Fig. 5: The UMA for multi-channel and physical-layer security communications.
a The concept illustration of the UMA for directly generating two independently modulated waveforms carrying different digital data streams. Each sub-metasurface is responsible for one modulated waveform generation. Two designated users at different locations can simultaneously and independently receive the information from the UMA. b, c Measured radiation patterns of the UMA at the m = −1 (CH1) and m = −2 (CH2) harmonic frequencies. The insets on the right present the measured decoded constellation diagrams of the two channels at the receiver end. The beam directions for the CH1 and CH2 are (−30o, 30o) and (0o, 30o) in (b) and (c), respectively. d The concept illustration of the UMA with the inherent direction modulation property at the fundamental frequency. Only the target user in the main beam direction can successfully decode the information, whereas eavesdroppers at other positions totally lose the information. e Measured radiation pattern of the UMA at the fundamental frequency, and the measured decoded constellation diagrams when the receiver is located in different directions. The physical-layer security communication link for other main-beam directions is validated in Supplementary Fig. S8a, b. CW continuous wave, Mod modulated, Ant. antenna, VSA vector signal analyzer, CH channel, EVM error vector magnitude.
