The aim of this paper is to investigate the dependency of antenna performance parameters of an inset feed rectangular microstrip patch antenna (RMPA) with the variation of notch width at 2.4 GHz. Various antenna performance parameters like return loss, radiation pattern, center operating frequency, directivity, gain and bandwidth of the proposed and designed antenna are obtained by using advanced design system (ADS) momentum. The purpose of this analysis is to find out the optimum inset width of an inset feed RMPA for WiMax (2.2 ~3.4 GHz) application with better bandwidth and improved return loss. A reduced return loss of -37.131 dB for 2.5 mm notch width was obtained. There is strong correlation of the resonant frequency with the notch width (\pmbr=0.98, p ≈ 0).