Small monopole antenna with modified slot ground plane for UWB applications

A novel microstrip-fed monopole antenna with modified structure is presented for ultra wideband (UWB) applications. The main body of the antenna consists of a quasi square radiating patch with tapered steps and a modified slotted ground plane. Due to the repeatedly cutting of three notches on the radiating patch and also inserting a rectangular slot and three tapered steps on the ground plane, new resonances and a wide bandwidth are obtained. By applying two sleeves with proper sizes to the antenna structure, even wider impedance bandwidth is achieved. The antenna has a compact size of 18×12×1.6mm
³
and covers the frequency range of 2.34 - 21.43 GHz (9.15:1; 160%). The impedance bandwidth improvement process of the proposed antenna is presented and discussed in detail.