An analysis of the ridged circular disc microstrip antenna element using the cavity model

To increase the bandwidth of a disc microstrip antenna, one should increase the thickness of the dielectric substrate. This results in difficulties in impedance matching. The ridged circular patch microstrip antenna discussed excited in the dominant mode has higher resonant frequencies and a wider bandwidth than the conventional circular patch antenna of the same size. It also provides better impedance matching. In this paper, a theoretical analysis of a ridged circular patch microstrip antenna element is presented by modeling it as a cylindrical cavity with a magnetic wall along its edge. The approach is based on conserving the reaction at the ridged position. Design graphs show the variation of the resonant frequency, quality factor, radiation efficiency at resonance and bandwidth (VSWR < 2), for the dominant mode as a function of the inner to outer disc radius ratio for different ridge thickness. The characteristic equation is derived for the ridged antenna element and its performance is compared with that of the conventional disc antenna of the same size.