transmission lines under the condition of calculating the high modes in the lines. Having the advantage of high accuracy and versatility

this method can be used for the analysis and optimization programs of microwave integrated circuits to improve the accuracy of circuit design. As an example

some results of discontinuities of microstrip circuits calculated with this method are given.