Space-Time Decoupled Metasurface Integrating Reflective Mixer and Phase Shifter Functions

Abstract: Electromagnetic (EM) information metasurface represents a class of 2D metamaterials that can swiftly manipulate their EM characteristics to convey specific information. Past researches present various strategies for embedding information within ambient EM waves through the superposition of time-varying quantized properties for each unit. Despite their capabilities, these approaches alone are insufficient for concurrently but independently realizing the creation of information and the allocation of spatial energy. In this work, we introduce a comprehensive approach named the space-time decoupled metasurface (STD-Metasurface), facilitating the simultaneous and independent control of information modulation and passive beamforming by incorporating reflective mixer and phase shifter functionalities into each unit. As a proof of concept, we present a minimalist design of single-diode unit where the ingenious utilization of analog switch bonds the digital signal and analog signal together. By inputting baseband analogue signals in a specific level range, STD-Metasurface prototype is capable of modulating them onto the envelopes of reflected EM waves without distortion meanwhile controlling the reflected radiation patterns by digital signals, even waveform superposition and spatial multiplexing. To demonstrate the superior capabilities of the STD-Metasurface, we have developed an experimental platform to highlight its practicality and potential applications as a reconfigurable backscatter transmitter and a dynamic Doppler-spoofing reflector array.