A directive communications antenna comprising upper and lower plates, each having a leading edge, and a parabolic reflecting cylinder disposed between and axially intersecting the plates so as to form a cavity having a focus line. The cavity is open adjacent the plate leading edges. Upper and lower lip...http://www.google.es/patents/US4876554?utm_source=gb-gplus-sharePatente US4876554 - Pillbox antenna and antenna assembly
