Microwave telemetry in high speed machine tools

The paper describes the development of a complex antenna system for data communication between the rotating and static part inside a spindle system of a machine tool with revolutions per minute up to 40000 RPM. The system is based on the transponder technology where power is induced via closed coupled coils to the rotating part and data is sent back wireless at 2.4 GHz to the static part. To maintain a stable and lossless data communication, it is necessary to achieve a circular horizontal diagram of the antenna array and to consider the nearfield conditions and the complex CAD data of the metallic and dielectric structures of the whole assembly, causing strong reflections, diffraction and refraction. This is done by a three-dimensional full-wave analysis of the device under consideration of all these effects. By optimization of the whole structure no bit errors occurred with full rotational speed within weeks.