Space-Time-Coding Digital Metasurfaces: Principles and Applications
Frequency synthesis, polarization conversion, and convolution operation. (a) Conceptual illustration of STC digital metasurfaces for frequency synthesis. Reproduced from . (b) The time-modulated waveform with 1-bit, 2-bit, and 3-bit quantized phases and continuous sawtooth wave phases, as well as the corresponding harmonic amplitude distributions. Reproduced from . (c) Conceptual illustration of TDC digital metasurfaces for polarization conversion. Reproduced from . (d) A polarization conversion diagram with some specific collocations of the - and -polarized phases, from which the RHCP, LHCP, and cross-LP are successfully synthesized. Reproduced from . (e) Conceptual illustration of TDC digital metasurfaces for convolution operation. Reproduced from . (f) An illustrative example of nonlinear convolution operation at the +1st harmonic frequency, as it can be observed that the original dual-beam pattern deviates from the normal axis to the angle with negligible distortion. Reproduced from .