Design of the feeding structures for the excitation of the microstrip line second higher order mode leaky-wave antenna

Two feeding structures for the excitation of the microstrip line second higher order mode as leaky-wave line sources are proposed in this paper. Since the second higher order mode of the microstrip line assumes a magnetic wall symmetry plane at the center of the strip as the dominant mode does, the feeding line adopted is coplanar waveguide (CPW). One of the feeding structures uses CPW on the same plane with the microstrip; while the other places the feeding CPW on the ground plane of the microstrip line. To suppress the excitation of the dominant mode, the slots of the feeding coplanar waveguide are placed appropriately. Experiments are conducted to exhibit the efficiency of the excitation schemes.