Arbitrary Waveform Generated Metasurface: A New Paradigm for Direct Modulation and Beamforming Decoupling

Passive arbitrary waveform generation (AWG) are especially important in a variety of fields like radar detection, wireless communications and integrated sensing and communications. Typically, backscatter devices are used to achieve passive signal reflection modulation to facilitate information transmission or to interfere with radar echoes. Reconfigurable Intelligent Surface (RIS) or Metasurface is a promising technology that combines the advantages of backscatter devices and reflective array antennas. Previous studies demonstrate diverse approaches to achieve reflection modulation by utilizing the superposition of the quantified reflective coefficient (RC) of each unit but suffer from the computing complexity of codebook sequence, the safety of communication, and the flexibility of modulation. To overcome the difficulties, we propose new paradigm of metasurface, i.e. AWG-RIS, that can independently generate arbitrary baseband waveforms and beam patterns based on a magnitude-phase decoupled unit design without altering the beam pattern. We proposed an analysis framework and introduce waveform factor and beamforming factor into the new model which provide the theoretical support for the flow from the control signal to the outgoing electromagnetic wave. Furthermore, we introduce the world's first prototype that demonstrates passive arbitrary waveform generation without altering the beam pattern. The experiments validate the generation of arbitrary waveforms and spectrograms, both for a single input and through the superposition of multiple inputs.