A coaxial dipole antenna includes a first radiator which is approximately one quarter wavelength long. A second radiator exhibits length less than one quarter wave length and is coupled to the feed port by a reactive element which has an electrical reactance which is insufficient to increase the electrical...http://www.google.com/patents/US4504834?utm_source=gb-gplus-sharePatent US4504834 - Coaxial dipole antenna with extended effective aperture
