Characteristics Verification of a Half-Wave Dipole Very Close to a Conducting Plane With Excellent Impedance Matching

A half-wave dipole located very close to a conducting plane with distance of lambda/30 is investigated. The configuration has an impedance matching function and a balanced feed built in the antenna structure so that an external matching or a balun is not required. The experimental result verifies the numerical analysis by method of moments (MoM), and well explains the predecessors' analytical results by classical methods. The maximum radiation occurs in the normal direction to a reflector plane. We have achieved a maximum gain of 8.4 dBi which is higher than that of a half-wave dipole with a quarter wavelength distance between the reflector. The bandwidth for -10 dB is about 2%. The electric field distribution is studied to show the creation and propagation of electromagnetic waves which correspond to the energy flows in the normal direction to the conductor plane and also sideward along the plane in a small amount. The field lines are shown to be frozen between the dipole and the conductor plane without propagation. Accordingly, this state may be called a quadruple mode