Experimental Demonstration of Planar Near-Field to Far-Field Transformation With Probe Correction Technique

The emergence of millimeter-wave-based 5G/Beyond 5G and 6G communication technologies has led to advancements in high data rates and low latency. However, there is a massive challenge in implementing the hardware platform including the millimeter-wave antenna. Over-the-air (OTA) testing is crucial for evaluating these antennas, often requiring large facilities to obtain far-field (FF) characteristics. In addition, the measurement accuracy is often limited mainly due to the path loss of the millimeter waves in the far field. Therefore, it is necessary to test the antenna in the near-field (NF) region. In this paper, we present a practical method for obtaining an FF pattern of the antenna-under-test by using an NF-to-FF transformation method with a probe correction technique. The feasibility of the process is validated by the OTA measurement results with a dedicated NF scanning system, which accurately reconstructs the FF patterns from the NF measurement results. A key contribution of this paper is the successful demonstration of a planar multi-patch antenna as an effective multi-probe for NF measurements, enabling a significant reduction in measurement time while maintaining high reconstruction accuracy. Its compact and planar form factor facilitates easy integration into space-constrained measurement setups, making it particularly suitable for automatic test equipment (ATE) and scalable testing systems.