A square-looped and an end-coupled resonator used in a planar ultra-wideband (UWB) antenna to achieve band-notched performance are presented here. To obtain notched performance in the wireless local area network band, both the square-looped and end-coupled resonator are designed and placed in a fork-shaped UWB antenna centre. The characteristics and schematic equivalent circuit of each resonator are also discussed. Parametric studies of a fork-shaped antenna with square-looped resonator are given as an example to explore the operating mechanism. Accordingly, the band-notched antenna can effectively select target bands by adjusting different resonator structures. The proposed antenna features flat gain-frequency response and group delay as well as 10-25 dB gain suppression in the notched band.