5G NR provides numerous technological advantages, but there will also be many technical challenges that need to be overcome during 5G NR testing. Since OTA measurements often require far field conditions in order to be carried out fast, easily and accurately, a high-quality quiet zone (QZ) is needed in which the wave fronts coming from a test antenna can be assumed to be plane. Larger QZs require a long distance between the device under test (DUT) and the test antenna, meaning large shielded chambers are needed in direct far field (DFF) setups. Conformance testing in the mmWave range also calls for black box testing, meaning the location and size of the antennas in OTA measurements are considered unknown.
To address the space constraints, Rohde & Schwarz employs the Compact Antenna Test Range (CATR) method, which has been approved by 3GPP. The method relies on indirect far field (IFF) technology to simulate far field conditions. The reflector used in a CATR setup transforms the incoming spherical wave front to a plane wave due to its parabolic shape. This requires extremely high precision in reflector manufacturing, with accuracy in the micrometer range. To achieve this high accuracy, Rohde & Schwarz has developed an innovative, fully automated manufacturing method, delivering considerably higher reproducibility than traditional, semi-automated processes.