In this paper, we present a planar highly shaped-beam antenna made up of a line source embedded in a structure containing a metal reflector and a dielectric layer coated with metal strips. We have fabricated and measured the radiation characteristics, including the return loss and radiation pattern. Besides, the rigorous mode-matching method incorporating the equivalent principle was employed to calculate the electromagnetic fields in the structure and the far-field radiation pattern. The good agreement between the measured and calculated results was found. This linearly polarized antenna radiates a uniform illumination pattern about 90 degree in the azimuthal plane, with 9% bandwidth around 11.5 GHz.