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 polarizer for a waveguide, comprising a main body for transmitting an electromagnetic wave, a first delay member being provided in the main body. A second delay member arranged downstream of the first delay member in the working direction (A) of the electromagnetic wave is provided in the main body, and the polarization axis (P.sub.2) of the second delay member is rotated relative to the polarization axis (P.sub.1) of the first delay member by a delay angle (β).

A waveguide includes a first double-ridge waveguide, a second double-ridge waveguide, and a polarization rotator. The first double-ridge waveguide provides a phase of an input electrical field rotated 0° or 90°. The second double-ridge outputs an electric field with a polarization that is perpendicular to a first polarization of the input electrical field. The polarization rotator is mounted between the first double-ridge waveguide and the second double-ridge waveguide and includes a frame, a dielectric layer, a first conducting pattern layer forming a first conductor and a second conductor, a first switch connected between the first conductor and the second conductor, a second conducting pattern layer forming a third conductor and a fourth conductor, and a second switch connected between the third conductor and the fourth conductor. Wherein a phase rotation of 90° or −90° is provided by the polarization rotator based on a state of the first and second switch.

A waveguide includes a first double-ridge waveguide, a second double-ridge waveguide, and a polarization rotator. The first double-ridge waveguide provides a phase of an input electrical field rotated 0° or 90°. The second double-ridge outputs an electric field with a polarization that is perpendicular to a first polarization of the input electrical field. The polarization rotator is mounted between the first double-ridge waveguide and the second double-ridge waveguide and includes a frame, a dielectric layer, a first conducting pattern layer forming a first conductor and a second conductor, a first switch connected between the first conductor and the second conductor, a second conducting pattern layer forming a third conductor and a fourth conductor, and a second switch connected between the third conductor and the fourth conductor. Wherein a phase rotation of 90° or −90° is provided by the polarization rotator based on a state of the first and second switch.

A tunable microwave system includes at least two elements, each element being chosen from a propagating guide, an evanescent guide, a resonator, and at least one coupling device arranged between the two elements and configured to couple the two elements to each other, the coupling device having a holder having an aperture and having at least one elongate element the shape of which is elongate in a polarization direction contained in a plane of the aperture, the elongate element being securely fastened to the perimeter of the aperture at at least one end, the coupling device being configured to be rotatable about an axis substantially perpendicular to the plane of the aperture so as to modify a value of the polarization direction and so that the coupling between the two elements is dependent on the value of the polarization direction.

A tunable microwave system includes at least two elements, each element being chosen from a propagating guide, an evanescent guide, a resonator, and at least one coupling device arranged between the two elements and configured to couple the two elements to each other, the coupling device having a holder having an aperture and having at least one elongate element the shape of which is elongate in a polarization direction contained in a plane of the aperture, the elongate element being securely fastened to the perimeter of the aperture at at least one end, the coupling device being configured to be rotatable about an axis substantially perpendicular to the plane of the aperture so as to modify a value of the polarization direction and so that the coupling between the two elements is dependent on the value of the polarization direction.

A full band waveguide orthomode transducer (OMT) includes first, second, and third waveguide sections coupled to one another, the first, second, and third waveguide sections respectively having a first port, a second port, and a third port. A first wire grid polarizer in the first waveguide section is transparent to electromagnetic signals having a first polarization and reflective of electromagnetic signals having a second polarization orthogonal to the first polarization. A second wire grid polarizer in the second waveguide section is transparent to electromagnetic signals having the second polarization and reflective of electromagnetic signals having the first polarization. The third waveguide section is configured to transmit and/or receive electromagnetic signals having the first polarization and/or the second polarization.

A full band waveguide orthomode transducer (OMT) includes first, second, and third waveguide sections coupled to one another, the first, second, and third waveguide sections respectively having a first port, a second port, and a third port. A first wire grid polarizer in the first waveguide section is transparent to electromagnetic signals having a first polarization and reflective of electromagnetic signals having a second polarization orthogonal to the first polarization. A second wire grid polarizer in the second waveguide section is transparent to electromagnetic signals having the second polarization and reflective of electromagnetic signals having the first polarization. The third waveguide section is configured to transmit and/or receive electromagnetic signals having the first polarization and/or the second polarization.

A polarizing screen includes an arrangement of at least one, electrically conductive, polarizing cell, which at least one cell is frequency- and polarization-selective, for transforming the polarization of the electric component E of the transverse electromagnetic (TEM) wave, received with linear polarization, into an electromagnetic wave with circular polarization. The four lateral walls of each section of waveguide forming a polarizing cell are each open over their entire length due to a median continuous slot, parallel to the direction of propagation of the incident electromagnetic wave, so as to form four angled electrically conductive plates. Each polarizing cell includes electrically conductive interconnection rods which interconnect the lateral walls and the four angled plates so that they are partially or completely rigidly connected and which form one or more electrical discontinuities, which are arranged at the ends of or inside the section of waveguide forming the polarizing cell and form one or more inductive or capacitive loads, or one or more (LC) resonators equivalent to an inductor and a capacitor connected in parallel or in series. The longitudinally open slots of the lateral walls and the elementary electrical discontinuities of each polarizing cell include geometric shapes and dimensions which provide total transmission of the incident wave, which is associated with a phase anisotropy of +90 or 90 according to the components E.sub.V and E.sub.H.

A polarizing screen includes an arrangement of at least one, electrically conductive, polarizing cell, which at least one cell is frequency- and polarization-selective, for transforming the polarization of the electric component E of the transverse electromagnetic (TEM) wave, received with linear polarization, into an electromagnetic wave with circular polarization. The four lateral walls of each section of waveguide forming a polarizing cell are each open over their entire length due to a median continuous slot, parallel to the direction of propagation of the incident electromagnetic wave, so as to form four angled electrically conductive plates. Each polarizing cell includes electrically conductive interconnection rods which interconnect the lateral walls and the four angled plates so that they are partially or completely rigidly connected and which form one or more electrical discontinuities, which are arranged at the ends of or inside the section of waveguide forming the polarizing cell and form one or more inductive or capacitive loads, or one or more (LC) resonators equivalent to an inductor and a capacitor connected in parallel or in series. The longitudinally open slots of the lateral walls and the elementary electrical discontinuities of each polarizing cell include geometric shapes and dimensions which provide total transmission of the incident wave, which is associated with a phase anisotropy of +90 or 90 according to the components E.sub.V and E.sub.H.