US Patent 7102582 Planar antenna and radio apparatus

A planar antenna is formed of a circuit substrate and a slot line formed on the circuit substrate for guiding an electromagnetic wave in an axial direction thereof, the planar antenna emitting the electromagnetic wave at an end part of said slot line, wherein the end part has a curved shape forming a focal point at a location on an axis of the slot line with offset by a distance of about a quarter wavelength of the electromagnetic wave, and wherein there is provided a conductor pattern having a length of about a half of the wavelength of the electromagnetic wave at the focal point.