Time Modulated Metasurface in X-Band for Radar Countermeasure

This study presents the design and implementation of reconfigurable metasurface time modulation in the X-band. Three layers form the time-modulated metasurface, with the middle layer switchable ground. The switching behavior of the PIN diode changes the reflection coefficient over time. Time-modulated complex-valued reflection coefficients produce harmonics with reduced reflected frequency component power and increased side-band power. The harmonic with reduced incidence frequency component power offers extra frequency shift and incorrect velocity information to X-band Doppler radar. A prototype with a thickness of 0.12${\lambda }_L$ and a periodicity of 0.26${\lambda }_L$ (the lowest frequency) is proposed. In the frequency range of 7.8–12.9 GHz, the measured spectrum of the reflected electromagnetic wave component at $f_{\mathrm{in}}$ ranges from −0 to −17 dB. The authors claim this is the first experimental proof of a time-modulated metasurface in the 7.8–12.9 GHz frequency range (X-band). The structure can disrupt X-band Doppler radar target recognition and tracking with a Doppler-like frequency shift in the reflected wave.