Abstract: A bi-polarized broadband annular radiation unit, for being installed on a metal reflective plate thus constituting a communication antenna and defining an annular construction by two pairs of orthogonally polarized dipoles, includes two pairs of orthogonally polarized dipoles, each dipole comprising two symmetrical unit arms of a single line sheet shape, one end of a unit arm being facing to a corresponding end of the other unit arm, and a distal end of each unit arm of at least one pair of dipoles is provided with a loading line; and a plurality of balun arms feeding power to and supporting respective dipoles, each balun arm including two parallel balun lines, and the top ends of the two balun lines being connected with corresponding ends of the two unit arms of a corresponding dipole. Each unit arm and the balun line and/or loading line connected to the same unit arm are made by sheet metal stamping forming process or casting process.