Multi-frequency Time Modulation for Harmonic Energy Redistribution Using Metasurfaces

Harmonic manipulations play a crucial role in wireless communication, sensing, and radar systems. Metasurfaces, composed of periodic arrays of subwavelength units, provide a novel approach to harmonic manipulation with low complexity and high efficiency. However, general metasurface-based harmonic manipulations primarily utilize spatial and temporal modulation while neglecting frequency variation in controls of metasurfaces. In this work, a multi-frequency time modulation (MFTM) method for metasurfaces is proposed to redistribute the harmonic energy more flexibly. By introducing frequency variation in temporal modulation of metasurfaces, this method can precisely customize the quantity, amplitude, and location of harmonics in the frequency domain. This method introduces a new degree of freedom in metasurface control, thereby enhancing the modulation capabilities of time-modulated metasurfaces (TMMs) without compromising the effectiveness of conventional spatial or temporal modulation methods. The harmonic control mechanism presented in this work may be applied in fields such as wireless communication, radar, and optics.