In this paper, an ultrawideband(UWB) antenna based on coplanar waveguide (CPW) feed was designed. The antenna consists of a lowcost FR4 dielectric substrate, two asymmetric ground plates centered on the feeder, and a splitring resonator.The antenna structure is simple and compact, and its size is only 31.6 mm×48 mm×1.6 mm.By adding a splitring resonator above the floor patch on one side, not only the operating band of the antenna is widened,but also the size of the antenna is reduced. The final antenna has a return loss of -10 dB and a bandwidth of 2.33~11.75 GHz.The results show that the antenna designed in this paper can be applied to wireless communication systems.