In the X-Band PASOTRON under development in CSIR-CEERI, a rippled wall waveguide is designed and developed as the slow wave structure. The dispersion characteristic of a slow wave structure is a very crucial parameter in deciding the operating point in a microwave tube. The resonant method technique is used here to measure the dispersion relation and axial modes of dominant transverse magnetic modes (TM01) in a slow wave structure with sinusoidal varying radius. The resonant method is simple to use as compared to non-resonant methods where we have to move a bead through the structure which makes process complicated. In the technique we use, an advantage of our structure being a resonant structure has been taken. The purpose of this work is to compare the simulation results of dispersion characteristics using CST simulation code with experimental results, which comes out to be in close agreement. © 2013 IEEE.