Experimental validation of Plane Wave Generator for 5G New Radio FR2 applications

Plan wave generators (PWG) provides an interesting alternative solution to carry out radiation pattern measurements in far-field (FF) conditions close to the device under test (DUT). Significant chamber space and material cost reduction are possible using this approach. A dual-polarized PWG concept for FR2 frequency band measurements has been presented recently with some preliminary system emulation results. This concept allows for live, Over-The-Air (OTA) testing for FR2 enabled devices including real user conditions such as live people and phantoms that is very important at FR2 frequencies. In this paper, complete system measurements are presented for validation of the concept. The PWG array consist of 172 dual polarized elements fed by a Beam-Forming-Network (BFN). The sampling of the radiating aperture provided by the array elements is sufficient to provide a flat phase front, and thus approximate FF condition at 1.2m distance, in a spherical Quite-Zone (QZ) of up to 380mm diameter, almost 40λ at the highest frequency. The limited sampling by the array elements cause taper and amplitude ripple in the QZ measured to within ± 1.5dB average value. This is acceptable for the intended user testing. The amplitude variation can be improved by adjusting the QZ size according to the DUT size and a variation as small as ±0.8dB can be obtained for a 15cm QZ size. Such performances are suitable for stand-alone modern smart phone device measurements. The PWG use optimized excitation for each frequency, a flat QZ bandwidth of up to 1.5GHz around each calibration frequency is measured, which is more than the current FR2 band-width requirements.