Space-Time-Modulated Reconfigurable Metamaterial Based on a Field-Focused Cavity for Nonreciprocal Transmission Control and Frequency Conversion.

Lorentz reciprocity is a fundamental physical property limiting advanced wave propagation control. Previously, special materials and magnetic bias were used to break the reciprocity; however, the approaches are limited by the bulky and costly implementation. To achieve nonreciprocity without magnetic bias, space-time-modulated metamaterials have been investigated for far-field wave propagation control.