A miniature UWB planar monopole antenna with 5 GHz band-rejection filter

A noble planar monopole antenna with a staircase shape and very small volume ( 25 /spl times/ 26 /spl times/ 1 mm/sup 3/ ) is proposed in this paper. With the use of a half-bowtie radiation element, the staircase-shape, and a modified ground plane structure, the proposed antenna has a very wide impedance bandwidth measured at about 11.6 GHz (2.9 GHz /spl sim/ 14.5 GHz, bandwidth ratio about 1:5) below VSWR 2 including the WLAN band notched in the vicinity of 5 GHz. An omni-directional radiation pattern is obtained. The electrical and physical characteristics of the proposed antenna make it attractive for use in ultrawide band systems.