Over-the-air (OTA) measurements are the standardized methods to evaluate radio performance in wireless systems. EMC issues such as interference and receiver desensitization are important factors. In this paper, OTA measurement challenges in the upcoming fiftth generation (5G) wireless systems are overviewed. Several key technologies that could be widely used in the 5G OTA measurements are discussed, including near-field to far-field transformation, anechoic chamber absorbers, and sampling antennas. The most important devices under test (DUT) for 5G OTA are chip sets, user equipment, and active array systems. The OTA test challenges for certification, research and development, and mass production for these DUTs are introduced.

Effective electromagnetic properties of aramid honeycomb board coated with a layer of multi-wall carbon nanotube or iron flakes composites were measured with waveguide method from 4 to 12 GHz. It was proved that homogenization theory could predict the effective permittivity or permeability of the honeycomb composites with good accuracy. The coated honeycomb composites of relatively high permittivity and permeability could potentially be used to develop dielectric or magnetic substrate for shielding layer or absorbing structures working at microwave frequencies.

For the fifth generation wireless communication system, millimeter-wave absorber has been frequently used in the measurement of high-power devices, such as transmitting antennas of base stations or satellite communication antennas, etc. The overheat inside the absorber can always be a matter of concern because it may lead to catastrophic fire in the anechoic chamber. A novel pyramidal structure with vent holes and heat sinks was proposed to improve the heat dissipation. The power-handling capability of the wave absorber could be improved by increasing the heat dissipation path without changing the characteristics of the base material. Multiphysics simulation was carried out to analyze the thermal-electromagnetic interaction. This absorber can be used to measure the high-power antenna and the radar system inside anechoic chambers, with power density up to 7 kW/m ² .