Wideband balanced antipodal double dipole antenna

A planar wideband balanced antipodal dipole element is proposed. It consists of two parallel printed dipole elements with a balanced antipodal structure. By properly choosing the separation between the dipoles and the length of them, a unidirectional radiation pattern is achieved. Prototypes are fabricated and measured. It is shown that an impedance bandwidth from 4.2 to 13.5 GHz about 105.1% is achieved. The antenna is measured by 27 mm × 19 mm which is only about 0.38λ_L×0.27λ_L (λ_L denotes the lowest cut-off frequency´s wavelength).