8K Real-Time Video-Transmission Using PDM and FDM in 220-GHz Band Based on Polarization Crosstalk Model and Optimization Strategy

Multidimensional multiplexing (MM) is a crucial technology for achieving high-capacity terahertz (THz) wireless communication. However, the non-ideal characteristics of polarization-related THz devices, such as the low cross-polarization isolation (XPI) of the ortho-mode transducer (OMT) and antenna mismatch, result in reduced power of co-polarization and increased power of cross-polarization signal in the receiver. This leads to high polarization crosstalk (PC), such as reduced signal-to-interference-plus-noise ratio (SINR) and degraded error vector magnitude (EVM) in the polarization division multiplexing (PDM) system. This article proposes a THz line-of-sight (LoS) dual linear polarized model to analyze the PC phenomenon, with consideration of polarization-related devices and transmitted power for the first time involving OMT antennas and channel (OACAO model). We explore influencing factors, including the imbalance of polarized transmitted power, XPI of OMT, antenna polarization mismatch, channel attenuation, and depolarization effect in 3D space. To deal with the PC problem, we adopt an XPI optimization strategy based on RF hardware debugging and a cross-polarization interference cancellation (XPIC) algorithm, which enhances XPI to 22-25 dB, and increases SINR by 1-2 dB. Finally, we establish our THz wireless system using PDM and frequency division multiplexing (FDM) in the 220-GHz band, demonstrating real-time transmission of uncompressed 8K video. Using 16-QAM and I/Q modulation, the wireless link succeeded in a total data rate of 83.2 Gb/s over 100 m with SINR exceeding 19.8 dB, and a block error rate (BLER) below 1e-9. This demonstration provides insight for future research on THz ultra-high-speed communication systems.