The paper presents a new design of a wideband low profile tapered slot array antenna. To achieve a low profile, a novel low-profile balun with a pair of cavities was invented. The new balun allows a planar power divider to be tightly integrated with array. The overall depth of the array is about 0.48λ at the lowest operating frequency. The measured results showed that the antenna has 3:1 bandwidth with reasonable gain and VSWR.