Waveguide polarizer, contactless signal transmission system and antenna device comprising the waveguide polarizer

A system for contactless signal transmission through a rotary joint, comprising:

• a transmitter on a first part of the rotary joint and a receiver on a second part of the rotary joint, the first part of the rotary joint and the second part of the rotary joint being opposite each other and separated by an air gap, a surface of the first part and a surface of the second part facing each other being perpendicular to a rotation axis of the rotary joint;
• and
• a choke in the air gap between the first part of the rotary joint and the second part of the rotary joint and contacting one of the first part of the rotary joint and the second part of the rotary joint, the choke comprising a printed circuit board having a circular through hole coaxial with the rotation axis of the rotary joint, and an electromagnetic chip having an electromagnetic bandgap adjacent to the hole in the printed circuit board, the choke being configured to prevent signal leakage through the air gap,
• wherein each of the transmitter and the receiver comprises a round hollow waveguide aligned with the rotation axis,
• wherein at least the transmitter comprises in a waveguide polarizer which is a portion of the round hollow waveguide, a diameter of the waveguide polarizer being smaller than a diameter of the round hollow waveguide, and
• wherein two longitudinal diametrically opposite grooves are formed in walls of the waveguide polarizer.