Apparatus for dual-band antenna and communications tower comprising such apparatus are provided. The apparatus comprises a first part (202) comprising first and second propagation paths configured to selectively propagate signals of a first frequency with either a first polarization state or a second polarization state, a transition part (204) rotatable between first and second transition positions to selectively propagate signals of a second frequency along the second signal path with the first polarisation state when in the first transition position and with the second polarisation state when in the second transition position and a rotator part rotatable between first and second rotator positions. Wherein, the rotator part is configured to orientate the polarisation of signals in the second signal path in order to couple the second signal path to an interface, and allow propagation of signals in the first signal path in either the first or second rotator positions.

A square waveguide (1) has four ridges (6a, 6b, 7a, 7b). The cross section of the square waveguide (1) perpendicular to a waveguide axial direction is square. Inside the square waveguide (1), two rectangular waveguide terminals (4, 5) are formed by partitioning the inside along the waveguide axial direction. A septum phase plate (2) formed to get narrower stepwisely as its gets closer to a square waveguide terminal (3) opposite to the rectangular waveguide terminals (4, 5) is provided. A projecting portion (8) is provided on a part of a ridge (7b) formed on a ridge-side wall surface opposite to a wall surface, the septum phase plate (2) being joined to the wall surface in a part where the septum phase plate has largest width, the projecting portion (8) being larger than other parts of the ridge (7b) in a cross-sectional shape perpendicular to the waveguide axial direction.

An apparatus and method for orthogonal rotation of a radiation E-field polarization rely on a radiating element including an offset-ridge waveguide and a single-mode first ridge waveguide functionally adjacent to the offset-ridge waveguide.

Disclosed is an antenna device including a rectangular waveguide (1) having a first opening end (2a) and a second opening end (2b), a septum phase plate (3) disposed inside the rectangular waveguide (1) in such a way as to partition the first opening end (2a) into two parts along a first direction perpendicular to a waveguide axial direction of the rectangular waveguide (1), a width of the septum phase plate in a second direction perpendicular to both the waveguide axial direction of the rectangular waveguide (1) and the first direction becoming narrower stepwise with advancing from the first opening end (2a.sub.1, 2a.sub.2) toward the second opening end (2b), and first projecting portions (4a, 4b) disposed on two respective first inner walls (1a, 1b) parallel to the septum phase plate (3), out of four inner walls of the rectangular waveguide (1), in such a way as to project toward an inside of the rectangular waveguide (1).

A directional coupler (100) comprises two hollow bodies (200, 201) forming two waveguide portions. Each hollow body has an open end arranged at a first side (10) of the hollow body and another open end arranged at a second side (20) of the hollow body opposite to the first side in a longitudinal direction (30) of the hollow body. The hollow body has a first cross section perpendicular to the longitudinal direction. A second cross section along the longitudinal direction defines a first plane of propagation of the electric field. The two waveguide portions have a common wall along the longitudinal direction (30) forming a septum (400) between the two waveguide portions on a second plane orthogonal to the first plane. The septum has an aperture (410) for coupling the two waveguide portions. The aperture has a shape comprising a part (420) slanted with respect to the longitudinal direction.

A square waveguide (1) has four ridges (6a, 6b, 7a, 7b). The cross section of the square waveguide (1) perpendicular to a waveguide axial direction is square. Inside the square waveguide (1), two rectangular waveguide terminals (4, 5) are formed by partitioning the inside along the waveguide axial direction. A septum phase plate (2) formed to get narrower stepwisely as its gets closer to a square waveguide terminal (3) opposite to the rectangular waveguide terminals (4, 5) is provided. A projecting portion (8) is provided on a part of a ridge (7b) formed on a ridge-side wall surface opposite to a wall surface, the septum phase plate (2) being joined to the wall surface in a part where the septum phase plate has largest width, the projecting portion (8) being larger than other parts of the ridge (7b) in a cross-sectional shape perpendicular to the waveguide axial direction.

An ultra-wideband linear-to-circular polarizer is disclosed. In accordance with embodiments of the invention, the polarizer includes a plurality of cascaded waveplates having biaxial permittivity or cascaded anisotropic sheet impedances. Each waveplate/sheet has a principal axis rotated at different angles relative to an adjacent waveplate/sheet about a z-axis of a 3-dimensional x, y, z coordinate system. Each waveplate is composed of a unit cell of an artificial anisotropic dielectric. Each sheet impedance is composed of an anisotropic metallic pattern. The polarizer further includes impedance matching layers disposed adjacent the cascaded waveplates/sheets.

Microwave antenna systems include a parabolic reflector antenna and a dual-band feed assembly. The dual-band feed assembly includes a coaxial waveguide structure and a sub-reflector. The coaxial waveguide structure includes a central waveguide and an outer waveguide that circumferentially surrounds the central waveguide. The sub-reflector is mounted proximate the distal end of the coaxial waveguide structure.

Disclosed is an antenna device including a rectangular waveguide (1) having a first opening end (2a) and a second opening end (2b), a septum phase plate (3) disposed inside the rectangular waveguide (1) in such a way as to partition the first opening end (2a) into two parts along a first direction perpendicular to a waveguide axial direction of the rectangular waveguide (1), a width of the septum phase plate in a second direction perpendicular to both the waveguide axial direction of the rectangular waveguide (1) and the first direction becoming narrower stepwise with advancing from the first opening end (2a.sub.1, 2a.sub.2) toward the second opening end (2b), and first projecting portions (4a, 4b) disposed on two respective first inner walls (1a, 1b) parallel to the septum phase plate (3), out of four inner walls of the rectangular waveguide (1), in such a way as to project toward an inside of the rectangular waveguide (1).

An ultra-wideband linear-to-circular polarizer is disclosed. In accordance with embodiments of the invention, the polarizer includes a plurality of cascaded waveplates having biaxial permittivity or cascaded anisotropic sheet impedances. Each waveplate/sheet has a principal axis rotated at different angles relative to an adjacent waveplate/sheet about a z-axis of a 3-dimensional x, y, z coordinate system. Each waveplate is composed of a unit cell of an artificial anisotropic dielectric. Each sheet impedance is composed of an anisotropic metallic pattern. The polarizer further includes impedance matching layers disposed adjacent the cascaded waveplates/sheets.