Test Zone Validation for FR2 MPAC Using Directional-Antenna-Based Virtual Array.

Over-the-air (OTA) testing methods have become an inevitable trend for performance testing of the fifth-generation (5G) new radio (NR) devices, due to their highly integrated transceiver design. Among various OTA testing methods, the 3-D multiprobe anechoic chamber (MPAC) method has been selected as the reference standard methodology for frequency range 2 (FR2) (24.25–52.6 GHz) multiple-input-multiple-output (MIMO) capable devices by the third-generation partnership project (3GPP). It is necessary to evaluate and validate the fidelity of the emulated spatial channels in a 3-D MPAC setup before practical measurements. The purpose of test zone validation is to evaluate how well the target channel models can be reconstructed in the test zone. The conventional method to validate the channel emulation performance of a 3-D MPAC setup is based on a virtual antenna array formed by omnidirectional antennas. In this article, a test zone validation method based on the virtual array composed of directional antennas is proposed for FR2 3-D MPAC setup. Compared with the conventional method, the proposed method can provide higher signal-to-noise ratio (SNR) in the measurements and require fewer measurement samples (i.e., virtual array elements) in the test zone. An extended sequential search algorithm is used as the postprocessing method to estimate the reconstructed channel spatial profiles in the test zone. The proposed method is validated by both numerical simulations and measurements with a standard 3-D channel model in a practical FR2 MPAC setup.