Wideband strip antenna surrounding a ground plate

A wideband planar antenna, which is composed of a ground plate and a strip surrounding the plate, is proposed. Wideband impedance matching with fractional bandwidth over 130% is achieved by making the distance between the strip and the ground plate stepwise so that the distance becomes wider in the tip side. The electric field in the slot line changes its direction without changing the traveling direction at the stepped section, and it is enabled to leak and radiate while traveling. It was also found that the matching frequency band can be greatly extended to the high frequency side by bending and extending the slot line to surround the ground plate. The lowest impedance matching frequency can be controlled by the strip width at the tip with keeping wideband impedance matching property.