Flexible dispersion engineering in metasurface-based leaky-wave antennas: leveraging spatio-temporally modulated impedance surfaces

This study aims to investigate dispersion engineering mechanisms within unilateral and bilateral metasurface-based leaky-wave antennas, presenting methodologies focused on space-time modulation of impedance boundary conditions. Utilizing the generalized framework based on the Floquet-wave expansion method, the research precisely investigates the effect of periodic space-time modulation on the dispersion characteristics of the leaky-wave antenna. The beam scanning mechanism has been investigated in the momentum and frequency domains. It is shown that by choosing the appropriate spatial-temporal variations in the boundary condition, the radiation beam may be steered in the desired direction and frequency. Through a comprehensive analysis encompassing parameters such as modulation depth, average surface impedance, and space-time modulation frequencies, the paper seeks to elucidate the intricate dynamics governing dispersion phenomena. Furthermore, the inquiry delves into the "rabbit's ears" phenomenon observed in bilateral space-time modulated leaky-wave antennas. Distinguishing this phenomenon from the conventional pure-space modulated impedance boundary conditions, the research aims to uncover its underlying mechanisms and provide insights into the antenna performance. In addressing this phenomenon, the study also proposes adjusting the temporal pumping frequency as a potential strategy to mitigate the adverse effects associated with the rabbit's ears phenomenon.