Abstract: A novel shipborne V/UHF broadband plane antenna is designed. The planar unsymmetrical dipoles are used for the antenna. The elliptical-fitting structure is adopted for upper radiator, and the exponentially graded ladder structure for lower radiator. The antenna input impedance and radiation pattern are calculated with finite differential time domain (FDTD) method. Within a bandwidth of 13.3:1, the voltage standing wave ratio(VSWR) is less than 2.9, the pattern distortion factor in horizontal plane is less than 3.8dB, and the antenna height is only 0.326λ_max. The theoretical values are compared with experimental results and both fit well.