Rotary joint

Rotary joints transmit high-frequency signals between two waveguide sections that can rotate relative to one another. They are used in particular where continuous or repeated rotation is required without interrupting the RF connection.

Typical applications include:

• Rotating radar and antenna systems

• Satellite and communications systems

• Antenna test rigs

• Scanners and positioning systems

• Laboratory set-ups for microwave and millimetre-wave measurements

The Mi-Wave series 355 rotary joints consist of two circular waveguide sections mounted on a rotating bearing. Signal transmission takes place in the low-loss TE01 mode, which minimises signal changes during rotation. Mi-Wave components exhibit low phase variation and insertion loss and can also be used for laboratory tests in which parameters such as phase variations in the radiated fields need to be determined. Some of these can also be combined with waveguide transitions.

High signal stability during rotation

In a rotary joint, insertion loss as well as amplitude and phase variation during rotation are particularly crucial. According to the manufacturer, the Mi-Wave series 355 achieves an amplitude variation of less than 0.2dB and a phase variation of less than 2°. This makes the components suitable for precise measurement set-ups in which, for example, the phase change of radiated fields is investigated.

The available frequency range extends from 11.6 to 150GHz. This covers applications from the microwave range right through to the millimetre-wave range.

Combination with rectangular waveguides

The rotary joints themselves operate with circular waveguides. For use in systems with rectangular waveguides, they can be combined with appropriate mode transitions. Mi-Wave provides series 330 transitions for this purpose, as well as an optional mode filter. This enables the design of a complete rotary joint unit for rectangular waveguide systems.

This concept is particularly interesting at very high frequencies, where conventional rotary joints reach their limits due to their mechanical dimensions or electrical properties. We look forward to advising you.