Novel designs of probe-fed broadband shorted patch antennas for ultra-wideband (UWB) applications are presented in this paper. In these designs, unequal resonance arms fed by a folded patch produce multi resonances to broaden the impedance bandwidth. In the first design, the antenna consists of an asymmetric E-shaped patch, a folded-patch feed and shorting pins. This antenna is achieved by four adjacent resonances with the measured −10 dB impedance bandwidth of 76.18%. The pins are utilized to miniaturize the size of the patch. By introducing a folded ramp-shaped feed in the similar structure with the first design, a wider bandwidth with the five resonances is obtained. This improved design introduces an antenna with an impedance bandwidth of more than 110% and a considerable size reduction compared to the first antenna. The antennas present resonance tuning ability within the impedance bandwidth by varying the length of unequal arms. In addition, parametric studies are performed by investigating the effects of different key parameters on obtaining optimal designs of the proposed antennas.
