任意波形生成超表面：直接调制与波束成形解耦的新范式
Arbitrary Waveform Generated Metasurface: A New Paradigm for Direct Modulation and Beamforming Decoupling
AI总结：
针对传统RIS反射调制存在的码本计算复杂、安全性与灵活性不足的问题，提出幅度相位解耦的AWG-RIS新概念，可独立生成任意波形与波束方向图，构建了理论框架并通过原型机实验验证了效果。
摘要：
信息超表面又称可重构智能表面（RIS），凭借其结构简单却具备出色电磁波操控能力的特性，已受到广泛关注。大量研究聚焦于利用RIS在无线通信、雷达探测、感知与通信一体化等多个领域实现高效且通用的信息传输。既往研究展示了多种利用各单元量化反射系数（RC）的叠加实现反射调制的方法，但这些方法存在码本序列计算复杂度高、通信安全性不足以及调制灵活性有限的问题。为应对这些挑战，我们提出一种信息超表面新概念——AWG-RIS，它通过幅度与相位解耦的设计，能够在不改变波束方向图的前提下，独立生成任意基带波形和波束方向图。AWG-RIS起到反射混频器的作用，可直接将目标信号嵌入入射电磁波中。随后，我们构建了一套分析框架，并在新模型中引入波形因子和波束成形因子，为从控制信号到出射电磁波的转换提供了理论支撑。此外，我们推出了全球首个原型机，展示了在保持波束方向图不变的情况下实现无源任意波形生成的能力。依托直接调制与波束成形的解耦特性，我们探索了相较于传统RIS在多个领域的额外应用场景。最后，我们开展的实验验证了任意波形及特定频谱图的生成效果。
英文摘要：
Information Metasurface, also known as reconfigurable intelligent surface (RIS) has gained significant attention owing to its impressive abilities in electromagnetic (EM) wave manipulation with simple structures. Numerous studies focus on achieving efficient and versatile information transmission using RIS across various fields like wireless communication, radar detection, integrated sensing, and communications, among others. Previous studies demonstrate diverse approaches to achieve reflection modulation by utilizing the superposition of the quantified reflection coefficient (RC) of each unit but suffer from the computing complexity of codebook sequence, the safety of communication, and the flexibility of modulation. To address these challenges, we introduce a novel concept of information metasurface, namely AWG-RIS, which is capable of independently producing arbitrary baseband waveforms and beam patterns through a design that decouples magnitude and phase, without changing the beam pattern. The AWG-RIS functions as a reflection mixer, directly embedding the intended signal into the incoming EM waves. Subsequently, we developed an analysis framework and introduced the waveform factor and beamforming factor into the new model, offering theoretical support for the transition from the control signal to the outgoing electromagnetic wave. Additionally, we unveil the world's first prototype showcasing passive arbitrary waveform generation while maintaining the beam pattern unaltered. Leveraging the decoupling of direct modulation and beamforming, we explore additional applications in several domains relative to traditional RISs. Finally, we present experiments that confirm the generation of arbitrary waveforms and particular spectrograms.
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