In this paper, we propose a method to generate Orbital Angular Momentum (OAM) carrying vortex waves inside a metallic circular waveguide (CW). These waves feature ability to carry multiple orthogonal modes at the same frequency, by the virtue of their unique spatial structure. In essence high data rate channels can be developed using such waves. In free space, OAM carrying vortex waves has beam divergence issues and a central NULL, which makes the waves unfavourable for free space communication. But, OAM modes in guided structures do not suffer from these drawbacks. This prospect of enhancement of communication spectrum provides the background for the study of vortex wave in the circular waveguides. In this work, a radial array of monopoles is designed to generate the vortex wave inside the waveguide. Further, we introduced the dielectric materials inside the waveguide in order to manipulate the operating frequency of the OAM modes. Simulation results shows that the various dielectric materials allow us to tune the working frequency of the OAM beam to a desired frequency.
