Microwave-network-based analysis and optimization of single sideband metasurface considering nonideal time modulation

Reflection-type time-modulated metasurfaces are designed to exhibit a complex reflection coefficient that varies in time, assuming a discrete number of reflection states. To maintain high efficiency, the metasurface is designed to have unitary amplitude and a discrete number of phase levels, with ideal abrupt transition from one phase state to another when the modulation is present. However, the overall reflection coefficient is affected by the rise/fall time of the control voltage, shifting away the overall response of the metasurface from the ideal one. In this article, we present a microwave-network-based method that allows speeding up the analysis and optimization of time-modulated metasurface in the presence of nonideal temporal modulation. Additionally, the proposed method speeds up the calculation for the scattering field from the metasurface, maintaining a high level of accuracy and reduced computational efforts. To validate its effectiveness, linear phase modulation and in-phase and quadrature (I–Q) modulation are considered for achieving single sideband (SSB) modulation of the illuminating signal. Both numerical and experimental results confirm the accuracy of the microwave-network-based method in estimating the reflection spectrum emerging from the metasurface. Additionally, after optimization, the harmonic generation is improved by 12% for the linear phase modulation and 7% for the I–Q modulation. These outcomes demonstrate the reliability and practicality of the entire approach.