The deployment of wideband extremely large antenna arrays has the promising of achieving Tbps data rates in the next-generation communication networks. However, due to the extremely wide bandwidth and large antenna array aperture, the near-field beam-split effect will severely degrade the actual transmission rates, which has not been investigated in existing works. To address this challenging problem, we first reveal the near-field beam-split effect and analyze the corresponding array gain loss. Then, a piecewise-far-field model with piecewise-linear phase characteristics is harnessed for approximating the near-field channel. Based on this, we conceive a phase-delay focusing method for mitigating the near-field beam-split effect. Moreover, we introduce a new metric, termed the effective Rayleigh distance, which is more accurate in distinguishing the far-field and near-field regions than the classical Rayleigh distance for practical communications. Finally, numerical results are provided to demonstrate the effectiveness of our methods.
翻译：宽带特大天线阵列的部署有望在下一代通信网络中达到Tbps数据率,然而,由于宽度极广和天线阵列孔径大,近地波束效应将严重降低实际传输率,而现有工程尚未对此进行调查。为了解决这一具有挑战性的问题,我们首先揭示近地波束效应,分析相应的阵列增益损失。然后,利用一个具有小丝线相特性的平面远方模型来接近近地信道。在此基础上,我们设想了一种以分阶段偏重为重点的方法来减轻近地波束效应。此外,我们还采用了一种称为有效的雷利格距离的新指标,在区分远地和近地区域方面比传统的雷利距离更精确,以便进行实际通信。最后,提供了数字结果,以证明我们的方法的有效性。
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