US Patent 8098207 Electronically scanned antenna

An aperture of an antenna for a radar system comprises a first waveguide comprising a first protrusion and a second protrusion, each protrusion extending longitudinally along one side of the first waveguide. The aperture further comprises a second waveguide comprising a third protrusion and a fourth protrusion, each protrusion extending longitudinally along one side of the second waveguide. The first and third protrusions and second and fourth protrusions adjoin to form a radio frequency choke at least partially suppressing cross polarization of radio frequencies between the first and second waveguides.