A coplanar waveguide fed asymmetric rectangular antenna with sufficient WLAN bandrejection is presented for ultra-wideband applications. The antenna uses an asymmetric rectangular patch, modified feedline, and defected coplanar ground plane for obtaining ultra-wideband performance. An inverted-L shaped slit in the radiating patch is used for realizing the WLAN band-rejection. The antenna is designed on a 1.6 mm thick FR-4 substrate having an area of 12×16 mm 2 (0.169λ L ×0.225λ L). An impedance bandwidth of 11.49 GHz with a WLAN band-notch from 5.15-5.86 GHz is achieved. In addition to this, desirable radiation characteristics in terms of stable radiation patterns, peak realized gain of 4.5 dBi, and maximum total efficiency of 81% are achieved in the pass-band. In the notchedband, the peak gain and total efficiency reduce to −1.3 dB and 40%, respectively. Measured results agree well with simulated results. This antenna structure has fractional bandwidth of 115.18% and a bandwidth dimension ratio of 3029, which is comparable or better than that of similar structures available in the literature. The proposed antenna has desirable time-domain performance in terms of fidelity factor, group delay, isolation, and S 21 phase.