Free space electromagnetic wave modulation using tunable metasurface absorber

This paper demonstrates the design, simulation and fabrication of a metasurface modulator that works in the X-band with flexible modulation depth and megahertz modulation frequency. Experimental results show that by adjusting the bias voltage applied to the metasurface modulator, the resonance absorption frequency of the metasurface modulator can be tuned from 8.4 GHz to 9.7 GHz, so that for a fixed frequency in this range, the reflectivity can be modulated between -0.2 dB and -9.2 dB. The modulation function is achieved by applying the modulating signal to the metasurface modulator as the bias voltage to make the metasurface switch between two levels of reflectivity, thus the message to be transmitted is attached to the amplitude-modulated reflection wave. In consideration of oblique incidence which is the common case in practical situation, a corner reflector is assembled with two mutually vertical metasurfaces and the effectiveness is also verified.