The coexistence issues caused by the spectrum overlapping between wideband system and other narrowband system has been a major concern. This paper proposed a compact ultra-wideband (UWB) antenna with a frequency notch at the WiMAX band. The proposed antenna consists of an octagon-shaped patch fed by a 50 Ω microstrip line. The ground plane is truncated to improve the overall bandwidth. An altered H-shaped slot is etched on the proposed radiator to introduce the band-notch function. The antenna demonstrates a good impedance matching over a bandwidth of 2.8 to 11 GHz with reasonable radiation patterns. The band rejection performance and gain reduction in the frequency band of 3.3 to 3.6 GHz is successfully achieved. Transient analysis of the designed antenna indicates stable signal transmission confirming its suitability for short-range UWB impulse radios. Additionally, the proposed antenna has a compact size of 26 × 32 mm2.