Pseudorandom Sequence (Space–) Time-Modulated Metasurfaces: Principles, Operations, and Applications

This article presents a novel class of (space–)time-modulated metasurfaces, namely, (space–)time metasurfaces that are modulated by pseudorandom sequence (PRS) waveforms. In contrast to their harmonically or quasi-harmonically modulated counterparts, these metasurfaces massively alter the temporal spectrum of the waves that they process; as a result, they exhibit distinct properties and offer complementary applications. These metasurfaces are assumed, here, to operate in the “slow-modulation” regime, where the fixed-state time between the state transition is much larger than the transient time associated with the dispersion of the media involved, which allows for the safe separation of the time-variance and frequency-dispersive effects of the system.