In this work, we address the key industry challenge of accurately capturing the propagation environment in live 5G commercial networks, which is essential for predicting radio device performance in realistic propagation conditions during the design phase. An advanced passive channel sounding system is designed to decode 5G downlink signals, such as the channel state information-reference signal (CSI-RS), and to resolve multipath parameters including delays, arrival angles, polarization, and complex amplitudes. To ensure measurement accuracy, the designed passive channel sounding system is rigorously calibrated and validated within a compact antenna test range (CATR) prior to field deployment. Furthermore, we propose a digital twin (DT) framework to create precise digital representations of electrical signals received on antennas of investigation through highprecision simulations, ensuring alignment with actual conditions among various locations and orientations for the antennas. The methodology begins with the precise digitization of 5G fading channel environments via the passive channel sounding process. Utilizing the acquired channel parameters and the complex radiation patterns of the targeted antennas, the DTs of the received electrical signals for the antennas can be computed. Field measurements, conducted using a standard dipole for electrical field scanning, validate the consistency between the DT predictions and measured results, thereby affirming the accuracy of both the passive channel sounding results and the proposed DT framework.
