In this paper, a full wave approach is used to analyze the propagation parameters of two coupled symmetric microstrip transmission line on dielectric multilayer substrate with dielectric overlay and a notch between the strips. The purpose of this analysis is to examine the validity of previously reported quasi-static techniques to higher frequencies for applications in the millimeter wave frequency range. The objective is to reduce the distortion of a transmission line that consists of two parallel microstrip lines on two dielectric substrates with a notch and a dielectric overlay. The distortion in such a transmission line is produced due to the difference in the phase velocities of the even and odd dominant modes. Techniques based on controlling the dielectric constant, height and width of the notch and the overlay are used to reduce distortion. The semi-analytical method of lines (MoL) technique is applied here to solve for the normalized phase velocities of the dominant even and odd modes for this planar microstrip transmission line configuration. The numerical results provide a detailed analysis of the transmission line controlling parameters for frequencies up to 100GHz .