Pyramidal-corrugated horn antenna for sector coverage

A microwave antenna for use in a sectorized cellular communication system comprises a wide-flare pyramidal horn having two pairs of opposed flared side walls. At least one of the two pairs of opposed walls has corrugated interior surfaces. The length of the horn and the flare angle of the walls having the corrugated interior surfaces are selected to produce a ratio Deltae/lambda greater than 1.5, where Deltae/lambda=[a/(2/lambda)] tan (alphae/2) is the spherical-wave error of said horn, lambda is the free space wavelength of the microwave signals to be transmitted by said antenna, alpha is the horn's aperture width, and alphae the half-angle of the horn in the horizontal plane.