A Novel High-Gain Printed Antenna Configuration Based on $\text{T}{\text{M}_{12}}$ Mode of Circular Disc

The fundamental (
$\text{TM}_{11}$
) mode of a circular patch antenna is generally used for broadside gain applications. However, other
$\text{TM}_{1\text{m}}$
modes (
${\text{m}} = {2},{3} \ldots $
) also radiate in the broadside direction with high directivities, but are avoided due to the occurrence of sidelobes in the radiation pattern. Here, a simple high-gain disc antenna configuration, using high dielectric constant substrates, operating in the
$\text{TM}_{12}$
mode, is presented. At first, through an analytical study, it is shown that by selecting an appropriate value of the dielectric constant, both high directivity and low sidelobe level (SLL) can be attained. Next, it is demonstrated that the excitation of adjacent modes can be reduced significantly by a proper selection of feed location. For a practical antenna design, it is also shown that the SLL can be further reduced using a finite ground plane size.