Title: Beam Squint Mitigation in Wideband Hybrid Beamformers: Full-TTD, Sparse-TTD, or Non-TTD? Show Chinese title

Title: 宽带混合波束成形器中的波束倾斜抑制：全TTD、稀疏TTD还是非TTD？

Abstract: Beam squint poses a fundamental challenge in wideband hybrid beamforming, particularly for mmWave and THz systems that demand both ultra-wide bandwidth and high directional beams. While conventional phase shifter-based beamformers may offer partial mitigation, True Time Delay (TTD) units provide a fundamentally more effective solution by enabling frequency-independent beam steering. However, the high cost of TTD units has recently driven much interest in Sparse-TTD architectures, which combine a limited number of TTDs with a higher number of conventional phase shifters to balance performance and cost. This paper provides a critical examination of beam squint mitigation strategies in wideband hybrid beamformers, comparing Full-TTD, Sparse-TTD, and Non-TTD architectures. We analyze recent Non-TTD approaches, specifically the scheme leveraging the wideband beam gain (WBBG) concept, evaluating their performance and cost characteristics against TTD-based solutions. A key focus is placed on the practical limitations of Sparse-TTD architectures, particularly the often-overlooked requirement for wideband phase shifters operating alongside TTDs, which can significantly impact performance and implementation cost in real-world scenarios, especially for ultra-wideband applications. Finally, we conduct a cost-performance analysis to examine the trade-offs inherent in each architecture and provide guidance on selecting the most suitable hybrid beamforming structure for various fractional bandwidth regimes. Show Chinese abstract

Abstract: 宽带混合波束成形中，波束失真构成了一个根本性挑战，尤其是在需要超宽频带和高方向性波束的毫米波和太赫兹系统中。 虽然基于常规相移器的波束成形器可能提供部分缓解，但真正的时间延迟（TTD）单元通过实现频率无关的波束转向，提供了根本上更有效的解决方案。 然而，TTD单元的高昂成本最近引发了对稀疏TTD架构的广泛关注，这些架构将有限数量的TTD与更多常规相移器结合，以平衡性能和成本。 本文对宽带混合波束成形中的波束失真缓解策略进行了关键性分析，比较了全TTD、稀疏TTD和非TTD架构。 我们分析了最近的非TTD方法，特别是利用宽带波束增益（WBBG）概念的方案，并将其性能和成本特性与基于TTD的解决方案进行对比。 重点研究了稀疏TTD架构的实际限制，尤其是经常被忽视的要求，即需要与TTD一起工作的宽带相移器，这在实际场景中，特别是在超宽频带应用中，可能会显著影响性能和实现成本。 最后，我们进行了成本-性能分析，以研究每种架构固有的权衡，并为不同分数带宽范围选择最合适的混合波束成形结构提供建议。