Advanced Artificial Doppler Shift Manipulation with Rotational Vortex Beams in Space-Time Digital-Coding RIS System: A Practical Approach

This paper presents a novel approach for generating and manipulating artificial Doppler shifts using rotational Orbital Angular Momentum (OAM) beams integrated with Space-Time Digital-Coding Reconfigurable Intelligent Surfaces (RIS). Traditional modulation schemes like Orthogonal Time Frequency Space (OTFS) modulation exhibit limitations in low-mobility and static scenarios due to minimal Doppler shifts. Our proposed system addresses these challenges by leveraging the rotational Doppler effect of OAM beams and the dynamic reconfigurability of RIS. We develop and validate a prototype capable of producing arbitrary Doppler signals, even in quasi-static environments, enhancing OTFS performance and broadening its application scope. This integration offers a versatile solution for advanced wireless communication systems, optimizing performance across varying mobility conditions. Experimental results demonstrate the effectiveness of our approach in generating controlled artificial Doppler shifts without moving, improving signal processing, and enhancing communication reliability.