In the quest to realize analog signal processing using subwavelength metasurfaces, in this paper, we present the first demonstration of programmable time-modulated metasurface processors based on the key properties of spatial Fourier transformation. Exploiting space-time coding strategy enables local, independent, and real-time engineering of not only amplitude but also phase profile of the contributing reflective digital meta-atoms at both central and harmonic frequencies. Several illustrative examples are demonstrated to show that the proposed multifunctional calculus metasurface is capable of implementing a large class of useful mathematical operators, including 1st- and 2nd-order spatial differentiation, 1st-order spatial integration, and integro-differential equation solving accompanied by frequency conversions. Unlike the recent proposals based on the Green’s function (GF) method, the designed time-modulated signal processor effectively operates for input signals containing wide spatial frequency bandwidths with an acceptable gain level. Proof-of-principle simulations are also reported to demonstrate the successful realization of image processing functions like edge detection. This time-varying wave-based computing system can set the direction for future developments of programmable metasurfaces with highly promising applications in ultrafast equation solving, real-time and continuous signal processing, and imaging.

中文翻译：

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通过时空数字超表面进行模拟信号处理

为了实现使用亚波长超颖表面的模拟信号处理，本文基于空间傅立叶变换的关键特性，对可编程时间调制超颖表面处理器进行了首次演示。利用时空编码策略，不仅可以在中心频率和谐波频率上进行局部，独立和实时的工程设计，不仅可以对幅度做出贡献，还可以对反射数字形亚原子的相位分布进行相位分析。演示了几个说明性示例，表明所提出的多功能微积分元表面能够实现一大类有用的数学运算符，包括一阶和二阶空间微分，一阶空间积分以及伴随频率的积分微分方程求解转换。与基于格林函数（GF）方法的最新建议不同，设计的时间调制信号处理器可有效地处理包含宽空间频率带宽且增益水平可接受的输入信号。还报道了原理证明仿真，以证明图像处理功能（如边缘检测）的成功实现。这种基于时变波的计算系统可以为可编程超颖表面的未来发展指明方向，在超快速方程求解，实时和连续信号处理以及成像方面具有广阔的应用前景。还报道了原理证明仿真，以证明图像处理功能（如边缘检测）的成功实现。这种基于时变波的计算系统可以为可编程超颖表面的未来发展指明方向，在超快速方程求解，实时和连续信号处理以及成像方面具有广阔的应用前景。还报道了原理证明仿真，以证明图像处理功能（如边缘检测）的成功实现。这种基于时变波的计算系统可以为可编程超颖表面的未来发展指明方向，在超快速方程求解，实时和连续信号处理以及成像方面具有广阔的应用前景。