Accurate Calibration of Truncated Spherical Near Field Systems with Different Ground Floors using the Substitution Technique

The calibration of the antenna measurements system is a fundamental step which directly influences the accuracy of any power-related quantity of the device under test. In some types of systems, the calibration can be more challenging than in others, and the selection of a proper calibration method is critical. In this paper, the calibration of the truncated spherical near-field ranges typically used for automotive tests is investigated, considering both absorbing and conductive floors. The analyses are carried out in a 12:1 scaled multi-probe system, allowing access to the “true”, full-sphere calibration which is used as reference. It will be demonstrated that the substitution (or transfer) method is an excellent calibration technique for these types of systems, if applied considering the efficiency of the reference antenna.