This article studies the spatial domain and polarization domain characteristics of multipath channels in a subway-like tunnel environment. Experiments were performed by rotating a horn antenna with 30◦ half power beamwidth (HPBW) in the azimuthal direction for two different transmitter-receiver (Tx-Rx) distances. The time domain measurement is conducted when carrier frequency is set as 1.8 GHz. The cross-polarization discrimination (XPD) is studied, and it is found that the maximum depolarized signals are from sidewalls. The characteristics of power azimuth spectrum (PAS) of co-polarized and cross-polarized signals follow a multi-cluster Gaussian distribution. Ray-tracing method is employed to investigate the wave propagation in the tunnel environment. The results demonstrate that the main multipath components (MPCs) are around the line-of-sight (LOS) direction, and the reflected waves are from the other end of the tunnel (RWET). The correlation coefficient of co-polarized configuration pursues an increasing function with respect to the Tx-Rx distance and a decreasing function with respect to the cross-polarized configuration.
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