Time-Modulated Metasurface for Harmonic Signals Frequency Conversion

Radar stealth relies on various deception and camouflage strategies. However, at the lower frequencies used by long-range surveillance systems, there are still very few functional strategies. The emergence of metasurfaces fortunately brought hopeful new horizons to this issue. In parallel, thanks to the integration of time-based elements, metasurface research has reached new heights in the last few years. One subsequent feature of particular interest in this work is the frequency shifting of waves granted by time modulation. In radar stealth context, such mechanism can be harnessed to serve Doppler cloaking strategies. By compensating the Doppler shift induced by the target's movement, one can tamper with velocity readings. This work therefore focuses on the development of a frequency-converting metasurface, evaluating its frequency shifting abilities along with some undesired effects, notably induced by incomplete phase variations and the use of varactor diodes and their parasitic resistive elements.