The Institute for Geodesy and Photogrammetry at ETH Zurich has recently developed a new absolute field calibration system for GNSS receiver antennas. The hardware consists of two Septentrio PolaRx5 multi-GNSS receivers and a 5 m baseline. A geodetic-grade choke ring antenna is located at one end, the antenna to be calibrated is mounted on an industrial 6-axis KUKA KR 6 robot at the other end of the baseline. The robot rotates and tilts the antenna in a predefined, randomized sequence consisting of 1440 to 2880 orientations, without changing the coordinates of the arbitrarily chosen antenna reference point (ARP), i.e., the ARP is kept fixed in space. Every orientation is hold for 1 second, while the receivers acquire data with 20 Hz. The observations are then processed in a custom software on the triple-difference level. Until now, the system is able to estimate Phase Centre Variations (PCVs) for all Code Division Multiple Access (CDMA) GNSS signals. Until know, PCVs were successfully generated for GPS L1 and L2, Galileo E1 and E5, with formal errors ranging between approximatively 0.35 mm for GPS L1 and 0.80 mm for Galileo E5 PCVs. The calibration system is currently undergoing validation. We will present technical details regarding the hardware (including the calibration procedure for the robot), technical details of the processing (observation equation, processing strategy and automation) and we will present the most recent validation results and comparisons for different GNSS signals and antennas.