Radiation by a dielectric-loaded cylindrical antenna with a wall airgap

Previous solutions for the radiation by a cylindrical antenna loaded with a single dielectric layer are extended to the multilayered case. For the sake of convenience, and without any loss of generality, only the 2-layered method of loading is considered by a boundary-value approach. Graphical results are presented to show the effect of the dielectric on the radiation pattern and conductance when the first layer is a thin air gap. It is shown that significant improvement in the pattern may be achieved with critical dimensions of the air gap. With a single or double layer, the dimensions may be selected to produce a broadside pattern similar to that of the unloaded dipole of less than half a wavelength. It is expected that this behaviour will be employed to improve the radiation characteristics when the antenna length is finite, provided that optimisation techniques are employed in designing the critical dimensions.