In this contribution, we present a time-modulated full-reflective metasurface able to realize a frequency shift of the illuminating electromagnetic wave. The metasurface consists of an array of metallic patches printed on a grounded electrically thin dielectric substrate. The patches are loaded by a set of varactors controlled by a low-frequency time-varying voltage signal. The varactors change in real-time the response of the metasurface realizing the required reflection response for achieving the frequency shift. We report here our preliminary results, showing the ability of the metasurface to reflect a frequency-shifted signal according to the modulation imparted by the varactors. The proposed metasurface is a bi-dimensional version of the recently proposed Doppler cloak, a spatiotemporally modulated metamaterial cover to be placed in front or wrapped around a moving object to restore locally the source illumination frequency, as if it were not in motion.
Ramaccia, D., Toscano, A., Bilotti, F., Sounas, D.L., Alu, A. (2019). Time-modulated reflective metasurface for the control of the reflected signal frequency. In 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, APSURSI 2019 - Proceedings (pp.1611-1612). Institute of Electrical and Electronics Engineers Inc. [10.1109/APUSNCURSINRSM.2019.8888506].