  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.
