Analysis of single shorted square microstrip antenna

Smaller size microstrip antennas are obtained by shorting the patch on its edge or inside the patch. Recently design of single shorting post loaded square microstrip antenna fed by microstrip line is reported. It is reported that for an appropriate position of shorting post, antenna can exhibit lower cross polar radiation pattern. In this paper, detailed analysis for explaining the lower cross polar radiation pattern in single shorting post placed square microstrip antenna is explained. The shorting of patch yields two resonant modes of which second higher order mode (TM
_3/2
,
₀
) is nearly equal to TM
₁₀
mode frequency of the shorted patch. At this resonant mode half wavelength variation in currents is observed along shorted patch length which exhibits smaller cross polar level bore sight radiation pattern. Further resonant length formulation at shorted TM
_1/2,0
and TM
_3/2,0
modes for varying shorting post positions is presented. Frequencies calculated using the same agrees closely with simulated results.