Analysis on bandwidth enhancement of compact probe-fed patch antenna with equivalent transmission line model

In this paper, a comprehensive study of miniaturised broadband microstrip patch antennas for ultra-wideband applications is presented. At first, design and analysis of a compact wideband basic antenna which is composed of a folded-patch feed, a symmetric E-shaped edge, a U-shaped-slot patch and shorting pins are studied and investigated. The measured -10 dB impedance bandwidth of the proposed basic antenna is about 92% in the frequency range 3.94-10.65 GHz. To explicitly demonstrate the mechanism of the bandwidth enhancement method, the equivalent transmission line model of the basic antenna is exhibited. This model contributes the effect of different parts used in the basic antenna structure in order to predict the broadband behaviour of it. Moreover, with the use of a V-shaped slot instead of the U-shaped slot on the patch, an improved antenna with a wider bandwidth in order to cover the frequency range from 4 to 14.4 GHz is obtained. This improved design introduces comparatively a simpler structure with considerable size reduction and an enhancement of 21% in impedance bandwidth compared with the basic antenna. Experimental investigations and detailed simulations based on the parametric study are performed to describe and optimise the broadband performance of the proposed designs.