A compact ultra-wideband monopole antenna with dual bandstop characteristics

A compact and simple ultra-wideband microstrip-fed planar antenna with double bandstop characteristic is presented. The antenna consists of a rectangular monopole and two Wshaped slots inserted into the radiating patch and the truncated ground plane. By using a W-shaped slot defected ground structure (DGS) in the feedline, a stopband of 800 MHz (from 5.1 to 5.9 GHz) for band rejection of wireless local area network(WLAN) is achieved. To obtain the other stopband (from 3.7-4.4 GHz), a same shaped slot is etched into the monopole. Moreover, the two stopbands can be controlled by adjusting the length of the slot respectively. The simulation results show that the designed antenna, with a compact size of 38.5 mm×42.5 mm, has an impedance bandwidth of 2.8-11 GHz for voltage standing wave ratio (VSWR) less than 2, besides two frequency stopbands of 3.7-4.4 GHz and 5.1-5.9 GHz. Moreover, the main features including omnidirectional H-plane radiation patterns and the appropriate impedance characteristic are achieved by beveling the radiating patch and the microstrip-fed line of the proposed antenna.