Figure 1: Rotating joint with a coaxial section
Whenever a stationary rectangular waveguide is to be connected to a rotating antenna, a rotating joint must be used.
A circular waveguide is normally used in a rotating joint. This is the most common design used for rotating joints.
The circular waveguide is designed so that it will operate in the E0,1 mode. The rectangular sections are attached as shown in the illustration to prevent the circular waveguide from operating in the wrong mode. Distance of the stubs is 3/4 λ so that a high impedance will be presented to any unwanted modes.
|The rotating section of the joint uses a choke joint to complete the electrical connection with the stationary section.|
Figure 2: Rotating joint with a circular waveguide