Effects of different shorting post position on shorted microstrip antenna characteristics

Two single layer single feed small shorted microstrip antennas with air dielectric (ε_r = 1.001) substrate are presented. At first characteristics of a single probe fed square microstrip antenna incorporating a shorting post of radius 0.6mm at four different positions are studied. After connecting a shorting post about 81% reduction in resonant frequency is achieved. Another circular patch antenna with shorting post of radius 0.6mm at four different positions is also studied. After connecting the shorting post about 48% reduction in resonant frequency is achieved. The maximum gain, return loss and radiation patterns of the shorted square and circular microstrip antennas at different shorting post positions are also shown.