Influence Analysis of mm-Wave DUT Mounting Fixture in 5G OTA Measurement

All of the test cases in the current version of TR 38.810 in 3GPP and CTIA millimeter-Wave (mm- Wave) test plan are limited to the free space configuration. However, the truly free-space condition does not exist for mm-Wave testing of 5G user equipment since no device can float in the air. Mounting fixtures and supporting structures are needed to fix the device under test (DUT) and move it in two axes. The influence of mounting fixture on 5G mm-Wave wireless device performance is analyzed in this paper. First, a common 4×1 patch array at 28 GHz is simulated as the performance baseline. Various mounting fixture thickness & various spacing between the DUT and the mounting fixture are simulated to get a quick understanding of the mounting fixture’s influence on DUT performance. In different configurations, the working frequency of the antenna would have different degrees of deviation, while the gain could decrease or increase accordingly. Then, to explain these phenomena, an equivalent circuit is extracted utilizing the transmission line theory. Finally, according to the findings, it is recommended that the thickness of the mounting structure should be equal to an integer time of 0.5 λg to minimize the impact of the fixture for practical mounting structure design.