A novel compact and broadband asymmetric coplanar wave guide (ACPW) antenna is presented. A method to extend the bandwidth of a metamaterial-inspired antenna based on a composite right/left-handed transmission line (CRLH-TL) and a modified ground plane is proposed. The ACPW antenna has a broadband characteristic by placing the zeroth-order resonance (ZOR), first-positive-order resonance (FPOR) of short-ended CRLH-TL and the modified ground plane’s two resonances, which are half and one lambda resonances, at all different frequencies with proper frequency intervals. The prototype of the proposed antenna has been implemented and measured. The measured $-\hbox{10-dB}$ fractional bandwidth is 109.1% (from 2.69 to 9.15 GHz) with high efficiency of over 65% and a low profile of $0.32{{{\lambda}}_0}\times 0.19{{{\lambda }}_0}$ (where ${{{\lambda }}_0}$ is the free-space wavelength at the first resonant frequency).