Rotary joint characterization using antenna measurements

Several elements contribute to antenna radiation pattern measurements inaccuracies: measurement system accuracy and drift, impact of temperature, reflectivity of the chamber and positioning system quality including rotary joints. The rotary joints constitute a specific problem: their contribution is a function of the axis position in which they are settled. As a consequence, characterization in situ of rotary joint is of main interest for compensation purposes. In this article we propose a rotary joint characterisation based on antenna measurement. The axis concerned by this method are the roll axis used for probe orientation and the roll axis that enforce the radiation pattern cut plane choice: these two axis are of main interest for 3D radiation measurements.