CATR-based multi-reflector setup for RRM testing of 5G NR mmWave devices

The Rohde & Schwarz R&S ATS1800C pioneered an innovative technology for OTA testing. The test chamber provides a gold-plated CATR reflector for building a large quiet zone (QZ), or usable measurement area, in an unequalled compact form factor. The device is a highly flexible solution that supports methods such as thermal and out-of-band testing. By adding the new side chamber option, the device now also supports RRM testing for two AoAs.

As opposed to the single-CATR R&S ATS1800C, the ATS1800M offers four CATR reflectors, each with an unequalled 30cm QZ. Since all four QZs overlap and form a combined QZ of 30cm at their intersection, the device under test (DUT) is encircled by a large QZ from every direction. This setup enables the DUT to be examined when exposed to signals coming simultaneously at different angles – just like in a real network. The large QZ results in a notably lower measurement uncertainty compared to competing solutions. The DUT can also be tested without knowing where the antennas are located within it ('black box testing'), making it an excellent solution for service providers.

RRM testing strives to use the limited RF resources as efficiently as feasible and avoid co-channel interference. The 3GPP specification for RRM testing defines five different pairs of angles, with relative angular differences of 30, 60, 90, 120 and 150 degrees between the base station signals. The ATS1800M can satisfy this demand with only three extra reflectors. The side chamber extension is retrofittable to existing ATS1800C units and reversible.