A substrate integrated waveguide based leaky-wave antenna with composite right-left-handed tapered slot unit cells is studied for a wideband radiation at the boresight. The antenna consists of a number of slotted-unit cells with varying slot lengths but the unchanged slot widths and the identical embedded rectangular patches. The measured gain at the boresight of the tapered LWA is greater than 9 dBi across a wide bandwidth of 4.4% (8.80 GHz-9.20 GHz).