3D Calibration of an Over-the-Air Testbed for GNSS CRPA Antenna Testing

This paper presents a novel approach to calibrate an over-the-air (OTA) testbed that can perform 3D full polarimetric wave field synthesis (WFS) to test controlled reception pattern antennas (CRPA) for global navigation satellite systems (GNSS). So far, 2D and 2. 5D WFS have been used for single polarization OTA testing as well as MIMO 4G/5G user equipment. Still, the level of accuracy in representing real-world scenarios remains a challenge, especially for testing GNSS systems. It is especially challenging given that the azimuth and elevation angles of the satellites with relation to the device under test (DUT) can be accurately represented only in a 3D environment. 3D WFS opens the doors for the emulation of more complex real-world scenarios, especially where multi-antenna receivers have to be tested. However, the challenge increases significantly in terms of hardware and its calibration. Instead of using three electromagnetic (EM) field probes to perform the calibration of the three orthogonal field vectors (x, y, z), this approach uses only one EM field probe to perform the entire calibration process for emulation of arbitrary polarized wave fields at the same point with the risk of field distortions. The limitations and accuracy of the proposed calibration procedure for full polarimetric WFS are discussed in this contribution.